Fix floating point clip rectangle rounding in raster and opengl paint engine

Fixes: QTBUG-83229
Pick-to: 5.15
Change-Id: If94028f27c9085e391acb9c423cde1b7c12bca36
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

src/gui/painting/qpaintengine_raster.cpp

@@ -1251,7 +1251,7 @@ void QRasterPaintEngine::clip(const QVectorPath &path, Qt::ClipOperation op)
 #endif
             const qreal *points = path.points();
             QRectF r(points[0], points[1], points[4]-points[0], points[5]-points[1]);
-            if (setClipRectInDeviceCoords(s->matrix.mapRect(r).toRect(), op))
+            if (setClipRectInDeviceCoords(s->matrix.mapRect(r).toAlignedRect(), op))
                 return;
         }
     }

src/opengl/qopenglpaintengine.cpp

@@ -2496,7 +2496,7 @@ void QOpenGL2PaintEngineEx::clip(const QVectorPath &path, Qt::ClipOperation op)
                 && qFuzzyIsNull(state()->matrix.m11())
                 && qFuzzyIsNull(state()->matrix.m22())))
         {
-            state()->rectangleClip = state()->rectangleClip.intersected(state()->matrix.mapRect(rect).toRect());
+            state()->rectangleClip = state()->rectangleClip.intersected(state()->matrix.mapRect(rect).toAlignedRect());
             d->updateClipScissorTest();
             return;
         }

tests/auto/gui/painting/qpainter/tst_qpainter.cpp

@@ -138,6 +138,7 @@ private slots:
 
     void disableEnableClipping();
     void setClipRect();
+    void clipRect();
     void setEqualClipRegionAndPath_data();
     void setEqualClipRegionAndPath();
 
@@ -1750,6 +1751,42 @@ void tst_QPainter::setClipRect()
     }
 }
 
+/*
+    Verify that the clipping works correctly.
+    The red outline should be covered by the blue rect on top and left,
+    while it should be clipped on the right and bottom and thus the red outline be visible
+
+    See: QTBUG-83229
+*/
+void tst_QPainter::clipRect()
+{
+    int width = 654;
+    int height = 480;
+    QRect rect(0, 0, width, height);
+
+    QImage image(width, height, QImage::Format_ARGB32);
+    QPainter p(&image);
+    qreal halfWidth = width / 2.0;
+    qreal halfHeight = height / 2.0;
+
+    QRectF clipRect = QRectF(halfWidth - halfWidth / 2.0, halfHeight - halfHeight / 2.0,
+                             halfWidth / 2.0, halfHeight / 2.0);
+
+    p.fillRect(rect, Qt::white);
+    p.setPen(Qt::red);
+    p.drawRect(clipRect);
+
+    p.setClipRect(clipRect, Qt::ReplaceClip);
+    p.fillRect(rect, Qt::blue);
+
+    p.end();
+
+    QCOMPARE(image.pixelColor(clipRect.left() + 1, clipRect.top()), QColor(Qt::blue));
+    QCOMPARE(image.pixelColor(clipRect.left(), clipRect.top() + 1), QColor(Qt::blue));
+    QCOMPARE(image.pixelColor(clipRect.left() + 1, clipRect.bottom()), QColor(Qt::red));
+    QCOMPARE(image.pixelColor(clipRect.right(), clipRect.top() + 1), QColor(Qt::red));
+}
+
 /*
     This tests the two different clipping approaches in QRasterPaintEngine,
     one when using a QRegion and one when using a QPainterPath. They should

tests/auto/gui/qopengl/tst_qopengl.cpp

@@ -93,6 +93,7 @@ private slots:
     void defaultSurfaceFormat();
     void imageFormatPainting();
     void nullTextureInitializtion();
+    void clipRect();
 
 #ifdef USE_GLX
     void glxContextWrap();
@@ -1686,6 +1687,74 @@ void tst_QOpenGL::nullTextureInitializtion()
     QVERIFY(!t.isCreated());
 }
 
+/*
+    Verify that the clipping works correctly.
+    The red outline should be covered by the blue rect on top and left,
+    while it should be clipped on the right and bottom and thus the red outline be visible
+
+    See: QTBUG-83229
+*/
+void tst_QOpenGL::clipRect()
+{
+#if defined(Q_OS_LINUX) && defined(Q_CC_GNU) && !defined(__x86_64__)
+    QSKIP("QTBUG-22617");
+#endif
+
+    QScopedPointer<QSurface> surface(createSurface(int(QSurface::Window)));
+
+    QOpenGLContext ctx;
+    QVERIFY(ctx.create());
+
+    QVERIFY(ctx.makeCurrent(surface.data()));
+
+    if (!QOpenGLFramebufferObject::hasOpenGLFramebufferObjects())
+        QSKIP("QOpenGLFramebufferObject not supported on this platform");
+
+    // No multisample with combined depth/stencil attachment:
+    QOpenGLFramebufferObjectFormat fboFormat;
+    fboFormat.setAttachment(QOpenGLFramebufferObject::CombinedDepthStencil);
+
+    // Uncomplicate things by using POT:
+    const QSize size(654, 480);
+    const QRect rect(QPoint(0, 0), size);
+    QOpenGLFramebufferObject fbo(size, fboFormat);
+
+    if (fbo.attachment() != QOpenGLFramebufferObject::CombinedDepthStencil)
+        QSKIP("FBOs missing combined depth~stencil support");
+
+    QVERIFY(fbo.bind());
+
+    QPainter fboPainter;
+    QOpenGLPaintDevice device(fbo.width(), fbo.height());
+    bool painterBegun = fboPainter.begin(&device);
+    QVERIFY(painterBegun);
+
+    qreal halfWidth = size.width() / 2.0;
+    qreal halfHeight = size.height() / 2.0;
+
+    QRectF clipRect = QRectF(halfWidth - halfWidth / 2.0, halfHeight - halfHeight / 2.0,
+                             halfWidth / 2.0, halfHeight / 2.0);
+
+    fboPainter.fillRect(rect, Qt::white);
+    fboPainter.setPen(Qt::red);
+    fboPainter.drawRect(clipRect);
+
+    fboPainter.setClipRect(clipRect, Qt::ReplaceClip);
+    fboPainter.fillRect(rect, Qt::blue);
+
+    fboPainter.end();
+
+    const QImage fb = fbo.toImage().convertToFormat(QImage::Format_RGB32);
+    QCOMPARE(fb.size(), size);
+
+    QCOMPARE(fb.pixelColor(clipRect.left() + 1, clipRect.top()), QColor(Qt::blue));
+    QCOMPARE(fb.pixelColor(clipRect.left(), clipRect.top() + 1), QColor(Qt::blue));
+    QCOMPARE(fb.pixelColor(clipRect.left() + 1, clipRect.bottom()), QColor(Qt::red));
+
+    // Enable this once QTBUG-85286 is fixed
+    //QCOMPARE(fb.pixelColor(clipRect.right(), clipRect.top() + 1), QColor(Qt::red));
+}
+
 QTEST_MAIN(tst_QOpenGL)
 
 #include "tst_qopengl.moc"