virtual: fix screencasting by output

Properly notify when the output changes.
Forward the texture that holds the output when requested.

src/backends/virtual/virtual_egl_backend.cpp

@@ -32,9 +32,9 @@ VirtualEglLayer::VirtualEglLayer(Output *output, VirtualEglBackend *backend)
 
 VirtualEglLayer::~VirtualEglLayer() = default;
 
-GLTexture *VirtualEglLayer::texture() const
+std::shared_ptr<GLTexture> VirtualEglLayer::texture() const
 {
-    return m_texture.get();
+    return m_texture;
 }
 
 std::optional<OutputLayerBeginFrameInfo> VirtualEglLayer::beginFrame()
@@ -57,6 +57,7 @@ std::optional<OutputLayerBeginFrameInfo> VirtualEglLayer::beginFrame()
 bool VirtualEglLayer::endFrame(const QRegion &renderedRegion, const QRegion &damagedRegion)
 {
     glFlush(); // flush pending rendering commands.
+    Q_EMIT m_output->outputChange(damagedRegion);
     return true;
 }
 
@@ -202,4 +203,13 @@ void VirtualEglBackend::present(Output *output)
     static_cast<VirtualOutput *>(output)->vsyncMonitor()->arm();
 }
 
+std::shared_ptr<GLTexture> VirtualEglBackend::textureForOutput(Output *output) const
+{
+    auto it = m_outputs.find(output);
+    if (it == m_outputs.end()) {
+        return nullptr;
+    }
+    return it->second->texture();
+}
+
 } // namespace

src/backends/virtual/virtual_egl_backend.h

@@ -10,6 +10,7 @@
 
 #include "abstract_egl_backend.h"
 #include "core/outputlayer.h"
+#include <memory>
 
 namespace KWin
 {
@@ -27,13 +28,13 @@ public:
     std::optional<OutputLayerBeginFrameInfo> beginFrame() override;
     bool endFrame(const QRegion &renderedRegion, const QRegion &damagedRegion) override;
 
-    GLTexture *texture() const;
+    std::shared_ptr<GLTexture> texture() const;
 
 private:
     VirtualEglBackend *const m_backend;
     Output *m_output;
     std::unique_ptr<GLFramebuffer> m_fbo;
-    std::unique_ptr<GLTexture> m_texture;
+    std::shared_ptr<GLTexture> m_texture;
 };
 
 /**
@@ -48,6 +49,7 @@ public:
     ~VirtualEglBackend() override;
     std::unique_ptr<SurfaceTexture> createSurfaceTextureInternal(SurfacePixmapInternal *pixmap) override;
     std::unique_ptr<SurfaceTexture> createSurfaceTextureWayland(SurfacePixmapWayland *pixmap) override;
+    std::shared_ptr<GLTexture> textureForOutput(Output *output) const override;
     OutputLayer *primaryLayer(Output *output) override;
     void present(Output *output) override;
     void init() override;