xcb: ensure the primary screen is added first

Currently, Qt windows without an explicit screen parameter always appear
on screen 0 despite the DISPLAY being set to :0.1. With this change,
the xcb backend adds the primary display at the beginning of the
screen list. QGuiApplication::primaryScreen() will then return that
display for all windows without an explicit screen.

Change-Id: I657c4ed92b9e0f0ed379e91c732dad9d69c4f5e0
Reviewed-by: Donald Carr <donald.carr@nokia.com>
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>

diff --git a/src/plugins/platforms/xcb/qxcbconnection.cpp b/src/plugins/platforms/xcb/qxcbconnection.cpp
index 40a54ff..679f3e7 100644 (file)
--- a/src/plugins/platforms/xcb/qxcbconnection.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection.cpp
@@ -98,6 +98,7 @@ static int nullErrorHandler(Display *, XErrorEvent *)
 
 QXcbConnection::QXcbConnection(QXcbNativeInterface *nativeInterface, const char *displayName)
     : m_connection(0)
+    , m_primaryScreen(0)
     , m_displayName(displayName ? QByteArray(displayName) : qgetenv("DISPLAY"))
     , m_nativeInterface(nativeInterface)
 #ifdef XCB_USE_XINPUT2_MAEMO
@@ -115,8 +116,6 @@ QXcbConnection::QXcbConnection(QXcbNativeInterface *nativeInterface, const char
     , has_randr_extension(false)
     , has_input_shape(false)
 {
-    m_primaryScreen = 0;
-
 #ifdef XCB_USE_XLIB
     Display *dpy = XOpenDisplay(m_displayName.constData());
     if (dpy) {
@@ -167,7 +166,14 @@ QXcbConnection::QXcbConnection(QXcbNativeInterface *nativeInterface, const char
 
     int screenNumber = 0;
     while (it.rem) {
-        m_screens << new QXcbScreen(this, it.data, screenNumber++);
+        QXcbScreen *screen = new QXcbScreen(this, it.data, screenNumber);
+        // make sure the primary screen appears first since it is used by QGuiApplication::primaryScreen()
+        if (m_primaryScreen == screenNumber) {
+            m_screens.prepend(screen);
+        } else {
+            m_screens.append(screen);
+        }
+        ++screenNumber;
         xcb_screen_next(&it);
     }