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, 13 insertions, 4 deletions

diff --git a/src/opengl/qglframebufferobject.cpp b/src/opengl/qglframebufferobject.cpp
index 4ef50e9334..49b28c36b9 100644
--- a/src/opengl/qglframebufferobject.cpp
+++ b/src/opengl/qglframebufferobject.cpp
@@ -472,6 +472,8 @@ void QGLFramebufferObjectPrivate::init(QGLFramebufferObject *q, const QSize &sz,
     if (!funcs.hasOpenGLFeature(QOpenGLFunctions::Framebuffers))
         return;
 
+    ctx->d_ptr->refreshCurrentFbo();
+
     size = sz;
     target = texture_target;
     // texture dimensions
@@ -1027,7 +1029,7 @@ bool QGLFramebufferObject::bind()
     d->funcs.glBindFramebuffer(GL_FRAMEBUFFER, d->fbo());
     d->valid = d->checkFramebufferStatus();
     if (d->valid && current)
-        current->d_ptr->current_fbo = d->fbo();
+        current->d_ptr->setCurrentFbo(d->fbo());
     return d->valid;
 }
 
@@ -1060,7 +1062,7 @@ bool QGLFramebufferObject::release()
 #endif
 
     if (current) {
-        current->d_ptr->current_fbo = current->d_ptr->default_fbo;
+        current->d_ptr->setCurrentFbo(current->d_ptr->default_fbo);
         d->funcs.glBindFramebuffer(GL_FRAMEBUFFER, current->d_ptr->default_fbo);
     }
 
@@ -1173,7 +1175,7 @@ bool QGLFramebufferObject::bindDefault()
         if (!functions.hasOpenGLFeature(QOpenGLFunctions::Framebuffers))
             return false;
 
-        ctx->d_ptr->current_fbo = ctx->d_ptr->default_fbo;
+        ctx->d_ptr->setCurrentFbo(ctx->d_ptr->default_fbo);
         functions.glBindFramebuffer(GL_FRAMEBUFFER, ctx->d_ptr->default_fbo);
 #ifdef QT_DEBUG
     } else {
@@ -1320,7 +1322,12 @@ bool QGLFramebufferObject::isBound() const
 {
     Q_D(const QGLFramebufferObject);
     const QGLContext *current = QGLContext::currentContext();
-    return current ? current->d_ptr->current_fbo == d->fbo() : false;
+    if (current) {
+        current->d_ptr->refreshCurrentFbo();
+        return current->d_ptr->current_fbo == d->fbo();
+    }
+
+    return false;
 }
 
 /*!
@@ -1400,6 +1407,8 @@ void QGLFramebufferObject::blitFramebuffer(QGLFramebufferObject *target, const Q
     const int ty0 = th - (targetRect.top() + targetRect.height());
     const int ty1 = th - targetRect.top();
 
+    ctx->d_ptr->refreshCurrentFbo();
+
     functions.glBindFramebuffer(GL_READ_FRAMEBUFFER, source ? source->handle() : 0);
     functions.glBindFramebuffer(GL_DRAW_FRAMEBUFFER, target ? target->handle() : 0);