Add ObjectMode coordinate mode to QGradient

The ObjectBoundingMode coordinate mode of QGradient allows specifying
the gradient coordinates relative to the object being painted. But if
the gradient brush also has a transformation, that transformation is
applied in the logical, not object, coordinate space. That behavior is
counterintuitive. However, changing it now would break existing
code. Instead, we introduce a new coordinate mode enum with the
expected behavior, and document the old one as deprecated.

This prepares to fix the bugs below in qtsvg, by making
it possible to specify the same behavior in Qt as SVG has.

[ChangeLog][QtGui][QGradient] Add ObjectMode coordinate mode
[ChangeLog][Important Behavior Changes] QDataStream version bumped up to 18 to account for changes in the serialization of QGradient.

Task-number: QTBUG-59978
Task-number: QTBUG-67995
Change-Id: I8820a2555359812f3e1a46e37d6ac2cc29a2091d
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

1 files changed, 10 insertions, 9 deletions

diff --git a/src/gui/painting/qemulationpaintengine.cpp b/src/gui/painting/qemulationpaintengine.cpp
index 49ecd3b318..638834ef3b 100644
--- a/src/gui/painting/qemulationpaintengine.cpp
+++ b/src/gui/painting/qemulationpaintengine.cpp
@@ -74,10 +74,11 @@ QPainterState *QEmulationPaintEngine::createState(QPainterState *orig) const
 
 static inline void combineXForm(QBrush *brush, const QRectF &r)
 {
-    QTransform t = brush->transform();
-    t.translate(r.x(), r.y());
-    t.scale(r.width(), r.height());
-    brush->setTransform(t);
+    QTransform t(r.width(), 0, 0, r.height(), r.x(), r.y());
+    if (brush->gradient()->coordinateMode() == QGradient::ObjectMode)
+        brush->setTransform(brush->transform() * t);
+    else
+        brush->setTransform(t * brush->transform());
 }
 
 void QEmulationPaintEngine::fill(const QVectorPath &path, const QBrush &brush)
@@ -96,7 +97,7 @@ void QEmulationPaintEngine::fill(const QVectorPath &path, const QBrush &brush)
         if (coMode > QGradient::LogicalMode) {
             QBrush copy = brush;
             const QPaintDevice *d = real_engine->painter()->device();
-            QRectF r = (coMode == QGradient::ObjectBoundingMode) ? path.controlPointRect() : QRectF(0, 0, d->width(), d->height());
+            QRectF r = (coMode == QGradient::StretchToDeviceMode) ? QRectF(0, 0, d->width(), d->height()) : path.controlPointRect();
             combineXForm(&copy, r);
             real_engine->fill(path, copy);
             return;
@@ -132,7 +133,7 @@ void QEmulationPaintEngine::stroke(const QVectorPath &path, const QPen &pen)
         QGradient::CoordinateMode coMode = brush.gradient()->coordinateMode();
         if (coMode > QGradient::LogicalMode) {
             const QPaintDevice *d = real_engine->painter()->device();
-            QRectF r = (coMode == QGradient::ObjectBoundingMode) ? path.controlPointRect() : QRectF(0, 0, d->width(), d->height());
+            QRectF r = (coMode == QGradient::StretchToDeviceMode) ? QRectF(0, 0, d->width(), d->height()) : path.controlPointRect();
             combineXForm(&brush, r);
             copy.setBrush(brush);
             real_engine->stroke(path, copy);
@@ -174,9 +175,9 @@ void QEmulationPaintEngine::drawTextItem(const QPointF &p, const QTextItem &text
             QBrush copy = s->pen.brush();
             const QPaintDevice *d = real_engine->painter()->device();
             const QTextItemInt &ti = static_cast<const QTextItemInt &>(textItem);
-            QRectF r = (g.coordinateMode() == QGradient::ObjectBoundingMode) ?
-                        QRectF(p.x(), p.y() - ti.ascent.toReal(), ti.width.toReal(), (ti.ascent + ti.descent + 1).toReal()) :
-                        QRectF(0, 0, d->width(), d->height());
+            QRectF r = (g.coordinateMode() == QGradient::StretchToDeviceMode) ?
+                        QRectF(0, 0, d->width(), d->height()) :
+                        QRectF(p.x(), p.y() - ti.ascent.toReal(), ti.width.toReal(), (ti.ascent + ti.descent + 1).toReal());
             combineXForm(&copy, r);
             g.setCoordinateMode(QGradient::LogicalMode);
             QBrush brush(g);