Add support for -qwindowicon command line argument.

[ChangeLog][QtGui][QGuiApplication] Add support for -icon command line
argument on X11, add -qwindowicon on all platforms.

Change-Id: Iacc602466699bf634d8b34aab7ed73c83fd9844f
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

src/gui/kernel/qguiapplication.cpp

@@ -495,6 +495,7 @@ static QWindowGeometrySpecification windowGeometrySpecification;
             \l{Session Management}{session}.
         \li  -qwindowgeometry, sets the geometry of the first window
         \li  -qwindowtitle, sets the title of the first window
+        \li  -qwindowicon, sets the default window icon
     \endlist
 
     The following standard command line options are available for X11:
@@ -1115,6 +1116,11 @@ void QGuiApplicationPrivate::createPlatformIntegration()
         } else if (arg == "-qwindowtitle" || (platformName == "xcb" && arg == "-title")) {
             if (++i < argc)
                 firstWindowTitle = QString::fromLocal8Bit(argv[i]);
+        } else if (arg == "-qwindowicon" || (platformName == "xcb" && arg == "-icon")) {
+            if (++i < argc) {
+                const QString icon = QString::fromLocal8Bit(argv[i]);
+                forcedWindowIcon = QDir::isAbsolutePath(icon) ? QIcon(icon) : QIcon::fromTheme(icon);
+            }
         } else {
             argv[j++] = argv[i];
         }

src/gui/kernel/qguiapplication_p.h

@@ -234,6 +234,7 @@ public:
     QInputMethod *inputMethod;
 
     QString firstWindowTitle;
+    QIcon forcedWindowIcon;
 
     static QList<QObject *> generic_plugin_list;
 #ifndef QT_NO_SHORTCUT

src/gui/kernel/qwindow.cpp

@@ -436,11 +436,14 @@ void QWindow::setVisible(bool visible)
         QCoreApplication::removePostedEvents(qApp, QEvent::Quit);
 
         if (type() == Qt::Window) {
-            QString &firstWindowTitle = QGuiApplicationPrivate::instance()->firstWindowTitle;
+            QGuiApplicationPrivate *app_priv = QGuiApplicationPrivate::instance();
+            QString &firstWindowTitle = app_priv->firstWindowTitle;
             if (!firstWindowTitle.isEmpty()) {
                 setTitle(firstWindowTitle);
                 firstWindowTitle = QString();
             }
+            if (!app_priv->forcedWindowIcon.isNull())
+                setIcon(app_priv->forcedWindowIcon);
         }
 
         QShowEvent showEvent;

tests/auto/gui/kernel/qguiapplication/qguiapplication.pro

@@ -7,3 +7,5 @@ INCLUDEPATH += $$CORE_TEST_PATH
 TARGET = tst_qguiapplication
 QT += gui-private
 SOURCES += tst_qguiapplication.cpp
+
+RESOURCES = tst_qguiapplication.qrc

tests/auto/gui/kernel/qguiapplication/tst_qguiapplication.cpp

@@ -61,6 +61,7 @@ class tst_QGuiApplication: public tst_QCoreApplication
 private slots:
     void displayName();
     void firstWindowTitle();
+    void windowIcon();
     void focusObject();
     void allWindows();
     void topLevelWindows();
@@ -95,6 +96,24 @@ void tst_QGuiApplication::firstWindowTitle()
     QCOMPARE(window.title(), QString("User Title"));
 }
 
+void tst_QGuiApplication::windowIcon()
+{
+    int argc = 3;
+    char *argv[] = { const_cast<char*>("tst_qguiapplication"), const_cast<char*>("-qwindowicon"), const_cast<char*>(":/icons/usericon.png") };
+    QGuiApplication app(argc, argv);
+    QIcon appIcon(":/icons/appicon.png");
+    app.setWindowIcon(appIcon);
+
+    QWindow window;
+    window.show();
+
+    QIcon userIcon(":/icons/usericon.png");
+    // Comparing icons is hard. cacheKey() differs because the icon was independently loaded.
+    // So we use availableSizes, after making sure that the app and user icons do have different sizes.
+    QVERIFY(userIcon.availableSizes() != appIcon.availableSizes());
+    QCOMPARE(window.icon().availableSizes(), userIcon.availableSizes());
+}
+
 class DummyWindow : public QWindow
 {
 public:

tests/auto/gui/kernel/qguiapplication/tst_qguiapplication.qrc

@@ -0,0 +1,6 @@
+<!DOCTYPE RCC><RCC version="1.0">
+<qresource prefix="/">
+  <file>icons/usericon.png</file>
+  <file>icons/appicon.png</file>
+</qresource>
+</RCC>