Changeset 54811 in webkit

Timestamp:

Feb 16, 2010 1:17:44 AM (14 years ago)

Author:

eric@webkit.org

Message:

2010-02-16 Noam Rosenthal <​noam.rosenthal@nokia.com>

Reviewed by Ariya Hidayat.

[Qt] canvas clipping is buggy
​https://bugs.webkit.org/show_bug.cgi?id=32405

Apparently the bug was in GraphicsContext::roundToDevicePixels, we
didn't take unto accounts rotation, so the device pixels were rounded
incorrectly. The new formula is a 1:1 copy from GraphicsContextCG so
it should be rather safe

Test: ​http://glimr.rubyforge.org/cake/canvas.html#Polaroids now looks right

• platform/graphics/qt/GraphicsContextQt.cpp: (WebCore::GraphicsContext::roundToDevicePixels): Copy the formula from GraphicsContextCG

Location:

trunk/WebCore

Files:

• ChangeLog (modified) (1 diff)
• platform/graphics/qt/GraphicsContextQt.cpp (modified) (1 diff)

trunk/WebCore/ChangeLog

@@ +1 @@
+2010-02-16  Noam Rosenthal  <noam.rosenthal@nokia.com>
+
+        Reviewed by Ariya Hidayat.
+
+        [Qt] canvas clipping is buggy
+        https://bugs.webkit.org/show_bug.cgi?id=32405
+
+        Apparently the bug was in GraphicsContext::roundToDevicePixels, we
+        didn't take unto accounts rotation, so the device pixels were rounded
+        incorrectly. The new formula is a 1:1 copy from GraphicsContextCG so
+        it should be rather safe
+
+        Test: http://glimr.rubyforge.org/cake/canvas.html#Polaroids now looks right
+
+        * platform/graphics/qt/GraphicsContextQt.cpp:
+        (WebCore::GraphicsContext::roundToDevicePixels): Copy the formula from
+        GraphicsContextCG
+
 2010-02-16  Yury Semikhatsky  <yurys@chromium.org>
 

trunk/WebCore/platform/graphics/qt/GraphicsContextQt.cpp

@@ -762 +762 @@
 FloatRect GraphicsContext::roundToDevicePixels(const FloatRect& frect)
 {
-    QRectF rect(frect);
-    rect = m_data->p()->deviceMatrix().mapRect(rect);
-
-    QRect result = rect.toRect(); //round it
-    return FloatRect(QRectF(result));
+    // It is not enough just to round to pixels in device space. The rotation part of the
+    // affine transform matrix to device space can mess with this conversion if we have a
+    // rotating image like the hands of the world clock widget. We just need the scale, so
+    // we get the affine transform matrix and extract the scale.
+    QPainter* painter = platformContext();
+    QTransform deviceTransform = painter->deviceTransform();
+    if (deviceTransform.isIdentity())
+        return frect;
+
+    qreal deviceScaleX = sqrtf(deviceTransform.m11() * deviceTransform.m11() + deviceTransform.m12() * deviceTransform.m12());
+    qreal deviceScaleY = sqrtf(deviceTransform.m21() * deviceTransform.m21() + deviceTransform.m22() * deviceTransform.m22());
+
+    QPoint deviceOrigin(frect.x() * deviceScaleX, frect.y() * deviceScaleY);
+    QPoint deviceLowerRight(frect.right() * deviceScaleX, frect.bottom() * deviceScaleY);
+
+    // Don't let the height or width round to 0 unless either was originally 0
+    if (deviceOrigin.y() == deviceLowerRight.y() && frect.height())
+        deviceLowerRight.setY(deviceLowerRight.y() + 1);
+    if (deviceOrigin.x() == deviceLowerRight.x() && frect.width())
+        deviceLowerRight.setX(deviceLowerRight.x() + 1);
+
+    FloatPoint roundedOrigin = FloatPoint(deviceOrigin.x() / deviceScaleX, deviceOrigin.y() / deviceScaleY);
+    FloatPoint roundedLowerRight = FloatPoint(deviceLowerRight.x() / deviceScaleX, deviceLowerRight.y() / deviceScaleY);
+    return FloatRect(roundedOrigin, roundedLowerRight - roundedOrigin);
 }