Implement startup notification spec again.

This functionality was in Qt4's qapplication_x11.cpp and was missing
from the XCB QPA plugin. Ported the code from xlib to xcb.

This code was actually tested (with plasma), unlike the Qt-4.8 code which
skipped every other character...
    for (uint i = 0; i < 20 && i + sent <= length; i++)
        xevent.xclient.data.b[i] = message[i + sent++];

Provide a QPA native-function for accessing the startup id, for cases where
an application doesn't show a window, but starts another app instead, or asks
a running app to show the window on its behalf.

Change-Id: If392179efddd70a51c45a8fab4fb9d753913094a
Reviewed-by: David Faure (KDE) <faure@kde.org>

src/plugins/platforms/xcb/qxcbconnection.cpp

@@ -344,6 +344,10 @@ QXcbConnection::QXcbConnection(QXcbNativeInterface *nativeInterface, const char
     m_drag = new QXcbDrag(this);
 #endif
 
+    m_startupId = qgetenv("DESKTOP_STARTUP_ID");
+    if (!m_startupId.isNull())
+        qunsetenv("DESKTOP_STARTUP_ID");
+
     sync();
 }
 

src/plugins/platforms/xcb/qxcbconnection.h

@@ -388,6 +388,9 @@ public:
     QXcbWindow *focusWindow() const { return m_focusWindow; }
     void setFocusWindow(QXcbWindow *);
 
+    QByteArray startupId() const { return m_startupId; }
+    void clearStartupId() { m_startupId.clear(); }
+
 private slots:
     void processXcbEvents();
 
@@ -516,6 +519,8 @@ private:
     Qt::MouseButtons m_buttons;
 
     QXcbWindow *m_focusWindow;
+
+    QByteArray m_startupId;
 };
 
 #define DISPLAY_FROM_XCB(object) ((Display *)(object->connection()->xlib_display()))

src/plugins/platforms/xcb/qxcbintegration.h

@@ -95,6 +95,8 @@ public:
     QStringList themeNames() const;
     QPlatformTheme *createPlatformTheme(const QString &name) const;
 
+    QXcbConnection *defaultConnection() const { return m_connections.first(); }
+
 private:
     QList<QXcbConnection *> m_connections;
 

src/plugins/platforms/xcb/qxcbnativeinterface.cpp

@@ -42,6 +42,7 @@
 #include "qxcbnativeinterface.h"
 
 #include "qxcbscreen.h"
+#include "qxcbintegration.h"
 
 #include <private/qguiapplication_p.h>
 #include <QtCore/QMap>
@@ -78,6 +79,7 @@ public:
         insert("apptime",QXcbNativeInterface::AppTime);
         insert("appusertime",QXcbNativeInterface::AppUserTime);
         insert("hintstyle", QXcbNativeInterface::ScreenHintStyle);
+        insert("startupid", QXcbNativeInterface::StartupId);
     }
 };
 
@@ -99,6 +101,25 @@ void QXcbNativeInterface::beep() // For QApplication::beep()
 #endif
 }
 
+void *QXcbNativeInterface::nativeResourceForIntegration(const QByteArray &resourceString)
+{
+    QByteArray lowerCaseResource = resourceString.toLower();
+    if (!qXcbResourceMap()->contains(lowerCaseResource))
+        return 0;
+
+    ResourceType resource = qXcbResourceMap()->value(lowerCaseResource);
+    void *result = 0;
+    switch (resource) {
+    case StartupId:
+        result = startupId();
+        break;
+    default:
+        break;
+    }
+
+    return result;
+}
+
 void *QXcbNativeInterface::nativeResourceForContext(const QByteArray &resourceString, QOpenGLContext *context)
 {
     QByteArray lowerCaseResource = resourceString.toLower();
@@ -196,6 +217,15 @@ void *QXcbNativeInterface::appUserTime(const QXcbScreen *screen)
     return reinterpret_cast<void *>(quintptr(screen->connection()->netWmUserTime()));
 }
 
+void *QXcbNativeInterface::startupId()
+{
+    QXcbIntegration* integration = static_cast<QXcbIntegration *>(QGuiApplicationPrivate::platformIntegration());
+    QXcbConnection *defaultConnection = integration->defaultConnection();
+    if (defaultConnection)
+        return reinterpret_cast<void *>(const_cast<char *>(defaultConnection->startupId().constData()));
+    return 0;
+}
+
 void QXcbNativeInterface::setAppTime(QScreen* screen, xcb_timestamp_t time)
 {
     static_cast<QXcbScreen *>(screen->handle())->connection()->setTime(time);

src/plugins/platforms/xcb/qxcbnativeinterface.h

@@ -65,11 +65,13 @@ public:
         GLXContext,
         AppTime,
         AppUserTime,
-        ScreenHintStyle
+        ScreenHintStyle,
+        StartupId
     };
 
     QXcbNativeInterface();
 
+    void *nativeResourceForIntegration(const QByteArray &resource) Q_DECL_OVERRIDE;
     void *nativeResourceForContext(const QByteArray &resourceString, QOpenGLContext *context);
     void *nativeResourceForScreen(const QByteArray &resource, QScreen *screen);
     void *nativeResourceForWindow(const QByteArray &resourceString, QWindow *window);
@@ -86,6 +88,7 @@ public:
     void *graphicsDeviceForWindow(QWindow *window);
     void *appTime(const QXcbScreen *screen);
     void *appUserTime(const QXcbScreen *screen);
+    void *startupId();
     static void setAppTime(QScreen *screen, xcb_timestamp_t time);
     static void setAppUserTime(QScreen *screen, xcb_timestamp_t time);
     static void *eglContextForContext(QOpenGLContext *context);

src/plugins/platforms/xcb/qxcbscreen.cpp

@@ -233,6 +233,40 @@ QWindow *QXcbScreen::topLevelAt(const QPoint &p) const
     return 0;
 }
 
+void QXcbScreen::windowShown(QXcbWindow *window)
+{
+    // Freedesktop.org Startup Notification
+    if (!connection()->startupId().isEmpty() && window->window()->isTopLevel()) {
+        sendStartupMessage(QByteArrayLiteral("remove: ID=") + connection()->startupId());
+        connection()->clearStartupId();
+    }
+}
+
+void QXcbScreen::sendStartupMessage(const QByteArray &message) const
+{
+    xcb_window_t rootWindow = root();
+
+    xcb_client_message_event_t ev;
+    ev.response_type = XCB_CLIENT_MESSAGE;
+    ev.format = 8;
+    ev.type = connection()->atom(QXcbAtom::_NET_STARTUP_INFO_BEGIN);
+    ev.window = rootWindow;
+    int sent = 0;
+    int length = message.length() + 1; // include NUL byte
+    const char *data = message.constData();
+    do {
+        if (sent == 20)
+            ev.type = connection()->atom(QXcbAtom::_NET_STARTUP_INFO);
+
+        const int start = sent;
+        const int numBytes = qMin(length - start, 20);
+        memcpy(ev.data.data8, data + start, numBytes);
+        xcb_send_event(connection()->xcb_connection(), false, rootWindow, XCB_EVENT_MASK_PROPERTY_CHANGE, (const char *) &ev);
+
+        sent += numBytes;
+    } while (sent < length);
+}
+
 const xcb_visualtype_t *QXcbScreen::visualForId(xcb_visualid_t visualid) const
 {
     QMap<xcb_visualid_t, xcb_visualtype_t>::const_iterator it = m_visuals.find(visualid);

src/plugins/platforms/xcb/qxcbscreen.h

@@ -87,6 +87,7 @@ public:
 
     xcb_window_t clientLeader() const { return m_clientLeader; }
 
+    void windowShown(QXcbWindow *window);
     QString windowManagerName() const { return m_windowManagerName; }
     bool syncRequestSupported() const { return m_syncRequestSupported; }
 
@@ -105,6 +106,7 @@ private:
     static bool xResource(const QByteArray &identifier,
                          const QByteArray &expectedIdentifier,
                          int *value);
+    void sendStartupMessage(const QByteArray &message) const;
 
     xcb_screen_t *m_screen;
     xcb_randr_crtc_t m_crtc;

src/plugins/platforms/xcb/qxcbwindow.cpp

@@ -46,6 +46,7 @@
 #include <QtGui/QIcon>
 #include <QtGui/QRegion>
 
+#include "qxcbintegration.h"
 #include "qxcbconnection.h"
 #include "qxcbscreen.h"
 #include "qxcbdrag.h"
@@ -653,6 +654,9 @@ void QXcbWindow::show()
         updateNetWmUserTime(connection()->time());
 
     Q_XCB_CALL(xcb_map_window(xcb_connection(), m_window));
+
+    m_screen->windowShown(this);
+
     xcb_flush(xcb_connection());
 
     connection()->sync();