From c6844b30bc85f2d9fbe760a9b1adb4dd8d3f4c20 Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Sun, 3 Mar 2024 11:39:45 +1100
Subject: [PATCH 01/29] Test naive filtering of uploads directory.

---
 .../tests/fonts/font-library/wpFontsDir.php   | 35 +++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
index a8f79888315bd..0fd66778cd5a8 100644
--- a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
+++ b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
@@ -69,4 +69,39 @@ function set_new_values( $defaults ) {
 
 		$this->assertSame( static::$dir_defaults, $font_dir, 'The wp_get_font_dir() method should return the default values.' );
 	}
+
+	public function test_fonts_dir_filters_do_not_trigger_infinite_loop() {
+		/*
+		 * Naive filtering of uploads directory to return font directory.
+		 *
+		 * This emulates the approach a plugin developer may take to
+		 * add the filter when extending the font library functionality.
+		 */
+		add_filter( 'upload_dir', 'wp_get_font_dir' );
+
+		add_filter(
+			'upload_dir',
+			function ( $upload_dir ) {
+				static $count = 0;
+				++$count;
+				// It may be hit a couple of times, at five iterations assume an infinite loop.
+				$this->assertLessThan( 5, $count, 'Filtering uploads directory should not trigger infinite loop.' );
+				return $upload_dir;
+			},
+			5
+		);
+
+		/*
+		 * Filter the font directory to return the uploads directory.
+		 *
+		 * The emulates a moving font files back to the uploads directory due
+		 * to file system structure.
+		 */
+		add_filter( 'font_dir', 'wp_get_upload_dir' );
+
+		wp_get_upload_dir();
+
+		// This will never be hit if an infinite loop is triggered.
+		$this->assertTrue( true );
+	}
 }

From b64bfae6ef2e0d06225ae79af4629598b1bbd6b6 Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Sun, 3 Mar 2024 11:49:38 +1100
Subject: [PATCH 02/29] Prevent infinite loop filtering fonts directory. Props
 @costdev.

---
 src/wp-includes/fonts.php | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index 690aaa5ffc343..ea3424e73a14b 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -96,8 +96,11 @@ function wp_unregister_font_collection( string $slug ) {
  *
  * @since 6.5.0
  *
- * @return array $defaults {
- *     Array of information about the upload directory.
+ * @param array|null $font_dir Optional. Array of unfiltered uploads directory.
+ *                             This is used when the function is called from
+ *                             the upload_dir filter. Default null.
+ * @return array {
+ *     Array of information about the font upload directory.
  *
  *     @type string       $path    Base directory and subdirectory or full path to the fonts upload directory.
  *     @type string       $url     Base URL and subdirectory or absolute URL to the fonts upload directory.
@@ -107,13 +110,23 @@ function wp_unregister_font_collection( string $slug ) {
  *     @type string|false $error   False or error message.
  * }
  */
-function wp_get_font_dir() {
+function wp_get_font_dir( $font_dir = null ) {
+	if ( doing_filter( 'font_dir' ) ) {
+		/*
+		 * The font_dir filter is being run, avoid an infinite loop.
+		 *
+		 * This indicates that a plugin is calling wp_upload_dir() while filtering
+		 * the font directory and avoids an infinite loop.
+		 */
+		return $font_dir;
+	}
+
 	$site_path = '';
 	if ( is_multisite() && ! ( is_main_network() && is_main_site() ) ) {
 		$site_path = '/sites/' . get_current_blog_id();
 	}
 
-	$defaults = array(
+	$font_dir = array(
 		'path'    => path_join( WP_CONTENT_DIR, 'fonts' ) . $site_path,
 		'url'     => untrailingslashit( content_url( 'fonts' ) ) . $site_path,
 		'subdir'  => '',
@@ -129,9 +142,9 @@ function wp_get_font_dir() {
 	 *
 	 * @since 6.5.0
 	 *
-	 * @param array $defaults The original fonts directory data.
+	 * @param array $font_dir The original fonts directory data.
 	 */
-	return apply_filters( 'font_dir', $defaults );
+	return apply_filters( 'font_dir', $font_dir );
 }
 
 /**

From c1edfbafdac9f0cc8056393e88217202b1bfce82 Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Sun, 3 Mar 2024 12:14:04 +1100
Subject: [PATCH 03/29] Restore naive filtering to rest end point.

---
 .../class-wp-rest-font-faces-controller.php    | 18 ++----------------
 1 file changed, 2 insertions(+), 16 deletions(-)

diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
index 3b3a338b838ec..46eeeccf31c46 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
@@ -856,21 +856,7 @@ protected function sanitize_src( $value ) {
 	 */
 	protected function handle_font_file_upload( $file ) {
 		add_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
-
-		/*
-		 * Set the upload directory to the fonts directory.
-		 *
-		 * wp_get_font_dir() contains the 'font_dir' hook, whose callbacks are
-		 * likely to call wp_get_upload_dir().
-		 *
-		 * To avoid an infinite loop, don't hook wp_get_font_dir() to 'upload_dir'.
-		 * Instead, just pass its return value to the 'upload_dir' callback.
-		 */
-		$font_dir       = wp_get_font_dir();
-		$set_upload_dir = function () use ( $font_dir ) {
-			return $font_dir;
-		};
-		add_filter( 'upload_dir', $set_upload_dir );
+		add_filter( 'upload_dir', 'wp_get_font_dir' );
 
 		$overrides = array(
 			'upload_error_handler' => array( $this, 'handle_font_file_upload_error' ),
@@ -888,7 +874,7 @@ protected function handle_font_file_upload( $file ) {
 
 		$uploaded_file = wp_handle_upload( $file, $overrides );
 
-		remove_filter( 'upload_dir', $set_upload_dir );
+		remove_filter( 'upload_dir', 'wp_get_font_dir' );
 		remove_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
 
 		return $uploaded_file;

From 19cc1c71176e5f351ee8feca0e103426b2bc2904 Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Wed, 6 Mar 2024 10:25:40 +1100
Subject: [PATCH 04/29] =?UTF-8?q?Thought=20bubble=E2=80=A6?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 src/wp-includes/fonts.php                     | 88 ++++++++++++-------
 .../class-wp-rest-font-faces-controller.php   |  4 +-
 .../fonts/font-library/fontLibraryHooks.php   |  4 +-
 .../tests/fonts/font-library/wpFontsDir.php   |  2 +-
 4 files changed, 59 insertions(+), 39 deletions(-)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index ea3424e73a14b..88a658bc2d9df 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -92,41 +92,65 @@ function wp_unregister_font_collection( string $slug ) {
 }
 
 /**
- * Returns an array containing the current fonts upload directory's path and URL.
+ * Lightweight, don't create directory.
  *
- * @since 6.5.0
+ * @todo Get in a committable state if it's decided to do this.
  *
- * @param array|null $font_dir Optional. Array of unfiltered uploads directory.
- *                             This is used when the function is called from
- *                             the upload_dir filter. Default null.
- * @return array {
- *     Array of information about the font upload directory.
- *
- *     @type string       $path    Base directory and subdirectory or full path to the fonts upload directory.
- *     @type string       $url     Base URL and subdirectory or absolute URL to the fonts upload directory.
- *     @type string       $subdir  Subdirectory
- *     @type string       $basedir Path without subdir.
- *     @type string       $baseurl URL path without subdir.
- *     @type string|false $error   False or error message.
- * }
+ * @return array
+ */
+function wp_get_font_dir() {
+	return wp_font_dir( false );
+}
+
+/**
+ * Get and create the font directory.
+ *
+ * @todo Get in a committable state if it's decided to do this.
+ *
+ * @param bool $create_dir
+ * @param bool $refresh_cache
+ * @return array
+ */
+function wp_font_dir( $create_dir = true, $refresh_cache = false ) {
+	// Allow extenders to manipulate the font directory consistently.
+	add_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
+	$font_dir = wp_upload_dir( null, $create_dir, $refresh_cache );
+	remove_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
+	return $font_dir;
+}
+
+/**
+ * Apply the filter.
+ *
+ * @todo Get in a committable state if it's decided to do this.
+ *
+ * @param mixed $font_dir
+ * @return mixed
  */
-function wp_get_font_dir( $font_dir = null ) {
+function wp_apply_font_dir_filter( $font_dir ) {
 	if ( doing_filter( 'font_dir' ) ) {
-		/*
-		 * The font_dir filter is being run, avoid an infinite loop.
-		 *
-		 * This indicates that a plugin is calling wp_upload_dir() while filtering
-		 * the font directory and avoids an infinite loop.
-		 */
+		// Avoid an infinite loop.
 		return $font_dir;
 	}
 
+	return apply_filters( 'font_dir', $font_dir );
+}
+
+/**
+ * Default font filter.
+ *
+ * @todo Get in a committable state if it's decided to do this.
+ *
+ * @param mixed $font_dir
+ * @return void
+ */
+function wp_default_font_dir_filter() {
 	$site_path = '';
 	if ( is_multisite() && ! ( is_main_network() && is_main_site() ) ) {
 		$site_path = '/sites/' . get_current_blog_id();
 	}
 
-	$font_dir = array(
+	return array(
 		'path'    => path_join( WP_CONTENT_DIR, 'fonts' ) . $site_path,
 		'url'     => untrailingslashit( content_url( 'fonts' ) ) . $site_path,
 		'subdir'  => '',
@@ -134,19 +158,15 @@ function wp_get_font_dir( $font_dir = null ) {
 		'baseurl' => untrailingslashit( content_url( 'fonts' ) ) . $site_path,
 		'error'   => false,
 	);
-
-	/**
-	 * Filters the fonts directory data.
-	 *
-	 * This filter allows developers to modify the fonts directory data.
-	 *
-	 * @since 6.5.0
-	 *
-	 * @param array $font_dir The original fonts directory data.
-	 */
-	return apply_filters( 'font_dir', $font_dir );
 }
 
+/*
+ * Runs early to allow extenders to hook on to the filter.
+ *
+ * @todo Move to default filters so it's in a committable state if it's decided to do this.
+ */
+add_filter( 'font_dir', 'wp_default_font_dir_filter', 5 );
+
 /**
  * Deletes child font faces when a font family is deleted.
  *
diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
index 46eeeccf31c46..163c3d414c9e0 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
@@ -856,7 +856,7 @@ protected function sanitize_src( $value ) {
 	 */
 	protected function handle_font_file_upload( $file ) {
 		add_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
-		add_filter( 'upload_dir', 'wp_get_font_dir' );
+		add_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
 
 		$overrides = array(
 			'upload_error_handler' => array( $this, 'handle_font_file_upload_error' ),
@@ -874,7 +874,7 @@ protected function handle_font_file_upload( $file ) {
 
 		$uploaded_file = wp_handle_upload( $file, $overrides );
 
-		remove_filter( 'upload_dir', 'wp_get_font_dir' );
+		remove_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
 		remove_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
 
 		return $uploaded_file;
diff --git a/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php b/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
index 083c12202aa34..9cf3cfd7706c0 100644
--- a/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
+++ b/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
@@ -73,13 +73,13 @@ protected function upload_font_file( $font_filename ) {
 		$font_file_path = DIR_TESTDATA . '/fonts/' . $font_filename;
 
 		add_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
-		add_filter( 'upload_dir', 'wp_get_font_dir' );
+		add_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
 		$font_file = wp_upload_bits(
 			$font_filename,
 			null,
 			file_get_contents( $font_file_path )
 		);
-		remove_filter( 'upload_dir', 'wp_get_font_dir' );
+		remove_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
 		remove_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
 
 		return $font_file;
diff --git a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
index 0fd66778cd5a8..6c5affa8c9fd2 100644
--- a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
+++ b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
@@ -77,7 +77,7 @@ public function test_fonts_dir_filters_do_not_trigger_infinite_loop() {
 		 * This emulates the approach a plugin developer may take to
 		 * add the filter when extending the font library functionality.
 		 */
-		add_filter( 'upload_dir', 'wp_get_font_dir' );
+		add_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
 
 		add_filter(
 			'upload_dir',

From a10dbe4f6ece3a3b9af17a55f0c1376926e6fee2 Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Thu, 7 Mar 2024 14:10:06 +1100
Subject: [PATCH 05/29] Improve comment.

---
 src/wp-includes/fonts.php | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index 88a658bc2d9df..fe9c41b3f7c77 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -112,7 +112,13 @@ function wp_get_font_dir() {
  * @return array
  */
 function wp_font_dir( $create_dir = true, $refresh_cache = false ) {
-	// Allow extenders to manipulate the font directory consistently.
+	/*
+	 * Allow extenders to manipulate the font directory consistently.
+	 *
+	 * This ensures the upload_dir filter is fired both when using
+	 * this function directly and when using the upload directory
+	 * is filtered in the Font Face REST API endpoint.
+	 */
 	add_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
 	$font_dir = wp_upload_dir( null, $create_dir, $refresh_cache );
 	remove_filter( 'upload_dir', 'wp_apply_font_dir_filter' );

From 2b21c6dd7643031365a65438633036d414ed0c4f Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Thu, 7 Mar 2024 14:12:19 +1100
Subject: [PATCH 06/29] Move the font directory filter registration.

---
 src/wp-includes/default-filters.php | 2 ++
 src/wp-includes/fonts.php           | 7 -------
 2 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/src/wp-includes/default-filters.php b/src/wp-includes/default-filters.php
index 3f7e43f8615bc..17343df20415d 100644
--- a/src/wp-includes/default-filters.php
+++ b/src/wp-includes/default-filters.php
@@ -751,6 +751,8 @@
 add_action( 'deleted_post', '_wp_after_delete_font_family', 10, 2 );
 add_action( 'before_delete_post', '_wp_before_delete_font_face', 10, 2 );
 add_action( 'init', '_wp_register_default_font_collections' );
+// Filter the font upload directory. Runs early to ensure the default directory is applied at priority 10 (default).
+add_filter( 'font_dir', 'wp_default_font_dir_filter', 5 );
 
 // It might be nice to use a filter instead of an action, but the `WP_REST_Templates_Controller` doesn't
 // provide one (unlike e.g. `WP_REST_Posts_Controller`, which has `rest_pre_insert_{$this->post_type}`).
diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index fe9c41b3f7c77..7a9227a09d3c0 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -166,13 +166,6 @@ function wp_default_font_dir_filter() {
 	);
 }
 
-/*
- * Runs early to allow extenders to hook on to the filter.
- *
- * @todo Move to default filters so it's in a committable state if it's decided to do this.
- */
-add_filter( 'font_dir', 'wp_default_font_dir_filter', 5 );
-
 /**
  * Deletes child font faces when a font family is deleted.
  *

From ba51db258690a2a49c49865395ff615bb8e0ddbc Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Thu, 7 Mar 2024 14:23:26 +1100
Subject: [PATCH 07/29] Remove cache option: N/A for fonts.

---
 src/wp-includes/fonts.php | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index 7a9227a09d3c0..ed7be2baadb05 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -111,7 +111,7 @@ function wp_get_font_dir() {
  * @param bool $refresh_cache
  * @return array
  */
-function wp_font_dir( $create_dir = true, $refresh_cache = false ) {
+function wp_font_dir( $create_dir = true ) {
 	/*
 	 * Allow extenders to manipulate the font directory consistently.
 	 *
@@ -120,7 +120,7 @@ function wp_font_dir( $create_dir = true, $refresh_cache = false ) {
 	 * is filtered in the Font Face REST API endpoint.
 	 */
 	add_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
-	$font_dir = wp_upload_dir( null, $create_dir, $refresh_cache );
+	$font_dir = wp_upload_dir( null, $create_dir, false );
 	remove_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
 	return $font_dir;
 }

From d0ef78ea43b09158503fe13b97eb4ab6e8fe9f53 Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Thu, 7 Mar 2024 14:23:35 +1100
Subject: [PATCH 08/29] Docblocks.

---
 src/wp-includes/fonts.php | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index ed7be2baadb05..545f704f304c8 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -92,24 +92,38 @@ function wp_unregister_font_collection( string $slug ) {
 }
 
 /**
- * Lightweight, don't create directory.
+ * Retrieves uploads directory information.
  *
- * @todo Get in a committable state if it's decided to do this.
+ * Same as wp_font_dir() but "light weight" as it doesn't attempt to create the font uploads directory.
+ * Intended for use in themes, when only 'basedir' and 'baseurl' are needed, generally in all cases
+ * when not uploading files.
+ *
+ * @since 6.5.0
+ *
+ * @see wp_font_dir()
  *
- * @return array
+ * @return array See wp_font_dir() for description.
  */
 function wp_get_font_dir() {
 	return wp_font_dir( false );
 }
 
 /**
- * Get and create the font directory.
+ * Returns an array containing the current fonts upload directory's path and URL.
  *
- * @todo Get in a committable state if it's decided to do this.
+ * @since 6.5.0
  *
- * @param bool $create_dir
- * @param bool $refresh_cache
- * @return array
+ * @param bool $create_dir Optional. Whether to check and create the font uploads directory. Default true.
+ * @return array $defaults {
+ *     Array of information about the upload directory.
+ *
+ *     @type string       $path    Base directory and subdirectory or full path to the fonts upload directory.
+ *     @type string       $url     Base URL and subdirectory or absolute URL to the fonts upload directory.
+ *     @type string       $subdir  Subdirectory
+ *     @type string       $basedir Path without subdir.
+ *     @type string       $baseurl URL path without subdir.
+ *     @type string|false $error   False or error message.
+ * }
  */
 function wp_font_dir( $create_dir = true ) {
 	/*

From 327700200c639ea16fd7ce2e31cc85175e9050b4 Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Thu, 7 Mar 2024 14:27:48 +1100
Subject: [PATCH 09/29] Improve comment.

---
 src/wp-includes/fonts.php | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index 545f704f304c8..1338b59a4a0e6 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -129,9 +129,9 @@ function wp_font_dir( $create_dir = true ) {
 	/*
 	 * Allow extenders to manipulate the font directory consistently.
 	 *
-	 * This ensures the upload_dir filter is fired both when using
-	 * this function directly and when using the upload directory
-	 * is filtered in the Font Face REST API endpoint.
+	 * Ensures the upload_dir filter is fired both when calling this function
+	 * directly and when the upload directory is filtered in the Font Face
+	 * REST API endpoint.
 	 */
 	add_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
 	$font_dir = wp_upload_dir( null, $create_dir, false );

From db876de9c6b343a7e4dd8ec735330b00e2d6c9ec Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Thu, 7 Mar 2024 14:34:13 +1100
Subject: [PATCH 10/29] More docblocks.

---
 src/wp-includes/fonts.php | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index 1338b59a4a0e6..015201b554934 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -140,12 +140,15 @@ function wp_font_dir( $create_dir = true ) {
 }
 
 /**
- * Apply the filter.
+ * Wrapper for apply_filters( 'font_dir', $font_dir ).
  *
- * @todo Get in a committable state if it's decided to do this.
+ * Allows developers to manipulate the font directory used by the
+ * font library.
  *
- * @param mixed $font_dir
- * @return mixed
+ * @since 6.5.0
+ *
+ * @param string $font_dir The font directory.
+ * @return string The modified font directory.
  */
 function wp_apply_font_dir_filter( $font_dir ) {
 	if ( doing_filter( 'font_dir' ) ) {
@@ -157,12 +160,20 @@ function wp_apply_font_dir_filter( $font_dir ) {
 }
 
 /**
- * Default font filter.
+ * Modify the default font directory.
+ *
+ * This function should not be called directly, use wp_get_font_dir() instead.
+ *
+ * Modifies the default font directory used by WordPress to the subdirectory fonts
+ * within the content directory. This function should not be called directly but
+ * rather applied to the {@see 'font_dir'} hook.
  *
- * @todo Get in a committable state if it's decided to do this.
+ * @access private
+ * @since 6.5.0
  *
- * @param mixed $font_dir
- * @return void
+ * @see wp_get_font_dir()
+ *
+ * @return array See wp_font_dir() for description.
  */
 function wp_default_font_dir_filter() {
 	$site_path = '';

From cec16c6e90f215fad880ead9e65ebf2440ee3ea8 Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Thu, 7 Mar 2024 15:32:30 +1100
Subject: [PATCH 11/29] Use static for closure.

Co-authored-by: Mukesh Panchal <mukeshpanchal27@users.noreply.github.com>
---
 tests/phpunit/tests/fonts/font-library/wpFontsDir.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
index 6c5affa8c9fd2..90a5eadfbdf29 100644
--- a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
+++ b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
@@ -81,7 +81,7 @@ public function test_fonts_dir_filters_do_not_trigger_infinite_loop() {
 
 		add_filter(
 			'upload_dir',
-			function ( $upload_dir ) {
+			static function ( $upload_dir ) {
 				static $count = 0;
 				++$count;
 				// It may be hit a couple of times, at five iterations assume an infinite loop.

From 94c576bc4ff5b0f2e93aeb412653258dc6b27d7a Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Thu, 7 Mar 2024 15:41:45 +1100
Subject: [PATCH 12/29] Revert "Use static for closure."

This reverts commit cec16c6e90f215fad880ead9e65ebf2440ee3ea8.
---
 tests/phpunit/tests/fonts/font-library/wpFontsDir.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
index 90a5eadfbdf29..6c5affa8c9fd2 100644
--- a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
+++ b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
@@ -81,7 +81,7 @@ public function test_fonts_dir_filters_do_not_trigger_infinite_loop() {
 
 		add_filter(
 			'upload_dir',
-			static function ( $upload_dir ) {
+			function ( $upload_dir ) {
 				static $count = 0;
 				++$count;
 				// It may be hit a couple of times, at five iterations assume an infinite loop.

From eff1763869878d9071dd2103fc647586d55fc22c Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Fri, 8 Mar 2024 14:16:42 +1100
Subject: [PATCH 13/29] Font uploads.

---
 src/wp-includes/fonts.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index 015201b554934..e05a934d71b8f 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -92,7 +92,7 @@ function wp_unregister_font_collection( string $slug ) {
 }
 
 /**
- * Retrieves uploads directory information.
+ * Retrieves font uploads directory information.
  *
  * Same as wp_font_dir() but "light weight" as it doesn't attempt to create the font uploads directory.
  * Intended for use in themes, when only 'basedir' and 'baseurl' are needed, generally in all cases

From 48aca491b180d3892725d35743eeadd311756c66 Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Mon, 11 Mar 2024 08:30:47 +1100
Subject: [PATCH 14/29] Dockblock improvements

Co-authored-by: Colin Stewart <79332690+costdev@users.noreply.github.com>
---
 src/wp-includes/fonts.php | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index e05a934d71b8f..a85c8ac056517 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -140,7 +140,10 @@ function wp_font_dir( $create_dir = true ) {
 }
 
 /**
+ * Applies filters to manipulate the font directory used by the font library.
+ * 
  * Wrapper for apply_filters( 'font_dir', $font_dir ).
+ * Does not apply filters if already doing the {@see 'font_dir'} filter.
  *
  * Allows developers to manipulate the font directory used by the
  * font library.
@@ -160,7 +163,7 @@ function wp_apply_font_dir_filter( $font_dir ) {
 }
 
 /**
- * Modify the default font directory.
+ * Modifies the default font directory.
  *
  * This function should not be called directly, use wp_get_font_dir() instead.
  *

From 5117eef291bd58a9bd1eb1c104aaf0c77b0e91c3 Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Mon, 11 Mar 2024 08:33:46 +1100
Subject: [PATCH 15/29] Avoid duplicate assertions testing for loop.

---
 tests/phpunit/tests/fonts/font-library/wpFontsDir.php | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
index 6c5affa8c9fd2..d0c1ffedd1f7a 100644
--- a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
+++ b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
@@ -84,8 +84,10 @@ public function test_fonts_dir_filters_do_not_trigger_infinite_loop() {
 			function ( $upload_dir ) {
 				static $count = 0;
 				++$count;
-				// It may be hit a couple of times, at five iterations assume an infinite loop.
-				$this->assertLessThan( 5, $count, 'Filtering uploads directory should not trigger infinite loop.' );
+				// The filter may be applied a couple of times, at five iterations assume an infinite loop.
+				if ( $count >= 5 ) {
+					$this->fail( 'Filtering the uploads directory triggered an infinite loop.' );
+				}
 				return $upload_dir;
 			},
 			5

From 4b76a9cfa3ebe6643ccae67503eb8eb3c1a9c03b Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Mon, 11 Mar 2024 08:35:20 +1100
Subject: [PATCH 16/29] Doc fix.: this not the.

---
 tests/phpunit/tests/fonts/font-library/wpFontsDir.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
index d0c1ffedd1f7a..2b86fba3cf55c 100644
--- a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
+++ b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
@@ -96,7 +96,7 @@ function ( $upload_dir ) {
 		/*
 		 * Filter the font directory to return the uploads directory.
 		 *
-		 * The emulates a moving font files back to the uploads directory due
+		 * This emulates a moving font files back to the uploads directory due
 		 * to file system structure.
 		 */
 		add_filter( 'font_dir', 'wp_get_upload_dir' );

From addadc3b21ec0d8f039a18021c6235480c9b928b Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Mon, 11 Mar 2024 08:38:58 +1100
Subject: [PATCH 17/29] Font upload, not upload dir.

---
 src/wp-includes/fonts.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index a85c8ac056517..8687c43312805 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -115,7 +115,7 @@ function wp_get_font_dir() {
  *
  * @param bool $create_dir Optional. Whether to check and create the font uploads directory. Default true.
  * @return array $defaults {
- *     Array of information about the upload directory.
+ *     Array of information about the font upload directory.
  *
  *     @type string       $path    Base directory and subdirectory or full path to the fonts upload directory.
  *     @type string       $url     Base URL and subdirectory or absolute URL to the fonts upload directory.

From c1ac4e3b6d875cfa6193e966b04f5c02d8316e34 Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Mon, 11 Mar 2024 08:39:10 +1100
Subject: [PATCH 18/29] Trolling?

---
 src/wp-includes/fonts.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index 8687c43312805..c3de6fd983e2f 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -141,7 +141,7 @@ function wp_font_dir( $create_dir = true ) {
 
 /**
  * Applies filters to manipulate the font directory used by the font library.
- * 
+ *
  * Wrapper for apply_filters( 'font_dir', $font_dir ).
  * Does not apply filters if already doing the {@see 'font_dir'} filter.
  *

From 1c870cc5dd1b4a97253eb062f0127f6bcc5c8050 Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Tue, 12 Mar 2024 09:04:03 +1100
Subject: [PATCH 19/29] Rename function.

---
 src/wp-includes/default-filters.php | 2 +-
 src/wp-includes/fonts.php           | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/wp-includes/default-filters.php b/src/wp-includes/default-filters.php
index 2d7512a47fc60..3c99b52be2a78 100644
--- a/src/wp-includes/default-filters.php
+++ b/src/wp-includes/default-filters.php
@@ -752,7 +752,7 @@
 add_action( 'before_delete_post', '_wp_before_delete_font_face', 10, 2 );
 add_action( 'init', '_wp_register_default_font_collections' );
 // Filter the font upload directory. Runs early to ensure the default directory is applied at priority 10 (default).
-add_filter( 'font_dir', 'wp_default_font_dir_filter', 5 );
+add_filter( 'font_dir', 'wp_default_font_dir', 5 );
 
 // Add ignoredHookedBlocks metadata attribute to the template and template part post types.
 add_filter( 'rest_pre_insert_wp_template', 'inject_ignored_hooked_blocks_metadata_attributes', 10, 2 );
diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index c3de6fd983e2f..1276b62fe4486 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -178,7 +178,7 @@ function wp_apply_font_dir_filter( $font_dir ) {
  *
  * @return array See wp_font_dir() for description.
  */
-function wp_default_font_dir_filter() {
+function wp_default_font_dir() {
 	$site_path = '';
 	if ( is_multisite() && ! ( is_main_network() && is_main_site() ) ) {
 		$site_path = '/sites/' . get_current_blog_id();

From 1c3b7ac2da9af56c85c844928c6e024bbcf34039 Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Tue, 12 Mar 2024 09:09:36 +1100
Subject: [PATCH 20/29] Filter the font directory late.

---
 src/wp-includes/fonts.php                                     | 4 ++--
 .../endpoints/class-wp-rest-font-faces-controller.php         | 4 ++--
 tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php   | 4 ++--
 tests/phpunit/tests/fonts/font-library/wpFontsDir.php         | 2 +-
 4 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index 1276b62fe4486..cf37a2c9aaa26 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -133,9 +133,9 @@ function wp_font_dir( $create_dir = true ) {
 	 * directly and when the upload directory is filtered in the Font Face
 	 * REST API endpoint.
 	 */
-	add_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
+	add_filter( 'upload_dir', 'wp_apply_font_dir_filter', 20 );
 	$font_dir = wp_upload_dir( null, $create_dir, false );
-	remove_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
+	remove_filter( 'upload_dir', 'wp_apply_font_dir_filter', 20 );
 	return $font_dir;
 }
 
diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
index 163c3d414c9e0..ebb9d69ed8c1e 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
@@ -856,7 +856,7 @@ protected function sanitize_src( $value ) {
 	 */
 	protected function handle_font_file_upload( $file ) {
 		add_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
-		add_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
+		add_filter( 'upload_dir', 'wp_apply_font_dir_filter', 20 );
 
 		$overrides = array(
 			'upload_error_handler' => array( $this, 'handle_font_file_upload_error' ),
@@ -874,7 +874,7 @@ protected function handle_font_file_upload( $file ) {
 
 		$uploaded_file = wp_handle_upload( $file, $overrides );
 
-		remove_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
+		remove_filter( 'upload_dir', 'wp_apply_font_dir_filter', 20 );
 		remove_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
 
 		return $uploaded_file;
diff --git a/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php b/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
index 9cf3cfd7706c0..b665dfd7841c5 100644
--- a/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
+++ b/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
@@ -73,13 +73,13 @@ protected function upload_font_file( $font_filename ) {
 		$font_file_path = DIR_TESTDATA . '/fonts/' . $font_filename;
 
 		add_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
-		add_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
+		add_filter( 'upload_dir', 'wp_apply_font_dir_filter', 20 );
 		$font_file = wp_upload_bits(
 			$font_filename,
 			null,
 			file_get_contents( $font_file_path )
 		);
-		remove_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
+		remove_filter( 'upload_dir', 'wp_apply_font_dir_filter', 20 );
 		remove_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
 
 		return $font_file;
diff --git a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
index 2b86fba3cf55c..e4aaf45ee343a 100644
--- a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
+++ b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
@@ -77,7 +77,7 @@ public function test_fonts_dir_filters_do_not_trigger_infinite_loop() {
 		 * This emulates the approach a plugin developer may take to
 		 * add the filter when extending the font library functionality.
 		 */
-		add_filter( 'upload_dir', 'wp_apply_font_dir_filter' );
+		add_filter( 'upload_dir', 'wp_apply_font_dir_filter', 20 );
 
 		add_filter(
 			'upload_dir',

From fb2cfc36e1bc319582c1081813c3babbe26b2b4e Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Tue, 12 Mar 2024 09:14:35 +1100
Subject: [PATCH 21/29] Document late running hook.

---
 src/wp-includes/fonts.php                                  | 4 ++++
 .../endpoints/class-wp-rest-font-faces-controller.php      | 7 +++++++
 2 files changed, 11 insertions(+)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index cf37a2c9aaa26..93c0acf50767d 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -132,6 +132,10 @@ function wp_font_dir( $create_dir = true ) {
 	 * Ensures the upload_dir filter is fired both when calling this function
 	 * directly and when the upload directory is filtered in the Font Face
 	 * REST API endpoint.
+	 *
+	 * The filter runs at priority 20 to ensure it runs after any filters
+	 * added at the default priority by plugins modifying the upload path
+	 * or URL.
 	 */
 	add_filter( 'upload_dir', 'wp_apply_font_dir_filter', 20 );
 	$font_dir = wp_upload_dir( null, $create_dir, false );
diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
index ebb9d69ed8c1e..5b8dea1b56286 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
@@ -856,6 +856,13 @@ protected function sanitize_src( $value ) {
 	 */
 	protected function handle_font_file_upload( $file ) {
 		add_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
+		/*
+		 * Filter the upload directory to return the fonts directory..
+		 *
+		 * The filter runs at priority 20 to ensure it runs after any filters
+		 * added at the default priority by plugins modifying the upload path
+		 * or URL.
+		*/
 		add_filter( 'upload_dir', 'wp_apply_font_dir_filter', 20 );
 
 		$overrides = array(

From 52103f63b6905f3bcb980303b3bfa9905a58c9d2 Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Wed, 13 Mar 2024 10:10:10 +1100
Subject: [PATCH 22/29] Rename function to use plural filters.

Co-authored-by: costdev <costdev@git.wordpress.org>
---
 src/wp-includes/fonts.php                                   | 6 +++---
 .../endpoints/class-wp-rest-font-faces-controller.php       | 4 ++--
 tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php | 4 ++--
 tests/phpunit/tests/fonts/font-library/wpFontsDir.php       | 2 +-
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index 93c0acf50767d..a2f27dde00d3e 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -137,9 +137,9 @@ function wp_font_dir( $create_dir = true ) {
 	 * added at the default priority by plugins modifying the upload path
 	 * or URL.
 	 */
-	add_filter( 'upload_dir', 'wp_apply_font_dir_filter', 20 );
+	add_filter( 'upload_dir', 'wp_apply_font_dir_filters', 20 );
 	$font_dir = wp_upload_dir( null, $create_dir, false );
-	remove_filter( 'upload_dir', 'wp_apply_font_dir_filter', 20 );
+	remove_filter( 'upload_dir', 'wp_apply_font_dir_filters', 20 );
 	return $font_dir;
 }
 
@@ -157,7 +157,7 @@ function wp_font_dir( $create_dir = true ) {
  * @param string $font_dir The font directory.
  * @return string The modified font directory.
  */
-function wp_apply_font_dir_filter( $font_dir ) {
+function wp_apply_font_dir_filters( $font_dir ) {
 	if ( doing_filter( 'font_dir' ) ) {
 		// Avoid an infinite loop.
 		return $font_dir;
diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
index c40313e8cc265..7807d42f3aff0 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
@@ -863,7 +863,7 @@ protected function handle_font_file_upload( $file ) {
 		 * added at the default priority by plugins modifying the upload path
 		 * or URL.
 		*/
-		add_filter( 'upload_dir', 'wp_apply_font_dir_filter', 20 );
+		add_filter( 'upload_dir', 'wp_apply_font_dir_filters', 20 );
 
 		$overrides = array(
 			'upload_error_handler' => array( $this, 'handle_font_file_upload_error' ),
@@ -880,7 +880,7 @@ protected function handle_font_file_upload( $file ) {
 
 		$uploaded_file = wp_handle_upload( $file, $overrides );
 
-		remove_filter( 'upload_dir', 'wp_apply_font_dir_filter', 20 );
+		remove_filter( 'upload_dir', 'wp_apply_font_dir_filters', 20 );
 		remove_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
 
 		return $uploaded_file;
diff --git a/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php b/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
index b665dfd7841c5..0df6a47edcd1c 100644
--- a/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
+++ b/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
@@ -73,13 +73,13 @@ protected function upload_font_file( $font_filename ) {
 		$font_file_path = DIR_TESTDATA . '/fonts/' . $font_filename;
 
 		add_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
-		add_filter( 'upload_dir', 'wp_apply_font_dir_filter', 20 );
+		add_filter( 'upload_dir', 'wp_apply_font_dir_filters', 20 );
 		$font_file = wp_upload_bits(
 			$font_filename,
 			null,
 			file_get_contents( $font_file_path )
 		);
-		remove_filter( 'upload_dir', 'wp_apply_font_dir_filter', 20 );
+		remove_filter( 'upload_dir', 'wp_apply_font_dir_filters', 20 );
 		remove_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
 
 		return $font_file;
diff --git a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
index e4aaf45ee343a..43fc7b1cacd20 100644
--- a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
+++ b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
@@ -77,7 +77,7 @@ public function test_fonts_dir_filters_do_not_trigger_infinite_loop() {
 		 * This emulates the approach a plugin developer may take to
 		 * add the filter when extending the font library functionality.
 		 */
-		add_filter( 'upload_dir', 'wp_apply_font_dir_filter', 20 );
+		add_filter( 'upload_dir', 'wp_apply_font_dir_filters', 20 );
 
 		add_filter(
 			'upload_dir',

From 21673e562876fda21d0b6edd21045bb6fe8f7f2a Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Thu, 14 Mar 2024 08:51:31 +1100
Subject: [PATCH 23/29] Remove a a typo.

Co-authored-by: Colin Stewart <79332690+costdev@users.noreply.github.com>
---
 tests/phpunit/tests/fonts/font-library/wpFontsDir.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
index 43fc7b1cacd20..64c69e51b6fdb 100644
--- a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
+++ b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
@@ -96,7 +96,7 @@ function ( $upload_dir ) {
 		/*
 		 * Filter the font directory to return the uploads directory.
 		 *
-		 * This emulates a moving font files back to the uploads directory due
+		 * This emulates moving font files back to the uploads directory due
 		 * to file system structure.
 		 */
 		add_filter( 'font_dir', 'wp_get_upload_dir' );

From 118313240685c1bf5c9ab3ca5f3f36b9db47897c Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Thu, 14 Mar 2024 09:34:19 +1100
Subject: [PATCH 24/29] Run filter at default priority.

As the filter is created while getting the upload directory in `wp_upload_dir()` the core filter should be added after any plugins filter the uploads directory during the init or an earlier hook.
---
 src/wp-includes/fonts.php                                     | 4 ++--
 .../endpoints/class-wp-rest-font-faces-controller.php         | 4 ++--
 tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php   | 4 ++--
 tests/phpunit/tests/fonts/font-library/wpFontsDir.php         | 2 +-
 4 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index a2f27dde00d3e..eeeb64cec7e56 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -137,9 +137,9 @@ function wp_font_dir( $create_dir = true ) {
 	 * added at the default priority by plugins modifying the upload path
 	 * or URL.
 	 */
-	add_filter( 'upload_dir', 'wp_apply_font_dir_filters', 20 );
+	add_filter( 'upload_dir', 'wp_apply_font_dir_filters' );
 	$font_dir = wp_upload_dir( null, $create_dir, false );
-	remove_filter( 'upload_dir', 'wp_apply_font_dir_filters', 20 );
+	remove_filter( 'upload_dir', 'wp_apply_font_dir_filters' );
 	return $font_dir;
 }
 
diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
index 7807d42f3aff0..7225e08b45247 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
@@ -863,7 +863,7 @@ protected function handle_font_file_upload( $file ) {
 		 * added at the default priority by plugins modifying the upload path
 		 * or URL.
 		*/
-		add_filter( 'upload_dir', 'wp_apply_font_dir_filters', 20 );
+		add_filter( 'upload_dir', 'wp_apply_font_dir_filters' );
 
 		$overrides = array(
 			'upload_error_handler' => array( $this, 'handle_font_file_upload_error' ),
@@ -880,7 +880,7 @@ protected function handle_font_file_upload( $file ) {
 
 		$uploaded_file = wp_handle_upload( $file, $overrides );
 
-		remove_filter( 'upload_dir', 'wp_apply_font_dir_filters', 20 );
+		remove_filter( 'upload_dir', 'wp_apply_font_dir_filters' );
 		remove_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
 
 		return $uploaded_file;
diff --git a/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php b/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
index 0df6a47edcd1c..a19784f6c10be 100644
--- a/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
+++ b/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
@@ -73,13 +73,13 @@ protected function upload_font_file( $font_filename ) {
 		$font_file_path = DIR_TESTDATA . '/fonts/' . $font_filename;
 
 		add_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
-		add_filter( 'upload_dir', 'wp_apply_font_dir_filters', 20 );
+		add_filter( 'upload_dir', 'wp_apply_font_dir_filters' );
 		$font_file = wp_upload_bits(
 			$font_filename,
 			null,
 			file_get_contents( $font_file_path )
 		);
-		remove_filter( 'upload_dir', 'wp_apply_font_dir_filters', 20 );
+		remove_filter( 'upload_dir', 'wp_apply_font_dir_filters' );
 		remove_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
 
 		return $font_file;
diff --git a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
index 64c69e51b6fdb..602cf5975c76e 100644
--- a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
+++ b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
@@ -77,7 +77,7 @@ public function test_fonts_dir_filters_do_not_trigger_infinite_loop() {
 		 * This emulates the approach a plugin developer may take to
 		 * add the filter when extending the font library functionality.
 		 */
-		add_filter( 'upload_dir', 'wp_apply_font_dir_filters', 20 );
+		add_filter( 'upload_dir', 'wp_apply_font_dir_filters' );
 
 		add_filter(
 			'upload_dir',

From 0204b99022a78a74b8bb81713a98ed6aa4cc7411 Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Sat, 16 Mar 2024 09:57:16 +1100
Subject: [PATCH 25/29] Remove out of date comment.

---
 src/wp-includes/fonts.php                                 | 4 ----
 .../endpoints/class-wp-rest-font-faces-controller.php     | 8 +-------
 2 files changed, 1 insertion(+), 11 deletions(-)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index eeeb64cec7e56..d6a6c55136361 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -132,10 +132,6 @@ function wp_font_dir( $create_dir = true ) {
 	 * Ensures the upload_dir filter is fired both when calling this function
 	 * directly and when the upload directory is filtered in the Font Face
 	 * REST API endpoint.
-	 *
-	 * The filter runs at priority 20 to ensure it runs after any filters
-	 * added at the default priority by plugins modifying the upload path
-	 * or URL.
 	 */
 	add_filter( 'upload_dir', 'wp_apply_font_dir_filters' );
 	$font_dir = wp_upload_dir( null, $create_dir, false );
diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
index 7225e08b45247..8ea6e12326712 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
@@ -856,13 +856,7 @@ protected function sanitize_src( $value ) {
 	 */
 	protected function handle_font_file_upload( $file ) {
 		add_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
-		/*
-		 * Filter the upload directory to return the fonts directory..
-		 *
-		 * The filter runs at priority 20 to ensure it runs after any filters
-		 * added at the default priority by plugins modifying the upload path
-		 * or URL.
-		*/
+		// Filter the upload directory to return the fonts directory..
 		add_filter( 'upload_dir', 'wp_apply_font_dir_filters' );
 
 		$overrides = array(

From eccdbac221f6747b14cff107591bbddeb99745ac Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Thu, 21 Mar 2024 15:28:10 +1100
Subject: [PATCH 26/29] Merge default getter and filtering function. Rename.

---
 src/wp-includes/default-filters.php           |  2 -
 src/wp-includes/fonts.php                     | 60 +++++++++----------
 .../class-wp-rest-font-faces-controller.php   |  6 +-
 .../fonts/font-library/fontLibraryHooks.php   |  4 +-
 .../tests/fonts/font-library/wpFontsDir.php   |  2 +-
 5 files changed, 35 insertions(+), 39 deletions(-)

diff --git a/src/wp-includes/default-filters.php b/src/wp-includes/default-filters.php
index 3c99b52be2a78..884357f41350a 100644
--- a/src/wp-includes/default-filters.php
+++ b/src/wp-includes/default-filters.php
@@ -751,8 +751,6 @@
 add_action( 'deleted_post', '_wp_after_delete_font_family', 10, 2 );
 add_action( 'before_delete_post', '_wp_before_delete_font_face', 10, 2 );
 add_action( 'init', '_wp_register_default_font_collections' );
-// Filter the font upload directory. Runs early to ensure the default directory is applied at priority 10 (default).
-add_filter( 'font_dir', 'wp_default_font_dir', 5 );
 
 // Add ignoredHookedBlocks metadata attribute to the template and template part post types.
 add_filter( 'rest_pre_insert_wp_template', 'inject_ignored_hooked_blocks_metadata_attributes', 10, 2 );
diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index d6a6c55136361..9a56a0fd6b5e5 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -114,7 +114,7 @@ function wp_get_font_dir() {
  * @since 6.5.0
  *
  * @param bool $create_dir Optional. Whether to check and create the font uploads directory. Default true.
- * @return array $defaults {
+ * @return array {
  *     Array of information about the font upload directory.
  *
  *     @type string       $path    Base directory and subdirectory or full path to the fonts upload directory.
@@ -133,58 +133,36 @@ function wp_font_dir( $create_dir = true ) {
 	 * directly and when the upload directory is filtered in the Font Face
 	 * REST API endpoint.
 	 */
-	add_filter( 'upload_dir', 'wp_apply_font_dir_filters' );
+	add_filter( 'upload_dir', 'wp_filter_font_directory' );
 	$font_dir = wp_upload_dir( null, $create_dir, false );
-	remove_filter( 'upload_dir', 'wp_apply_font_dir_filters' );
+	remove_filter( 'upload_dir', 'wp_filter_font_directory' );
 	return $font_dir;
 }
 
 /**
- * Applies filters to manipulate the font directory used by the font library.
+ * Returns the font directory for use by the font library.
  *
- * Wrapper for apply_filters( 'font_dir', $font_dir ).
- * Does not apply filters if already doing the {@see 'font_dir'} filter.
- *
- * Allows developers to manipulate the font directory used by the
- * font library.
+ * This function is a callback for the 'upload_dir' filter. It is used not
+ * intended to be called directly. Use wp_get_font_dir() instead.
  *
  * @since 6.5.0
+ * @access private
  *
  * @param string $font_dir The font directory.
  * @return string The modified font directory.
  */
-function wp_apply_font_dir_filters( $font_dir ) {
+function wp_filter_font_directory( $font_dir ) {
 	if ( doing_filter( 'font_dir' ) ) {
 		// Avoid an infinite loop.
 		return $font_dir;
 	}
 
-	return apply_filters( 'font_dir', $font_dir );
-}
-
-/**
- * Modifies the default font directory.
- *
- * This function should not be called directly, use wp_get_font_dir() instead.
- *
- * Modifies the default font directory used by WordPress to the subdirectory fonts
- * within the content directory. This function should not be called directly but
- * rather applied to the {@see 'font_dir'} hook.
- *
- * @access private
- * @since 6.5.0
- *
- * @see wp_get_font_dir()
- *
- * @return array See wp_font_dir() for description.
- */
-function wp_default_font_dir() {
 	$site_path = '';
 	if ( is_multisite() && ! ( is_main_network() && is_main_site() ) ) {
 		$site_path = '/sites/' . get_current_blog_id();
 	}
 
-	return array(
+	$font_dir = array(
 		'path'    => path_join( WP_CONTENT_DIR, 'fonts' ) . $site_path,
 		'url'     => untrailingslashit( content_url( 'fonts' ) ) . $site_path,
 		'subdir'  => '',
@@ -192,6 +170,26 @@ function wp_default_font_dir() {
 		'baseurl' => untrailingslashit( content_url( 'fonts' ) ) . $site_path,
 		'error'   => false,
 	);
+
+	/**
+	 * Filters the fonts directory data.
+	 *
+	 * This filter allows developers to modify the fonts directory data.
+	 *
+	 * @since 6.5.0
+	 *
+	 * @param array $font_dir {
+	 *     Array of information about the font upload directory.
+	 *
+	 *     @type string       $path    Base directory and subdirectory or full path to the fonts upload directory.
+	 *     @type string       $url     Base URL and subdirectory or absolute URL to the fonts upload directory.
+	 *     @type string       $subdir  Subdirectory
+	 *     @type string       $basedir Path without subdir.
+	 *     @type string       $baseurl URL path without subdir.
+	 *     @type string|false $error   False or error message.
+	 * }
+	 */
+	return apply_filters( 'font_dir', $font_dir );
 }
 
 /**
diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
index 8ea6e12326712..c47de3e82d309 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
@@ -856,8 +856,8 @@ protected function sanitize_src( $value ) {
 	 */
 	protected function handle_font_file_upload( $file ) {
 		add_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
-		// Filter the upload directory to return the fonts directory..
-		add_filter( 'upload_dir', 'wp_apply_font_dir_filters' );
+		// Filter the upload directory to return the fonts directory.
+		add_filter( 'upload_dir', 'wp_filter_font_directory' );
 
 		$overrides = array(
 			'upload_error_handler' => array( $this, 'handle_font_file_upload_error' ),
@@ -874,7 +874,7 @@ protected function handle_font_file_upload( $file ) {
 
 		$uploaded_file = wp_handle_upload( $file, $overrides );
 
-		remove_filter( 'upload_dir', 'wp_apply_font_dir_filters' );
+		remove_filter( 'upload_dir', 'wp_filter_font_directory' );
 		remove_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
 
 		return $uploaded_file;
diff --git a/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php b/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
index a19784f6c10be..50e2c627b2362 100644
--- a/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
+++ b/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
@@ -73,13 +73,13 @@ protected function upload_font_file( $font_filename ) {
 		$font_file_path = DIR_TESTDATA . '/fonts/' . $font_filename;
 
 		add_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
-		add_filter( 'upload_dir', 'wp_apply_font_dir_filters' );
+		add_filter( 'upload_dir', 'wp_filter_font_directory' );
 		$font_file = wp_upload_bits(
 			$font_filename,
 			null,
 			file_get_contents( $font_file_path )
 		);
-		remove_filter( 'upload_dir', 'wp_apply_font_dir_filters' );
+		remove_filter( 'upload_dir', 'wp_filter_font_directory' );
 		remove_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
 
 		return $font_file;
diff --git a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
index 602cf5975c76e..4c802792aff03 100644
--- a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
+++ b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
@@ -77,7 +77,7 @@ public function test_fonts_dir_filters_do_not_trigger_infinite_loop() {
 		 * This emulates the approach a plugin developer may take to
 		 * add the filter when extending the font library functionality.
 		 */
-		add_filter( 'upload_dir', 'wp_apply_font_dir_filters' );
+		add_filter( 'upload_dir', 'wp_filter_font_directory' );
 
 		add_filter(
 			'upload_dir',

From 22764e3650e38b56737f5f558d9a2125710b08dc Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Fri, 22 Mar 2024 10:21:10 +1100
Subject: [PATCH 27/29] Rename function. Props @swissspidy.

---
 src/wp-includes/fonts.php                                   | 6 +++---
 .../endpoints/class-wp-rest-font-faces-controller.php       | 4 ++--
 tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php | 4 ++--
 tests/phpunit/tests/fonts/font-library/wpFontsDir.php       | 2 +-
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index 9a56a0fd6b5e5..41f65b1341571 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -133,9 +133,9 @@ function wp_font_dir( $create_dir = true ) {
 	 * directly and when the upload directory is filtered in the Font Face
 	 * REST API endpoint.
 	 */
-	add_filter( 'upload_dir', 'wp_filter_font_directory' );
+	add_filter( 'upload_dir', '_wp_filter_font_directory' );
 	$font_dir = wp_upload_dir( null, $create_dir, false );
-	remove_filter( 'upload_dir', 'wp_filter_font_directory' );
+	remove_filter( 'upload_dir', '_wp_filter_font_directory' );
 	return $font_dir;
 }
 
@@ -151,7 +151,7 @@ function wp_font_dir( $create_dir = true ) {
  * @param string $font_dir The font directory.
  * @return string The modified font directory.
  */
-function wp_filter_font_directory( $font_dir ) {
+function _wp_filter_font_directory( $font_dir ) {
 	if ( doing_filter( 'font_dir' ) ) {
 		// Avoid an infinite loop.
 		return $font_dir;
diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
index c47de3e82d309..c7f72d4ec1d9d 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-font-faces-controller.php
@@ -857,7 +857,7 @@ protected function sanitize_src( $value ) {
 	protected function handle_font_file_upload( $file ) {
 		add_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
 		// Filter the upload directory to return the fonts directory.
-		add_filter( 'upload_dir', 'wp_filter_font_directory' );
+		add_filter( 'upload_dir', '_wp_filter_font_directory' );
 
 		$overrides = array(
 			'upload_error_handler' => array( $this, 'handle_font_file_upload_error' ),
@@ -874,7 +874,7 @@ protected function handle_font_file_upload( $file ) {
 
 		$uploaded_file = wp_handle_upload( $file, $overrides );
 
-		remove_filter( 'upload_dir', 'wp_filter_font_directory' );
+		remove_filter( 'upload_dir', '_wp_filter_font_directory' );
 		remove_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
 
 		return $uploaded_file;
diff --git a/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php b/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
index 50e2c627b2362..c288a1ae93845 100644
--- a/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
+++ b/tests/phpunit/tests/fonts/font-library/fontLibraryHooks.php
@@ -73,13 +73,13 @@ protected function upload_font_file( $font_filename ) {
 		$font_file_path = DIR_TESTDATA . '/fonts/' . $font_filename;
 
 		add_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
-		add_filter( 'upload_dir', 'wp_filter_font_directory' );
+		add_filter( 'upload_dir', '_wp_filter_font_directory' );
 		$font_file = wp_upload_bits(
 			$font_filename,
 			null,
 			file_get_contents( $font_file_path )
 		);
-		remove_filter( 'upload_dir', 'wp_filter_font_directory' );
+		remove_filter( 'upload_dir', '_wp_filter_font_directory' );
 		remove_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
 
 		return $font_file;
diff --git a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
index 4c802792aff03..282393677b042 100644
--- a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
+++ b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
@@ -77,7 +77,7 @@ public function test_fonts_dir_filters_do_not_trigger_infinite_loop() {
 		 * This emulates the approach a plugin developer may take to
 		 * add the filter when extending the font library functionality.
 		 */
-		add_filter( 'upload_dir', 'wp_filter_font_directory' );
+		add_filter( 'upload_dir', '_wp_filter_font_directory' );
 
 		add_filter(
 			'upload_dir',

From cf211ae8117adbdc844ddd70bef04301c01c094f Mon Sep 17 00:00:00 2001
From: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>
Date: Fri, 22 Mar 2024 10:21:19 +1100
Subject: [PATCH 28/29] Document use of filter.

---
 src/wp-includes/fonts.php | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/wp-includes/fonts.php b/src/wp-includes/fonts.php
index 41f65b1341571..74feee1ac9cf7 100644
--- a/src/wp-includes/fonts.php
+++ b/src/wp-includes/fonts.php
@@ -142,9 +142,19 @@ function wp_font_dir( $create_dir = true ) {
 /**
  * Returns the font directory for use by the font library.
  *
- * This function is a callback for the 'upload_dir' filter. It is used not
+ * This function is a callback for the {@see 'upload_dir'} filter. It is not
  * intended to be called directly. Use wp_get_font_dir() instead.
  *
+ * The function can be used when extending the font library to modify the upload
+ * destination for font files via the upload_dir filter. The recommended way to
+ * do this is:
+ *
+ * ```php
+ * add_filter( 'upload_dir', '_wp_filter_font_directory' );
+ * // Your code to upload or sideload a font file.
+ * remove_filter( 'upload_dir', '_wp_filter_font_directory' );
+ * ```
+ *
  * @since 6.5.0
  * @access private
  *

From 35f8e1bbcd2a33aee33d8e7b346d2fe5a19c29a9 Mon Sep 17 00:00:00 2001
From: Pascal Birchler <pascal.birchler@gmail.com>
Date: Fri, 22 Mar 2024 11:33:23 +0100
Subject: [PATCH 29/29] Add ticket reference

---
 tests/phpunit/tests/fonts/font-library/wpFontsDir.php | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
index 282393677b042..5021aefb59d95 100644
--- a/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
+++ b/tests/phpunit/tests/fonts/font-library/wpFontsDir.php
@@ -70,6 +70,9 @@ function set_new_values( $defaults ) {
 		$this->assertSame( static::$dir_defaults, $font_dir, 'The wp_get_font_dir() method should return the default values.' );
 	}
 
+	/**
+	 * @ticket 60652
+	 */
 	public function test_fonts_dir_filters_do_not_trigger_infinite_loop() {
 		/*
 		 * Naive filtering of uploads directory to return font directory.