backends/drm: restrict damage area to the screen's size

Scissor rectangles going outside of the framebuffer cause OpenGL warnings

BUG: 492152

src/backends/drm/drm_egl_layer_surface.cpp

@@ -193,7 +193,7 @@ bool EglGbmLayerSurface::endRendering(const QRegion &damagedRegion, OutputFrame
         m_surface->shadowDamageJournal.add(damagedRegion);
         QRegion repaint;
         for (const QRect &rect : logicalRepaint) {
-            repaint |= scaledRect(rect, m_surface->scale).toAlignedRect();
+            repaint |= scaledRect(rect, m_surface->scale).toAlignedRect() & QRect(QPoint(), m_surface->gbmSwapchain->size());
         }
 
         GLFramebuffer *fbo = m_surface->currentSlot->framebuffer();
@@ -609,7 +609,7 @@ std::shared_ptr<DrmFramebuffer> EglGbmLayerSurface::importWithEgl(Surface *surfa
     for (const QRect &logical : damagedRegion) {
         deviceDamage |= scaledRect(logical, surface->scale).toAlignedRect();
     }
-    const QRegion repaint = deviceDamage | surface->importDamageJournal.accumulate(slot->age(), infiniteRegion());
+    const QRegion repaint = (deviceDamage | surface->importDamageJournal.accumulate(slot->age(), infiniteRegion())) & QRect(QPoint(), m_surface->gbmSwapchain->size());
     surface->importDamageJournal.add(deviceDamage);
 
     GLFramebuffer *fbo = slot->framebuffer();