Use fallback stroker for cosmetic strokes with asymetric transforms

Reviewed-by: Samuel

2 files changed, 14 insertions, 3 deletions

diff --git a/src/gui/painting/qtransform.cpp b/src/gui/painting/qtransform.cpp
index 8118450..1bd5842 100644
--- a/src/gui/painting/qtransform.cpp
+++ b/src/gui/painting/qtransform.cpp
@@ -2214,12 +2214,14 @@ bool qt_scaleForTransform(const QTransform &transform, qreal *scale)
 {
     const QTransform::TransformationType type = transform.type();
     if (type <= QTransform::TxTranslate) {
-        *scale = 1;
+        if (scale)
+            *scale = 1;
         return true;
     } else if (type == QTransform::TxScale) {
         const qreal xScale = qAbs(transform.m11());
         const qreal yScale = qAbs(transform.m22());
-        *scale = qMax(xScale, yScale);
+        if (scale)
+            *scale = qMax(xScale, yScale);
         return qFuzzyCompare(xScale, yScale);
     }
 
@@ -2227,7 +2229,8 @@ bool qt_scaleForTransform(const QTransform &transform, qreal *scale)
                          + transform.m21() * transform.m21();
     const qreal yScale = transform.m12() * transform.m12()
                          + transform.m22() * transform.m22();
-    *scale = qSqrt(qMax(xScale, yScale));
+    if (scale)
+        *scale = qSqrt(qMax(xScale, yScale));
     return type == QTransform::TxRotate && qFuzzyCompare(xScale, yScale);
 }
 
diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index d20700f..1527e72 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -1221,6 +1221,9 @@ void QGL2PaintEngineEx::fill(const QVectorPath &path, const QBrush &brush)
     }
 }
 
+extern bool qt_scaleForTransform(const QTransform &transform, qreal *scale); // qtransform.cpp
+
+
 void QGL2PaintEngineEx::stroke(const QVectorPath &path, const QPen &pen)
 {
     Q_D(QGL2PaintEngineEx);
@@ -1231,6 +1234,11 @@ void QGL2PaintEngineEx::stroke(const QVectorPath &path, const QPen &pen)
         return;
 
     QOpenGL2PaintEngineState *s = state();
+    if (pen.isCosmetic() && !qt_scaleForTransform(s->transform(), 0)) {
+        // QTriangulatingStroker class is not meant to support cosmetically sheared strokes.
+        QPaintEngineEx::stroke(path, pen);
+        return;
+    }
 
     ensureActive();