Fix transformed raster fonts on Windows

We removed all Q_WS_WIN code when going to Qt 5. One of the things
removed was the condition that we do painter path text rendering
for transformed, non-ttf fonts, since the GDI engine does not support
transforming those. This has now been reintroduced and adapted to the
QPA way of doing things, by checking for it in the font engine subclass.

Then there was the problem that QStaticText only supports cases
where the font engine can transform the glyphs. Thus we need to fall
back to regular text drawing in drawStaticText() for unsupported cases,
and we need to skip the optimized path in the raster engine (which
goes to drawStaticTextItem)

Task-number: QTBUG-30932
Change-Id: I17ba7355ee127811b0e77bb3a9b9db092e99893b
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

src/gui/painting/qpaintengine_raster.cpp

@@ -3078,7 +3078,8 @@ void QRasterPaintEngine::drawTextItem(const QPointF &p, const QTextItem &textIte
         ti.fontEngine->getGlyphPositions(ti.glyphs, matrix, ti.flags, glyphs, positions);
 
         drawCachedGlyphs(glyphs.size(), glyphs.constData(), positions.constData(), ti.fontEngine);
-    } else if (matrix.type() < QTransform::TxProject) {
+    } else if (matrix.type() < QTransform::TxProject
+               && ti.fontEngine->supportsTransformation(matrix)) {
         bool invertible;
         QTransform invMat = matrix.inverted(&invertible);
         if (!invertible)

src/gui/painting/qpainter.cpp

@@ -5727,17 +5727,20 @@ void QPainter::drawStaticText(const QPointF &topLeftPosition, const QStaticText
         staticText_d->needsRelayout = true;
     }
 
-    // If we don't have an extended paint engine, or if the painter is projected,
-    // we go through standard code path
-    if (d->extended == 0 || !d->state->matrix.isAffine()) {
-        staticText_d->paintText(topLeftPosition, this);
-        return;
-    }
-
     QFontEngine *fe = staticText_d->font.d->engineForScript(QChar::Script_Common);
     if (fe->type() == QFontEngine::Multi)
         fe = static_cast<QFontEngineMulti *>(fe)->engine(0);
 
+    // If we don't have an extended paint engine, if the painter is projected,
+    // or if the font engine does not support the matrix, we go through standard
+    // code path
+    if (d->extended == 0
+            || !d->state->matrix.isAffine()
+            || !fe->supportsTransformation(d->state->matrix)) {
+        staticText_d->paintText(topLeftPosition, this);
+        return;
+    }
+
     bool engineRequiresPretransform = d->extended->requiresPretransformedGlyphPositions(fe, d->state->matrix);
     if (staticText_d->untransformedCoordinates && engineRequiresPretransform) {
         // The coordinates are untransformed, and the engine can't deal with that

src/plugins/platforms/windows/qwindowsfontengine.cpp

@@ -1412,5 +1412,11 @@ void QWindowsMultiFontEngine::loadEngine(int at)
     // TODO: increase cost in QFontCache for the font engine loaded here
 }
 
+bool QWindowsFontEngine::supportsTransformation(const QTransform &transform) const
+{
+    // Support all transformations for ttf files, and translations for raster fonts
+    return ttf || transform.type() <= QTransform::TxTranslate;
+}
+
 QT_END_NAMESPACE
 

src/plugins/platforms/windows/qwindowsfontengine.h

@@ -123,6 +123,7 @@ public:
     virtual QImage alphaRGBMapForGlyph(glyph_t t, QFixed subPixelPosition, const QTransform &xform);
 
     virtual QFontEngine *cloneWithSize(qreal pixelSize) const;
+    virtual bool supportsTransformation(const QTransform &transform) const;
 
 #ifndef Q_CC_MINGW
     virtual void getGlyphBearings(glyph_t glyph, qreal *leftBearing = 0, qreal *rightBearing = 0);