xcb: Add experimental legacy support for native X11 painting

This commit revives the old native QPixmap and QPaintEngine
implementations that were present in Qt4. The backing store supports
regular raster windows in this commit. Support for render-to-texture
widgets and OpenGL compositing will be added in a follow-up commit.

Change-Id: I80a9c4f0c42a6f68f571dfee930d95000d5dd950
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 203 insertions, 0 deletions

diff --git a/src/plugins/platforms/xcb/nativepainting/qbackingstore_x11.cpp b/src/plugins/platforms/xcb/nativepainting/qbackingstore_x11.cpp
new file mode 100644
index 0000000000..2dd2cdd9e3
--- /dev/null
+++ b/src/plugins/platforms/xcb/nativepainting/qbackingstore_x11.cpp
@@ -0,0 +1,203 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the plugins of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** As a special exception, The Qt Company gives you certain additional
+** rights. These rights are described in The Qt Company LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qbackingstore_x11_p.h"
+#include "qxcbwindow.h"
+#include "qpixmap_x11_p.h"
+
+#include <private/qhighdpiscaling_p.h>
+#include <QPainter>
+
+#if QT_CONFIG(xrender)
+# include <X11/extensions/Xrender.h>
+#endif
+
+#include <X11/Xlib.h>
+
+#ifndef None
+#define None 0L
+#endif
+
+QT_BEGIN_NAMESPACE
+
+QXcbNativeBackingStore::QXcbNativeBackingStore(QWindow *window)
+    : QPlatformBackingStore(window)
+    , m_translucentBackground(false)
+{
+    if (QXcbWindow *w = static_cast<QXcbWindow *>(window->handle()))
+        m_translucentBackground = w->connection()->hasXRender() && QImage::toPixelFormat(w->imageFormat()).alphaSize() > 0;
+}
+
+QXcbNativeBackingStore::~QXcbNativeBackingStore()
+{}
+
+QPaintDevice *QXcbNativeBackingStore::paintDevice()
+{
+    return &m_pixmap;
+}
+
+void QXcbNativeBackingStore::flush(QWindow *window, const QRegion &region, const QPoint &offset)
+{
+    if (m_pixmap.isNull())
+        return;
+
+    QSize pixmapSize = m_pixmap.size();
+
+    QRegion clipped = region;
+    clipped &= QRect(QPoint(), QHighDpi::toNativePixels(window->size(), window));
+    clipped &= QRect(0, 0, pixmapSize.width(), pixmapSize.height()).translated(-offset);
+
+    QRect br = clipped.boundingRect();
+    if (br.isNull())
+        return;
+
+    QXcbWindow *platformWindow = static_cast<QXcbWindow *>(window->handle());
+    if (!platformWindow) {
+        qWarning("QXcbBackingStore::flush: QWindow has no platform window (QTBUG-32681)");
+        return;
+    }
+
+    Window wid = platformWindow->xcb_window();
+    Pixmap pid = qt_x11PixmapHandle(m_pixmap);
+
+    QVector<XRectangle> clipRects = qt_region_to_xrectangles(clipped);
+
+#if QT_CONFIG(xrender)
+    if (m_translucentBackground)
+    {
+        XWindowAttributes attrib;
+        XGetWindowAttributes(display(), wid, &attrib);
+        XRenderPictFormat *format = XRenderFindVisualFormat(display(), attrib.visual);
+
+        Picture srcPic = qt_x11PictureHandle(m_pixmap);
+        Picture dstPic = XRenderCreatePicture(display(), wid, format, 0, 0);
+
+        XRenderSetPictureClipRectangles(display(), dstPic, 0, 0, clipRects.constData(), clipRects.size());
+
+        XRenderComposite(display(), PictOpSrc, srcPic, None, dstPic,
+                         br.x() + offset.x(), br.y() + offset.y(),
+                         0, 0,
+                         br.x(), br.y(),
+                         br.width(), br.height());
+
+        XRenderFreePicture(display(), dstPic);
+    }
+    else
+#endif
+    {
+        GC gc = XCreateGC(display(), wid, 0, Q_NULLPTR);
+
+        if (clipRects.size() != 1)
+            XSetClipRectangles(display(), gc, 0, 0, clipRects.data(), clipRects.size(), YXBanded);
+
+        XCopyArea(display(), pid, wid, gc, br.x() + offset.x(), br.y() + offset.y(), br.width(), br.height(), br.x(), br.y());
+        XFreeGC(display(), gc);
+    }
+
+
+    if (platformWindow->needsSync()) {
+        platformWindow->updateSyncRequestCounter();
+    } else {
+        XFlush(display());
+    }
+}
+
+QImage QXcbNativeBackingStore::toImage() const
+{
+    return m_pixmap.toImage();
+}
+
+void QXcbNativeBackingStore::resize(const QSize &size, const QRegion &staticContents)
+{
+    if (size == m_pixmap.size())
+        return;
+
+    QPixmap newPixmap(size);
+
+#if QT_CONFIG(xrender)
+    if (m_translucentBackground && newPixmap.depth() != 32)
+        qt_x11Pixmap(newPixmap)->convertToARGB32();
+#endif
+
+    if (!m_pixmap.isNull()) {
+        Pixmap from = qt_x11PixmapHandle(m_pixmap);
+        Pixmap to = qt_x11PixmapHandle(newPixmap);
+        QRect br = staticContents.boundingRect().intersected(QRect(QPoint(0, 0), size));
+
+        if (!br.isEmpty()) {
+            GC gc = XCreateGC(display(), to, 0, Q_NULLPTR);
+            XCopyArea(display(), from, to, gc, br.x(), br.y(), br.width(), br.height(), br.x(), br.y());
+            XFreeGC(display(), gc);
+        }
+    }
+
+    m_pixmap = newPixmap;
+}
+
+bool QXcbNativeBackingStore::scroll(const QRegion &area, int dx, int dy)
+{
+    if (m_pixmap.isNull())
+        return false;
+
+    QRect rect = area.boundingRect();
+    Pixmap pix = qt_x11PixmapHandle(m_pixmap);
+
+    GC gc = XCreateGC(display(), pix, 0, Q_NULLPTR);
+    XCopyArea(display(), pix, pix, gc,
+              rect.x(), rect.y(), rect.width(), rect.height(),
+              rect.x()+dx, rect.y()+dy);
+    XFreeGC(display(), gc);
+    return true;
+}
+
+void QXcbNativeBackingStore::beginPaint(const QRegion &region)
+{
+#if QT_CONFIG(xrender)
+    if (m_translucentBackground) {
+        const QVector<XRectangle> xrects = qt_region_to_xrectangles(region);
+        const XRenderColor color = { 0, 0, 0, 0 };
+        XRenderFillRectangles(display(), PictOpSrc,
+                              qt_x11PictureHandle(m_pixmap), &color,
+                              xrects.constData(), xrects.size());
+    }
+#else
+    Q_UNUSED(region);
+#endif
+}
+
+Display *QXcbNativeBackingStore::display() const
+{
+    return static_cast<Display *>(static_cast<QXcbWindow *>(window()->handle())->connection()->xlib_display());
+}
+
+QT_END_NAMESPACE