Disable subpixel shifting for y axis on Windows (#38440)

Release Notes:

- N/A

---------

Co-authored-by: Jakub Konka <kubkon@jakubkonka.com>

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

@@ -1,6 +1,6 @@
 use crate::{
     Bounds, DevicePixels, Font, FontFeatures, FontId, FontMetrics, FontRun, FontStyle, FontWeight,
-    GlyphId, LineLayout, Pixels, PlatformTextSystem, Point, RenderGlyphParams, SUBPIXEL_VARIANTS,
+    GlyphId, LineLayout, Pixels, PlatformTextSystem, Point, RenderGlyphParams, SUBPIXEL_VARIANTS_X,
     ShapedGlyph, ShapedRun, SharedString, Size, point, size,
 };
 use anyhow::{Context as _, Ok, Result};
@@ -276,7 +276,7 @@ impl CosmicTextSystemState {
         let font = &self.loaded_fonts[params.font_id.0].font;
         let subpixel_shift = params
             .subpixel_variant
-            .map(|v| v as f32 / (SUBPIXEL_VARIANTS as f32 * params.scale_factor));
+            .map(|v| v as f32 / (SUBPIXEL_VARIANTS_X as f32 * params.scale_factor));
         let image = self
             .swash_cache
             .get_image(
@@ -311,7 +311,7 @@ impl CosmicTextSystemState {
             let font = &self.loaded_fonts[params.font_id.0].font;
             let subpixel_shift = params
                 .subpixel_variant
-                .map(|v| v as f32 / (SUBPIXEL_VARIANTS as f32 * params.scale_factor));
+                .map(|v| v as f32 / (SUBPIXEL_VARIANTS_X as f32 * params.scale_factor));
             let mut image = self
                 .swash_cache
                 .get_image(

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

@@ -1,7 +1,7 @@
 use crate::{
     Bounds, DevicePixels, Font, FontFallbacks, FontFeatures, FontId, FontMetrics, FontRun,
     FontStyle, FontWeight, GlyphId, LineLayout, Pixels, PlatformTextSystem, Point,
-    RenderGlyphParams, Result, SUBPIXEL_VARIANTS, ShapedGlyph, ShapedRun, SharedString, Size,
+    RenderGlyphParams, Result, SUBPIXEL_VARIANTS_X, ShapedGlyph, ShapedRun, SharedString, Size,
     point, px, size, swap_rgba_pa_to_bgra,
 };
 use anyhow::anyhow;
@@ -395,7 +395,7 @@ impl MacTextSystemState {
 
             let subpixel_shift = params
                 .subpixel_variant
-                .map(|v| v as f32 / SUBPIXEL_VARIANTS as f32);
+                .map(|v| v as f32 / SUBPIXEL_VARIANTS_X as f32);
             cx.set_allows_font_smoothing(true);
             cx.set_text_drawing_mode(CGTextDrawingMode::CGTextFill);
             cx.set_gray_fill_color(0.0, 1.0);

crates/gpui/src/platform/windows/direct_write.rs

@@ -723,11 +723,10 @@ impl DirectWriteState {
             dx: 0.0,
             dy: 0.0,
         };
-        let subpixel_shift = params
-            .subpixel_variant
-            .map(|v| v as f32 / SUBPIXEL_VARIANTS as f32);
-        let baseline_origin_x = subpixel_shift.x / params.scale_factor;
-        let baseline_origin_y = subpixel_shift.y / params.scale_factor;
+        let baseline_origin_x =
+            params.subpixel_variant.x as f32 / SUBPIXEL_VARIANTS_X as f32 / params.scale_factor;
+        let baseline_origin_y =
+            params.subpixel_variant.y as f32 / SUBPIXEL_VARIANTS_Y as f32 / params.scale_factor;
 
         let mut rendering_mode = DWRITE_RENDERING_MODE1::default();
         let mut grid_fit_mode = DWRITE_GRID_FIT_MODE::default();
@@ -859,7 +858,7 @@ impl DirectWriteState {
         let bitmap_size = glyph_bounds.size;
         let subpixel_shift = params
             .subpixel_variant
-            .map(|v| v as f32 / SUBPIXEL_VARIANTS as f32);
+            .map(|v| v as f32 / SUBPIXEL_VARIANTS_X as f32);
         let baseline_origin_x = subpixel_shift.x / params.scale_factor;
         let baseline_origin_y = subpixel_shift.y / params.scale_factor;
 

crates/gpui/src/text_system.rs

@@ -41,7 +41,13 @@ pub struct FontId(pub usize);
 #[derive(Hash, PartialEq, Eq, Clone, Copy, Debug)]
 pub struct FontFamilyId(pub usize);
 
-pub(crate) const SUBPIXEL_VARIANTS: u8 = 4;
+pub(crate) const SUBPIXEL_VARIANTS_X: u8 = 4;
+
+pub(crate) const SUBPIXEL_VARIANTS_Y: u8 = if cfg!(target_os = "windows") {
+    1
+} else {
+    SUBPIXEL_VARIANTS_X
+};
 
 /// The GPUI text rendering sub system.
 pub struct TextSystem {

crates/gpui/src/window.rs

@@ -11,8 +11,8 @@ use crate::{
     MouseMoveEvent, MouseUpEvent, Path, Pixels, PlatformAtlas, PlatformDisplay, PlatformInput,
     PlatformInputHandler, PlatformWindow, Point, PolychromeSprite, PromptButton, PromptLevel, Quad,
     Render, RenderGlyphParams, RenderImage, RenderImageParams, RenderSvgParams, Replay, ResizeEdge,
-    SMOOTH_SVG_SCALE_FACTOR, SUBPIXEL_VARIANTS, ScaledPixels, Scene, Shadow, SharedString, Size,
-    StrikethroughStyle, Style, SubscriberSet, Subscription, SystemWindowTab,
+    SMOOTH_SVG_SCALE_FACTOR, SUBPIXEL_VARIANTS_X, SUBPIXEL_VARIANTS_Y, ScaledPixels, Scene, Shadow,
+    SharedString, Size, StrikethroughStyle, Style, SubscriberSet, Subscription, SystemWindowTab,
     SystemWindowTabController, TabHandles, TaffyLayoutEngine, Task, TextStyle, TextStyleRefinement,
     TransformationMatrix, Underline, UnderlineStyle, WindowAppearance, WindowBackgroundAppearance,
     WindowBounds, WindowControls, WindowDecorations, WindowOptions, WindowParams, WindowTextSystem,
@@ -2944,9 +2944,10 @@ impl Window {
         let element_opacity = self.element_opacity();
         let scale_factor = self.scale_factor();
         let glyph_origin = origin.scale(scale_factor);
+
         let subpixel_variant = Point {
-            x: (glyph_origin.x.0.fract() * SUBPIXEL_VARIANTS as f32).floor() as u8,
-            y: (glyph_origin.y.0.fract() * SUBPIXEL_VARIANTS as f32).floor() as u8,
+            x: (glyph_origin.x.0.fract() * SUBPIXEL_VARIANTS_X as f32).floor() as u8,
+            y: (glyph_origin.y.0.fract() * SUBPIXEL_VARIANTS_Y as f32).floor() as u8,
         };
         let params = RenderGlyphParams {
             font_id,