Drop support for X11 overlay windows in QPainter render backend

It's unused.

platformsupport/scenes/qpainter/backend.cpp

@@ -23,15 +23,6 @@ QPainterBackend::~QPainterBackend()
 {
 }
 
-OverlayWindow* QPainterBackend::overlayWindow()
-{
-    return nullptr;
-}
-
-void QPainterBackend::showOverlay()
-{
-}
-
 void QPainterBackend::screenGeometryChanged(const QSize &size)
 {
     Q_UNUSED(size)

platformsupport/scenes/qpainter/backend.h

@@ -14,33 +14,15 @@ class QRegion;
 class QSize;
 class QString;
 
-namespace KWin {
-class OverlayWindow;
+namespace KWin
+{
 
 class QPainterBackend
 {
 public:
     virtual ~QPainterBackend();
     virtual void present(int mask, const QRegion &damage) = 0;
-
-    /**
-     * @brief Returns the OverlayWindow used by the backend.
-     *
-     * A backend does not have to use an OverlayWindow, this is mostly for the X world.
-     * In case the backend does not use an OverlayWindow it is allowed to return @c null.
-     * It's the task of the caller to check whether it is @c null.
-     *
-     * @return :OverlayWindow*
-     */
-    virtual OverlayWindow *overlayWindow();
-    virtual bool usesOverlayWindow() const = 0;
     virtual void prepareRenderingFrame() = 0;
-    /**
-     * @brief Shows the Overlay Window
-     *
-     * Default implementation does nothing.
-     */
-    virtual void showOverlay();
     /**
      * @brief React on screen geometry changes.
      *

plugins/platforms/drm/scene_qpainter_drm_backend.cpp

@@ -124,11 +124,6 @@ void DrmQPainterBackend::present(int mask, const QRegion &damage)
     }
 }
 
-bool DrmQPainterBackend::usesOverlayWindow() const
-{
-    return false;
-}
-
 bool DrmQPainterBackend::perScreenRendering() const
 {
     return true;

plugins/platforms/drm/scene_qpainter_drm_backend.h

@@ -30,7 +30,6 @@ public:
     QImage *buffer() override;
     QImage *bufferForScreen(int screenId) override;
     bool needsFullRepaint() const override;
-    bool usesOverlayWindow() const override;
     void prepareRenderingFrame() override;
     void present(int mask, const QRegion &damage) override;
     bool perScreenRendering() const override;

plugins/platforms/fbdev/scene_qpainter_fb_backend.cpp

@@ -82,11 +82,6 @@ void FramebufferQPainterBackend::present(int mask, const QRegion &damage)
     p.drawImage(QPoint(0, 0), m_backend->isBGR() ? m_renderBuffer.rgbSwapped() : m_renderBuffer);
 }
 
-bool FramebufferQPainterBackend::usesOverlayWindow() const
-{
-    return false;
-}
-
 bool FramebufferQPainterBackend::perScreenRendering() const
 {
     return true;

plugins/platforms/fbdev/scene_qpainter_fb_backend.h

@@ -27,7 +27,6 @@ public:
     QImage *buffer() override;
     QImage *bufferForScreen(int screenId) override;
     bool needsFullRepaint() const override;
-    bool usesOverlayWindow() const override;
     void prepareRenderingFrame() override;
     void present(int mask, const QRegion &damage) override;
     bool perScreenRendering() const override;

plugins/platforms/virtual/scene_qpainter_virtual_backend.cpp

@@ -65,11 +65,6 @@ void VirtualQPainterBackend::present(int mask, const QRegion &damage)
     }
 }
 
-bool VirtualQPainterBackend::usesOverlayWindow() const
-{
-    return false;
-}
-
 bool VirtualQPainterBackend::perScreenRendering() const
 {
     return true;

plugins/platforms/virtual/scene_qpainter_virtual_backend.h

@@ -29,7 +29,6 @@ public:
     QImage *buffer() override;
     QImage *bufferForScreen(int screenId) override;
     bool needsFullRepaint() const override;
-    bool usesOverlayWindow() const override;
     void prepareRenderingFrame() override;
     void present(int mask, const QRegion &damage) override;
     bool perScreenRendering() const override;

plugins/platforms/wayland/scene_qpainter_wayland_backend.cpp

@@ -142,11 +142,6 @@ WaylandQPainterBackend::~WaylandQPainterBackend()
 {
 }
 
-bool WaylandQPainterBackend::usesOverlayWindow() const
-{
-    return false;
-}
-
 bool WaylandQPainterBackend::perScreenRendering() const
 {
     return true;

plugins/platforms/wayland/scene_qpainter_wayland_backend.h

@@ -64,8 +64,6 @@ public:
     explicit WaylandQPainterBackend(WaylandBackend *b);
     ~WaylandQPainterBackend() override;
 
-    bool usesOverlayWindow() const override;
-
     QImage *buffer() override;
     QImage *bufferForScreen(int screenId) override;
 

plugins/platforms/x11/windowed/scene_qpainter_x11_backend.cpp

@@ -80,11 +80,6 @@ void X11WindowedQPainterBackend::present(int mask, const QRegion &damage)
     }
 }
 
-bool X11WindowedQPainterBackend::usesOverlayWindow() const
-{
-    return false;
-}
-
 bool X11WindowedQPainterBackend::perScreenRendering() const
 {
     return true;

plugins/platforms/x11/windowed/scene_qpainter_x11_backend.h

@@ -32,7 +32,6 @@ public:
     QImage *buffer() override;
     QImage *bufferForScreen(int screenId) override;
     bool needsFullRepaint() const override;
-    bool usesOverlayWindow() const override;
     void prepareRenderingFrame() override;
     void present(int mask, const QRegion &damage) override;
     bool perScreenRendering() const override;

plugins/scenes/qpainter/scene_qpainter.cpp

@@ -117,7 +117,6 @@ qint64 SceneQPainter::paint(const QRegion &_damage, const QList<Toplevel *> &top
         m_painter->restore();
         m_painter->end();
     }
-    m_backend->showOverlay();
     m_backend->present(mask, overallUpdate);
 
     // do cleanup

plugins/scenes/qpainter/scene_qpainter.h

@@ -169,13 +169,13 @@ public:
 inline
 bool SceneQPainter::usesOverlayWindow() const
 {
-    return m_backend->usesOverlayWindow();
+    return false;
 }
 
 inline
 OverlayWindow* SceneQPainter::overlayWindow() const
 {
-    return m_backend->overlayWindow();
+    return nullptr;
 }
 
 inline