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, 11 insertions, 7 deletions

diff --git a/src/gui/painting/qpainter.cpp b/src/gui/painting/qpainter.cpp
index 4a18df899e..41e81c5fbe 100644
--- a/src/gui/painting/qpainter.cpp
+++ b/src/gui/painting/qpainter.cpp
@@ -530,7 +530,10 @@ static inline QBrush stretchGradientToUserSpace(const QBrush &brush, const QRect
     g.setCoordinateMode(QGradient::LogicalMode);
 
     QBrush b(g);
-    b.setTransform(gradientToUser * b.transform());
+    if (brush.gradient()->coordinateMode() == QGradient::ObjectMode)
+        b.setTransform(b.transform() * gradientToUser);
+    else
+        b.setTransform(gradientToUser * b.transform());
     return b;
 }
 
@@ -569,7 +572,7 @@ void QPainterPrivate::drawStretchedGradient(const QPainterPath &path, DrawOperat
         } else {
             needsFill = true;
 
-            if (brushMode == QGradient::ObjectBoundingMode) {
+            if (brushMode == QGradient::ObjectBoundingMode || brushMode == QGradient::ObjectMode) {
                 Q_ASSERT(engine->hasFeature(QPaintEngine::PatternTransform));
                 boundingRect = path.boundingRect();
                 q->setBrush(stretchGradientToUserSpace(brush, boundingRect));
@@ -613,11 +616,11 @@ void QPainterPrivate::drawStretchedGradient(const QPainterPath &path, DrawOperat
                 changedBrush = true;
             }
 
-            if (penMode == QGradient::ObjectBoundingMode) {
+            if (penMode == QGradient::ObjectBoundingMode || penMode == QGradient::ObjectMode) {
                 Q_ASSERT(engine->hasFeature(QPaintEngine::PatternTransform));
 
                 // avoid computing the bounding rect twice
-                if (!needsFill || brushMode != QGradient::ObjectBoundingMode)
+                if (!needsFill || (brushMode != QGradient::ObjectBoundingMode && brushMode != QGradient::ObjectMode))
                     boundingRect = path.boundingRect();
 
                 QPen p = pen;
@@ -849,8 +852,8 @@ void QPainterPrivate::updateEmulationSpecifier(QPainterState *s)
         gradientStretch |= (brushMode == QGradient::StretchToDeviceMode);
         gradientStretch |= (penMode == QGradient::StretchToDeviceMode);
 
-        objectBoundingMode |= (brushMode == QGradient::ObjectBoundingMode);
-        objectBoundingMode |= (penMode == QGradient::ObjectBoundingMode);
+        objectBoundingMode |= (brushMode == QGradient::ObjectBoundingMode || brushMode == QGradient::ObjectMode);
+        objectBoundingMode |= (penMode == QGradient::ObjectBoundingMode || penMode == QGradient::ObjectMode);
     }
     if (gradientStretch)
         s->emulationSpecifier |= QGradient_StretchToDevice;
@@ -6857,7 +6860,8 @@ static inline bool needsResolving(const QBrush &brush)
     Qt::BrushStyle s = brush.style();
     return ((s == Qt::LinearGradientPattern || s == Qt::RadialGradientPattern ||
              s == Qt::ConicalGradientPattern) &&
-            brush.gradient()->coordinateMode() == QGradient::ObjectBoundingMode);
+            (brush.gradient()->coordinateMode() == QGradient::ObjectBoundingMode ||
+             brush.gradient()->coordinateMode() == QGradient::ObjectMode));
 }
 
 /*!