Observe GL context loss in ShaderEffectItem

This is a backport of commit: 01928c91ff0ae76cdb02f50af3c62368e28cafb6
with change id: I8281e77f7285ea0046bdf092ab827cae3b00a6d2
from qt5/qtquick1 to qt4.

Task-number: QTBUG-28136
Change-Id: Idbeffce919d85f55df5184f8a8c9a89649687f93
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>

2 files changed, 7 insertions, 38 deletions

diff --git a/src/imports/shaders/shadereffectitem.cpp b/src/imports/shaders/shadereffectitem.cpp
index 330cc85..ab2698b 100644
--- a/src/imports/shaders/shadereffectitem.cpp
+++ b/src/imports/shaders/shadereffectitem.cpp
@@ -199,10 +199,6 @@ Rectangle {
 
 */
 
-#ifdef Q_OS_SYMBIAN
-#define OBSERVE_GL_CONTEXT_LOSS 1
-#endif
-
 ShaderEffectItem::ShaderEffectItem(QDeclarativeItem *parent)
     : QDeclarativeItem(parent)
     , m_program(0)
@@ -219,21 +215,15 @@ ShaderEffectItem::ShaderEffectItem(QDeclarativeItem *parent)
     , m_hasShaderPrograms(false)
     , m_mirrored(false)
     , m_defaultVertexShader(true)
-    , m_contextObserver(0)
 {
     setFlag(QGraphicsItem::ItemHasNoContents, false);
     connect(this, SIGNAL(visibleChanged()), this, SLOT(handleVisibilityChange()));
     m_active = isVisible();
-
-#ifndef OBSERVE_GL_CONTEXT_LOSS
-    m_program = new QGLShaderProgram(this);
-#endif
 }
 
 ShaderEffectItem::~ShaderEffectItem()
 {
     reset();
-    delete m_contextObserver;
 }
 
 
@@ -413,30 +403,15 @@ void ShaderEffectItem::renderEffect(QPainter *painter, const QMatrix4x4 &matrix)
     if (!painter || !painter->device())
         return;
 
-#ifdef OBSERVE_GL_CONTEXT_LOSS
-    QGLContext *context = const_cast <QGLContext*> (QGLContext::currentContext());
-    if (!m_program || !m_contextObserver || !m_contextObserver->isValid()) {
-        // Context has changed, re-create QGLShaderProgram
-        if (context) {
-            delete m_program;
-            m_program = 0;
-
-            delete m_contextObserver;
-            m_contextObserver = 0;
-
+    if (!m_program || !m_program->programId()) {
+        // Deleted due to deactivation, to save GPU memory,
+        // or invalidated due to GL context change.
+        delete m_program;
+        if (QGLContext::currentContext())
             m_program = new QGLShaderProgram(this);
-            m_contextObserver = new QGLFramebufferObject(QSize(2,2));
-
-            if (!m_contextObserver || !m_program) {
-                delete m_program;
-                m_program = 0;
-                delete m_contextObserver;
-                m_contextObserver = 0;
-                qWarning() << "ShaderEffectItem::renderEffect - Creating QGLShaderProgram or QGLFrameBufferObject failed!";
-            }
-        }
+        if (!m_program)
+            qWarning() << "ShaderEffectItem::renderEffect - Creating QGLShaderProgram failed!";
     }
-#endif
 
     if (!m_program)
         return;
@@ -683,14 +658,10 @@ void ShaderEffectItem::setActive(bool enable)
     }
 
     // QGLShaderProgram is deleted when not active (to minimize GPU memory usage).
-#ifdef OBSERVE_GL_CONTEXT_LOSS
     if (!m_active && m_program) {
         delete m_program;
         m_program = 0;
-        delete m_contextObserver;
-        m_contextObserver = 0;
     }
-#endif
 
     emit activeChanged();
     markDirty();
diff --git a/src/imports/shaders/shadereffectitem.h b/src/imports/shaders/shadereffectitem.h
index 5260cdc..a32e7dc 100644
--- a/src/imports/shaders/shadereffectitem.h
+++ b/src/imports/shaders/shadereffectitem.h
@@ -143,8 +143,6 @@ private:
     bool m_hasShaderPrograms : 1;
     bool m_mirrored : 1;
     bool m_defaultVertexShader : 1;
-
-    QGLFramebufferObject* m_contextObserver;
 };
 
 QT_END_HEADER