gpui: Add dynamic padding to prevent glyph clipping in text rendering on macOS (#45957)

Jony Lab , Claude Sonnet 4.5 , and Jason Lee created 1 week ago

Here may caused by [font-kit](https://github.com/servo/font-kit), I was
tried to use
[render-glyph](https://github.com/servo/font-kit/blob/main/examples/render-glyph.rs)
example and also use the same option with `Transform2F::from_scale(2.0)`
for `raster_bounds`.

Then the `raster_bounds` will result same issue like the GPUI's font
rendering issue.

| Transform2F::default() | Transform2F::from_scale(2.) |
| --- | -- |
| <img width="943" height="638" alt="image"
src="https://github.com/user-attachments/assets/9b827c63-2cbb-45d3-bd62-b0e058a46614"
/> | <img width="943" height="638" alt="image"
src="https://github.com/user-attachments/assets/ee977a9b-2a7b-4b78-873b-146b2953c0db"
/> |

## Before

<img width="1032" height="1398" alt="SCR-20260105-pgcp-2"
src="https://github.com/user-attachments/assets/ebeb04cc-3a92-4333-99fc-8733a63b2553"
/>

## After

<img width="1032" height="1414" alt="SCR-20260105-pfny-1"
src="https://github.com/user-attachments/assets/063d0452-56d7-447c-810b-fee7c891235b"
/>

Release Notes:

- Fixed incorrect rendering of characters at large font sizes on macOS

---------

Co-authored-by: Claude Sonnet 4.5 <[e-mail]>
Co-authored-by: Jason Lee <[e-mail]>

Change summary

crates/gpui/src/platform/mac/text_system.rs | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

Detailed changes

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

@@ -356,16 +356,22 @@ impl MacTextSystemState {
 
     fn raster_bounds(&self, params: &RenderGlyphParams) -> Result<Bounds<DevicePixels>> {
         let font = &self.fonts[params.font_id.0];
-        let scale = Transform2F::from_scale(params.scale_factor);
-        Ok(font
+        let mut bounds: Bounds<DevicePixels> = font
             .raster_bounds(
                 params.glyph_id.0,
                 params.font_size.into(),
-                scale,
+                Transform2F::from_scale(params.scale_factor),
                 HintingOptions::None,
                 font_kit::canvas::RasterizationOptions::GrayscaleAa,
             )?
-            .into())
+            .into();
+
+        // Adjust the x position to account for the scale factor to avoid glyph clipped.
+        let x_offset = DevicePixels(bounds.origin.x.0 / params.scale_factor as i32);
+        bounds.origin.x -= x_offset;
+        bounds.size.width += x_offset;
+
+        Ok(bounds)
     }
 
     fn rasterize_glyph(