Fix for current_fbo getting out of sync in QtOpenGL

When using QGLWidget in combination with QOpenGLFramebufferObject from
QtGui, instead of QGLFramebufferObject from QtOpenGL, the current_fbo
variable doesn't get updated when framebuffer object bindings change.

To ensure that the QGLWidget correctly releases the currently bound
framebuffer object when using a QPainter, we keep track of whether
QOpenGLFramebufferObject has modified the current FBO binding, and if
that's the case we need to read the OpenGL state directly instead of
relying on a cached value.

Change-Id: If7e0bd936e202cad07365b5ce641ee01d2251930
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index 1e49d95087..35f08e0092 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -510,6 +510,35 @@ void QGLContextPrivate::setupSharing() {
     }
 }
 
+void QGLContextPrivate::refreshCurrentFbo()
+{
+    QOpenGLContextPrivate *guiGlContextPrivate =
+        guiGlContext ? QOpenGLContextPrivate::get(guiGlContext) : 0;
+
+    // if QOpenGLFramebufferObjects have been used in the mean-time, we've lost our cached value
+    if (guiGlContextPrivate && guiGlContextPrivate->qgl_current_fbo_invalid) {
+        GLint current;
+        QOpenGLFunctions *funcs = qgl_functions();
+        funcs->glGetIntegerv(GL_FRAMEBUFFER_BINDING, &current);
+
+        current_fbo = current;
+
+        guiGlContextPrivate->qgl_current_fbo_invalid = false;
+    }
+}
+
+void QGLContextPrivate::setCurrentFbo(GLuint fbo)
+{
+    current_fbo = fbo;
+
+    QOpenGLContextPrivate *guiGlContextPrivate =
+        guiGlContext ? QOpenGLContextPrivate::get(guiGlContext) : 0;
+
+    if (guiGlContextPrivate)
+        guiGlContextPrivate->qgl_current_fbo_invalid = false;
+}
+
+
 /*!
     \fn bool QGLFormat::doubleBuffer() const