core: Drop Platform::warpPointer()

It's odd to manipulate host cursor position and it's not highly
important, for example we haven't had a need to warp the cursor on
wayland.

The main motivation behind this change is to slim down the Platform to
make it more output oriented.

src/backends/drm/drm_backend.cpp

@@ -77,7 +77,6 @@ DrmBackend::DrmBackend(Session *session, QObject *parent)
     , m_explicitGpus(splitPathList(qEnvironmentVariable("KWIN_DRM_DEVICES"), ':'))
     , m_dpmsFilter()
 {
-    setSupportsPointerWarping(true);
     setSupportsGammaControl(true);
 }
 

src/backends/virtual/virtual_backend.cpp

@@ -30,7 +30,6 @@ VirtualBackend::VirtualBackend(QObject *parent)
         }
     }
 
-    setSupportsPointerWarping(true);
     setSupportsGammaControl(true);
 }
 

src/backends/x11/windowed/x11_windowed_backend.cpp

@@ -155,7 +155,6 @@ void X11WindowedInputBackend::initialize()
 
 X11WindowedBackend::X11WindowedBackend()
 {
-    setSupportsPointerWarping(true);
 }
 
 X11WindowedBackend::~X11WindowedBackend()
@@ -656,13 +655,6 @@ std::unique_ptr<InputBackend> X11WindowedBackend::createInputBackend()
     return std::make_unique<X11WindowedInputBackend>(this);
 }
 
-void X11WindowedBackend::warpPointer(const QPointF &globalPos)
-{
-    const xcb_window_t w = m_outputs.at(0)->window();
-    xcb_warp_pointer(m_connection, w, w, 0, 0, 0, 0, globalPos.x(), globalPos.y());
-    xcb_flush(m_connection);
-}
-
 xcb_window_t X11WindowedBackend::windowForScreen(Output *output) const
 {
     if (!output) {

src/backends/x11/windowed/x11_windowed_backend.h

@@ -117,7 +117,6 @@ public:
     std::unique_ptr<OpenGLBackend> createOpenGLBackend() override;
     std::unique_ptr<QPainterBackend> createQPainterBackend() override;
     std::unique_ptr<InputBackend> createInputBackend() override;
-    void warpPointer(const QPointF &globalPos) override;
 
     QVector<CompositingType> supportedCompositors() const override
     {

src/core/platform.cpp

@@ -134,10 +134,6 @@ void Platform::removeVirtualOutput(Output *output)
     Q_ASSERT(!output);
 }
 
-void Platform::warpPointer(const QPointF &globalPos)
-{
-}
-
 bool Platform::supportsNativeFence() const
 {
     if (Compositor *compositor = Compositor::self()) {

src/core/platform.h

@@ -74,7 +74,6 @@ public:
      * The default implementation creates an InputRedirectionCursor.
      */
     virtual void createPlatformCursor(QObject *parent = nullptr);
-    virtual void warpPointer(const QPointF &globalPos);
     /**
      * Whether our Compositing EGL display supports creating native EGL fences.
      */
@@ -203,10 +202,6 @@ public:
     {
         m_deviceIdentifier = identifier;
     }
-    bool supportsPointerWarping() const
-    {
-        return m_pointerWarping;
-    }
     int initialOutputCount() const
     {
         return m_initialOutputCount;
@@ -304,10 +299,6 @@ protected:
     {
         return m_deviceIdentifier;
     }
-    void setSupportsPointerWarping(bool set)
-    {
-        m_pointerWarping = set;
-    }
     void setSupportsGammaControl(bool set)
     {
         m_supportsGammaControl = set;
@@ -317,7 +308,6 @@ private:
     bool m_ready = false;
     QSize m_initialWindowSize;
     QByteArray m_deviceIdentifier;
-    bool m_pointerWarping = false;
     int m_initialOutputCount = 1;
     qreal m_initialOutputScale = 1;
     EGLDisplay m_eglDisplay;

src/pointer_input.cpp

@@ -815,17 +815,13 @@ void PointerInputRedirection::updateButton(uint32_t button, InputRedirection::Po
 void PointerInputRedirection::warp(const QPointF &pos)
 {
     if (supportsWarping()) {
-        kwinApp()->platform()->warpPointer(pos);
         processMotionAbsolute(pos, waylandServer()->seat()->timestamp());
     }
 }
 
 bool PointerInputRedirection::supportsWarping() const
 {
-    if (!inited()) {
-        return false;
-    }
-    return kwinApp()->platform()->supportsPointerWarping();
+    return inited();
 }
 
 void PointerInputRedirection::updateAfterScreenChange()