backends/wayland: Pass linux-dmabuf buffers for cursor layer

This lets us avoid reading fbo data back.

src/backends/wayland/wayland_egl_backend.cpp

@@ -233,8 +233,6 @@ WaylandEglCursorLayer::WaylandEglCursorLayer(WaylandOutput *output, WaylandEglBa
 WaylandEglCursorLayer::~WaylandEglCursorLayer()
 {
     eglMakeCurrent(m_backend->eglDisplay(), EGL_NO_SURFACE, EGL_NO_SURFACE, m_backend->context());
-    m_framebuffer.reset();
-    m_texture.reset();
 }
 
 qreal WaylandEglCursorLayer::scale() const
@@ -275,24 +273,32 @@ std::optional<OutputLayerBeginFrameInfo> WaylandEglCursorLayer::beginFrame()
     }
 
     const QSize bufferSize = m_size.expandedTo(QSize(64, 64));
-    if (!m_texture || m_texture->size() != bufferSize) {
-        m_texture = std::make_unique<GLTexture>(GL_RGBA8, bufferSize);
-        m_framebuffer = std::make_unique<GLFramebuffer>(m_texture.get());
+    if (!m_swapchain || m_swapchain->size() != bufferSize) {
+        const WaylandLinuxDmabufV1 *dmabuf = m_backend->backend()->display()->linuxDmabuf();
+        const uint32_t format = DRM_FORMAT_ARGB8888;
+        if (!dmabuf->formats().contains(format)) {
+            qCCritical(KWIN_WAYLAND_BACKEND) << "DRM_FORMAT_ARGB8888 is unsupported";
+            return std::nullopt;
+        }
+        const QVector<uint64_t> modifiers = dmabuf->formats().value(format);
+        m_swapchain = std::make_unique<WaylandEglLayerSwapchain>(bufferSize, format, modifiers, m_backend);
     }
 
+    m_buffer = m_swapchain->acquire();
     return OutputLayerBeginFrameInfo{
-        .renderTarget = RenderTarget(m_framebuffer.get()),
+        .renderTarget = RenderTarget(m_buffer->framebuffer()),
         .repaint = infiniteRegion(),
     };
 }
 
 bool WaylandEglCursorLayer::endFrame(const QRegion &renderedRegion, const QRegion &damagedRegion)
 {
-    // Technically, we could pass a linux-dmabuf buffer, but host kwin does not support that atm.
-    const QImage image = m_texture->toImage().mirrored(false, true);
-    KWayland::Client::Buffer::Ptr buffer = m_output->backend()->display()->shmPool()->createBuffer(image);
-    m_output->cursor()->update(buffer, m_scale, m_hotspot);
+    // Flush rendering commands to the dmabuf.
+    glFlush();
 
+    m_output->cursor()->update(m_buffer->buffer(), m_scale, m_hotspot);
+
+    m_swapchain->release(m_buffer);
     return true;
 }
 

src/backends/wayland/wayland_egl_backend.h

@@ -115,8 +115,8 @@ public:
 private:
     WaylandOutput *m_output;
     WaylandEglBackend *m_backend;
-    std::unique_ptr<GLFramebuffer> m_framebuffer;
-    std::unique_ptr<GLTexture> m_texture;
+    std::unique_ptr<WaylandEglLayerSwapchain> m_swapchain;
+    std::shared_ptr<WaylandEglLayerBuffer> m_buffer;
     QPoint m_hotspot;
     QSize m_size;
     qreal m_scale = 1.0;

src/backends/wayland/wayland_output.cpp

@@ -83,7 +83,7 @@ void WaylandCursor::disable()
     }
 }
 
-void WaylandCursor::update(KWayland::Client::Buffer::Ptr buffer, qreal scale, const QPoint &hotspot)
+void WaylandCursor::update(wl_buffer *buffer, qreal scale, const QPoint &hotspot)
 {
     if (m_buffer != buffer || m_scale != scale || m_hotspot != hotspot) {
         m_buffer = buffer;

src/backends/wayland/wayland_output.h

@@ -46,7 +46,7 @@ public:
 
     void enable();
     void disable();
-    void update(KWayland::Client::Buffer::Ptr buffer, qreal scale, const QPoint &hotspot);
+    void update(wl_buffer *buffer, qreal scale, const QPoint &hotspot);
 
 private:
     void sync();
@@ -54,7 +54,7 @@ private:
     WaylandBackend *const m_backend;
     KWayland::Client::Pointer *m_pointer = nullptr;
     std::unique_ptr<KWayland::Client::Surface> m_surface;
-    KWayland::Client::Buffer::Ptr m_buffer;
+    wl_buffer *m_buffer = nullptr;
     QPoint m_hotspot;
     qreal m_scale = 1;
     bool m_enabled = true;

src/backends/wayland/wayland_qpainter_backend.cpp

@@ -184,7 +184,7 @@ std::optional<OutputLayerBeginFrameInfo> WaylandQPainterCursorLayer::beginFrame(
 bool WaylandQPainterCursorLayer::endFrame(const QRegion &renderedRegion, const QRegion &damagedRegion)
 {
     KWayland::Client::Buffer::Ptr buffer = m_output->backend()->display()->shmPool()->createBuffer(m_backingStore);
-    m_output->cursor()->update(buffer, m_scale, m_hotspot);
+    m_output->cursor()->update(*buffer.lock(), m_scale, m_hotspot);
     return true;
 }