Make it possible to use the -visual argument

for xcb applications to use a specific visual id when creating windows.

Also make it possible to retrieve the visual id of a specific window
with QXcbWindowFunctions::visualId(QWindow *window).

UINT_MAX is used as an invalid visualId.

Change-Id: If62ada119ce8f9174cc211f53bbf1ce1bb7d021a
Reviewed-by: Andy Shaw <andy.shaw@digia.com>

8 files changed, 116 insertions, 25 deletions

diff --git a/src/platformheaders/xcbfunctions/qxcbwindowfunctions.h b/src/platformheaders/xcbfunctions/qxcbwindowfunctions.h
index f9008039a1..ae05cf52a9 100644
--- a/src/platformheaders/xcbfunctions/qxcbwindowfunctions.h
+++ b/src/platformheaders/xcbfunctions/qxcbwindowfunctions.h
@@ -72,6 +72,17 @@ public:
         if (func)
             func(window, type);
     }
+
+    typedef uint (*VisualId)(QWindow *window);
+    static const QByteArray visualIdIdentifier() { return QByteArrayLiteral("XcbVisualId"); }
+
+    static uint visualId(QWindow *window)
+    {
+        QXcbWindowFunctions::VisualId func = reinterpret_cast<VisualId>(QGuiApplication::platformFunction(visualIdIdentifier()));
+        if (func)
+            return func(window);
+        return UINT_MAX;
+    }
 };
 
 
diff --git a/src/plugins/platforms/xcb/qxcbconnection.cpp b/src/plugins/platforms/xcb/qxcbconnection.cpp
index 3d65b789a4..94f4c2a2d3 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection.cpp
@@ -66,6 +66,7 @@
 #include <X11/Xlib.h>
 #include <X11/Xlib-xcb.h>
 #include <X11/Xlibint.h>
+#include <X11/Xutil.h>
 #endif
 
 #if defined(XCB_USE_XINPUT2)
@@ -437,9 +438,10 @@ void QXcbConnection::initializeScreens()
         qCDebug(lcQpaScreen) << "primary output is" << m_screens.first()->name();
 }
 
-QXcbConnection::QXcbConnection(QXcbNativeInterface *nativeInterface, bool canGrabServer, const char *displayName)
+QXcbConnection::QXcbConnection(QXcbNativeInterface *nativeInterface, bool canGrabServer, xcb_visualid_t defaultVisualId, const char *displayName)
     : m_connection(0)
     , m_canGrabServer(canGrabServer)
+    , m_defaultVisualId(defaultVisualId)
     , m_primaryScreenNumber(0)
     , m_displayName(displayName ? QByteArray(displayName) : qgetenv("DISPLAY"))
     , m_nativeInterface(nativeInterface)
@@ -1351,6 +1353,21 @@ void *QXcbConnection::xlib_display() const
 {
     return m_xlib_display;
 }
+
+void *QXcbConnection::createVisualInfoForDefaultVisualId() const
+{
+    if (m_defaultVisualId == UINT_MAX)
+        return 0;
+    XVisualInfo info;
+    memset(&info, 0, sizeof info);
+    info.visualid = m_defaultVisualId;
+
+    int count = 0;
+    XVisualInfo *retVisual = XGetVisualInfo(DISPLAY_FROM_XCB(this), VisualIDMask, &info, &count);
+    Q_ASSERT(count < 2);
+    return retVisual;
+}
+
 #endif
 
 void QXcbConnection::processXcbEvents()
diff --git a/src/plugins/platforms/xcb/qxcbconnection.h b/src/plugins/platforms/xcb/qxcbconnection.h
index 91547dd697..e4274eca4d 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.h
+++ b/src/plugins/platforms/xcb/qxcbconnection.h
@@ -370,7 +370,7 @@ class Q_XCB_EXPORT QXcbConnection : public QObject
 {
     Q_OBJECT
 public:
-    QXcbConnection(QXcbNativeInterface *nativeInterface, bool canGrabServer, const char *displayName = 0);
+    QXcbConnection(QXcbNativeInterface *nativeInterface, bool canGrabServer, xcb_visualid_t defaultVisualId, const char *displayName = 0);
     ~QXcbConnection();
 
     QXcbConnection *connection() const { return const_cast<QXcbConnection *>(this); }
@@ -400,8 +400,13 @@ public:
 
     QXcbWMSupport *wmSupport() const { return m_wmSupport.data(); }
     xcb_window_t rootWindow();
+
+    bool hasDefaultVisualId() const { return m_defaultVisualId != UINT_MAX; }
+    xcb_visualid_t defaultVisualId() const { return m_defaultVisualId; }
+
 #ifdef XCB_USE_XLIB
     void *xlib_display() const;
+    void *createVisualInfoForDefaultVisualId() const;
 #endif
 
 #if defined(XCB_USE_XINPUT2)
@@ -564,6 +569,7 @@ private:
     xcb_connection_t *m_connection;
     const xcb_setup_t *m_setup;
     bool m_canGrabServer;
+    xcb_visualid_t m_defaultVisualId;
 
     QList<QXcbVirtualDesktop *> m_virtualDesktops;
     QList<QXcbScreen *> m_screens;
@@ -632,6 +638,7 @@ private:
 };
 
 #define DISPLAY_FROM_XCB(object) ((Display *)(object->connection()->xlib_display()))
+#define CREATE_VISUALINFO_FROM_DEFAULT_VISUALID(object) ((XVisualInfo *)(object->connection()->createVisualInfoForDefaultVisualId()))
 
 template<typename T>
 xcb_generic_event_t *QXcbConnection::checkEvent(T &checker)
diff --git a/src/plugins/platforms/xcb/qxcbintegration.cpp b/src/plugins/platforms/xcb/qxcbintegration.cpp
index 2547e537a7..fc06f1a7b0 100644
--- a/src/plugins/platforms/xcb/qxcbintegration.cpp
+++ b/src/plugins/platforms/xcb/qxcbintegration.cpp
@@ -116,6 +116,7 @@ QXcbIntegration::QXcbIntegration(const QStringList &parameters, int &argc, char
     : m_services(new QGenericUnixServices)
     , m_instanceName(0)
     , m_canGrab(true)
+    , m_defaultVisualId(UINT_MAX)
 {
     m_instance = this;
 
@@ -143,6 +144,12 @@ QXcbIntegration::QXcbIntegration(const QStringList &parameters, int &argc, char
                 noGrabArg = true;
             else if (arg == "-dograb")
                 doGrabArg = true;
+            else if (arg == "-visual" && i < argc - 1) {
+                bool ok = false;
+                m_defaultVisualId = QByteArray(argv[++i]).toUInt(&ok, 0);
+                if (!ok)
+                    m_defaultVisualId = UINT_MAX;
+            }
             else
                 argv[j++] = argv[i];
         }
@@ -167,12 +174,12 @@ QXcbIntegration::QXcbIntegration(const QStringList &parameters, int &argc, char
     if (canNotGrabEnv)
         m_canGrab = false;
 
-    m_connections << new QXcbConnection(m_nativeInterface.data(), m_canGrab, displayName);
+    m_connections << new QXcbConnection(m_nativeInterface.data(), m_canGrab, m_defaultVisualId, displayName);
 
     for (int i = 0; i < parameters.size() - 1; i += 2) {
         qCDebug(lcQpaScreen) << "connecting to additional display: " << parameters.at(i) << parameters.at(i+1);
         QString display = parameters.at(i) + QLatin1Char(':') + parameters.at(i+1);
-        m_connections << new QXcbConnection(m_nativeInterface.data(), m_canGrab, display.toLatin1().constData());
+        m_connections << new QXcbConnection(m_nativeInterface.data(), m_canGrab, m_defaultVisualId, display.toLatin1().constData());
     }
 
     m_fontDatabase.reset(new QGenericUnixFontDatabase());
diff --git a/src/plugins/platforms/xcb/qxcbintegration.h b/src/plugins/platforms/xcb/qxcbintegration.h
index 4212d53810..4e2a3c2bbd 100644
--- a/src/plugins/platforms/xcb/qxcbintegration.h
+++ b/src/plugins/platforms/xcb/qxcbintegration.h
@@ -39,6 +39,8 @@
 
 #include "qxcbexport.h"
 
+#include <xcb/xcb.h>
+
 QT_BEGIN_NAMESPACE
 
 class QXcbConnection;
@@ -123,6 +125,7 @@ private:
     mutable QByteArray m_wmClass;
     const char *m_instanceName;
     bool m_canGrab;
+    xcb_visualid_t m_defaultVisualId;
 
     static QXcbIntegration *m_instance;
 };
diff --git a/src/plugins/platforms/xcb/qxcbnativeinterface.cpp b/src/plugins/platforms/xcb/qxcbnativeinterface.cpp
index bfba7f2b6a..8bf9003af7 100644
--- a/src/plugins/platforms/xcb/qxcbnativeinterface.cpp
+++ b/src/plugins/platforms/xcb/qxcbnativeinterface.cpp
@@ -392,6 +392,9 @@ QFunctionPointer QXcbNativeInterface::platformFunction(const QByteArray &functio
     if (function == QXcbWindowFunctions::setWmWindowTypeIdentifier()) {
         return QFunctionPointer(QXcbWindow::setWmWindowTypeStatic);
     }
+    if (function == QXcbWindowFunctions::visualIdIdentifier()) {
+        return QFunctionPointer(QXcbWindowFunctions::VisualId(QXcbWindow::visualIdStatic));
+    }
     return Q_NULLPTR;
 }
 
diff --git a/src/plugins/platforms/xcb/qxcbwindow.cpp b/src/plugins/platforms/xcb/qxcbwindow.cpp
index b5d0741fa6..77c431edb2 100644
--- a/src/plugins/platforms/xcb/qxcbwindow.cpp
+++ b/src/plugins/platforms/xcb/qxcbwindow.cpp
@@ -388,7 +388,16 @@ void QXcbWindow::create()
         m_window = platformScreen->root();
         m_depth = platformScreen->screen()->root_depth;
         m_visualId = platformScreen->screen()->root_visual;
-        const xcb_visualtype_t *visual = platformScreen->visualForId(m_visualId);
+        const xcb_visualtype_t *visual = 0;
+        if (connection()->hasDefaultVisualId()) {
+            visual = platformScreen->visualForId(connection()->defaultVisualId());
+            if (visual)
+                m_visualId = connection()->defaultVisualId();
+            if (!visual)
+                qWarning() << "Could not use default visual id. Falling back to root_visual for screen.";
+        }
+        if (!visual)
+            visual = platformScreen->visualForId(m_visualId);
         m_imageFormat = imageFormatForVisual(m_depth, visual->red_mask, visual->blue_mask, &m_imageRgbSwap);
         connection()->addWindowEventListener(m_window, this);
         return;
@@ -442,7 +451,12 @@ void QXcbWindow::create()
 
 #ifdef XCB_USE_XLIB
     if (QGuiApplicationPrivate::platformIntegration()->hasCapability(QPlatformIntegration::OpenGL)) {
-        XVisualInfo *visualInfo = static_cast<XVisualInfo *>(createVisual());
+        XVisualInfo *visualInfo = Q_NULLPTR;
+        if (connection()->hasDefaultVisualId())
+            visualInfo = CREATE_VISUALINFO_FROM_DEFAULT_VISUALID(this);
+        if (!visualInfo)
+            visualInfo = static_cast<XVisualInfo *>(createVisual());
+
         if (!visualInfo && window()->surfaceType() == QSurface::OpenGLSurface)
             qFatal("Could not initialize OpenGL");
 
@@ -477,35 +491,49 @@ void QXcbWindow::create()
     if (!m_window)
     {
         m_window = xcb_generate_id(xcb_connection());
-        m_visualId = platformScreen->screen()->root_visual;
+        m_visualId = UINT_MAX;
+        const xcb_visualtype_t *visual = Q_NULLPTR;
         m_depth = platformScreen->screen()->root_depth;
 
         uint32_t mask = 0;
         uint32_t values[3];
 
-        if (m_format.alphaBufferSize() == 8) {
-            xcb_depth_iterator_t depthIter = xcb_screen_allowed_depths_iterator(platformScreen->screen());
-            while (depthIter.rem) {
-                if (depthIter.data->depth == 32) {
-                    xcb_visualtype_iterator_t visualIter = xcb_depth_visuals_iterator(depthIter.data);
-                    if (visualIter.rem) {
-                        m_visualId = visualIter.data->visual_id;
-                        m_depth = 32;
-                        uint32_t colormap = xcb_generate_id(xcb_connection());
-                        xcb_create_colormap(xcb_connection(), XCB_COLORMAP_ALLOC_NONE, colormap,
-                                            xcb_parent_id, m_visualId);
-                        mask |= XCB_CW_BACK_PIXEL | XCB_CW_BORDER_PIXEL | XCB_CW_COLORMAP;
-                        values[0] = platformScreen->screen()->white_pixel;
-                        values[1] = platformScreen->screen()->black_pixel;
-                        values[2] = colormap;
-                        break;
+        if (connection()->hasDefaultVisualId()) {
+            m_visualId = connection()->defaultVisualId();
+            visual = platformScreen->visualForId(m_visualId);
+        }
+
+        if (!visual) {
+            if (connection()->hasDefaultVisualId())
+                qWarning("Failed to use default visual id. Falling back to using screens root_visual");
+
+            m_visualId = platformScreen->screen()->root_visual;
+
+            if (m_format.alphaBufferSize() == 8) {
+                xcb_depth_iterator_t depthIter = xcb_screen_allowed_depths_iterator(platformScreen->screen());
+                while (depthIter.rem) {
+                    if (depthIter.data->depth == 32) {
+                        xcb_visualtype_iterator_t visualIter = xcb_depth_visuals_iterator(depthIter.data);
+                        if (visualIter.rem) {
+                            m_visualId = visualIter.data->visual_id;
+                            m_depth = 32;
+                            uint32_t colormap = xcb_generate_id(xcb_connection());
+                            xcb_create_colormap(xcb_connection(), XCB_COLORMAP_ALLOC_NONE, colormap,
+                                                xcb_parent_id, m_visualId);
+                            mask |= XCB_CW_BACK_PIXEL | XCB_CW_BORDER_PIXEL | XCB_CW_COLORMAP;
+                            values[0] = platformScreen->screen()->white_pixel;
+                            values[1] = platformScreen->screen()->black_pixel;
+                            values[2] = colormap;
+                            break;
+                        }
                     }
+                    xcb_depth_next(&depthIter);
                 }
-                xcb_depth_next(&depthIter);
             }
+
+            visual = platformScreen->visualForId(m_visualId);
         }
 
-        const xcb_visualtype_t *visual = platformScreen->visualForId(m_visualId);
         m_imageFormat = imageFormatForVisual(m_depth, visual->red_mask, visual->blue_mask, &m_imageRgbSwap);
         const QRect xRect = mapToNative(rect, platformScreen);
 
@@ -1680,6 +1708,13 @@ void QXcbWindow::setWmWindowTypeStatic(QWindow *window, QXcbWindowFunctions::WmW
         window->setProperty(wm_window_type_property_id, QVariant::fromValue(static_cast<int>(windowTypes)));
 }
 
+uint QXcbWindow::visualIdStatic(QWindow *window)
+{
+    if (window && window->handle())
+        return static_cast<QXcbWindow *>(window->handle())->visualId();
+    return UINT_MAX;
+}
+
 QXcbWindowFunctions::WmWindowTypes QXcbWindow::wmWindowTypes() const
 {
     QXcbWindowFunctions::WmWindowTypes result(0);
@@ -2531,6 +2566,11 @@ void QXcbWindow::setAlertState(bool enabled)
     changeNetWmState(enabled, atom(QXcbAtom::_NET_WM_STATE_DEMANDS_ATTENTION));
 }
 
+uint QXcbWindow::visualId() const
+{
+    return m_visualId;
+}
+
 bool QXcbWindow::needsSync() const
 {
     return m_syncState == SyncAndConfigureReceived;
diff --git a/src/plugins/platforms/xcb/qxcbwindow.h b/src/plugins/platforms/xcb/qxcbwindow.h
index fbf3cfe172..512bc54255 100644
--- a/src/plugins/platforms/xcb/qxcbwindow.h
+++ b/src/plugins/platforms/xcb/qxcbwindow.h
@@ -139,10 +139,13 @@ public:
     void updateNetWmUserTime(xcb_timestamp_t timestamp);
 
     static void setWmWindowTypeStatic(QWindow *window, QXcbWindowFunctions::WmWindowTypes windowTypes);
+    static uint visualIdStatic(QWindow *window);
 
     QXcbWindowFunctions::WmWindowTypes wmWindowTypes() const;
     void setWmWindowType(QXcbWindowFunctions::WmWindowTypes types);
 
+    uint visualId() const;
+
     bool needsSync() const;
 
     void postSyncWindowRequest();