VGImage readback support in QPixmap on OpenVG.

Enable readback of pixel data for pixmaps that are constructed directly
from a VGImage. These do not have any backing data in main memory
(i.e. 'source' is null), however certain operations, like toImage(),
fill(), or painting into the pixmap do not work without it. With this
patch the data is read back via vgGetImageSubData when needed.

Task-number: QT-4669
Reviewed-by: Jani Hautakangas

5 files changed, 148 insertions, 12 deletions

diff --git a/src/openvg/qpixmapdata_vg.cpp b/src/openvg/qpixmapdata_vg.cpp
index c5da115..47de5ab 100644
--- a/src/openvg/qpixmapdata_vg.cpp
+++ b/src/openvg/qpixmapdata_vg.cpp
@@ -105,6 +105,8 @@ void QVGPixmapData::destroyImageAndContext()
     if (vgImage != VG_INVALID_HANDLE) {
         // We need to have a context current to destroy the image.
 #if !defined(QT_NO_EGL)
+        if (!context)
+            context = qt_vg_create_context(0, QInternal::Pixmap);
         if (context->isCurrent()) {
             destroyImages();
         } else {
@@ -243,10 +245,7 @@ void QVGPixmapData::fill(const QColor &color)
 {
     if (!isValid())
         return;
-
-    if (source.isNull())
-        source = QVolatileImage(w, h, sourceFormat());
-
+    forceToImage();
     if (source.depth() == 1) {
         // Pick the best approximate color in the image's colortable.
         int gray = qGray(color.rgba());
@@ -258,13 +257,11 @@ void QVGPixmapData::fill(const QColor &color)
     } else {
         source.fill(PREMUL(color.rgba()));
     }
-
-    // Re-upload the image to VG the next time toVGImage() is called.
-    recreate = true;
 }
 
 bool QVGPixmapData::hasAlphaChannel() const
 {
+    ensureReadback(true);
     if (!source.isNull())
         return source.hasAlphaChannel();
     else
@@ -273,6 +270,8 @@ bool QVGPixmapData::hasAlphaChannel() const
 
 void QVGPixmapData::setAlphaChannel(const QPixmap &alphaChannel)
 {
+    if (!isValid())
+        return;
     forceToImage();
     source.setAlphaChannel(alphaChannel);
 }
@@ -281,12 +280,11 @@ QImage QVGPixmapData::toImage() const
 {
     if (!isValid())
         return QImage();
-
+    ensureReadback(true);
     if (source.isNull()) {
         source = QVolatileImage(w, h, sourceFormat());
         recreate = true;
     }
-
     return source.toImage();
 }
 
@@ -476,18 +474,42 @@ int QVGPixmapData::metric(QPaintDevice::PaintDeviceMetric metric) const
     }
 }
 
-// Force the pixmap data to be backed by some valid data.
+// Ensures that the pixmap is backed by some valid data and forces the data to
+// be re-uploaded to the VGImage when toVGImage() is called next time.
 void QVGPixmapData::forceToImage()
 {
     if (!isValid())
         return;
 
+    ensureReadback(false);
+
     if (source.isNull())
         source = QVolatileImage(w, h, sourceFormat());
 
     recreate = true;
 }
 
+void QVGPixmapData::ensureReadback(bool readOnly) const
+{
+    if (vgImage != VG_INVALID_HANDLE && source.isNull()) {
+        source = QVolatileImage(w, h, sourceFormat());
+        source.beginDataAccess();
+        vgGetImageSubData(vgImage, source.bits(), source.bytesPerLine(),
+                          qt_vg_image_to_vg_format(source.format()),
+                          0, 0, w, h);
+        source.endDataAccess();
+        if (readOnly) {
+            recreate = false;
+        } else {
+            // Once we did a readback, the original VGImage must be destroyed
+            // because it may be shared (e.g. created via SgImage) and a subsequent
+            // upload of the image data may produce unexpected results.
+            const_cast<QVGPixmapData *>(this)->destroyImages();
+            recreate = true;
+        }
+    }
+}
+
 QImage::Format QVGPixmapData::sourceFormat() const
 {
     return QImage::Format_ARGB32_Premultiplied;
diff --git a/src/openvg/qpixmapdata_vg_p.h b/src/openvg/qpixmapdata_vg_p.h
index c4fd47f..80ff1cb 100644
--- a/src/openvg/qpixmapdata_vg_p.h
+++ b/src/openvg/qpixmapdata_vg_p.h
@@ -55,7 +55,7 @@
 
 #include <QtGui/private/qpixmap_raster_p.h>
 #include <QtGui/private/qvolatileimage_p.h>
-#include <private/qvg_p.h>
+#include "qvg_p.h"
 
 #if defined(Q_OS_SYMBIAN)
 class RSGImage;
@@ -126,6 +126,13 @@ public:
     // VGImage objects to reuse storage.
     virtual void reclaimImages();
 
+    // If vgImage is valid but source is null, copies pixel data from GPU back
+    // into main memory and destroys vgImage. For a normal pixmap this function
+    // does nothing, however if the pixmap was created directly from a VGImage
+    // (e.g. via SgImage on Symbian) then by doing the readback this ensures
+    // that QImage-based functions can operate too.
+    virtual void ensureReadback(bool readOnly) const;
+
     QSize size() const { return QSize(w, h); }
 
 #if defined(Q_OS_SYMBIAN)
diff --git a/src/openvg/qvg_symbian.cpp b/src/openvg/qvg_symbian.cpp
index 22cbb3c..c6521fd 100644
--- a/src/openvg/qvg_symbian.cpp
+++ b/src/openvg/qvg_symbian.cpp
@@ -127,7 +127,7 @@ void QVGPixmapData::fromNativeType(void* pixmap, NativeType type)
         }
 
         is_null = (w <= 0 || h <= 0);
-        source = QVolatileImage(); // vgGetImageSubData() some day?
+        source = QVolatileImage(); // readback will be done later, only when needed
         recreate = false;
         prevSize = QSize(w, h);
         updateSerial();
diff --git a/tests/auto/qpixmap/qpixmap.pro b/tests/auto/qpixmap/qpixmap.pro
index ff8258f..e6a8257 100644
--- a/tests/auto/qpixmap/qpixmap.pro
+++ b/tests/auto/qpixmap/qpixmap.pro
@@ -25,6 +25,7 @@ wince*: {
    LIBS += -lfbscli.dll -lbitgdi.dll -lgdi.dll
    contains(QT_CONFIG, openvg) {
        LIBS += $$QMAKE_LIBS_OPENVG
+       QT *= openvg
    }
 } else {
    DEFINES += SRCDIR=\\\"$$PWD\\\"
diff --git a/tests/auto/qpixmap/tst_qpixmap.cpp b/tests/auto/qpixmap/tst_qpixmap.cpp
index 62a6eb4..bd9c26f 100644
--- a/tests/auto/qpixmap/tst_qpixmap.cpp
+++ b/tests/auto/qpixmap/tst_qpixmap.cpp
@@ -68,6 +68,10 @@
 #include <fbs.h>
 #include <gdi.h>
 #include <bitdev.h>
+#if !defined(QT_NO_OPENVG)
+#include <QtOpenVG/qvg.h>
+#include <QtOpenVG/private/qpixmapdata_vg_p.h>
+#endif
 #endif
 
 #ifdef Q_WS_X11
@@ -185,6 +189,10 @@ private slots:
     void toImageDeepCopy();
 
     void loadAsBitmapOrPixmap();
+
+#if defined(Q_OS_SYMBIAN) && !defined(QT_NO_OPENVG)
+    void vgImageReadBack();
+#endif
 };
 
 static bool lenientCompare(const QPixmap &actual, const QPixmap &expected)
@@ -1767,6 +1775,104 @@ void tst_QPixmap::toImageDeepCopy()
     QVERIFY(first != second);
 }
 
+#if defined(Q_OS_SYMBIAN) && !defined(QT_NO_OPENVG)
+Q_OPENVG_EXPORT VGImage qPixmapToVGImage(const QPixmap& pixmap);
+class FriendlyVGPixmapData : public QVGPixmapData
+{
+public:
+    FriendlyVGPixmapData(PixelType type) : QVGPixmapData(type) { }
+    bool sourceIsNull() { return source.isNull(); }
+    friend QPixmap pixmapFromVGImage(VGImage image);
+};
+QPixmap pixmapFromVGImage(VGImage image)
+{
+    if (image != VG_INVALID_HANDLE) {
+        int w = vgGetParameteri(image, VG_IMAGE_WIDTH);
+        int h = vgGetParameteri(image, VG_IMAGE_HEIGHT);
+        FriendlyVGPixmapData *pd = new FriendlyVGPixmapData(QPixmapData::PixmapType);
+        pd->resize(w, h);
+        pd->vgImage = image;
+        pd->recreate = false;
+        pd->prevSize = QSize(pd->w, pd->h);
+        return QPixmap(pd);
+    }
+    return QPixmap();
+}
+class Content : public QWidget
+{
+public:
+    void paintEvent(QPaintEvent *) {
+        QPainter painter(this);
+        QColor testPixel(qRgb(200, 150, 100));
+        if (pm.isNull()) { // first phase: create a VGImage
+            painter.beginNativePainting();
+            vgimage = vgCreateImage(VG_sARGB_8888_PRE, w, h, VG_IMAGE_QUALITY_FASTER);
+            QImage img(20, 10, QImage::Format_ARGB32_Premultiplied);
+            img.fill(qRgb(0, 0, 0));
+            QPainter p(&img);
+            p.fillRect(0, 0, img.width(), img.height(), testPixel);
+            p.end();
+            vgImageSubData(vgimage, img.bits(), img.bytesPerLine(), VG_sARGB_8888_PRE, 0, 0, img.width(), img.height());
+            // Now the area 0,0 20x10 (in OpenVG coords) is filled with some color.
+            painter.endNativePainting();
+        } else { // second phase: check if readback works
+            painter.drawPixmap(0, 0, pm);
+            // Drawing should not cause readback, this is important for performance;
+            noreadback_ok = static_cast<FriendlyVGPixmapData *>(pm.pixmapData())->sourceIsNull();
+            // However toImage() requires readback.
+            QImage img = pm.toImage();
+            readback_ok = img.width() == pm.width();
+            readback_ok &= img.height() == pm.height();
+            readback_ok &= !static_cast<FriendlyVGPixmapData *>(pm.pixmapData())->sourceIsNull();
+            uint pix = img.pixel(1, 1);
+            content_ok = qRed(pix) == testPixel.red();
+            content_ok &= qGreen(pix) == testPixel.green();
+            content_ok &= qBlue(pix) == testPixel.blue();
+            pix = img.pixel(img.width() - 1, img.height() - 1);
+            content_ok &= qRed(pix) == 0;
+            content_ok &= qGreen(pix) == 0;
+            content_ok &= qBlue(pix) == 0;
+        }
+    }
+    int w;
+    int h;
+    VGImage vgimage;
+    QPixmap pm;
+    bool noreadback_ok;
+    bool readback_ok;
+    bool content_ok;
+};
+void tst_QPixmap::vgImageReadBack()
+{
+    QPixmap tmp(10, 20);
+    if (tmp.pixmapData()->classId() == QPixmapData::OpenVGClass) {
+        Content c;
+        c.w = 50;
+        c.h = 60;
+        c.vgimage = VG_INVALID_HANDLE;
+        c.noreadback_ok = c.readback_ok = c.content_ok = false;
+        c.showFullScreen();
+        QTest::qWaitForWindowShown(&c);
+        QVERIFY(c.vgimage != VG_INVALID_HANDLE);
+        QPixmap pm = pixmapFromVGImage(c.vgimage);
+        QVERIFY(!pm.isNull());
+        QCOMPARE(pm.width(), c.w);
+        QCOMPARE(pm.height(), c.h);
+        QVERIFY(qPixmapToVGImage(pm) == c.vgimage);
+        QVERIFY(static_cast<FriendlyVGPixmapData *>(pm.pixmapData())->sourceIsNull());
+        c.pm = pm;
+        // Make sure the second phase in paintEvent is executed too.
+        c.hide();
+        c.showFullScreen();
+        QTest::qWaitForWindowShown(&c);
+        QVERIFY(c.noreadback_ok);
+        QVERIFY(c.readback_ok);
+        QVERIFY(c.content_ok);
+    } else {
+        QSKIP("Not using openvg graphicssystem", SkipSingle);
+    }
+}
+#endif // Symbian & OpenVG
 
 QTEST_MAIN(tst_QPixmap)
 #include "tst_qpixmap.moc"