Fixed GL2 engine shader manager to work with more than one context.

I added a QGLContextResource class which can be used internally in Qt
for sharing resources between contexts. The QGLContextResource is a
hash map where the context is used as 'key', and the resource is the
'value'. All the sharing contexts point to the same resource, and the
resource is automatically deleted when it is not referenced any more.
Now, the shader manager uses the QGLContextResource class.

I also added a pointer to a struct in the QGLContextPrivate class. The
struct is shared between all the sharing contexts and is deleted
automatically. Currently, the struct only contains the resolved OpenGL
function pointers.

The shared context register code has been simplified.

Reviewed-by: Tom

3 files changed, 27 insertions, 9 deletions

diff --git a/src/opengl/gl2paintengineex/qglengineshadermanager.cpp b/src/opengl/gl2paintengineex/qglengineshadermanager.cpp
index 27636f4..d7c91b8 100644
--- a/src/opengl/gl2paintengineex/qglengineshadermanager.cpp
+++ b/src/opengl/gl2paintengineex/qglengineshadermanager.cpp
@@ -49,6 +49,28 @@
 
 QT_BEGIN_NAMESPACE
 
+static void QGLEngineShaderManager_free(void *ptr)
+{
+    delete reinterpret_cast<QGLEngineShaderManager *>(ptr);
+}
+
+Q_GLOBAL_STATIC_WITH_ARGS(QGLContextResource, qt_shader_managers, (QGLEngineShaderManager_free))
+
+QGLEngineShaderManager *QGLEngineShaderManager::managerForContext(const QGLContext *context)
+{
+    QGLEngineShaderManager *p = reinterpret_cast<QGLEngineShaderManager *>(qt_shader_managers()->value(context));
+    if (!p) {
+        QGLContext *oldContext = const_cast<QGLContext *>(QGLContext::currentContext());
+        if (oldContext != context)
+            const_cast<QGLContext *>(context)->makeCurrent();
+        p = new QGLEngineShaderManager(const_cast<QGLContext *>(context));
+        qt_shader_managers()->insert(context, p);
+        if (oldContext && oldContext != context)
+            oldContext->makeCurrent();
+    }
+    return p;
+}
+
 const char* QGLEngineShaderManager::qglEngineShaderSourceCode[] = {
     0,0,0,0,0,0,0,0,0,0,
     0,0,0,0,0,0,0,0,0,0,
diff --git a/src/opengl/gl2paintengineex/qglengineshadermanager_p.h b/src/opengl/gl2paintengineex/qglengineshadermanager_p.h
index 442edfe..99711bd40 100644
--- a/src/opengl/gl2paintengineex/qglengineshadermanager_p.h
+++ b/src/opengl/gl2paintengineex/qglengineshadermanager_p.h
@@ -220,6 +220,7 @@
 #include <QGLShader>
 #include <QGLShaderProgram>
 #include <QPainter>
+#include <private/qgl_p.h>
 
 QT_BEGIN_HEADER
 
@@ -314,6 +315,8 @@ public:
     QGLShaderProgram* simpleProgram(); // Used to draw into e.g. stencil buffers
     QGLShaderProgram* blitProgram(); // Used to blit a texture into the framebuffer
 
+    static QGLEngineShaderManager *managerForContext(const QGLContext *context);
+
     enum ShaderName {
         MainVertexShader,
         MainWithTexCoordsVertexShader,
diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index 2bfbf4a..9b0321d 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -266,10 +266,6 @@ extern QImage qt_imageForBrush(int brushStyle, bool invert);
 
 QGL2PaintEngineExPrivate::~QGL2PaintEngineExPrivate()
 {
-    if (shaderManager) {
-        delete shaderManager;
-        shaderManager = 0;
-    }
 }
 
 void QGL2PaintEngineExPrivate::updateTextureFilter(GLenum target, GLenum wrapMode, bool smoothPixmapTransform, GLuint id)
@@ -1209,11 +1205,8 @@ bool QGL2PaintEngineEx::begin(QPaintDevice *pdev)
     qt_resolve_version_2_0_functions(d->ctx);
 #endif
 
-    if (d->shaderManager) {
-        d->shaderManager->setDirty();
-    } else {
-        d->shaderManager = new QGLEngineShaderManager(d->ctx);
-    }
+    d->shaderManager = QGLEngineShaderManager::managerForContext(d->ctx);
+    d->shaderManager->setDirty();
 
     glViewport(0, 0, d->width, d->height);