1 files changed, 86 insertions, 0 deletions
diff --git a/src/quicknativestyle/items/qquickstyleitemscrollviewcorner.cpp b/src/quicknativestyle/items/qquickstyleitemscrollviewcorner.cpp
new file mode 100644
index 0000000000..d6ce12434a
--- /dev/null
+++ b/src/quicknativestyle/items/qquickstyleitemscrollviewcorner.cpp
@@ -0,0 +1,86 @@
+// Copyright (C) 2020 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#include "qquickstyleitemscrollviewcorner.h"
+
+StyleItemGeometry QQuickStyleItemScrollViewCorner::calculateGeometry()
+{
+    QStyleOptionSlider styleOption;
+    initStyleOption(styleOption);
+
+    StyleItemGeometry geometry;
+
+    // The size of the corner should be the width of the vertical
+    // scrollbar and the height of the horizontal scrollbar.
+    styleOption.orientation = Qt::Vertical;
+    const auto vScrollBarWidth = style()->sizeFromContents(QStyle::CT_ScrollBar, &styleOption, QSize(0, 0)).width();
+    styleOption.orientation = Qt::Horizontal;
+    const auto hScrollBarHeight = style()->sizeFromContents(QStyle::CT_ScrollBar, &styleOption, QSize(0, 0)).height();
+
+    geometry.minimumSize = QSize(vScrollBarWidth, hScrollBarHeight);
+    geometry.implicitSize = geometry.minimumSize;
+
+    return geometry;
+}
+
+void QQuickStyleItemScrollViewCorner::paintEvent(QPainter *painter) const
+{
+    QStyleOptionSlider styleOption;
+    initStyleOption(styleOption);
+
+    // Grab a center piece of a vertical scrollbar groove onto a QImage, and use this
+    // image to draw a corner. We draw the corner by first drawing the piece as it is, and
+    // then rotate it 90 degrees, clip it into a triangle, and draw it once more on top.
+    // The result is that we end up with one vertical and one horizontal triangle that
+    // together form a filled corner rectangle.
+
+    styleOption.orientation = Qt::Vertical;
+
+    const qreal scale = window()->effectiveDevicePixelRatio();
+    const int grooveWidth = minimumSize().width();
+    const int grooveHeight = minimumSize().height();
+    const QSize scrollBarMinSize = style()->sizeFromContents(QStyle::CT_ScrollBar, &styleOption, QSize(0, 0));
+    const QSize scrollBarSize = scrollBarMinSize + QSize(0, grooveHeight);
+    const int hStart = scrollBarMinSize.height() / 2;
+    const QRect targetImageRect(0, hStart * scale, grooveWidth * scale, grooveHeight * scale);
+
+    QImage scrollBarImage(scrollBarSize * scale, QImage::Format_ARGB32_Premultiplied);
+    scrollBarImage.setDevicePixelRatio(scale);
+    scrollBarImage.fill(Qt::transparent);
+    QPainter scrollBarPainter(&scrollBarImage);
+    styleOption.rect = QRect(QPoint(0, 0), scrollBarSize);
+    style()->drawComplexControl(QStyle::CC_ScrollBar, &styleOption, &scrollBarPainter);
+
+    // Draw vertical groove
+    painter->drawImage(QPoint(0, 0), scrollBarImage, targetImageRect);
+
+    QPainterPath path;
+    path.moveTo(0, 0);
+    path.lineTo(0, grooveHeight);
+    path.lineTo(grooveWidth, grooveHeight);
+    path.closeSubpath();
+
+    QTransform transform;
+    transform.translate(grooveWidth, 0);
+    transform.rotate(90);
+
+    painter->save();
+    painter->setCompositionMode(QPainter::CompositionMode_Source);
+    painter->setClipPath(path);
+    painter->setTransform(transform);
+    // Draw horizontal groove, clipped to a triangle
+    painter->drawImage(QPoint(0, 0), scrollBarImage, targetImageRect);
+    painter->restore();
+}
+
+void QQuickStyleItemScrollViewCorner::initStyleOption(QStyleOptionSlider &styleOption) const
+{
+    initStyleOptionBase(styleOption);
+
+    styleOption.subControls = QStyle::SC_ScrollBarGroove;
+    styleOption.activeSubControls = QStyle::SC_None;
+    styleOption.pageStep = 1000;
+    styleOption.minimum = 0;
+    styleOption.maximum = 1;
+    styleOption.sliderValue = 0;
+}