CpuTextureManager: Use a single FBO for all textures

Author: adazem009

src/cputexturemanager.cpp

@@ -164,15 +164,27 @@ bool CpuTextureManager::readTexture(
     QOpenGLFunctions glF;
     glF.initializeOpenGLFunctions();
 
-    // Create a FBO for the texture
-    unsigned int fbo;
-    glF.glGenFramebuffers(1, &fbo);
-    glF.glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+    // Create global FBO
+    if (m_fbo == 0) {
+        glF.glGenFramebuffers(1, &m_fbo);
+
+        QObject::connect(QOpenGLContext::currentContext(), &QOpenGLContext::aboutToBeDestroyed, []() {
+            if (QOpenGLContext::currentContext()) {
+                QOpenGLFunctions glF;
+                glF.initializeOpenGLFunctions();
+                glF.glDeleteFramebuffers(1, &m_fbo);
+                m_fbo = 0;
+            }
+        });
+    }
+
+    // Bind the texture to the global FBO
+    glF.glBindFramebuffer(GL_FRAMEBUFFER, m_fbo);
     glF.glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, handle, 0);
 
     if (glF.glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
         qWarning() << "error: framebuffer incomplete (CpuTextureManager)";
-        glF.glDeleteFramebuffers(1, &fbo);
+        glF.glBindFramebuffer(GL_FRAMEBUFFER, 0);
         return false;
     }
 
@@ -310,7 +322,6 @@ bool CpuTextureManager::readTexture(
 
     // Cleanup
     glF.glBindFramebuffer(GL_FRAMEBUFFER, 0);
-    glF.glDeleteFramebuffers(1, &fbo);
 
     return true;
 }

src/cputexturemanager.h

@@ -42,6 +42,7 @@ class CpuTextureManager
             GLubyte **data,
             std::vector<QPoint> &points) const;
 
+        static inline GLuint m_fbo = 0;          // single FBO for all texture managers
         std::unordered_map<GLuint, GLubyte *> m_textureData;
         std::unordered_map<GLuint, std::vector<QPoint>> m_convexHullPoints;
 };

test/texture/cputexturemanager_test.cpp

@@ -130,6 +130,7 @@ TEST_F(CpuTextureManagerTest, TextureDataAndHullPoints)
     ASSERT_EQ(hullPoints, refHullPoints2);
 
     // Cleanup
+    emit context.aboutToBeDestroyed();
     context.doneCurrent();
 }
 
@@ -175,6 +176,7 @@ TEST_F(CpuTextureManagerTest, GetPointColor)
     // TODO: Test point transform (graphic effects that change shape)
 
     // Cleanup
+    emit context.aboutToBeDestroyed();
     context.doneCurrent();
 }
 
@@ -219,5 +221,6 @@ TEST_F(CpuTextureManagerTest, TextureContainsPoint)
     // TODO: Test point transform (graphic effects that change shape)
 
     // Cleanup
+    emit context.aboutToBeDestroyed();
     context.doneCurrent();
 }