macOS: Try improving legibility for dark themes and low-DPI displays

crates/gpui/src/color.rs

@@ -444,6 +444,13 @@ impl Hsla {
         self.a == 0.0
     }
 
+    /// Returns true if the color is considered "light", false otherwise.
+    pub fn is_light(&self) -> bool {
+        const ONE_THIRD: f32 = 1. / 3.;
+        let Rgba { r, g, b, .. } = self.to_rgb();
+        r >= ONE_THIRD && g >= ONE_THIRD && b >= ONE_THIRD && r + g + b >= 2.
+    }
+
     /// Blends `other` on top of `self` based on `other`'s alpha value. The resulting color is a combination of `self`'s and `other`'s colors.
     ///
     /// If `other`'s alpha value is 1.0 or greater, `other` color is fully opaque, thus `other` is returned as the output color.

crates/gpui/src/platform/mac/text_system.rs

@@ -1,3 +1,4 @@
+use super::open_type::apply_features_and_fallbacks;
 use crate::{
     point, px, size, swap_rgba_pa_to_bgra, Bounds, DevicePixels, Font, FontFallbacks, FontFeatures,
     FontId, FontMetrics, FontRun, FontStyle, FontWeight, GlyphId, LineLayout, Pixels,
@@ -14,10 +15,13 @@ use core_foundation::{
     string::CFString,
 };
 use core_graphics::{
-    base::{kCGImageAlphaPremultipliedLast, CGGlyph},
+    base::{
+        kCGBitmapByteOrder32Little, kCGImageAlphaNoneSkipLast, kCGImageAlphaPremultipliedLast,
+        CGGlyph,
+    },
     color_space::CGColorSpace,
-    context::CGContext,
-    display::CGPoint,
+    context::{CGBlendMode, CGContext, CGTextDrawingMode},
+    display::{CGPoint, CGRect, CGSize},
 };
 use core_text::{
     font::CTFont,
@@ -45,11 +49,6 @@ use pathfinder_geometry::{
 use smallvec::SmallVec;
 use std::{borrow::Cow, char, cmp, convert::TryFrom, sync::Arc};
 
-use super::open_type::apply_features_and_fallbacks;
-
-#[allow(non_upper_case_globals)]
-const kCGImageAlphaOnly: u32 = 7;
-
 pub(crate) struct MacTextSystem(RwLock<MacTextSystemState>);
 
 #[derive(Clone, PartialEq, Eq, Hash)]
@@ -360,30 +359,63 @@ impl MacTextSystemState {
             }
             let bitmap_size = bitmap_size;
 
-            let mut bytes;
-            let cx;
-            if params.is_emoji {
-                bytes = vec![0; bitmap_size.width.0 as usize * 4 * bitmap_size.height.0 as usize];
-                cx = CGContext::create_bitmap_context(
-                    Some(bytes.as_mut_ptr() as *mut _),
-                    bitmap_size.width.0 as usize,
-                    bitmap_size.height.0 as usize,
-                    8,
-                    bitmap_size.width.0 as usize * 4,
-                    &CGColorSpace::create_device_rgb(),
-                    kCGImageAlphaPremultipliedLast,
-                );
+            let color_type = if params.is_emoji {
+                kCGImageAlphaPremultipliedLast
             } else {
-                bytes = vec![0; bitmap_size.width.0 as usize * bitmap_size.height.0 as usize];
-                cx = CGContext::create_bitmap_context(
-                    Some(bytes.as_mut_ptr() as *mut _),
-                    bitmap_size.width.0 as usize,
-                    bitmap_size.height.0 as usize,
-                    8,
-                    bitmap_size.width.0 as usize,
-                    &CGColorSpace::create_device_gray(),
-                    kCGImageAlphaOnly,
+                kCGImageAlphaNoneSkipLast
+            };
+            let mut bytes =
+                vec![0; bitmap_size.width.0 as usize * 4 * bitmap_size.height.0 as usize];
+            let cx = CGContext::create_bitmap_context(
+                Some(bytes.as_mut_ptr() as *mut _),
+                bitmap_size.width.0 as usize,
+                bitmap_size.height.0 as usize,
+                8,
+                bitmap_size.width.0 as usize * 4,
+                &CGColorSpace::create_device_rgb(),
+                kCGBitmapByteOrder32Little | color_type,
+            );
+            cx.set_allows_font_subpixel_positioning(true);
+            cx.set_should_subpixel_position_fonts(true);
+            cx.set_allows_font_subpixel_quantization(false);
+            cx.set_should_subpixel_quantize_fonts(false);
+            if !params.is_emoji {
+                cx.set_should_smooth_fonts(true);
+                cx.set_should_antialias(true);
+
+                let background_color;
+                let foreground_color;
+                if params.is_light {
+                    background_color = [0., 0., 0.];
+                    foreground_color = [1., 1., 1.];
+                } else {
+                    background_color = [1., 1., 1.];
+                    foreground_color = [0., 0., 0.];
+                }
+
+                cx.set_blend_mode(CGBlendMode::Copy);
+                cx.set_rgb_fill_color(
+                    background_color[0],
+                    background_color[1],
+                    background_color[2],
+                    1.,
+                );
+                cx.fill_rect(CGRect {
+                    origin: CGPoint { x: 0.0, y: 0.0 },
+                    size: CGSize {
+                        width: bitmap_size.width.0 as CGFloat,
+                        height: bitmap_size.height.0 as CGFloat,
+                    },
+                });
+                cx.set_blend_mode(CGBlendMode::Normal);
+
+                cx.set_rgb_fill_color(
+                    foreground_color[0],
+                    foreground_color[1],
+                    foreground_color[2],
+                    1.,
                 );
+                cx.set_text_drawing_mode(CGTextDrawingMode::CGTextFill);
             }
 
             // Move the origin to bottom left and account for scaling, this
@@ -400,10 +432,7 @@ impl MacTextSystemState {
             let subpixel_shift = params
                 .subpixel_variant
                 .map(|v| v as f32 / SUBPIXEL_VARIANTS as f32);
-            cx.set_allows_font_subpixel_positioning(true);
-            cx.set_should_subpixel_position_fonts(true);
-            cx.set_allows_font_subpixel_quantization(false);
-            cx.set_should_subpixel_quantize_fonts(false);
+
             self.fonts[params.font_id.0]
                 .native_font()
                 .clone_with_font_size(f32::from(params.font_size) as CGFloat)
@@ -421,6 +450,19 @@ impl MacTextSystemState {
                 for pixel in bytes.chunks_exact_mut(4) {
                     swap_rgba_pa_to_bgra(pixel);
                 }
+            } else {
+                let mut index = 0;
+                bytes.retain_mut(|value| {
+                    index += 1;
+                    if index % 4 == 0 {
+                        if !params.is_light {
+                            *value = 255 - *value;
+                        }
+                        true
+                    } else {
+                        false
+                    }
+                });
             }
 
             Ok((bitmap_size, bytes))

crates/gpui/src/text_system.rs

@@ -657,6 +657,7 @@ pub(crate) struct RenderGlyphParams {
     pub(crate) subpixel_variant: Point<u8>,
     pub(crate) scale_factor: f32,
     pub(crate) is_emoji: bool,
+    pub(crate) is_light: bool,
 }
 
 impl Eq for RenderGlyphParams {}
@@ -669,6 +670,7 @@ impl Hash for RenderGlyphParams {
         self.subpixel_variant.hash(state);
         self.scale_factor.to_bits().hash(state);
         self.is_emoji.hash(state);
+        self.is_light.hash(state);
     }
 }
 

crates/gpui/src/window.rs

@@ -2443,6 +2443,7 @@ impl<'a> WindowContext<'a> {
             subpixel_variant,
             scale_factor,
             is_emoji: false,
+            is_light: color.is_light(),
         };
 
         let raster_bounds = self.text_system().raster_bounds(&params)?;
@@ -2507,6 +2508,7 @@ impl<'a> WindowContext<'a> {
             subpixel_variant: Default::default(),
             scale_factor,
             is_emoji: true,
+            is_light: false,
         };
 
         let raster_bounds = self.text_system().raster_bounds(&params)?;