Cache the current QOpenGLFramebufferObject

This doesn't cover FBOs bound directly with glBindFramebuffer(),
but it's perfect to create a fast path for code we know uses QOGLFBO,
thus avoiding expensive glGetIntegerv() driver calls.

The use case is to use this in QSG24BitTextMaskShader::activate(), where
we need to check if the current FBO is sRGB capable.

Change-Id: I434eeeb7e6a3d16be9327315536ad7280245085d
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/gui/kernel/qopenglcontext_p.h b/src/gui/kernel/qopenglcontext_p.h
index 4a746bf12b..7c8c698a7d 100644
--- a/src/gui/kernel/qopenglcontext_p.h
+++ b/src/gui/kernel/qopenglcontext_p.h
@@ -61,6 +61,7 @@ QT_BEGIN_NAMESPACE
 
 class QOpenGLFunctions;
 class QOpenGLContext;
+class QOpenGLFramebufferObject;
 class QOpenGLMultiGroupSharedResource;
 
 class Q_GUI_EXPORT QOpenGLSharedResource
@@ -204,6 +205,7 @@ public:
         , workaround_missingPrecisionQualifiers(false)
         , active_engine(0)
         , qgl_current_fbo_invalid(false)
+        , qgl_current_fbo(Q_NULLPTR)
         , defaultFboRedirect(0)
     {
         requestedFormat = QSurfaceFormat::defaultFormat();
@@ -242,6 +244,11 @@ public:
 
     bool qgl_current_fbo_invalid;
 
+    // Set and unset in QOpenGLFramebufferObject::bind()/unbind().
+    // (Only meaningful for QOGLFBO since an FBO might be bound by other means)
+    // Saves us from querying the driver for the current FBO in most paths.
+    QOpenGLFramebufferObject *qgl_current_fbo;
+
     QVariant nativeHandle;
     GLuint defaultFboRedirect;