only create the FBO once, or recreate if the size has changed

widgets/glWidget/QtBaseViewer.cc

@@ -138,6 +138,7 @@ glViewer::glViewer( QGraphicsScene* _scene,
   glDebugLogger_(0),
 #endif
   pickCache_(0),
+  mouseCache_(0),
   updatePickCache_(true),
   pickCacheSupported_(true),
   constrainedRotationAxis_(std::numeric_limits<double>::quiet_NaN(), 0, 0),
@@ -217,6 +218,8 @@ glViewer::~glViewer()
   delete glstate_;
 
   deleteGLDebugLogger();
+  if (mouseCache_ != nullptr)
+      deleteQFBO(mouseCache_);
 }
 
 
@@ -1571,10 +1574,24 @@ void glViewer::mousePressEvent(QGraphicsSceneMouseEvent* _e)
 
   emit signalMakeActive();
   const GLuint prevFBO = ACG::GLState::getFramebufferDraw();
-  QFramebufferObject* nonMultisampledFBO;
-  GLuint fboHandle;
-  int samples = 0;
-  createQFBO(nonMultisampledFBO,&fboHandle,glWidth(),glHeight(),&samples);
+  static unsigned int creationHeight = 0;
+  static unsigned int creationWidth = 0;
+  static GLuint fboHandle;
+  //recreate FBO if gl area was resized
+  if (mouseCache_ != nullptr && (glWidth() != creationWidth || glHeight() != creationHeight))
+  {
+      deleteQFBO(mouseCache_);
+      mouseCache_ = nullptr;
+  }
+
+  if (mouseCache_ == nullptr)
+  {
+      int samples = 0;
+      creationHeight = glHeight();
+      creationWidth = glWidth();
+      createQFBO(mouseCache_, &fboHandle, creationWidth, creationHeight, &samples);
+  }
+
   ACG::GLState::bindFramebuffer(GL_FRAMEBUFFER_EXT, fboHandle);
   glScene_->update ();
 
@@ -1617,8 +1634,6 @@ void glViewer::mousePressEvent(QGraphicsSceneMouseEvent* _e)
   }
   //restore old FBO
   ACG::GLState::bindFramebuffer(GL_FRAMEBUFFER_EXT,prevFBO);
-  //cleanup
-  deleteQFBO(nonMultisampledFBO);
 }
 
 

widgets/glWidget/QtBaseViewer.hh

@@ -889,6 +889,7 @@ private:
 
     /// Framebuffer object that holds the pick cache
     QFramebufferObject* pickCache_;
+    QFramebufferObject* mouseCache_;
 
     /// Should the pick cache be updated
     bool updatePickCache_;