Add support for dashed borders to GPUI (#27139)

Features:

* Scales dash spacing with border width.
* Laying out dashes around rounded corners.
* Varying border widths with rounded corners - now uses an ellipse for the inner edge of the border.
* When there are no rounded corners, each straight border is laid out separately, so that the dashes to meet at the corners.
* All sides of each dash are antialiased.

![image](https://github.com/user-attachments/assets/b3789a98-a5be-4f97-9736-c4e59615afe6)

![image](https://github.com/user-attachments/assets/739bdc57-4580-42c8-bfc3-6e287411a408)

Release Notes:

- N/A

---------

Co-authored-by: Michael Sloan <michael@zed.dev>
Co-authored-by: Ben <ben@zed.dev>

crates/gpui/src/window.rs

@@ -1,18 +1,18 @@
 use crate::{
     point, prelude::*, px, size, transparent_black, Action, AnyDrag, AnyElement, AnyTooltip,
-    AnyView, App, AppContext, Arena, Asset, AsyncWindowContext, AvailableSpace, Background, Bounds,
-    BoxShadow, Context, Corners, CursorStyle, Decorations, DevicePixels, DispatchActionListener,
-    DispatchNodeId, DispatchTree, DisplayId, Edges, Effect, Entity, EntityId, EventEmitter,
-    FileDropEvent, FontId, Global, GlobalElementId, GlyphId, GpuSpecs, Hsla, InputHandler, IsZero,
-    KeyBinding, KeyContext, KeyDownEvent, KeyEvent, Keystroke, KeystrokeEvent, LayoutId,
-    LineLayoutIndex, Modifiers, ModifiersChangedEvent, MonochromeSprite, MouseButton, MouseEvent,
-    MouseMoveEvent, MouseUpEvent, Path, Pixels, PlatformAtlas, PlatformDisplay, PlatformInput,
-    PlatformInputHandler, PlatformWindow, Point, PolychromeSprite, PromptLevel, Quad, Render,
-    RenderGlyphParams, RenderImage, RenderImageParams, RenderSvgParams, Replay, ResizeEdge,
-    ScaledPixels, Scene, Shadow, SharedString, Size, StrikethroughStyle, Style, SubscriberSet,
-    Subscription, TaffyLayoutEngine, Task, TextStyle, TextStyleRefinement, TransformationMatrix,
-    Underline, UnderlineStyle, WindowAppearance, WindowBackgroundAppearance, WindowBounds,
-    WindowControls, WindowDecorations, WindowOptions, WindowParams, WindowTextSystem,
+    AnyView, App, AppContext, Arena, Asset, AsyncWindowContext, AvailableSpace, Background,
+    BorderStyle, Bounds, BoxShadow, Context, Corners, CursorStyle, Decorations, DevicePixels,
+    DispatchActionListener, DispatchNodeId, DispatchTree, DisplayId, Edges, Effect, Entity,
+    EntityId, EventEmitter, FileDropEvent, FontId, Global, GlobalElementId, GlyphId, GpuSpecs,
+    Hsla, InputHandler, IsZero, KeyBinding, KeyContext, KeyDownEvent, KeyEvent, Keystroke,
+    KeystrokeEvent, LayoutId, LineLayoutIndex, Modifiers, ModifiersChangedEvent, MonochromeSprite,
+    MouseButton, MouseEvent, MouseMoveEvent, MouseUpEvent, Path, Pixels, PlatformAtlas,
+    PlatformDisplay, PlatformInput, PlatformInputHandler, PlatformWindow, Point, PolychromeSprite,
+    PromptLevel, Quad, Render, RenderGlyphParams, RenderImage, RenderImageParams, RenderSvgParams,
+    Replay, ResizeEdge, ScaledPixels, Scene, Shadow, SharedString, Size, StrikethroughStyle, Style,
+    SubscriberSet, Subscription, TaffyLayoutEngine, Task, TextStyle, TextStyleRefinement,
+    TransformationMatrix, Underline, UnderlineStyle, WindowAppearance, WindowBackgroundAppearance,
+    WindowBounds, WindowControls, WindowDecorations, WindowOptions, WindowParams, WindowTextSystem,
     SMOOTH_SVG_SCALE_FACTOR, SUBPIXEL_VARIANTS,
 };
 use anyhow::{anyhow, Context as _, Result};
@@ -2335,13 +2335,13 @@ impl Window {
         let opacity = self.element_opacity();
         self.next_frame.scene.insert_primitive(Quad {
             order: 0,
-            pad: 0,
             bounds: quad.bounds.scale(scale_factor),
             content_mask: content_mask.scale(scale_factor),
             background: quad.background.opacity(opacity),
             border_color: quad.border_color.opacity(opacity),
             corner_radii: quad.corner_radii.scale(scale_factor),
             border_widths: quad.border_widths.scale(scale_factor),
+            border_style: quad.border_style,
         });
     }
 
@@ -4107,6 +4107,8 @@ pub struct PaintQuad {
     pub border_widths: Edges<Pixels>,
     /// The color of the quad's borders.
     pub border_color: Hsla,
+    /// The style of the quad's borders.
+    pub border_style: BorderStyle,
 }
 
 impl PaintQuad {
@@ -4150,6 +4152,7 @@ pub fn quad(
     background: impl Into<Background>,
     border_widths: impl Into<Edges<Pixels>>,
     border_color: impl Into<Hsla>,
+    border_style: BorderStyle,
 ) -> PaintQuad {
     PaintQuad {
         bounds,
@@ -4157,6 +4160,7 @@ pub fn quad(
         background: background.into(),
         border_widths: border_widths.into(),
         border_color: border_color.into(),
+        border_style,
     }
 }
 
@@ -4168,16 +4172,22 @@ pub fn fill(bounds: impl Into<Bounds<Pixels>>, background: impl Into<Background>
         background: background.into(),
         border_widths: (0.).into(),
         border_color: transparent_black(),
+        border_style: BorderStyle::default(),
     }
 }
 
 /// Creates a rectangle outline with the given bounds, border color, and a 1px border width
-pub fn outline(bounds: impl Into<Bounds<Pixels>>, border_color: impl Into<Hsla>) -> PaintQuad {
+pub fn outline(
+    bounds: impl Into<Bounds<Pixels>>,
+    border_color: impl Into<Hsla>,
+    border_style: BorderStyle,
+) -> PaintQuad {
     PaintQuad {
         bounds: bounds.into(),
         corner_radii: (0.).into(),
         background: transparent_black().into(),
         border_widths: (1.).into(),
         border_color: border_color.into(),
+        border_style,
     }
 }