backends/drm: move tracking of legacy direct scanout presentation to DrmPipeline

The behavior between direct scanout and normal presentation being different is an
implementation detail of DrmPipeline, the output layers shouldn't need to care

src/backends/drm/drm_egl_layer.cpp

@@ -160,11 +160,6 @@ std::shared_ptr<DrmFramebuffer> EglGbmLayer::currentBuffer() const
     return m_scanoutBuffer ? m_scanoutBuffer : m_surface.currentBuffer();
 }
 
-bool EglGbmLayer::hasDirectScanoutBuffer() const
-{
-    return m_scanoutBuffer != nullptr;
-}
-
 void EglGbmLayer::releaseBuffers()
 {
     m_scanoutBuffer.reset();

src/backends/drm/drm_egl_layer.h

@@ -33,7 +33,6 @@ public:
     bool scanout(SurfaceItem *surfaceItem) override;
     bool checkTestBuffer() override;
     std::shared_ptr<DrmFramebuffer> currentBuffer() const override;
-    bool hasDirectScanoutBuffer() const override;
     QRegion currentDamage() const override;
     std::shared_ptr<GLTexture> texture() const override;
     ColorDescription colorDescription() const;

src/backends/drm/drm_layer.cpp

@@ -31,9 +31,4 @@ DrmPipelineLayer::DrmPipelineLayer(DrmPipeline *pipeline)
     : m_pipeline(pipeline)
 {
 }
-
-bool DrmPipelineLayer::hasDirectScanoutBuffer() const
-{
-    return false;
-}
 }

src/backends/drm/drm_layer.h

@@ -38,7 +38,6 @@ public:
 
     virtual bool checkTestBuffer() = 0;
     virtual std::shared_ptr<DrmFramebuffer> currentBuffer() const = 0;
-    virtual bool hasDirectScanoutBuffer() const;
 
 protected:
     DrmPipeline *const m_pipeline;

src/backends/drm/drm_pipeline.cpp

@@ -70,7 +70,11 @@ bool DrmPipeline::testScanout()
         }
         // no other way to test than to do it.
         // As we only have a maximum of one test per scanout cycle, this is fine
-        return presentLegacy() == Error::None;
+        const bool ret = presentLegacy() == Error::None;
+        if (ret) {
+            m_didLegacyScanoutHack = true;
+        }
+        return ret;
     }
 }
 
@@ -98,8 +102,9 @@ DrmPipeline::Error DrmPipeline::present()
         m_commitThread->addCommit(std::move(primaryPlaneUpdate));
         return Error::None;
     } else {
-        if (m_primaryLayer->hasDirectScanoutBuffer()) {
+        if (m_didLegacyScanoutHack) {
             // already presented
+            m_didLegacyScanoutHack = false;
             return Error::None;
         }
         return presentLegacy();

src/backends/drm/drm_pipeline.h

@@ -167,6 +167,7 @@ private:
     DrmConnector *m_connector = nullptr;
 
     bool m_modesetPresentPending = false;
+    bool m_didLegacyScanoutHack = false;
 
     struct State
     {