Don't assume SurfaceCursorSource has wl_shm buffer

The SurfaceCursorSource assumes that the cursor surface has a wl_shm
buffer attached to it, which is a bad assumption, as the client can
attach a buffer of any type to the surface. Furthermore, the cursor
surface can have custom transforms applied to it, for example a
wp_viewport, which current code fails to handle.

src/cursorsource.cpp

@@ -6,7 +6,6 @@
 
 #include "cursorsource.h"
 #include "cursor.h"
-#include "wayland/shmclientbuffer.h"
 #include "wayland/surface_interface.h"
 
 namespace KWin
@@ -17,11 +16,6 @@ CursorSource::CursorSource(QObject *parent)
 {
 }
 
-QImage CursorSource::image() const
-{
-    return m_image;
-}
-
 QSizeF CursorSource::size() const
 {
     return m_size;
@@ -39,6 +33,11 @@ ShapeCursorSource::ShapeCursorSource(QObject *parent)
     connect(&m_delayTimer, &QTimer::timeout, this, &ShapeCursorSource::selectNextSprite);
 }
 
+QImage ShapeCursorSource::image() const
+{
+    return m_image;
+}
+
 QByteArray ShapeCursorSource::shape() const
 {
     return m_shape;
@@ -124,13 +123,6 @@ KWaylandServer::SurfaceInterface *SurfaceCursorSource::surface() const
 
 void SurfaceCursorSource::refresh()
 {
-    auto buffer = qobject_cast<KWaylandServer::ShmClientBuffer *>(m_surface->buffer());
-    if (buffer) {
-        m_image = buffer->data().copy();
-        m_image.setDevicePixelRatio(m_surface->bufferScale());
-    } else {
-        m_image = QImage();
-    }
     m_size = m_surface->size();
     Q_EMIT changed();
 }
@@ -154,18 +146,10 @@ void SurfaceCursorSource::update(KWaylandServer::SurfaceInterface *surface, cons
         m_surface = surface;
 
         if (m_surface) {
-            auto buffer = qobject_cast<KWaylandServer::ShmClientBuffer *>(surface->buffer());
-            if (buffer) {
-                m_image = buffer->data().copy();
-                m_image.setDevicePixelRatio(surface->bufferScale());
-            } else {
-                m_image = QImage();
-            }
             m_size = surface->size();
 
             connect(m_surface, &KWaylandServer::SurfaceInterface::committed, this, &SurfaceCursorSource::refresh);
         } else {
-            m_image = QImage();
             m_size = QSizeF(0, 0);
         }
     }

src/cursorsource.h

@@ -32,7 +32,6 @@ class KWIN_EXPORT CursorSource : public QObject
 public:
     explicit CursorSource(QObject *parent = nullptr);
 
-    QImage image() const;
     QSizeF size() const;
     QPointF hotspot() const;
 
@@ -40,7 +39,6 @@ Q_SIGNALS:
     void changed();
 
 protected:
-    QImage m_image;
     QSizeF m_size = QSizeF(0, 0);
     QPointF m_hotspot;
 };
@@ -55,6 +53,8 @@ class KWIN_EXPORT ShapeCursorSource : public CursorSource
 public:
     explicit ShapeCursorSource(QObject *parent = nullptr);
 
+    QImage image() const;
+
     QByteArray shape() const;
     void setShape(const QByteArray &shape);
     void setShape(Qt::CursorShape shape);
@@ -71,6 +71,7 @@ private:
     QByteArray m_shape;
     QVector<KXcursorSprite> m_sprites;
     QTimer m_delayTimer;
+    QImage m_image;
     int m_currentSprite = -1;
 };