egui_glium: add support for transparent windows

Also support non-decorated windows (without border)

eframe/CHANGELOG.md

@@ -1,15 +1,15 @@
 # Changelog for eframe
-
 All notable changes to the `eframe` crate.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 
 ## Unreleased
+* You can now turn your window transparent with the `App::transparent` option.
+* You can now disable window decorations with the `App::decorated` option.
 
 
 ## 0.10.0 - 2021-02-28
-
 * [You can now set your own app icons](https://github.com/emilk/egui/pull/193).
 * You can control the initial size of the native window with `App::initial_window_size`.
 * You can control the maximum egui web canvas size with `App::max_size_points`.
@@ -17,15 +17,12 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 
 ## 0.9.0 - 2021-02-07
-
 * [Add support for HTTP body](https://github.com/emilk/egui/pull/139).
 
 
 ## 0.8.0 - 2021-01-17
-
 * Simplify `TextureAllocator` interface.
 
 
 ## 0.7.0 - 2021-01-04
-
 * Initial release of `eframe`

egui_demo_lib/src/apps/demo/demo_windows.rs

@@ -129,12 +129,17 @@ impl DemoWindows {
             show_menu_bar(ui);
         });
 
-        // Just get a background to put the windows on instead of using whatever the clear color is
-        let frame = egui::Frame {
-            fill: ctx.style().visuals.extreme_bg_color,
-            ..egui::Frame::none()
-        };
-        egui::CentralPanel::default().frame(frame).show(ctx, |_| {});
+        {
+            let mut fill = ctx.style().visuals.extreme_bg_color;
+            if !cfg!(target_arch = "wasm32") {
+                // Native: WrapApp uses a transparent window, so let's show that off:
+                // NOTE: the OS compositor assumes "normal" blending, so we need to hack it:
+                let [r, g, b, _] = fill.to_array();
+                fill = egui::Color32::from_rgba_premultiplied(r, g, b, 180);
+            }
+            let frame = egui::Frame::none().fill(fill);
+            egui::CentralPanel::default().frame(frame).show(ctx, |_| {});
+        }
 
         self.windows(ctx);
     }

egui_demo_lib/src/wrap_app.rs

@@ -54,6 +54,14 @@ impl epi::App for WrapApp {
         self.backend_panel.max_size_points_active
     }
 
+    // Let's show off that we support transparent windows (on native):
+    fn transparent(&self) -> bool {
+        true
+    }
+    fn clear_color(&self) -> egui::Rgba {
+        egui::Rgba::TRANSPARENT // we set a `CentralPanel` fill color in `demo_windows.rs`
+    }
+
     fn warm_up_enabled(&self) -> bool {
         // The example windows use a lot of emojis. Pre-cache them by running one frame where everything is open
         #[cfg(debug_assertions)]

egui_glium/CHANGELOG.md

@@ -9,18 +9,15 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 
 ## 0.10.0 - 2021-02-28
-
 * [Add shaders for GLSL 1.2, GLSL ES 1.0 and 3.0](https://github.com/emilk/egui/pull/187)
   - now `egui` works well on old hardware which supports OpenGL 2.1 only like Raspberry Pi 1 and Zero.
 
 
 ## 0.9.0 - 2021-02-07
-
 * Nothing new
 
 
 ## 0.8.0 - 2021-01-17
-
 ### Fixed 🐛
 
 * Fix a bug where key releases weren't sent to egui
@@ -28,39 +25,31 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 
 ## 0.7.0 - 2021-01-04
-
 ### Changed
-
 * `http` `persistence` and `time` are now optional (and opt-in) features.
 
 
 ## 0.6.0 - 2020-12-26
-
 ### Added
-
 * `egui_glium` will auto-save your app state every 30 seconds.
 * `egui_glium` can now set windows as fixed size (e.g. the user can't resize the window). See `egui::App::is_resizable()`.
 
 ### Changed
-
 * `egui_glium` will now save you app state to [a better directory](https://docs.rs/directories-next/2.0.0/directories_next/struct.ProjectDirs.html#method.data_dir).
 * `egui_glium::run`: the parameter `app` now has signature `Box<dyn App>` (you need to add `Box::new(app)` to your code).
 * Window title is now passed via the `trait` function `egui::App::name()`.
 
 ### Fixed 🐛
-
 * Serialize window size in logical points instead of physical pixels.
 * Window position is now restored on restart.
 
+
 ## 0.5.0 - 2020-12-13
-
 ### Changed
-
 * FileStorage::from_path now takes `Into<Path>` instead of `String`
 
 
 ## 0.4.0 - 2020-11-28
-
 Started changelog. Features:
 
 * Input

egui_glium/src/backend.rs

@@ -56,19 +56,19 @@ impl epi::RepaintSignal for GliumRepaintSignal {
 }
 
 fn create_display(
-    title: &str,
-    initial_size_points: Option<Vec2>,
+    app: &dyn epi::App,
     window_settings: Option<WindowSettings>,
-    is_resizable: bool,
     window_icon: Option<glutin::window::Icon>,
     event_loop: &glutin::event_loop::EventLoop<RequestRepaintEvent>,
 ) -> glium::Display {
     let mut window_builder = glutin::window::WindowBuilder::new()
-        .with_decorations(true)
-        .with_resizable(is_resizable)
-        .with_title(title)
+        .with_decorations(app.decorated())
+        .with_resizable(app.is_resizable())
+        .with_title(app.name())
         .with_window_icon(window_icon)
-        .with_transparent(false);
+        .with_transparent(app.transparent());
+
+    let initial_size_points = app.initial_window_size();
 
     if let Some(window_settings) = &window_settings {
         window_builder = window_settings.initialize_size(window_builder);
@@ -149,14 +149,7 @@ pub fn run(mut app: Box<dyn epi::App>) -> ! {
     let window_settings = deserialize_window_settings(&storage);
     let event_loop = glutin::event_loop::EventLoop::with_user_event();
     let icon = load_icon(app.icon_data());
-    let display = create_display(
-        app.name(),
-        app.initial_window_size(),
-        window_settings,
-        app.is_resizable(),
-        icon,
-        &event_loop,
-    );
+    let display = create_display(&*app, window_settings, icon, &event_loop);
 
     let repaint_signal = std::sync::Arc::new(GliumRepaintSignal(std::sync::Mutex::new(
         event_loop.create_proxy(),

epi/src/lib.rs

@@ -130,13 +130,28 @@ pub trait App {
     /// This is the background of your windows if you don't set a central panel.
     fn clear_color(&self) -> egui::Rgba {
         // NOTE: a bright gray makes the shadows of the windows look weird.
-        egui::Color32::from_rgb(12, 12, 12).into()
+        // We use a bit of transparency so that if the user switches on the
+        // `transparent()` option they get immediate results.
+        egui::Color32::from_rgba_unmultiplied(12, 12, 12, 180).into()
     }
 
     /// The application icon, e.g. in the Windows task bar etc.
     fn icon_data(&self) -> Option<IconData> {
         None
     }
+
+    /// On desktop: add window decorations (i.e. a frame around your app)?
+    /// If false it will be difficult to move and resize the app.
+    fn decorated(&self) -> bool {
+        true
+    }
+
+    /// On desktop: make the window transparent.
+    /// You control the transparency with [`Self::clear_color()`].
+    /// You should avoid having a [`egui::CentralPanel`], or make sure its frame is also transparent.
+    fn transparent(&self) -> bool {
+        false
+    }
 }
 
 /// Image data for the icon.