Move resetOpenGLState out of QQFBO

QQFBO is not the only client of resetOpenGLState. Although in theory
third-party GL code that integrates with QtQuick should reset its
state, in practice it doesn't. By making resetOpenGLState
only available into QQFBO, now we're blocking a Qt5->6 upgrade path.

There's also no compelling reason for this function to be in QQFBO
at all, so move it out to as a free function in a ad-hoc new namespace.

Change-Id: Ic8e5c7e244db37a5b6257d516e6aea3a9db44898
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

1 files changed, 3 insertions, 77 deletions

diff --git a/src/quick/items/qquickframebufferobject.cpp b/src/quick/items/qquickframebufferobject.cpp
index 66fa8818c0..03de94756d 100644
--- a/src/quick/items/qquickframebufferobject.cpp
+++ b/src/quick/items/qquickframebufferobject.cpp
@@ -41,7 +41,6 @@
 
 #include <QOpenGLFramebufferObject>
 #include <QOpenGLFunctions>
-#include <private/qopenglvertexarrayobject_p.h>
 #include <private/qquickitem_p.h>
 #include <private/qsgadaptationlayer_p.h>
 #include <qsgtextureprovider.h>
@@ -49,6 +48,7 @@
 
 #include <QSGSimpleTextureNode>
 #include <QSGRendererInterface>
+#include <QQuickOpenGLUtils>
 
 QT_BEGIN_NAMESPACE
 
@@ -209,7 +209,6 @@ public:
         , renderPending(true)
         , invalidatePending(false)
         , devicePixelRatio(1)
-        , vaoHelper(nullptr)
     {
         qsgnode_set_description(this, QStringLiteral("fbonode"));
     }
@@ -220,7 +219,6 @@ public:
         delete texture();
         delete fbo;
         delete msDisplayFbo;
-        delete vaoHelper;
     }
 
     void scheduleRender()
@@ -241,7 +239,7 @@ public Q_SLOTS:
             renderPending = false;
 
             window->beginExternalCommands();
-            renderer->resetOpenGLState();
+            QQuickOpenGLUtils::resetOpenGLState();
 
             fbo->bind();
             QOpenGLContext::currentContext()->functions()->glViewport(0, 0, fbo->width(), fbo->height());
@@ -277,7 +275,6 @@ public:
     bool invalidatePending;
 
     qreal devicePixelRatio;
-    QOpenGLVertexArrayObjectHelper *vaoHelper;
 };
 
 static inline bool isOpenGL(QSGRenderContext *rc)
@@ -477,7 +474,7 @@ QOpenGLFramebufferObject *QQuickFramebufferObject::Renderer::framebufferObject()
  * context. This means that the state might have been modified by Quick before
  * invoking this function.
  *
- * \note It is recommended to call resetOpenGLState() before
+ * \note It is recommended to call QQuickOpenGLUtils::resetOpenGLState() before
  * returning. This resets OpenGL state used by the Qt Quick renderer and thus
  * avoids interference from the state changes made by the rendering code in this
  * function.
@@ -553,77 +550,6 @@ void QQuickFramebufferObject::Renderer::update()
         ((QSGFramebufferObjectNode *) data)->scheduleRender();
 }
 
-/*!
-    Call this function to reset the OpenGL context its default state.
-
-    The scene graph uses the OpenGL context and will both rely on and
-    clobber its state. When mixing raw OpenGL commands with scene
-    graph rendering, this function provides a convenient way of
-    resetting the OpenGL context state back to its default values.
-
-    This function does not touch state in the fixed-function pipeline.
-
-    \warning This function will only reset the OpenGL context in
-    relation to what may be changed internally as part of the OpenGL
-    scene graph. It does not reset anything that has been changed
-    externally such as direct OpenGL calls done inside the application
-    code if those same calls are not used internally. (for example,
-    various OpenGL 3.x or 4.x specific state)
-
-    \since 6.0
- */
-void QQuickFramebufferObject::Renderer::resetOpenGLState()
-{
-    QOpenGLContext *ctx = QOpenGLContext::currentContext();
-    if (!ctx || !data)
-        return;
-
-    QOpenGLFunctions *gl = ctx->functions();
-
-    gl->glBindBuffer(GL_ARRAY_BUFFER, 0);
-    gl->glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
-
-    QOpenGLVertexArrayObjectHelper *&vaoHelper(static_cast<QSGFramebufferObjectNode *>(data)->vaoHelper);
-    if (!vaoHelper)
-        vaoHelper = new QOpenGLVertexArrayObjectHelper(ctx);
-    if (vaoHelper->isValid())
-        vaoHelper->glBindVertexArray(0);
-
-    if (ctx->isOpenGLES() || (gl->openGLFeatures() & QOpenGLFunctions::FixedFunctionPipeline)) {
-        int maxAttribs;
-        gl->glGetIntegerv(GL_MAX_VERTEX_ATTRIBS, &maxAttribs);
-        for (int i=0; i<maxAttribs; ++i) {
-            gl->glVertexAttribPointer(i, 4, GL_FLOAT, GL_FALSE, 0, nullptr);
-            gl->glDisableVertexAttribArray(i);
-        }
-    }
-
-    gl->glActiveTexture(GL_TEXTURE0);
-    gl->glBindTexture(GL_TEXTURE_2D, 0);
-
-    gl->glDisable(GL_DEPTH_TEST);
-    gl->glDisable(GL_STENCIL_TEST);
-    gl->glDisable(GL_SCISSOR_TEST);
-
-    gl->glColorMask(true, true, true, true);
-    gl->glClearColor(0, 0, 0, 0);
-
-    gl->glDepthMask(true);
-    gl->glDepthFunc(GL_LESS);
-    gl->glClearDepthf(1);
-
-    gl->glStencilMask(0xff);
-    gl->glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
-    gl->glStencilFunc(GL_ALWAYS, 0, 0xff);
-
-    gl->glDisable(GL_BLEND);
-    gl->glBlendFunc(GL_ONE, GL_ZERO);
-
-    gl->glUseProgram(0);
-
-    QOpenGLFramebufferObject::bindDefault();
-}
-
 #include "qquickframebufferobject.moc"
 #include "moc_qquickframebufferobject.cpp"