Add macOS-specific has_shadow and with_has_shadow to ViewportBuilder

crates/egui-winit/src/lib.rs

@@ -1623,6 +1623,7 @@ pub fn create_winit_window_attributes(
         title_shown: _title_shown,
         titlebar_buttons_shown: _titlebar_buttons_shown,
         titlebar_shown: _titlebar_shown,
+        has_shadow: _has_shadow,
 
         // Windows:
         drag_and_drop: _drag_and_drop,
@@ -1767,7 +1768,8 @@ pub fn create_winit_window_attributes(
             .with_titlebar_buttons_hidden(!_titlebar_buttons_shown.unwrap_or(true))
             .with_titlebar_transparent(!_titlebar_shown.unwrap_or(true))
             .with_fullsize_content_view(_fullsize_content_view.unwrap_or(false))
-            .with_movable_by_window_background(_movable_by_window_background.unwrap_or(false));
+            .with_movable_by_window_background(_movable_by_window_background.unwrap_or(false))
+            .with_has_shadow(_has_shadow.unwrap_or(true));
     }
 
     window_attributes

crates/egui/src/viewport.rs

@@ -295,6 +295,7 @@ pub struct ViewportBuilder {
     pub title_shown: Option<bool>,
     pub titlebar_buttons_shown: Option<bool>,
     pub titlebar_shown: Option<bool>,
+    pub has_shadow: Option<bool>,
 
     // windows:
     pub drag_and_drop: Option<bool>,
@@ -381,6 +382,10 @@ impl ViewportBuilder {
     /// The default is `false`.
     /// If this is not working, it's because the graphic context doesn't support transparency,
     /// you will need to set the transparency in the eframe!
+    ///
+    /// ## Platform-specific
+    ///
+    /// **macOS:** When using this feature to create an overlay-like UI, you likely want to combine this with [`Self::with_has_shadow`] set to `false` in order to avoid ghosting artifacts.
     #[inline]
     pub fn with_transparent(mut self, transparent: bool) -> Self {
         self.transparent = Some(transparent);
@@ -434,7 +439,6 @@ impl ViewportBuilder {
     }
 
     /// macOS: Set to `true` to allow the window to be moved by dragging the background.
-    ///
     /// Enabling this feature can result in unexpected behaviour with draggable UI widgets such as sliders.
     #[inline]
     pub fn with_movable_by_background(mut self, value: bool) -> Self {
@@ -463,6 +467,19 @@ impl ViewportBuilder {
         self
     }
 
+    /// macOS: Set to `false` to make the window render without a drop shadow.
+    ///
+    /// The default is `true`.
+    ///
+    /// Disabling this feature can solve ghosting issues experienced if using [`Self::with_transparent`].
+    ///
+    /// Look at winit for more details
+    #[inline]
+    pub fn with_has_shadow(mut self, has_shadow: bool) -> Self {
+        self.has_shadow = Some(has_shadow);
+        self
+    }
+
     /// windows: Whether show or hide the window icon in the taskbar.
     #[inline]
     pub fn with_taskbar(mut self, show: bool) -> Self {
@@ -654,6 +671,7 @@ impl ViewportBuilder {
             title_shown: new_title_shown,
             titlebar_buttons_shown: new_titlebar_buttons_shown,
             titlebar_shown: new_titlebar_shown,
+            has_shadow: new_has_shadow,
             close_button: new_close_button,
             minimize_button: new_minimize_button,
             maximize_button: new_maximize_button,
@@ -824,6 +842,11 @@ impl ViewportBuilder {
             recreate_window = true;
         }
 
+        if new_has_shadow.is_some() && self.has_shadow != new_has_shadow {
+            self.has_shadow = new_has_shadow;
+            recreate_window = true;
+        }
+
         if new_taskbar.is_some() && self.taskbar != new_taskbar {
             self.taskbar = new_taskbar;
             recreate_window = true;