Shrink to a floating button instead of hiding

With "Shrink to Button" on, the dismiss key shrinks the window to just
itself: a see-through button that can be dragged anywhere. Tapping it
grows the keyboard back around it, kept on screen. KWin moves and
resizes the window through a one-off script, as Wayland clients can't
place themselves.

Also moves the window back on screen whenever it appears (KWin remembers
where the button was), and releases the mouse after a window manager
move or resize, which used to eat the next press on the grab bar.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

qml/Main.qml

@@ -9,6 +9,8 @@ Window {
     required property Settings settings
     required property Diagnostics diagnostics
     property var placement: null // FloatingWindow, set from C++
+    property var collapse: null // CollapseController, set from C++
+    readonly property bool collapsed: collapse?.collapsed ?? false
     property bool settingsOpen: false
     // Height of the key area, for C++ keeping key sizes when rows change.
     readonly property real keysHeight: keyboard.height
@@ -16,23 +18,31 @@ Window {
     // Transparent room above the keyboard for long-press popups on the top row.
     readonly property real popupMargin: 90
     // Outside this, input passes through to whatever is below the window.
-    readonly property rect inputRegion: keyboard.alternates.open
+    readonly property rect inputRegion: collapsed
+        ? Qt.rect(floatingButton.x, floatingButton.y, floatingButton.width, floatingButton.height)
+        : keyboard.alternates.open
         ? Qt.rect(0, 0, width, height)
         : Qt.rect(panel.x, panel.y, panel.width, panel.height)
     // Empty when nothing shows through, so the compositor skips the blur.
-    readonly property rect blurRegion: settings.blurBackground && settings.backgroundOpacity < 1
+    readonly property rect blurRegion: !collapsed && settings.blurBackground && settings.backgroundOpacity < 1
         ? Qt.rect(panel.x, panel.y, panel.width, panel.height)
         : Qt.rect(0, 0, 0, 0)
 
     width: 1000
     height: 340 + popupMargin
-    minimumWidth: 480
-    minimumHeight: 180 + popupMargin
+    // None while shrunk to the floating button.
+    minimumWidth: collapsed ? 0 : 480
+    minimumHeight: collapsed ? 0 : 180 + popupMargin
     visible: false
     color: "transparent"
 
     onInputRegionChanged: placement?.setInputRegion(inputRegion)
     onBlurRegionChanged: placement?.setBlurRegion(blurRegion, Theme.windowRadius)
+    // For CollapseController.
+    function dismissKeyRect() {
+        return keyboard.keyRect("dismiss");
+    }
+
     onPlacementChanged: {
         placement?.setInputRegion(inputRegion);
         placement?.setBlurRegion(blurRegion, Theme.windowRadius);
@@ -41,6 +51,7 @@ Window {
     Rectangle {
         id: panel
         anchors { fill: parent; topMargin: root.popupMargin }
+        visible: !root.collapsed
         radius: Theme.windowRadius
         color: Qt.rgba(Theme.background.r, Theme.background.g, Theme.background.b, root.settings.backgroundOpacity)
 
@@ -66,7 +77,7 @@ Window {
             id: handle
             anchors { left: parent.left; right: parent.right; bottom: parent.bottom }
             pillWidth: Math.min(120, width - 2 * (quickToggles.x + quickToggles.width + 12))
-            onDragStarted: root.startSystemMove()
+            onDragStarted: root.placement.startMove()
         }
 
         SettingsButton {
@@ -86,7 +97,20 @@ Window {
 
         ResizeHandle {
             anchors { right: parent.right; bottom: parent.bottom }
-            onDragStarted: root.startSystemResize(Qt.RightEdge | Qt.BottomEdge)
+            onDragStarted: root.placement.startResize(Qt.RightEdge | Qt.BottomEdge)
         }
     }
+
+    FloatingButton {
+        id: floatingButton
+        readonly property rect keyRect: root.collapse?.keyRect ?? Qt.rect(0, 0, 0, 0)
+        // Over the key while the window is full size, then in the shrunk window.
+        x: Math.max(0, Math.min(keyRect.x, root.width - width))
+        y: Math.max(0, Math.min(keyRect.y, root.height - height))
+        width: keyRect.width
+        height: keyRect.height
+        visible: root.collapsed
+        onTapped: root.collapse.expand()
+        onDragStarted: root.placement.startMove()
+    }
 }