add with_taskbar to viewport builder (#3958)

Allows removing the taskbar icon of a viewport.

This can be useful when making an overlay type viewport (window is
always on top).

crates/egui-winit/src/lib.rs

@@ -1498,6 +1498,7 @@ pub fn create_winit_window_builder<T>(
 
         // Windows:
         drag_and_drop: _drag_and_drop,
+        taskbar: _taskbar,
 
         // wayland:
         app_id: _app_id,
@@ -1575,9 +1576,14 @@ pub fn create_winit_window_builder<T>(
     }
 
     #[cfg(target_os = "windows")]
-    if let Some(enable) = _drag_and_drop {
+    {
         use winit::platform::windows::WindowBuilderExtWindows as _;
-        window_builder = window_builder.with_drag_and_drop(enable);
+        if let Some(enable) = _drag_and_drop {
+            window_builder = window_builder.with_drag_and_drop(enable);
+        }
+        if let Some(show) = _taskbar {
+            window_builder = window_builder.with_skip_taskbar(!show);
+        }
     }
 
     #[cfg(target_os = "macos")]

crates/egui/src/viewport.rs

@@ -283,7 +283,6 @@ pub struct ViewportBuilder {
     pub icon: Option<Arc<IconData>>,
     pub active: Option<bool>,
     pub visible: Option<bool>,
-    pub drag_and_drop: Option<bool>,
 
     // macOS:
     pub fullsize_content_view: Option<bool>,
@@ -291,6 +290,10 @@ pub struct ViewportBuilder {
     pub titlebar_buttons_shown: Option<bool>,
     pub titlebar_shown: Option<bool>,
 
+    // windows:
+    pub drag_and_drop: Option<bool>,
+    pub taskbar: Option<bool>,
+
     pub close_button: Option<bool>,
     pub minimize_button: Option<bool>,
     pub maximize_button: Option<bool>,
@@ -442,6 +445,13 @@ impl ViewportBuilder {
         self
     }
 
+    /// windows: Whether show or hide the window icon in the taskbar.
+    #[inline]
+    pub fn with_taskbar(mut self, show: bool) -> Self {
+        self.taskbar = Some(show);
+        self
+    }
+
     /// Requests the window to be of specific dimensions.
     ///
     /// If this is not set, some platform-specific dimensions will be used.
@@ -602,6 +612,7 @@ impl ViewportBuilder {
             maximize_button: new_maximize_button,
             window_level: new_window_level,
             mouse_passthrough: new_mouse_passthrough,
+            taskbar: new_taskbar,
         } = new_vp_builder;
 
         let mut commands = Vec::new();
@@ -758,6 +769,11 @@ impl ViewportBuilder {
             recreate_window = true;
         }
 
+        if new_taskbar.is_some() && self.taskbar != new_taskbar {
+            self.taskbar = new_taskbar;
+            recreate_window = true;
+        }
+
         if new_fullsize_content_view.is_some()
             && self.fullsize_content_view != new_fullsize_content_view
         {