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

6 files changed, 228 insertions, 63 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);
 
diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index 0169ea2..f51b271 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -3363,8 +3363,13 @@ bool QGLWidget::event(QEvent *e)
 #elif defined(Q_WS_WIN)
     if (e->type() == QEvent::ParentChange) {
         QGLContext *newContext = new QGLContext(d->glcx->requestedFormat(), this);
-        qgl_share_reg()->replaceShare(d->glcx, newContext);
+        QList<const QGLContext *> shares = qgl_share_reg()->shares(d->glcx);
         setContext(newContext);
+        for (int i = 0; i < shares.size(); ++i) {
+            if (newContext != shares.at(i))
+                qgl_share_reg()->addShare(newContext, shares.at(i));
+        }
+
         // the overlay needs to be recreated as well
         delete d->olcx;
         if (isValid() && context()->format().hasOverlay()) {
@@ -4612,4 +4617,156 @@ bool QGLDrawable::autoFillBackground() const
         return false;
 }
 
+
+bool QGLShareRegister::checkSharing(const QGLContext *context1, const QGLContext *context2) {
+    bool sharing = (context1 && context2 && context1->d_ptr->groupResources == context2->d_ptr->groupResources);
+    return sharing;
+}
+
+void QGLShareRegister::addShare(const QGLContext *context, const QGLContext *share) {
+    Q_ASSERT(context && share);
+    if (context->d_ptr->groupResources == share->d_ptr->groupResources)
+        return;
+
+    // Make sure 'context' is not already shared with another group of contexts.
+    Q_ASSERT(reg.find(context->d_ptr->groupResources) == reg.end());
+    Q_ASSERT(context->d_ptr->groupResources->refs == 1);
+
+    // Free 'context' group resources and make it use the same resources as 'share'.
+    delete context->d_ptr->groupResources;
+    context->d_ptr->groupResources = share->d_ptr->groupResources;
+    context->d_ptr->groupResources->refs.ref();
+
+    // Maintain a list of all the contexts in each group of sharing contexts.
+    SharingHash::iterator it = reg.find(share->d_ptr->groupResources);
+    if (it == reg.end())
+        it = reg.insert(share->d_ptr->groupResources, ContextList() << share);
+    it.value() << context;
+}
+
+QList<const QGLContext *> QGLShareRegister::shares(const QGLContext *context) {
+    SharingHash::const_iterator it = reg.find(context->d_ptr->groupResources);
+    if (it == reg.end())
+        return ContextList();
+    return it.value();
+}
+
+void QGLShareRegister::removeShare(const QGLContext *context) {
+    SharingHash::iterator it = reg.find(context->d_ptr->groupResources);
+    if (it == reg.end())
+        return;
+
+    int count = it.value().removeAll(context);
+    Q_ASSERT(count == 1);
+
+    Q_ASSERT(it.value().size() != 0);
+    if (it.value().size() == 1)
+        reg.erase(it);
+}
+
+QGLContextResource::QGLContextResource(FreeFunc f, QObject *parent)
+    : QObject(parent), free(f)
+{
+    connect(QGLSignalProxy::instance(), SIGNAL(aboutToDestroyContext(const QGLContext *)), this, SLOT(aboutToDestroyContext(const QGLContext *)));
+}
+
+QGLContextResource::~QGLContextResource()
+{
+    while (!m_resources.empty())
+        remove(m_resources.begin().key());
+}
+
+void QGLContextResource::insert(const QGLContext *key, void *value)
+{
+    QList<const QGLContext *> shares = qgl_share_reg()->shares(key);
+    if (shares.size() == 0)
+        shares.append(key);
+    void *oldValue = 0;
+    for (int i = 0; i < shares.size(); ++i) {
+        ResourceHash::iterator it = m_resources.find(shares.at(i));
+        if (it != m_resources.end()) {
+            Q_ASSERT(oldValue == 0 || oldValue == it.value());
+            oldValue = it.value();
+            it.value() = value;
+        } else {
+            m_resources.insert(shares.at(i), value);
+        }
+    }
+    if (oldValue != 0 && oldValue != value) {
+        QGLContext *oldContext = const_cast<QGLContext *>(QGLContext::currentContext());
+        if (oldContext != key)
+            const_cast<QGLContext *>(key)->makeCurrent();
+        free(oldValue);
+        if (oldContext && oldContext != key)
+            oldContext->makeCurrent();
+    }
+}
+
+void *QGLContextResource::value(const QGLContext *key)
+{
+    ResourceHash::const_iterator it = m_resources.find(key);
+    // Check if there is a value associated with 'key'.
+    if (it != m_resources.end())
+        return it.value();
+    // Check if there is a value associated with sharing contexts.
+    QList<const QGLContext *> shares = qgl_share_reg()->shares(key);
+    for (int i = 0; i < shares.size() && it == m_resources.end(); ++i)
+        it = m_resources.find(shares.at(i));
+    if (it == m_resources.end())
+        return 0; // Didn't find anything.
+
+    // Found something! Share this info with all the buddies.
+    for (int i = 0; i < shares.size(); ++i)
+        m_resources.insert(shares.at(i), it.value());
+    return it.value();
+}
+
+void QGLContextResource::remove(const QGLContext *key)
+{
+    QList<const QGLContext *> shares = qgl_share_reg()->shares(key);
+    if (shares.size() == 0)
+        shares.append(key);
+    void *oldValue = 0;
+    for (int i = 0; i < shares.size(); ++i) {
+        ResourceHash::iterator it = m_resources.find(shares.at(i));
+        if (it != m_resources.end()) {
+            Q_ASSERT(oldValue == 0 || oldValue == it.value());
+            oldValue = it.value();
+            m_resources.erase(it);
+        }
+    }
+    if (oldValue != 0) {
+        QGLContext *oldContext = const_cast<QGLContext *>(QGLContext::currentContext());
+        if (oldContext != key)
+            const_cast<QGLContext *>(key)->makeCurrent();
+        free(oldValue);
+        if (oldContext && oldContext != key)
+            oldContext->makeCurrent();
+    }
+}
+
+void QGLContextResource::aboutToDestroyContext(const QGLContext *key)
+{
+    ResourceHash::iterator it = m_resources.find(key);
+    if (it == m_resources.end())
+        return;
+
+    QList<const QGLContext *> shares = qgl_share_reg()->shares(key);
+    if (shares.size() > 1) {
+        Q_ASSERT(key->isSharing());
+        // At least one of the shared contexts must stay in the cache.
+        // Otherwise, the value pointer is lost.
+        for (int i = 0; i < 2/*shares.size()*/; ++i)
+            m_resources.insert(shares.at(i), it.value());
+    } else {
+        QGLContext *oldContext = const_cast<QGLContext *>(QGLContext::currentContext());
+        if (oldContext != key)
+            const_cast<QGLContext *>(key)->makeCurrent();
+        free(it.value());
+        if (oldContext && oldContext != key)
+            oldContext->makeCurrent();
+    }
+    m_resources.erase(it);
+}
+
 QT_END_NAMESPACE
diff --git a/src/opengl/qgl.h b/src/opengl/qgl.h
index 86555da..31b9543 100644
--- a/src/opengl/qgl.h
+++ b/src/opengl/qgl.h
@@ -364,6 +364,7 @@ private:
     friend class QGLPixmapData;
     friend class QGLPixmapFilterBase;
     friend class QGLTextureGlyphCache;
+    friend class QGLShareRegister;
     friend QGLFormat::OpenGLVersionFlags QGLFormat::openGLVersionFlags();
 #ifdef Q_WS_MAC
 public:
diff --git a/src/opengl/qgl_p.h b/src/opengl/qgl_p.h
index ac19d64..fda0257 100644
--- a/src/opengl/qgl_p.h
+++ b/src/opengl/qgl_p.h
@@ -196,12 +196,19 @@ public:
 #endif
 };
 
+struct QGLContextGroupResources
+{
+    QGLContextGroupResources() : refs(1) { }
+    QGLExtensionFuncs extensionFuncs;
+    QAtomicInt refs;
+};
+
 class QGLContextPrivate
 {
     Q_DECLARE_PUBLIC(QGLContext)
 public:
-    explicit QGLContextPrivate(QGLContext *context) : internal_context(false), q_ptr(context) {}
-    ~QGLContextPrivate() {}
+    explicit QGLContextPrivate(QGLContext *context) : internal_context(false), q_ptr(context) {groupResources = new QGLContextGroupResources;}
+    ~QGLContextPrivate() {if (!groupResources->refs.deref()) delete groupResources;}
     GLuint bindTexture(const QImage &image, GLenum target, GLint format, const qint64 key,
                        bool clean = false);
     GLuint bindTexture(const QPixmap &pixmap, GLenum target, GLint format, bool clean);
@@ -257,14 +264,14 @@ public:
     QGLContext *q_ptr;
     QGLFormat::OpenGLVersionFlags version_flags;
 
-    QGLExtensionFuncs extensionFuncs;
+    QGLContextGroupResources *groupResources;
     GLint max_texture_size;
 
     GLuint current_fbo;
     QPaintEngine *active_engine;
 
 #ifdef Q_WS_WIN
-    static inline QGLExtensionFuncs& qt_get_extension_funcs(const QGLContext *ctx) { return ctx->d_ptr->extensionFuncs; }
+    static inline QGLExtensionFuncs& qt_get_extension_funcs(const QGLContext *ctx) { return ctx->d_ptr->groupResources->extensionFuncs; }
 #endif
 
 #if defined(Q_WS_X11) || defined(Q_WS_MAC) || defined(Q_WS_QWS)
@@ -371,62 +378,21 @@ struct QGLThreadContext {
 };
 extern QThreadStorage<QGLThreadContext *> qgl_context_storage;
 
-typedef QMultiHash<const QGLContext *, const QGLContext *> QGLSharingHash;
 class QGLShareRegister
 {
 public:
     QGLShareRegister() {}
     ~QGLShareRegister() { reg.clear(); }
 
-    bool checkSharing(const QGLContext *context1, const QGLContext *context2, const QGLContext * skip=0) {
-        if (context1 == context2)
-            return true;
-        QList<const QGLContext *> shares = reg.values(context1);
-        for (int k=0; k<shares.size(); ++k) {
-            const QGLContext *ctx = shares.at(k);
-            if (ctx == skip) // avoid an indirect circular loop (infinite recursion)
-                continue;
-            if (ctx == context2)
-                return true;
-            if (checkSharing(ctx, context2, context1))
-                return true;
-        }
-        return false;
-    }
-
-    void addShare(const QGLContext *context, const QGLContext *share) {
-        reg.insert(context, share); // context sharing works both ways
-        reg.insert(share, context);
-    }
-
-    void removeShare(const QGLContext *context) {
-        QGLSharingHash::iterator it = reg.begin();
-        while (it != reg.end()) {
-            if (it.key() == context || it.value() == context)
-                it = reg.erase(it);
-            else
-                ++it;
-        }
-    }
-
-    void replaceShare(const QGLContext *oldContext, const QGLContext *newContext) {
-        QGLSharingHash::iterator it = reg.begin();
-        while (it != reg.end()) {
-            if (it.key() == oldContext)
-                reg.insert(newContext, it.value());
-            else if (it.value() == oldContext)
-                reg.insert(it.key(), newContext);
-            ++it;
-        }
-        removeShare(oldContext);
-    }
-
-    QList<const QGLContext *> shares(const QGLContext *context) {
-        return reg.values(context);
-    }
-
+    bool checkSharing(const QGLContext *context1, const QGLContext *context2);
+    void addShare(const QGLContext *context, const QGLContext *share);
+    QList<const QGLContext *> shares(const QGLContext *context);
+    void removeShare(const QGLContext *context);
 private:
-    QGLSharingHash reg;
+    // Use a context's 'groupResources' pointer to uniquely identify a group.
+    typedef QList<const QGLContext *> ContextList;
+    typedef QHash<const QGLContextGroupResources *, ContextList> SharingHash;
+    SharingHash reg;
 };
 
 extern Q_OPENGL_EXPORT QGLShareRegister* qgl_share_reg();
@@ -464,6 +430,29 @@ inline GLenum qt_gl_preferredTextureTarget()
 #endif
 }
 
+// One resource per group of shared contexts.
+class QGLContextResource : public QObject
+{
+    Q_OBJECT
+public:
+    typedef void (*FreeFunc)(void *);
+    QGLContextResource(FreeFunc f, QObject *parent = 0);
+    ~QGLContextResource();
+    // Set resource 'value' for 'key' and all its shared contexts.
+    void insert(const QGLContext *key, void *value);
+    // Return resource for 'key' or a shared context.
+    void *value(const QGLContext *key);
+    // Free resource for 'key' and all its shared contexts.
+    void remove(const QGLContext *key);
+private slots:
+    // Remove entry 'key' from cache and delete resource if there are no shared contexts.
+    void aboutToDestroyContext(const QGLContext *key);
+private:
+    typedef QHash<const QGLContext *, void *> ResourceHash;
+    ResourceHash m_resources;
+    FreeFunc free;
+};
+
 QT_END_NAMESPACE
 
 #endif // QGL_P_H