Correctly handle using GL pixmaps that still have an active engine.

In the case where a GL pixmap is used when there it still has an active
engine we need to ensure that the pixmap has been flushed from the
render FBO first. The newly added QGLPixmapData::copyBackFromRenderFbo()
handles this.

In addition, because several GL 2 paint engines can be active on the same
context at the same time, we can't make any assumptions and need to call
the newly added QGL2PaintEngineEx::ensureCreated() in the beginning of
any state-dependent paint engine function.
QGL2PaintEngineEx::ensureCreated() correctly transfers control to the
current engine if a different engine is active.

Running lance with -pixmap and -graphicssystem opengl works correctly
with the GL pixmap backend now.

2 files changed, 47 insertions, 3 deletions

diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index fe70020..8bf3182 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -805,6 +805,7 @@ void QGL2PaintEngineEx::fill(const QVectorPath &path, const QBrush &brush)
 {
     Q_D(QGL2PaintEngineEx);
 
+    ensureActive();
     d->setBrush(&brush);
     d->fill(path);
     d->setBrush(&(state()->brush)); // reset back to the state's brush
@@ -814,6 +815,7 @@ void QGL2PaintEngineEx::stroke(const QVectorPath &path, const QPen &pen)
 {
     Q_D(QGL2PaintEngineEx);
 
+    ensureActive();
     if (pen.style() == Qt::NoPen)
         return;
 
@@ -832,7 +834,6 @@ void QGL2PaintEngineEx::stroke(const QVectorPath &path, const QPen &pen)
         d->setBrush(&(state()->brush));
     } else
         return QPaintEngineEx::stroke(path, pen);
-
 }
 
 void QGL2PaintEngineEx::penChanged()
@@ -887,6 +888,7 @@ void QGL2PaintEngineEx::transformChanged()
 void QGL2PaintEngineEx::drawPixmap(const QRectF& dest, const QPixmap & pixmap, const QRectF & src)
 {
     Q_D(QGL2PaintEngineEx);
+    ensureActive();
     d->transferMode(ImageDrawingMode);
 
     QGLContext *ctx = d->ctx;
@@ -905,6 +907,7 @@ void QGL2PaintEngineEx::drawImage(const QRectF& dest, const QImage& image, const
                         Qt::ImageConversionFlags)
 {
     Q_D(QGL2PaintEngineEx);
+    ensureActive();
     d->transferMode(ImageDrawingMode);
 
     QGLContext *ctx = d->ctx;
@@ -921,6 +924,7 @@ void QGL2PaintEngineEx::drawImage(const QRectF& dest, const QImage& image, const
 void QGL2PaintEngineEx::drawTextItem(const QPointF &p, const QTextItem &textItem)
 {
     Q_D(QGL2PaintEngineEx);
+    ensureActive();
     QOpenGLPaintEngineState *s = state();
 
     const QTextItemInt &ti = static_cast<const QTextItemInt &>(textItem);
@@ -974,6 +978,9 @@ void QGL2PaintEngineExPrivate::drawCachedGlyphs(const QPointF &p, const QTextIte
     const QImage &image = cache->image();
     int margin = cache->glyphMargin();
 
+    if (image.isNull())
+        return;
+
     ctx->d_func()->bindTexture(image, GL_TEXTURE_2D, GL_RGBA, true);
 
     updateTextureFilter(GL_TEXTURE_2D, GL_REPEAT, false);
@@ -1085,6 +1092,16 @@ bool QGL2PaintEngineEx::end()
 {
     Q_D(QGL2PaintEngineEx);
     QGLContext *ctx = d->ctx;
+    if (ctx->d_ptr->active_engine != this) {
+        QGL2PaintEngineEx *engine = static_cast<QGL2PaintEngineEx *>(d->last_engine);
+        if (engine) {
+            QGL2PaintEngineExPrivate *p = static_cast<QGL2PaintEngineExPrivate *>(engine->d_ptr);
+            p->transferMode(DefaultMode);
+            p->drawable.doneCurrent();
+        }
+        d->drawable.makeCurrent();
+    }
+
     glUseProgram(0);
     d->transferMode(DefaultMode);
     d->drawable.swapBuffers();
@@ -1106,6 +1123,31 @@ bool QGL2PaintEngineEx::end()
     return false;
 }
 
+void QGL2PaintEngineEx::ensureActive()
+{
+    Q_D(QGL2PaintEngineEx);
+    QGLContext *ctx = d->ctx;
+
+    if (isActive() && ctx->d_ptr->active_engine != this) {
+        QGL2PaintEngineEx *engine = static_cast<QGL2PaintEngineEx *>(ctx->d_ptr->active_engine);
+        if (engine) {
+            QGL2PaintEngineExPrivate *p = static_cast<QGL2PaintEngineExPrivate *>(engine->d_ptr);
+            p->transferMode(DefaultMode);
+            p->drawable.doneCurrent();
+        }
+        d->drawable.makeCurrent();
+
+        ctx->d_ptr->active_engine = this;
+
+        glDisable(GL_DEPTH_TEST);
+        glDisable(GL_SCISSOR_TEST);
+
+        glViewport(0, 0, d->width, d->height);
+        setState(state());
+        d->updateDepthClip();
+    }
+}
+
 
 /////////////////////////////////// State/Clipping stolen from QOpenGLPaintEngine //////////////////////////////////////////
 
@@ -1246,6 +1288,7 @@ void QGL2PaintEngineExPrivate::updateDepthClip()
 
     Q_Q(QGL2PaintEngineEx);
 
+    q->ensureActive();
     glDisable(GL_DEPTH_TEST);
     glDisable(GL_SCISSOR_TEST);
 
@@ -1305,7 +1348,7 @@ void QGL2PaintEngineEx::setState(QPainterState *new_state)
     QOpenGLPaintEngineState *old_state = state();
     const bool needsDepthClipUpdate = !old_state
             || s->clipEnabled != old_state->clipEnabled
-            || s->clipEnabled && s->clipRegion != old_state->clipRegion;
+            || (s->clipEnabled && s->clipRegion != old_state->clipRegion);
 
     QPaintEngineEx::setState(s);
 
diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h b/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
index 10e5337..b31f685 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
@@ -80,6 +80,8 @@ public:
     bool begin(QPaintDevice *device);
     bool end();
 
+    void ensureActive();
+
     virtual void fill(const QVectorPath &path, const QBrush &brush);
     virtual void stroke(const QVectorPath &path, const QPen &pen);
     virtual void clip(const QVectorPath &path, Qt::ClipOperation op);
@@ -102,7 +104,6 @@ public:
 
     Type type() const { return OpenGL; }
 
-
     // State stuff is just for clipping and ripped off from QGLPaintEngine
     void setState(QPainterState *s);
     QPainterState *createState(QPainterState *orig) const;