Improved QPainter API for allowing native painting in GL / VG.

Previously we were using QPaintEngine::syncState() which is not ideal
naming-wise, since it actually prepares for native painting instead of
syncing the painter's state to native state.

Reviewed-by: Trond

11 files changed, 100 insertions, 43 deletions

diff --git a/dist/changes-4.6.0 b/dist/changes-4.6.0
index 8c2c2c8..194d670 100644
--- a/dist/changes-4.6.0
+++ b/dist/changes-4.6.0
@@ -49,10 +49,13 @@ information about a particular change.
    this is that Nokia focuses on OpenGL for desktop hardware accelerated
    rendering.
 
- - When mixing OpenGL and QPainter calls you need to first call syncState()
-   on the paint engine, for example "painter->paintEngine()->syncState()".
-   This is to ensure that the engine flushes any pending drawing and sets up
-   the GL modelview/projection matrices properly.
+ - When mixing OpenGL and QPainter calls you need to surround your custom
+   OpenGL calls with QPainter::beginNativePainting() and
+   QPainter::endNativePainting().
+   This is to ensure that the paint engine flushes any pending drawing and sets
+   up the GL modelview/projection matrices properly before you can issue custom
+   OpenGL calls, and to let the paint engine synchronize to the painter state
+   before resuming regular QPainter based drawing.
 
  - Graphics View has undergone heavy optimization work, and as a result of
    this work, the following behavior changes were introduced.
diff --git a/examples/opengl/hellogl_es2/glwidget.cpp b/examples/opengl/hellogl_es2/glwidget.cpp
index 9a2a83e..50a7797 100644
--- a/examples/opengl/hellogl_es2/glwidget.cpp
+++ b/examples/opengl/hellogl_es2/glwidget.cpp
@@ -266,7 +266,7 @@ void GLWidget::paintGL()
     QPainter painter;
     painter.begin(this);
 
-    painter.paintEngine()->syncState();
+    painter.beginNativePainting();
 
     glClearColor(0.1f, 0.1f, 0.2f, 1.0f);
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
@@ -302,6 +302,8 @@ void GLWidget::paintGL()
     glDisable(GL_DEPTH_TEST);
     glDisable(GL_CULL_FACE);
 
+    painter.endNativePainting();
+
     if (m_showBubbles)
         foreach (Bubble *bubble, bubbles) {
             bubble->drawBubble(&painter);
diff --git a/examples/openvg/star/starwidget.cpp b/examples/openvg/star/starwidget.cpp
index 1a64fc9..ab11bdb 100644
--- a/examples/openvg/star/starwidget.cpp
+++ b/examples/openvg/star/starwidget.cpp
@@ -91,7 +91,7 @@ void StarWidget::paintEvent(QPaintEvent *)
 
     // Flush the state changes to the OpenVG implementation
     // and prepare to perform raw OpenVG calls.
-    painter.paintEngine()->syncState();
+    painter.beginNativePainting();
 
     // Cache the path if we haven't already.
     if (path == VG_INVALID_HANDLE) {
@@ -109,7 +109,7 @@ void StarWidget::paintEvent(QPaintEvent *)
     vgDrawPath(path, VG_FILL_PATH | VG_STROKE_PATH);
 
     // Restore normal QPainter operations.
-    painter.paintEngine()->syncState();
+    painter.endNativePainting();
 
     painter.end();
 }
diff --git a/src/gui/painting/qpaintengineex_p.h b/src/gui/painting/qpaintengineex_p.h
index cf3aad7..1ba2153 100644
--- a/src/gui/painting/qpaintengineex_p.h
+++ b/src/gui/painting/qpaintengineex_p.h
@@ -204,6 +204,9 @@ public:
 
     virtual void sync() {}
 
+    virtual void beginNativePainting() {}
+    virtual void endNativePainting() {}
+
     virtual QPixmapFilter *createPixmapFilter(int /*type*/) const { return 0; }
 
 protected:
diff --git a/src/gui/painting/qpainter.cpp b/src/gui/painting/qpainter.cpp
index e1a6e80..cba4ad9 100644
--- a/src/gui/painting/qpainter.cpp
+++ b/src/gui/painting/qpainter.cpp
@@ -1889,6 +1889,45 @@ QPaintEngine *QPainter::paintEngine() const
     return d->engine;
 }
 
+/*!
+    Flushes the painting pipeline and prepares for the user issuing
+    native painting commands. Must be followed by a call to
+    endNativePainting().
+
+    \sa endNativePainting()
+*/
+void QPainter::beginNativePainting()
+{
+    Q_D(QPainter);
+    if (!d->engine) {
+        qWarning("QPainter::beginNativePainting: Painter not active");
+        return;
+    }
+
+    if (d->extended)
+        d->extended->beginNativePainting();
+}
+
+/*!
+    Restores the painter after manually issuing native painting commands.
+    Lets the painter restore any native state that it relies on before
+    calling any other painter commands.
+
+    \sa beginNativePainting()
+*/
+void QPainter::endNativePainting()
+{
+    Q_D(const QPainter);
+    if (!d->engine) {
+        qWarning("QPainter::beginNativePainting: Painter not active");
+        return;
+    }
+
+    if (d->extended)
+        d->extended->endNativePainting();
+    else
+        d->engine->syncState();
+}
 
 /*!
     Returns the font metrics for the painter if the painter is
diff --git a/src/gui/painting/qpainter.h b/src/gui/painting/qpainter.h
index 14d1cf8..1bb97c6 100644
--- a/src/gui/painting/qpainter.h
+++ b/src/gui/painting/qpainter.h
@@ -423,6 +423,9 @@ public:
     static QPaintDevice *redirected(const QPaintDevice *device, QPoint *offset = 0);
     static void restoreRedirected(const QPaintDevice *device);
 
+    void beginNativePainting();
+    void endNativePainting();
+
 #ifdef QT3_SUPPORT
 
     inline QT3_SUPPORT void setBackgroundColor(const QColor &color) { setBackground(color); }
diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index 136a078..ca33101 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -675,7 +675,7 @@ void QGL2PaintEngineExPrivate::drawTexture(const QGLRect& dest, const QGLRect& s
     glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
 }
 
-void QGL2PaintEngineEx::sync()
+void QGL2PaintEngineEx::beginNativePainting()
 {
     Q_D(QGL2PaintEngineEx);
     ensureActive();
@@ -721,6 +721,12 @@ void QGL2PaintEngineEx::sync()
     d->needsSync = true;
 }
 
+void QGL2PaintEngineEx::endNativePainting()
+{
+    Q_D(QGL2PaintEngineEx);
+    d->needsSync = true;
+}
+
 const QGLContext *QGL2PaintEngineEx::context()
 {
     Q_D(QGL2PaintEngineEx);
diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h b/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
index 7b734e3..2eec4d5 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
@@ -133,7 +133,9 @@ public:
     inline const QOpenGL2PaintEngineState *state() const {
         return static_cast<const QOpenGL2PaintEngineState *>(QPaintEngineEx::state());
     }
-    virtual void sync();
+
+    void beginNativePainting();
+    void endNativePainting();
 
     const QGLContext* context();
 
diff --git a/src/opengl/qglpixmapfilter.cpp b/src/opengl/qglpixmapfilter.cpp
index df7811e..83fddd1 100644
--- a/src/opengl/qglpixmapfilter.cpp
+++ b/src/opengl/qglpixmapfilter.cpp
@@ -338,7 +338,6 @@ bool QGLPixmapBlurFilter::processGL(QPainter *painter, const QPointF &pos, const
 
     QGL2PaintEngineEx *engine = static_cast<QGL2PaintEngineEx *>(painter->paintEngine());
 
-    engine->syncState();
     painter->save();
 
     // ensure GL_LINEAR filtering is used
diff --git a/src/openvg/qpaintengine_vg.cpp b/src/openvg/qpaintengine_vg.cpp
index d2c7b8b..09eb646 100644
--- a/src/openvg/qpaintengine_vg.cpp
+++ b/src/openvg/qpaintengine_vg.cpp
@@ -3072,43 +3072,42 @@ void QVGPaintEngine::setState(QPainterState *s)
     }
 }
 
-// Called from QPaintEngine::syncState() to force a state flush.
-// This should be called before and after raw VG operations.
-void QVGPaintEngine::updateState(const QPaintEngineState &state)
+void QVGPaintEngine::beginNativePainting()
 {
-    Q_UNUSED(state);
     Q_D(QVGPaintEngine);
 
-    if (!(d->rawVG)) {
-        // About to enter raw VG mode: flush pending changes and make
-        // sure that all matrices are set to the current transformation.
-        QVGPainterState *s = this->state();
-        d->ensurePen(s->pen);
-        d->ensureBrush(s->brush);
-        d->ensurePathTransform();
-        d->setTransform(VG_MATRIX_IMAGE_USER_TO_SURFACE, d->imageTransform);
+    // About to enter raw VG mode: flush pending changes and make
+    // sure that all matrices are set to the current transformation.
+    QVGPainterState *s = this->state();
+    d->ensurePen(s->pen);
+    d->ensureBrush(s->brush);
+    d->ensurePathTransform();
+    d->setTransform(VG_MATRIX_IMAGE_USER_TO_SURFACE, d->imageTransform);
 #if !defined(QVG_NO_DRAW_GLYPHS)
-        d->setTransform(VG_MATRIX_GLYPH_USER_TO_SURFACE, d->pathTransform);
+    d->setTransform(VG_MATRIX_GLYPH_USER_TO_SURFACE, d->pathTransform);
 #endif
-        d->rawVG = true;
-    } else {
-        // Exiting raw VG mode: force all state values to be
-        // explicitly set on the VG engine to undo any changes
-        // that were made by the raw VG function calls.
-        QPaintEngine::DirtyFlags dirty = d->dirty;
-        d->clearModes();
-        d->forcePenChange = true;
-        d->forceBrushChange = true;
-        d->penType = (VGPaintType)0;
-        d->brushType = (VGPaintType)0;
-        d->clearColor = QColor();
-        d->fillPaint = d->brushPaint;
-        restoreState(QPaintEngine::AllDirty);
-        d->dirty = dirty;
-        d->rawVG = false;
-        vgSetPaint(d->penPaint, VG_STROKE_PATH);
-        vgSetPaint(d->brushPaint, VG_FILL_PATH);
-    }
+    d->rawVG = true;
+}
+
+void QVGPaintEngine::endNativePainting()
+{
+    Q_D(QVGPaintEngine);
+    // Exiting raw VG mode: force all state values to be
+    // explicitly set on the VG engine to undo any changes
+    // that were made by the raw VG function calls.
+    QPaintEngine::DirtyFlags dirty = d->dirty;
+    d->clearModes();
+    d->forcePenChange = true;
+    d->forceBrushChange = true;
+    d->penType = (VGPaintType)0;
+    d->brushType = (VGPaintType)0;
+    d->clearColor = QColor();
+    d->fillPaint = d->brushPaint;
+    restoreState(QPaintEngine::AllDirty);
+    d->dirty = dirty;
+    d->rawVG = false;
+    vgSetPaint(d->penPaint, VG_STROKE_PATH);
+    vgSetPaint(d->brushPaint, VG_FILL_PATH);
 }
 
 QPixmapFilter *QVGPaintEngine::createPixmapFilter(int type) const
diff --git a/src/openvg/qpaintengine_vg_p.h b/src/openvg/qpaintengine_vg_p.h
index 469ec9e..f0a7838 100644
--- a/src/openvg/qpaintengine_vg_p.h
+++ b/src/openvg/qpaintengine_vg_p.h
@@ -140,7 +140,8 @@ public:
     QVGPainterState *state() { return static_cast<QVGPainterState *>(QPaintEngineEx::state()); }
     const QVGPainterState *state() const { return static_cast<const QVGPainterState *>(QPaintEngineEx::state()); }
 
-    void updateState(const QPaintEngineState &state);
+    void beginNativePainting();
+    void endNativePainting();
 
     QPixmapFilter *createPixmapFilter(int type) const;