Allow to have different clearColor per RenderView

Previously the clearColor was the same for the whole frame using the first
RenderView's clear color. In some cases (FBO rendering) we may want the
renderer to set/update the clear color between RenderViews.

Change-Id: I85318d10a8ae0b03a8e5576ec39e15b14f1bc21d
Reviewed-by: Andy Nichols <andy.nichols@theqtcompany.com>

3 files changed, 18 insertions, 4 deletions

diff --git a/src/render/backend/qgraphicscontext.cpp b/src/render/backend/qgraphicscontext.cpp
index e42bcbfac..1280f8439 100644
--- a/src/render/backend/qgraphicscontext.cpp
+++ b/src/render/backend/qgraphicscontext.cpp
@@ -132,7 +132,7 @@ void QGraphicsContext::initialize()
     qCDebug(Backend) << "VAO support = " << m_supportsVAO;
 }
 
-bool QGraphicsContext::beginDrawing(QSurface *surface, const QColor &clearColor)
+bool QGraphicsContext::beginDrawing(QSurface *surface, const QColor &color)
 {
     Q_ASSERT(surface);
     Q_ASSERT(m_gl);
@@ -156,7 +156,7 @@ bool QGraphicsContext::beginDrawing(QSurface *surface, const QColor &clearColor)
         initialize();
     }
 
-    m_gl->functions()->glClearColor(clearColor.redF(), clearColor.greenF(), clearColor.blueF(), clearColor.alphaF());
+    clearColor(color);
 
     if (m_activeShader)
         m_activeShader = NULL;
@@ -651,6 +651,11 @@ GLuint QGraphicsContext::boundFrameBufferObject()
     return m_glHelper->boundFrameBufferObject();
 }
 
+void QGraphicsContext::clearColor(const QColor &color)
+{
+    m_gl->functions()->glClearColor(color.redF(), color.greenF(), color.blueF(), color.alphaF());
+}
+
 /*!
     \internal
     \returns a texture unit for a texture, -1 if all texture units are assigned.
diff --git a/src/render/backend/qgraphicscontext_p.h b/src/render/backend/qgraphicscontext_p.h
index b2796e72e..33eaff7a3 100644
--- a/src/render/backend/qgraphicscontext_p.h
+++ b/src/render/backend/qgraphicscontext_p.h
@@ -90,7 +90,7 @@ public:
 
     int id() const; // unique, small integer ID of this context
 
-    bool beginDrawing(QSurface *surface, const QColor &clearColor);
+    bool beginDrawing(QSurface *surface, const QColor &color);
     void clearBackBuffer(QClearBuffer::BufferType buffers);
     void endDrawing(bool swapBuffers);
 
@@ -178,6 +178,7 @@ public:
     void    enableAlphaCoverage();
     void    disableAlphaCoverage();
     GLuint  boundFrameBufferObject();
+    void    clearColor(const QColor &color);
 
     // Helper methods
     static GLint elementType(GLint type);
diff --git a/src/render/backend/renderer.cpp b/src/render/backend/renderer.cpp
index f11f0e2df..78805c47e 100644
--- a/src/render/backend/renderer.cpp
+++ b/src/render/backend/renderer.cpp
@@ -596,8 +596,9 @@ void Renderer::submitRenderViews(int maxFrameCount)
         if (renderViewsCount <= 0)
             continue;
 
+        QColor previousClearColor = renderViews.first()->clearColor();
         // Bail out if we cannot make the OpenGL context current (e.g. if the window has been destroyed)
-        if (!m_graphicsContext->beginDrawing(m_surface, renderViews.first()->clearColor())) {
+        if (!m_graphicsContext->beginDrawing(m_surface, previousClearColor)) {
             qDeleteAll(renderViews);
             m_renderQueues->popFrameQueue();
             break;
@@ -622,6 +623,13 @@ void Renderer::submitRenderViews(int maxFrameCount)
             // Activate RenderTarget
             m_graphicsContext->activateRenderTarget(m_renderTargetManager->data(renderViews[i]->renderTargetHandle()),
                                                     renderViews[i]->attachmentPack(), defaultFboId);
+
+            // Set clear color if different
+            if (previousClearColor != renderViews[i]->clearColor()) {
+                previousClearColor = renderViews[i]->clearColor();
+                m_graphicsContext->clearColor(previousClearColor);
+            }
+
             // Clear BackBuffer
             m_graphicsContext->clearBackBuffer(renderViews[i]->clearBuffer());
             // Set the Viewport