[blitter] Work on tst_QPixmap::clear()

By default QPixmap may not hasAlphaChannel(), only if setMask()
or fill() with a transparent color is called a QPixmap will
hasAlphaChannel().

Make the QBlittablePlatformPixmap remember if there is an alpha
channel, pass this as parameter in createBlittable to make it
clear that this is required and not optional.

Update the DirectFB plugin to handle this parameter to create a
RGB32 or ARGB Surface depending on the alpha value, also only use
PreMultiplied alpha when using ARGB. Separate the two constructors
for the QDirectFbBlitter to either adopt a DirectFB Surface or to
create one.

Cherry-picked-from: qtbase:ab50b60f5cc237d5620f3ff3b2eb44c857f8f60b

Change-Id: I8abf82408ecd2d075fc6f241ace8be2a34ac56e7
Reviewed-by: Jørgen Lind <jorgen.lind@nokia.com>

Merge-request: 1492
Reviewed-by: Jørgen Lind <jorgen.lind@nokia.com>

2 files changed, 15 insertions, 3 deletions

diff --git a/src/gui/image/qpixmap_blitter.cpp b/src/gui/image/qpixmap_blitter.cpp
index f8fb538..c73e6a9 100644
--- a/src/gui/image/qpixmap_blitter.cpp
+++ b/src/gui/image/qpixmap_blitter.cpp
@@ -58,6 +58,7 @@ static int global_ser_no = 0;
 
 QBlittablePixmapData::QBlittablePixmapData()
     : QPixmapData(QPixmapData::PixmapType,BlitterClass)
+    , m_alpha(false)
 #ifdef QT_BLITTER_RASTEROVERLAY
     ,m_rasterOverlay(0), m_unmergedCopy(0)
 #endif //QT_BLITTER_RASTEROVERLAY
@@ -77,7 +78,7 @@ QBlittable *QBlittablePixmapData::blittable() const
 {
     if (!m_blittable) {
         QBlittablePixmapData *that = const_cast<QBlittablePixmapData *>(this);
-        that->m_blittable.reset(this->createBlittable(QSize(w,h)));
+        that->m_blittable.reset(this->createBlittable(QSize(w,h), m_alpha));
     }
 
     return m_blittable.data();
@@ -136,7 +137,16 @@ void QBlittablePixmapData::fill(const QColor &color)
     if (color.alpha() == 255 && blittable()->capabilities() & QBlittable::SolidRectCapability) {
         blittable()->unlock();
         blittable()->fillRect(QRectF(0,0,w,h),color);
-    }else {
+    } else {
+        // Need to be backed with an alpha channel now. It would be nice
+        // if we could just change the format, e.g. when going from
+        // RGB32 -> ARGB8888.
+        if (color.alpha() != 255 && !hasAlphaChannel()) {
+            m_blittable.reset(0);
+            m_engine.reset(0);
+            m_alpha = true;
+        }
+
         uint pixel;
         switch (blittable()->lock()->format()) {
         case QImage::Format_ARGB32_Premultiplied:
@@ -182,6 +192,7 @@ bool QBlittablePixmapData::hasAlphaChannel() const
 void QBlittablePixmapData::fromImage(const QImage &image,
                                      Qt::ImageConversionFlags flags)
 {
+    m_alpha = image.hasAlphaChannel();
     resize(image.width(),image.height());
     markRasterOverlay(QRect(0,0,w,h));
     QImage *thisImg = buffer();
diff --git a/src/gui/image/qpixmap_blitter_p.h b/src/gui/image/qpixmap_blitter_p.h
index 9b809ca..4742a83 100644
--- a/src/gui/image/qpixmap_blitter_p.h
+++ b/src/gui/image/qpixmap_blitter_p.h
@@ -55,7 +55,7 @@ public:
     QBlittablePixmapData();
     ~QBlittablePixmapData();
 
-    virtual QBlittable *createBlittable(const QSize &size) const = 0;
+    virtual QBlittable *createBlittable(const QSize &size, bool alpha) const = 0;
     QBlittable *blittable() const;
     void setBlittable(QBlittable *blittable);
 
@@ -85,6 +85,7 @@ public:
 protected:
     QScopedPointer<QBlitterPaintEngine> m_engine;
     QScopedPointer<QBlittable> m_blittable;
+    bool m_alpha;
 
 #ifdef QT_BLITTER_RASTEROVERLAY
     QImage *m_rasterOverlay;