backends/drm: ensure correct format+modifiers pairs for surfaces

When the crtcs get switched around between outputs, their primary
planes and thus the supported formats also get switched around. In
order to make sure that doesn't cause any problems, always check
whether or not the format+modifiers used are supported.

src/backends/drm/egl_gbm_backend.cpp

@@ -552,6 +552,10 @@ bool EglGbmBackend::doesRenderFit(const Output &output, const Output::RenderData
     if (output.forceXrgb8888 && render.gbmSurface->format() != DRM_FORMAT_XRGB8888) {
         return false;
     }
+    if (!output.output->isFormatSupported(render.gbmSurface->format())
+        || output.output->supportedModifiers(render.gbmSurface->format()) != render.gbmSurface->modifiers()) {
+        return false;
+    }
     QSize surfaceSize = output.output->bufferSize();
     if (surfaceSize != render.gbmSurface->size()) {
         return false;

src/backends/drm/gbm_surface.cpp

@@ -40,6 +40,7 @@ GbmSurface::GbmSurface(DrmGpu *gpu, const QSize &size, uint32_t format, QVector<
     , m_gpu(gpu)
     , m_size(size)
     , m_format(format)
+    , m_modifiers(modifiers)
 {
     if (!m_surface) {
         qCCritical(KWIN_DRM) << "Could not create gbm surface!" << strerror(errno);
@@ -138,4 +139,9 @@ uint32_t GbmSurface::format() const
     return m_format;
 }
 
+QVector<uint64_t> GbmSurface::modifiers() const
+{
+    return m_modifiers;
+}
+
 }

src/backends/drm/gbm_surface.h

@@ -40,6 +40,7 @@ public:
     QSize size() const;
     bool isValid() const;
     uint32_t format() const;
+    QVector<uint64_t> modifiers() const;
 
 private:
     gbm_surface *m_surface;
@@ -47,6 +48,7 @@ private:
     EGLSurface m_eglSurface = EGL_NO_SURFACE;
     QSize m_size;
     const uint32_t m_format;
+    const QVector<uint64_t> m_modifiers;
 
     QSharedPointer<GbmBuffer> m_currentBuffer;
     QSharedPointer<DrmGbmBuffer> m_currentDrmBuffer;