Added support for blitting to native child widgets in GL window surface.

Support blitting by copying from the top-level window's back buffer to
a temporary texture and then blitting from the texture to the native
child widget. Performance suffers, but it's better than failing.

Reviewed-by: Gunnar Sletta

5 files changed, 88 insertions, 60 deletions

diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index 62eff6e..dbd295f 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -2104,7 +2104,7 @@ void QGLContextPrivate::syncGlState()
 #undef ctx
 
 #ifdef QT_NO_EGL
-void QGLContextPrivate::swapRegion(const QRegion *)
+void QGLContextPrivate::swapRegion(const QRegion &)
 {
     Q_Q(QGLContext);
     q->swapBuffers();
diff --git a/src/opengl/qgl_egl.cpp b/src/opengl/qgl_egl.cpp
index c79c4cd..27f7ad9 100644
--- a/src/opengl/qgl_egl.cpp
+++ b/src/opengl/qgl_egl.cpp
@@ -276,12 +276,12 @@ EGLSurface QGLContextPrivate::eglSurfaceForDevice() const
     return eglSurface;
 }
 
-void QGLContextPrivate::swapRegion(const QRegion *region)
+void QGLContextPrivate::swapRegion(const QRegion &region)
 {
     if (!valid || !eglContext)
         return;
 
-    eglContext->swapBuffersRegion2NOK(eglSurfaceForDevice(), region);
+    eglContext->swapBuffersRegion2NOK(eglSurfaceForDevice(), &region);
 }
 
 void QGLWidget::setMouseTracking(bool enable)
diff --git a/src/opengl/qgl_p.h b/src/opengl/qgl_p.h
index 6c494ee..f86c77f 100644
--- a/src/opengl/qgl_p.h
+++ b/src/opengl/qgl_p.h
@@ -343,7 +343,7 @@ public:
 
     void setVertexAttribArrayEnabled(int arrayIndex, bool enabled = true);
     void syncGlState(); // Makes sure the GL context's state is what we think it is
-    void swapRegion(const QRegion *region);
+    void swapRegion(const QRegion &region);
 
 #if defined(Q_WS_WIN)
     void updateFormatVersion();
diff --git a/src/opengl/qwindowsurface_gl.cpp b/src/opengl/qwindowsurface_gl.cpp
index 8157b2a..9f3dcdf 100644
--- a/src/opengl/qwindowsurface_gl.cpp
+++ b/src/opengl/qwindowsurface_gl.cpp
@@ -275,6 +275,8 @@ struct QGLWindowSurfacePrivate
     QRegion paintedRegion;
     QSize size;
 
+    QSize textureSize;
+
     QList<QImage> buffers;
     QGLWindowSurfaceGLPaintDevice glDevice;
     QGLWindowSurface* q_ptr;
@@ -316,6 +318,7 @@ QGLWindowSurface::QGLWindowSurface(QWidget *window)
     d_ptr->pb = 0;
     d_ptr->fbo = 0;
     d_ptr->ctx = 0;
+    d_ptr->tex_id = 0;
 #if defined (QT_OPENGL_ES_2)
     d_ptr->tried_fbo = true;
     d_ptr->tried_pb = true;
@@ -433,7 +436,7 @@ static void drawTexture(const QRectF &rect, GLuint tex_id, const QSize &texSize,
 
 void QGLWindowSurface::beginPaint(const QRegion &)
 {
-    if (! context())
+    if (!context())
         return;
 
     int clearFlags = 0;
@@ -457,13 +460,42 @@ void QGLWindowSurface::endPaint(const QRegion &rgn)
     d_ptr->buffers.clear();
 }
 
-void QGLWindowSurface::flush(QWidget *widget, const QRegion &rgn, const QPoint &offset)
+static void blitTexture(QGLContext *ctx, GLuint texture, const QSize &viewport, const QSize &texSize, const QRect &targetRect, const QRect &sourceRect)
 {
-    if (context() && widget != window()) {
-        qWarning("No native child widget support in GL window surface without FBOs or pixel buffers");
-        return;
-    }
+    glDisable(GL_DEPTH_TEST);
+    glDisable(GL_SCISSOR_TEST);
+    glDisable(GL_BLEND);
+
+    glViewport(0, 0, viewport.width(), viewport.height());
+
+    QGLShaderProgram *blitProgram =
+        QGLEngineSharedShaders::shadersForContext(ctx)->blitProgram();
+    blitProgram->bind();
+    blitProgram->setUniformValue("imageTexture", 0 /*QT_IMAGE_TEXTURE_UNIT*/);
+
+    // The shader manager's blit program does not multiply the
+    // vertices by the pmv matrix, so we need to do the effect
+    // of the orthographic projection here ourselves.
+    QRectF r;
+    qreal w = viewport.width();
+    qreal h = viewport.height();
+    r.setLeft((targetRect.left() / w) * 2.0f - 1.0f);
+    if (targetRect.right() == (viewport.width() - 1))
+        r.setRight(1.0f);
+    else
+        r.setRight((targetRect.right() / w) * 2.0f - 1.0f);
+    r.setBottom((targetRect.top() / h) * 2.0f - 1.0f);
+    if (targetRect.bottom() == (viewport.height() - 1))
+        r.setTop(1.0f);
+    else
+        r.setTop((targetRect.bottom() / w) * 2.0f - 1.0f);
+
+    drawTexture(r, texture, texSize, sourceRect);
+}
+
 
+void QGLWindowSurface::flush(QWidget *widget, const QRegion &rgn, const QPoint &offset)
+{
     //### Find out why d_ptr->geometry_updated isn't always false.
     // flush() should not be called when d_ptr->geometry_updated is true. It assumes that either
     // d_ptr->fbo or d_ptr->pb is allocated and has the correct size.
@@ -534,12 +566,29 @@ void QGLWindowSurface::flush(QWidget *widget, const QRegion &rgn, const QPoint &
                 }
             }
 #endif
-            if (hasPartialUpdateSupport() &&
-                d_ptr->paintedRegion.boundingRect().width() * d_ptr->paintedRegion.boundingRect().height() <
-                geometry().width() * geometry().height() * 0.2) {
-                context()->d_func()->swapRegion(&d_ptr->paintedRegion);             
-            } else
-                context()->swapBuffers();
+            bool doingPartialUpdate = hasPartialUpdateSupport() && br.width() * br.height() < parent->geometry().width() * parent->geometry().height() * 0.2;
+            QGLContext *ctx = reinterpret_cast<QGLContext *>(parent->d_func()->extraData()->glContext);
+            if (widget != window()) {
+                if (initializeOffscreenTexture(window()->size()))
+                    qWarning() << "QGLWindowSurface: Flushing to native child widget, may lead to significant performance loss";
+                glBindTexture(target, d_ptr->tex_id);
+
+                const uint bottom = window()->height() - (br.y() + br.height());
+                glCopyTexSubImage2D(target, 0, br.x(), bottom, br.x(), bottom, br.width(), br.height());
+
+                glBindTexture(target, 0);
+
+                ctx->makeCurrent();
+                if (doingPartialUpdate)
+                    blitTexture(ctx, d_ptr->tex_id, parent->size(), window()->size(), rect, br);
+                else
+                    blitTexture(ctx, d_ptr->tex_id, parent->size(), window()->size(), parent->rect(), parent->rect().translated(offset + wOffset));
+            }
+
+            if (doingPartialUpdate)
+                ctx->d_func()->swapRegion(br);
+            else
+                ctx->swapBuffers();
 
             d_ptr->paintedRegion = QRegion();
         } else {
@@ -665,38 +714,10 @@ void QGLWindowSurface::flush(QWidget *widget, const QRegion &rgn, const QPoint &
     else if (d_ptr->fbo) {
         Q_UNUSED(target);
 
-        GLuint texture = d_ptr->fbo->texture();
-
-        glDisable(GL_DEPTH_TEST);
-
         if (d_ptr->fbo->isBound())
             d_ptr->fbo->release();
 
-        glViewport(0, 0, size.width(), size.height());
-
-        QGLShaderProgram *blitProgram =
-            QGLEngineSharedShaders::shadersForContext(ctx)->blitProgram();
-        blitProgram->bind();
-        blitProgram->setUniformValue("imageTexture", 0 /*QT_IMAGE_TEXTURE_UNIT*/);
-
-        // The shader manager's blit program does not multiply the
-        // vertices by the pmv matrix, so we need to do the effect
-        // of the orthographic projection here ourselves.
-        QRectF r;
-        qreal w = size.width() ? size.width() : 1.0f;
-        qreal h = size.height() ? size.height() : 1.0f;
-        r.setLeft((rect.left() / w) * 2.0f - 1.0f);
-        if (rect.right() == (size.width() - 1))
-            r.setRight(1.0f);
-        else
-            r.setRight((rect.right() / w) * 2.0f - 1.0f);
-        r.setBottom((rect.top() / h) * 2.0f - 1.0f);
-        if (rect.bottom() == (size.height() - 1))
-            r.setTop(1.0f);
-        else
-            r.setTop((rect.bottom() / w) * 2.0f - 1.0f);
-
-        drawTexture(r, texture, window()->size(), br);
+        blitTexture(ctx, d_ptr->fbo->texture(), size, window()->size(), rect, br);
     }
 #endif
 
@@ -719,7 +740,6 @@ void QGLWindowSurface::updateGeometry() {
         return;
     d_ptr->geometry_updated = false;
 
-
     QRect rect = geometry();
     hijackWindow(window());
     QGLContext *ctx = reinterpret_cast<QGLContext *>(window()->d_func()->extraData()->glContext);
@@ -740,11 +760,8 @@ void QGLWindowSurface::updateGeometry() {
 
     if (d_ptr->ctx) {
 #ifndef QT_OPENGL_ES_2
-        if (d_ptr->destructive_swap_buffers) {
-            glBindTexture(target, d_ptr->tex_id);
-            glTexImage2D(target, 0, GL_RGBA, rect.width(), rect.height(), 0, GL_RGB, GL_UNSIGNED_BYTE, 0);
-            glBindTexture(target, 0);
-        }
+        if (d_ptr->destructive_swap_buffers)
+            initializeOffscreenTexture(rect.size());
 #endif
         return;
     }
@@ -824,15 +841,8 @@ void QGLWindowSurface::updateGeometry() {
     ctx->makeCurrent();
 
 #ifndef QT_OPENGL_ES_2
-    if (d_ptr->destructive_swap_buffers) {
-        glGenTextures(1, &d_ptr->tex_id);
-        glBindTexture(target, d_ptr->tex_id);
-        glTexImage2D(target, 0, GL_RGBA, rect.width(), rect.height(), 0, GL_RGB, GL_UNSIGNED_BYTE, 0);
-
-        glTexParameterf(target, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
-        glTexParameterf(target, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
-        glBindTexture(target, 0);
-    }
+    if (d_ptr->destructive_swap_buffers)
+        initializeOffscreenTexture(rect.size());
 #endif
 
     qDebug() << "QGLWindowSurface: Using plain widget as window surface" << this;;
@@ -840,6 +850,23 @@ void QGLWindowSurface::updateGeometry() {
     d_ptr->ctx->d_ptr->internal_context = true;
 }
 
+bool QGLWindowSurface::initializeOffscreenTexture(const QSize &size)
+{
+    if (size == d_ptr->textureSize)
+        return false;
+
+    glGenTextures(1, &d_ptr->tex_id);
+    glBindTexture(GL_TEXTURE_2D, d_ptr->tex_id);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, size.width(), size.height(), 0, GL_RGB, GL_UNSIGNED_BYTE, 0);
+
+    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+    glBindTexture(GL_TEXTURE_2D, 0);
+
+    d_ptr->textureSize = size;
+    return true;
+}
+
 bool QGLWindowSurface::scroll(const QRegion &area, int dx, int dy)
 {
     // this code randomly fails currently for unknown reasons
diff --git a/src/opengl/qwindowsurface_gl_p.h b/src/opengl/qwindowsurface_gl_p.h
index ffc2e86..6906f35 100644
--- a/src/opengl/qwindowsurface_gl_p.h
+++ b/src/opengl/qwindowsurface_gl_p.h
@@ -107,6 +107,7 @@ private slots:
 
 private:
     void hijackWindow(QWidget *widget);
+    bool initializeOffscreenTexture(const QSize &size);
 
     QGLWindowSurfacePrivate *d_ptr;
 };