Implement an AlwaysOnTop window level

druid-shell/src/platform/gtk/window.rs

@@ -905,12 +905,14 @@ impl WindowHandle {
                 WindowLevel::Tooltip => WindowTypeHint::Tooltip,
                 WindowLevel::DropDown => WindowTypeHint::DropdownMenu,
                 WindowLevel::Modal => WindowTypeHint::Dialog,
+                WindowLevel::AlwaysOnTop => WindowTypeHint::Normal,
             };
 
             state.window.set_type_hint(hint);
         }
 
         self.set_override_redirect(level);
+        self.set_keep_above(level);
     }
 
     /// The override-redirect flag tells the window manager not to mess with the window; it should
@@ -930,6 +932,19 @@ impl WindowHandle {
         }
     }
 
+    fn set_keep_above(&self, level: WindowLevel) {
+        let keep_above = match level {
+            WindowLevel::AlwaysOnTop => true,
+            _ => false
+        };
+
+        if let Some(state) = self.state.upgrade() {
+            if let Some(window) = state.window.get_window() {
+                window.set_keep_above(keep_above);
+            }
+        }
+    }
+
     pub fn set_size(&self, size: Size) {
         if let Some(state) = self.state.upgrade() {
             let px = size.to_px(state.scale.get());

druid-shell/src/platform/mac/window.rs

@@ -92,6 +92,7 @@ mod levels {
             Tooltip => NSFloatingWindowLevel,
             DropDown => NSFloatingWindowLevel,
             Modal => NSModalPanelWindowLevel,
+            AlwaysOnTop => NSFloatingWindowLevel,
         }
     }
 }

druid-shell/src/platform/windows/window.rs

@@ -1307,7 +1307,7 @@ impl WindowBuilder {
 
     pub fn set_level(&mut self, level: WindowLevel) {
         match level {
-            WindowLevel::AppWindow | WindowLevel::Tooltip => self.level = Some(level),
+            WindowLevel::AppWindow | WindowLevel::Tooltip | WindowLevel::AlwaysOnTop => self.level = Some(level),
             _ => {
                 warn!("WindowBuilder::set_level({:?}) is currently unimplemented for Windows platforms.", level);
             }
@@ -1372,6 +1372,9 @@ impl WindowBuilder {
                         dwStyle = WS_OVERLAPPED;
                         dwExStyle = WS_EX_TOPMOST;
                     }
+                    WindowLevel::AlwaysOnTop => {
+                        dwExStyle = WS_EX_TOPMOST;
+                    }
                 }
             }
 

druid-shell/src/window.rs

@@ -158,6 +158,8 @@ pub enum WindowLevel {
     DropDown,
     /// A modal dialog
     Modal,
+    /// A top level app window that will stay above other windows
+    AlwaysOnTop
 }
 
 /// Contains the different states a Window can be in.