Make QOpenGLWidget public

QOpenGLWidget is now public.

In addition Qt::WA_AlwaysStackOnTop is introduced to support the
special case of semi-transparent QOpenGLWidget or QQuickWidget on
top of regular widgets.

hellogl_es2 becomes the qopenglwidget example. This example performs
painting both via QPainter and native GL commands and has the OpenGL
widget combined with other, normal widgets.

The widget stack receives some changes when it comes to renderToTexture
widgets like QQuickWidget and QOpenGLWidget. Calling update() will now
result in a paint event, which is essential for QOpenGLWidget since we
want it to behave like a regular widget. The dirty region handling is
extended specially for such widgets due to performance reasons.
(an OpenGL content update must not result in any backingstore painting,
and is thus handled as a different kind of dirtiness)

[ChangeLog] Added QOpenGLWidget. This widget serves as a replacement for QGLWidget.

Task-number: QTBUG-36899
Task-number: QTBUG-40086
Change-Id: Ibf7f82fea99b39edfffd2fc088e7e0eadbca25cf
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>

2 files changed, 35 insertions, 16 deletions

diff --git a/src/gui/painting/qplatformbackingstore.cpp b/src/gui/painting/qplatformbackingstore.cpp
index 3728b0bddd..e5b06f499c 100644
--- a/src/gui/painting/qplatformbackingstore.cpp
+++ b/src/gui/painting/qplatformbackingstore.cpp
@@ -90,6 +90,7 @@ struct QBackingstoreTextureInfo
 {
     GLuint textureId;
     QRect rect;
+    bool stacksOnTop;
 };
 
 Q_DECLARE_TYPEINFO(QBackingstoreTextureInfo, Q_MOVABLE_TYPE);
@@ -127,6 +128,12 @@ GLuint QPlatformTextureList::textureId(int index) const
     return d->textures.at(index).textureId;
 }
 
+bool QPlatformTextureList::stacksOnTop(int index) const
+{
+    Q_D(const QPlatformTextureList);
+    return d->textures.at(index).stacksOnTop;
+}
+
 QRect QPlatformTextureList::geometry(int index) const
 {
     Q_D(const QPlatformTextureList);
@@ -148,12 +155,13 @@ bool QPlatformTextureList::isLocked() const
     return d->locked;
 }
 
-void QPlatformTextureList::appendTexture(GLuint textureId, const QRect &geometry)
+void QPlatformTextureList::appendTexture(GLuint textureId, const QRect &geometry, bool stacksOnTop)
 {
     Q_D(QPlatformTextureList);
     QBackingstoreTextureInfo bi;
     bi.textureId = textureId;
     bi.rect = geometry;
+    bi.stacksOnTop = stacksOnTop;
     d->textures.append(bi);
 }
 
@@ -238,29 +246,39 @@ void QPlatformBackingStore::composeAndFlush(QWindow *window, const QRegion &regi
 
     QRect windowRect(QPoint(), window->size() * window->devicePixelRatio());
 
+    // Textures for renderToTexture widgets.
     for (int i = 0; i < textures->count(); ++i) {
-        GLuint textureId = textures->textureId(i);
-        funcs->glBindTexture(GL_TEXTURE_2D, textureId);
-
-        QRect targetRect = deviceRect(textures->geometry(i), window);
-        QMatrix4x4 target = QOpenGLTextureBlitter::targetTransform(targetRect, windowRect);
-        d_ptr->blitter->blit(textureId, target, QOpenGLTextureBlitter::OriginBottomLeft);
+        if (!textures->stacksOnTop(i)) {
+            QRect targetRect = deviceRect(textures->geometry(i), window);
+            QMatrix4x4 target = QOpenGLTextureBlitter::targetTransform(targetRect, windowRect);
+            d_ptr->blitter->blit(textures->textureId(i), target, QOpenGLTextureBlitter::OriginBottomLeft);
+        }
     }
 
-    GLuint textureId = toTexture(deviceRegion(region, window), &d_ptr->textureSize);
-    if (!textureId)
-        return;
-
     funcs->glEnable(GL_BLEND);
     funcs->glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 
-    QMatrix4x4 target = QOpenGLTextureBlitter::targetTransform(QRect(QPoint(), d_ptr->textureSize), windowRect);
-    d_ptr->blitter->setSwizzleRB(true);
-    d_ptr->blitter->blit(textureId, target, QOpenGLTextureBlitter::OriginTopLeft);
-    d_ptr->blitter->setSwizzleRB(false);
+    // Backingstore texture with the normal widgets.
+    GLuint textureId = toTexture(deviceRegion(region, window), &d_ptr->textureSize);
+    if (textureId) {
+        QMatrix4x4 target = QOpenGLTextureBlitter::targetTransform(QRect(QPoint(), d_ptr->textureSize), windowRect);
+        d_ptr->blitter->setSwizzleRB(true);
+        d_ptr->blitter->blit(textureId, target, QOpenGLTextureBlitter::OriginTopLeft);
+        d_ptr->blitter->setSwizzleRB(false);
+    }
+
+    // Textures for renderToTexture widgets that have WA_AlwaysStackOnTop set.
+    for (int i = 0; i < textures->count(); ++i) {
+        if (textures->stacksOnTop(i)) {
+            QRect targetRect = deviceRect(textures->geometry(i), window);
+            QMatrix4x4 target = QOpenGLTextureBlitter::targetTransform(targetRect, windowRect);
+            d_ptr->blitter->blit(textures->textureId(i), target, QOpenGLTextureBlitter::OriginBottomLeft);
+        }
+    }
 
     funcs->glDisable(GL_BLEND);
     d_ptr->blitter->release();
+
     context->swapBuffers(window);
 }
 
diff --git a/src/gui/painting/qplatformbackingstore.h b/src/gui/painting/qplatformbackingstore.h
index 4728622cac..fe0f460ed9 100644
--- a/src/gui/painting/qplatformbackingstore.h
+++ b/src/gui/painting/qplatformbackingstore.h
@@ -84,10 +84,11 @@ public:
     bool isEmpty() const { return count() == 0; }
     GLuint textureId(int index) const;
     QRect geometry(int index) const;
+    bool stacksOnTop(int index) const;
     void lock(bool on);
     bool isLocked() const;
 
-    void appendTexture(GLuint textureId, const QRect &geometry);
+    void appendTexture(GLuint textureId, const QRect &geometry, bool stacksOnTop = false);
     void clear();
 
  Q_SIGNALS: