From 7343d6689d60a62536e064453ae308974beb0107 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?L=C3=A9on=20Gersen?= <leongersen@gmail.com>
Date: Sat, 14 Aug 2021 20:29:14 +0200
Subject: [PATCH] Add support for sliders with ranges where min = max (#236,
 #359, #578, #633, #676, #790)

---
 documentation/slider-values.php |  2 +-
 src/nouislider.ts               | 24 +++++++++++++++++++-----
 tests/slider.html               |  1 +
 tests/slider_errors.js          | 10 ----------
 tests/slider_no_size.js         | 16 ++++++++++++++++
 5 files changed, 37 insertions(+), 16 deletions(-)
 create mode 100644 tests/slider_no_size.js

diff --git a/documentation/slider-values.php b/documentation/slider-values.php
index f31553da..4c4bfa56 100644
--- a/documentation/slider-values.php
+++ b/documentation/slider-values.php
@@ -54,7 +54,7 @@
 <section>
 
 	<div class="view">
-		<p>All values on the slider are part of a range. The range has a minimum and maximum value. The minimum value <a href="https://github.com/leongersen/noUiSlider/issues/676">cannot be equal to the maximum value</a>.</p>
+		<p>All values on the slider are part of a range. The range has a minimum and maximum value. If the minimum value is equal to the maximum value, handles are evenly spread across the slider.</p>
 
 		<div class="example">
 			<div id="slider-range"></div>
diff --git a/src/nouislider.ts b/src/nouislider.ts
index 32178655..e80a04f8 100644
--- a/src/nouislider.ts
+++ b/src/nouislider.ts
@@ -765,6 +765,10 @@ class Spectrum {
         return Math.max.apply(null, stepDecimals);
     }
 
+    public hasNoSize(): boolean {
+        return this.xVal[0] === this.xVal[this.xVal.length - 1];
+    }
+
     // Outside testing
     public convert(value: number): number {
         return this.getStep(this.toStepping(value));
@@ -950,11 +954,6 @@ function testRange(parsed: ParsedOptions, entry: Range): void {
         throw new Error("noUiSlider: Missing 'min' or 'max' in 'range'.");
     }
 
-    // Catch equal start or end.
-    if (entry.min === entry.max) {
-        throw new Error("noUiSlider: 'range' 'min' and 'max' cannot be equal.");
-    }
-
     parsed.spectrum = new Spectrum(entry, parsed.snap || false, parsed.singleStep);
 }
 
@@ -2738,6 +2737,21 @@ function scope(target: TargetElement, options: ParsedOptions, originalOptions: O
 
         let i = scope_HandleNumbers.length === 1 ? 0 : 1;
 
+        // Spread handles evenly across the slider if the range has no size (min=max)
+        if (isInit && scope_Spectrum.hasNoSize()) {
+            exactInput = true;
+
+            scope_Locations[0] = 0;
+
+            if (scope_HandleNumbers.length > 1) {
+                const space = 100 / (scope_HandleNumbers.length - 1);
+
+                scope_HandleNumbers.forEach(function(handleNumber) {
+                    scope_Locations[handleNumber] = handleNumber * space;
+                });
+            }
+        }
+
         // Secondary passes. Now that all base values are set, apply constraints.
         // Iterate all handles to ensure constraints are applied for the entire slider (Issue #1009)
         for (; i < scope_HandleNumbers.length; ++i) {
diff --git a/tests/slider.html b/tests/slider.html
index 2be8aadc..7e9e8f5a 100644
--- a/tests/slider.html
+++ b/tests/slider.html
@@ -86,6 +86,7 @@
 <script src="slider_classes.js"></script>
 <script src="slider_set-exactInput.js"></script>
 <script src="slider_drag_all.js"></script>
+<script src="slider_no_size.js"></script>
 
 <script src="addon_pips.js"></script>
 
diff --git a/tests/slider_errors.js b/tests/slider_errors.js
index 0c2f7936..c8180275 100644
--- a/tests/slider_errors.js
+++ b/tests/slider_errors.js
@@ -81,16 +81,6 @@ QUnit.test("Errors", function (assert) {
         });
     });
 
-    assert.throws(function () {
-        noUiSlider.create(slider, {
-            start: 10,
-            range: {
-                'min': 10,
-                'max': 10
-            }
-        });
-    });
-
     assert.throws(function () {
         noUiSlider.create(slider, {
             start: 10,
diff --git a/tests/slider_no_size.js b/tests/slider_no_size.js
new file mode 100644
index 00000000..b70a1cac
--- /dev/null
+++ b/tests/slider_no_size.js
@@ -0,0 +1,16 @@
+QUnit.test("Test init with min = max", function (assert) {
+
+    document.getElementById('qunit-fixture').innerHTML = '<div class="slider"></div>';
+
+    var slider = document.getElementById('qunit-fixture').querySelector('.slider');
+
+    noUiSlider.create(slider, {
+        start: [0, 0, 0],
+        range: {
+            'min': 0,
+            'max': 0
+        }
+    });
+
+    assert.deepEqual(slider.noUiSlider.getPositions(), [0, 50, 100]);
+});