emilk · lictex · Jan 9, 2023 · Jan 13, 2023 · Jan 13, 2023
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -6,6 +6,7 @@ NOTE: [`epaint`](crates/epaint/CHANGELOG.md), [`eframe`](crates/eframe/CHANGELOG
 
 ## Unreleased
 ### Added ⭐
+* Add `Context::(set_)shadow_painter` for overriding the default shadow implementation with custom one ([#2564](https://github.com/emilk/egui/pull/2564)).
 * `Event::Key` now has a `repeat` field that is set to `true` if the event was the result of a key-repeat ([#2435](https://github.com/emilk/egui/pull/2435)).
 * Add `Slider::drag_value_speed`, which lets you ask for finer precision when dragging the slider value rather than the actual slider.
 * Add `Memory::any_popup_open`, which returns true if any popup is currently open ([#2464](https://github.com/emilk/egui/pull/2464)).
@@ -14,6 +15,7 @@ NOTE: [`epaint`](crates/epaint/CHANGELOG.md), [`eframe`](crates/eframe/CHANGELOG
 * Add `Response::on_hover_and_drag_cursor`.
 
 ### Changed 🔧
+* `Frame::paint` now takes an extra `&Context` argument ([#2564](https://github.com/emilk/egui/pull/2564)).
 * Improved plot grid appearance ([#2412](https://github.com/emilk/egui/pull/2412)).
 * Improved the algorithm for picking the number of decimals to show when hovering values in the `Plot`.
 

diff --git a/crates/egui/src/containers/area.rs b/crates/egui/src/containers/area.rs
@@ -339,7 +339,7 @@ impl Area {
             //     Rect::from_center_size(area_rect.center(), visibility_factor * area_rect.size());
 
             let frame = frame.multiply_with_opacity(visibility_factor);
-            painter.add(frame.paint(area_rect));
+            painter.add(frame.paint(ctx, area_rect));
         }
     }
 }
@@ -378,10 +378,16 @@ impl Prepared {
             bounds.max.at_least(self.state.pos + Vec2::splat(32.0)),
         );
 
-        let shadow_radius = ctx.style().visuals.window_shadow.extrusion; // hacky
-        let clip_rect_margin = ctx.style().visuals.clip_rect_margin.max(shadow_radius);
+        let shadow = ctx.style().visuals.window_shadow; // hacky
+        let clip_rect_margin = ctx.style().visuals.clip_rect_margin;
 
-        let clip_rect = Rect::from_min_max(self.state.pos, bounds.max)
+        let clip_rect = ctx
+            .shadow_painter()
+            .shadow_clip_rect(
+                shadow,
+                Rect::from_min_max(self.state.pos, bounds.max),
+                Rounding::none(),
+            )
             .expand(clip_rect_margin)
             .intersect(bounds);
 

diff --git a/crates/egui/src/containers/fram 10000 e.rs b/crates/egui/src/containers/fram 10000 e.rs
@@ -222,7 +222,7 @@ impl Frame {
         InnerResponse::new(ret, response)
     }
 
-    pub fn paint(&self, outer_rect: Rect) -> Shape {
+    pub fn paint(&self, ctx: &Context, outer_rect: Rect) -> Shape {
         let Self {
             inner_margin: _,
             outer_margin: _,
@@ -242,8 +242,7 @@ impl Frame {
         if shadow == Default::default() {
             frame_shape
         } else {
-            let shadow = shadow.tessellate(outer_rect, rounding);
-            let shadow = Shape::Mesh(shadow);
+            let shadow = ctx.shadow_painter().paint(shadow, outer_rect, rounding);
             Shape::Vec(vec![shadow, frame_shape])
         }
     }
@@ -274,7 +273,7 @@ impl Prepared {
         } = self;
 
         if ui.is_rect_visible(paint_rect) {
-            let shape = frame.paint(paint_rect);
+            let shape = frame.paint(ui.ctx(), paint_rect);
             ui.painter().set(where_to_put_background, shape);
         }
 

diff --git a/crates/egui/src/context.rs b/crates/egui/src/context.rs
@@ -70,6 +70,8 @@ struct ContextImpl {
 
     #[cfg(feature = "accesskit")]
     is_accesskit_enabled: bool,
+
+    shadow_painter: ShadowPainter,
 }
 
 impl ContextImpl {
@@ -1024,6 +1026,14 @@ impl Context {
 
         Rect::from_min_size(pos, window.size())
     }
+
+    pub fn shadow_painter(&self) -> RwLockReadGuard<'_, ShadowPainter> {
+        RwLockReadGuard::map(self.read(), |f| &f.shadow_painter)
+    }
+
+    pub fn set_shadow_painter(&self, custom_shadow: ShadowPainter) {
+        self.write().shadow_painter = custom_shadow;
+    }
 }
 
 impl Context {

diff --git a/crates/epaint/CHANGELOG.md b/crates/epaint/CHANGELOG.md
@@ -3,6 +3,7 @@ All notable changes to the epaint crate will be documented in this file.
 
 
 ## Unreleased
+* Add `ShadowPainter` struct to support custom shadow implementions ([#2564](https://github.com/emilk/egui/pull/2564)).
 * Improve the look of thin white lines ([#2437](https://github.com/emilk/egui/pull/2437)).
 * Don't render `\r` (Carriage Return) ([#2452](https://github.com/emilk/egui/pull/2452)).
 * Fix bug in `Mesh::split_to_u16` ([#2459](https://github.com/emilk/egui/pull/2459)).

diff --git a/crates/epaint/src/lib.rs b/crates/epaint/src/lib.rs
@@ -32,7 +32,7 @@ pub use {
     bezier::{CubicBezierShape, QuadraticBezierShape},
     image::{ColorImage, FontImage, ImageData, ImageDelta},
     mesh::{Mesh, Mesh16, Vertex},
-    shadow::Shadow,
+    shadow::{Shadow, ShadowPainter},
     shape::{
         CircleShape, PaintCallback, PaintCallbackInfo, PathShape, RectShape, Rounding, Shape,
         TextShape,

diff --git a/crates/epaint/src/shadow.rs b/crates/epaint/src/shadow.rs
@@ -50,38 +50,72 @@ impl Shadow {
             color: Color32::from_black_alpha(16),
         }
     }
+}
+
+/// Functions for painting shadows
+pub struct ShadowPainter {
+    clip_rect: std::sync::Arc<dyn Fn(Shadow, Rect, Rounding) -> Rect + Send + Sync>,
+    paint: std::sync::Arc<dyn Fn(Shadow, Rect, Rounding) -> Shape + Send + Sync>,
+}
+impl ShadowPainter {
+    /// Create a custom [`ShadowPainter`].
+    /// For arguments, see [`Self::shadow_clip_rect`] and [`Self::paint`]
+    pub fn new(
+        clip_rect: impl Fn(Shadow, Rect, Rounding) -> Rect + Send + Sync + 'static,
+        paint: impl Fn(Shadow, Rect, Rounding) -> Shape + Send + Sync + 'static,
+    ) -> Self {
+        Self {
+            clip_rect: std::sync::Arc::new(clip_rect),
+            paint: std::sync::Arc::new(paint),
+        }
+    }
+
+    /// Transform (typically expand) a clip rect to fit the given shadow
+    pub fn shadow_clip_rect(&self, shadow: Shadow, content_rect: Rect, rounding: Rounding) -> Rect {
+        (self.clip_rect)(shadow, content_rect, rounding)
+    }
 
-    pub fn tessellate(&self, rect: Rect, rounding: impl Into<Rounding>) -> Mesh {
-        // tessellator.clip_rect = clip_rect; // TODO(emilk): culling
+    /// Convert a shadow into a [`Shape`]
+    pub fn paint(&self, shadow: Shadow, content_rect: Rect, rounding: Rounding) -> Shape {
+        (self.paint)(shadow, content_rect, rounding)
+    }
+}
+impl Default for ShadowPainter {
+    fn default() -> Self {
+        Self::new(
+            |shadow, rect, _| rect.expand(shadow.extrusion),
+            |shadow, rect, rounding| {
+                // tessellator.clip_rect = clip_rect; // TODO(emilk): culling
 
-        let Self { extrusion, color } = *self;
+                let Shadow { extrusion, color } = shadow;
 
-        let rounding: Rounding = rounding.into();
-        let half_ext = 0.5 * extrusion;
+                let half_ext = 0.5 * extrusion;
 
-        let ext_rounding = Rounding {
-            nw: rounding.nw + half_ext,
-            ne: rounding.ne + half_ext,
-            sw: rounding.sw + half_ext,
-            se: rounding.se + half_ext,
-        };
+                let ext_rounding = Rounding {
+                    nw: rounding.nw + half_ext,
+                    ne: rounding.ne + half_ext,
+                    sw: rounding.sw + half_ext,
+                    se: rounding.se + half_ext,
+                };
 
-        use crate::tessellator::*;
-        let rect = RectShape::filled(rect.expand(half_ext), ext_rounding, color);
-        let pixels_per_point = 1.0; // doesn't matter here
-        let font_tex_size = [1; 2]; // unused size we are not tessellating text.
-        let mut tessellator = Tessellator::new(
-            pixels_per_point,
-            TessellationOptions {
-                feathering: true,
-                feathering_size_in_pixels: extrusion * pixels_per_point,
-                ..Default::default()
+                use crate::tessellator::*;
+                let rect = RectShape::filled(rect.expand(half_ext), ext_rounding, color);
+                let pixels_per_point = 1.0; // doesn't matter here
+                let font_tex_size = [1; 2]; // unused size we are not tessellating text.
+                let mut tessellator = Tessellator::new(
+                    pixels_per_point,
+                    TessellationOptions {
+                        feathering: true,
+                        feathering_size_in_pixels: extrusion * pixels_per_point,
+                        ..Default::default()
+                    },
+                    font_tex_size,
+                    vec![],
+                );
+                let mut mesh = Mesh::default();
+                tessellator.tessellate_rect(&rect, &mut mesh);
+                Shape::Mesh(mesh)
             },
-            font_tex_size,
-            vec![],
-        );
-        let mut mesh = Mesh::default();
-        tessellator.tessellate_rect(&rect, &mut mesh);
-        mesh
+        )
     }
 }