Update clipping area when antialiasing changes

Antialiasing is disabled when the painter's antialiasing attribute
is set behind the clipping function(example `setClipPath` or
`setClipRegion`). The cause of this problem is that the
antialiasing state of the clipping region is not updated after the
antialiasing attribute is set.

A variable is required to record the painter's transformation state
set before the clipping function, because the transformation will be
applied to the clipping region, resulting in the abnormal clipping
region. The value of `s->matrix` is not accurate for the clipping fun-
ction.

Pick-to: 6.2
Fixes: QTBUG-97269
Change-Id: I409a9db32efc3b991ebb97ec9aed19bbddb273d8
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>

3 files changed, 41 insertions, 0 deletions

diff --git a/src/gui/painting/qpaintengine_raster.cpp b/src/gui/painting/qpaintengine_raster.cpp
index 76489da0b4..845291b61b 100644
--- a/src/gui/painting/qpaintengine_raster.cpp
+++ b/src/gui/painting/qpaintengine_raster.cpp
@@ -882,6 +882,9 @@ void QRasterPaintEngine::renderHintsChanged()
 
     Q_D(QRasterPaintEngine);
     d->recalculateFastImages();
+
+    if (was_aa != s->flags.antialiased)
+        d->updateClipping();
 }
 
 /*!
@@ -1245,6 +1248,7 @@ void QRasterPaintEngine::clip(const QVectorPath &path, Qt::ClipOperation op)
         ensureOutlineMapper();
         d->rasterize(d->outlineMapper->convertPath(path), qt_span_clip, &clipData, nullptr);
 
+        newClip->clipTransform = s->matrix;
         newClip->fixup();
 
         if (s->flags.has_clip_ownership)
@@ -1329,6 +1333,7 @@ bool QRasterPaintEngine::setClipRectInDeviceCoords(const QRect &r, Qt::ClipOpera
         return false;
     }
 
+    s->clip->clipTransform = s->matrix;
     qrasterpaintengine_dirty_clip(d, s);
     return true;
 }
@@ -1384,6 +1389,7 @@ void QRasterPaintEngine::clip(const QRegion &region, Qt::ClipOperation op)
         else if (curClip->hasRegionClip)
             newClip->setClipRegion(r & curClip->clipRegion);
 
+        newClip->clipTransform = s->matrix;
         qrasterpaintengine_dirty_clip(d, s);
     }
 }
@@ -3701,6 +3707,37 @@ void QRasterPaintEnginePrivate::rasterize(QT_FT_Outline *outline,
     free(rasterPoolOnHeap);
 }
 
+void QRasterPaintEnginePrivate::updateClipping()
+{
+    Q_Q(QRasterPaintEngine);
+    QRasterPaintEngineState *s = q->state();
+
+    if (!s->clipEnabled)
+        return;
+
+    bool noClipPath = s->clipPath.isEmpty();
+    bool noClipRegion = s->clipRegion.isEmpty();
+
+    if (noClipPath && noClipRegion)
+        return;
+
+    if (!s->clip)
+        return;
+
+    const QTransform stateTransform = s->matrix;
+    s->matrix = s->clip->clipTransform;
+
+    qrasterpaintengine_state_setNoClip(s);
+
+    if (noClipRegion) {
+        q->clip(qtVectorPathForPath(s->clipPath), s->clipOperation);
+    } else {
+        q->clip(s->clipRegion, s->clipOperation);
+    }
+
+    s->matrix = stateTransform;
+}
+
 void QRasterPaintEnginePrivate::recalculateFastImages()
 {
     Q_Q(QRasterPaintEngine);
diff --git a/src/gui/painting/qpaintengine_raster_p.h b/src/gui/painting/qpaintengine_raster_p.h
index d25fe4c3b3..9751eb3da8 100644
--- a/src/gui/painting/qpaintengine_raster_p.h
+++ b/src/gui/painting/qpaintengine_raster_p.h
@@ -276,6 +276,7 @@ public:
     void rasterize(QT_FT_Outline *outline, ProcessSpans callback, QSpanData *spanData, QRasterBuffer *rasterBuffer);
     void rasterize(QT_FT_Outline *outline, ProcessSpans callback, void *userData, QRasterBuffer *rasterBuffer);
     void updateMatrixData(QSpanData *spanData, const QBrush &brush, const QTransform &brushMatrix);
+    void updateClipping();
 
     void systemStateChanged() override;
 
@@ -374,6 +375,7 @@ public:
 
     QRect clipRect;
     QRegion clipRegion;
+    QTransform clipTransform;
 
     uint enabled : 1;
     uint hasRectClip : 1;
diff --git a/src/gui/painting/qpainter.cpp b/src/gui/painting/qpainter.cpp
index e5caf0813b..0ebc6253db 100644
--- a/src/gui/painting/qpainter.cpp
+++ b/src/gui/painting/qpainter.cpp
@@ -2844,6 +2844,7 @@ void QPainter::setClipRegion(const QRegion &r, Qt::ClipOperation op)
             d->state->clipInfo.clear();
         d->state->clipInfo.append(QPainterClipInfo(r, op, d->state->matrix));
         d->state->clipOperation = op;
+        d->state->clipRegion = r;
         return;
     }
 
@@ -3057,6 +3058,7 @@ void QPainter::setClipPath(const QPainterPath &path, Qt::ClipOperation op)
             d->state->clipInfo.clear();
         d->state->clipInfo.append(QPainterClipInfo(path, op, d->state->matrix));
         d->state->clipOperation = op;
+        d->state->clipPath = path;
         return;
     }