1 files changed, 35 insertions, 15 deletions

diff --git a/src/gui/image/qicon.cpp b/src/gui/image/qicon.cpp
index d9e1347e4b..ca77b73033 100644
--- a/src/gui/image/qicon.cpp
+++ b/src/gui/image/qicon.cpp
@@ -920,7 +920,7 @@ void QIcon::paint(QPainter *painter, const QRect &rect, Qt::Alignment alignment,
 */
 bool QIcon::isNull() const
 {
-    return !d;
+    return !d || d->engine->isNull();
 }
 
 /*!\internal
@@ -935,7 +935,12 @@ bool QIcon::isDetached() const
 void QIcon::detach()
 {
     if (d) {
-        if (d->ref.load() != 1) {
+        if (d->engine->isNull()) {
+            if (!d->ref.deref())
+                delete d;
+            d = 0;
+            return;
+        } else if (d->ref.load() != 1) {
             QIconPrivate *x = new QIconPrivate;
             x->engine = d->engine->clone();
             if (!d->ref.deref())
@@ -959,11 +964,10 @@ void QIcon::addPixmap(const QPixmap &pixmap, Mode mode, State state)
 {
     if (pixmap.isNull())
         return;
+    detach();
     if (!d) {
         d = new QIconPrivate;
         d->engine = new QPixmapIconEngine;
-    } else {
-        detach();
     }
     d->engine->addPixmap(pixmap, mode, state);
 }
@@ -1003,6 +1007,7 @@ void QIcon::addFile(const QString &fileName, const QSize &size, Mode mode, State
 {
     if (fileName.isEmpty())
         return;
+    detach();
     if (!d) {
 #ifndef QT_NO_LIBRARY
         QFileInfo info(fileName);
@@ -1025,8 +1030,6 @@ void QIcon::addFile(const QString &fileName, const QSize &size, Mode mode, State
             d = new QIconPrivate;
             d->engine = new QPixmapIconEngine;
         }
-    } else {
-        detach();
     }
 
     d->engine->addFile(fileName, size, mode, state);
@@ -1136,8 +1139,7 @@ QString QIcon::themeName()
     \since 4.6
 
     Returns the QIcon corresponding to \a name in the current
-    icon theme. If no such icon is found in the current theme
-    \a fallback is returned instead.
+    icon theme.
 
     The latest version of the freedesktop icon specification and naming
     specification can be obtained here:
@@ -1151,19 +1153,18 @@ QString QIcon::themeName()
 
     \snippet code/src_gui_image_qicon.cpp 3
 
-    Or if you want to provide a guaranteed fallback for platforms that
-    do not support theme icons, you can use the second argument:
-
-    \snippet code/src_gui_image_qicon.cpp 4
-
     \note By default, only X11 will support themed icons. In order to
     use themed icons on Mac and Windows, you will have to bundle a
     compliant theme in one of your themeSearchPaths() and set the
     appropriate themeName().
 
+    \note Qt will make use of GTK's icon-theme.cache if present to speed up
+    the lookup. These caches can be generated using gtk-update-icon-cache:
+    \l{https://developer.gnome.org/gtk3/stable/gtk-update-icon-cache.html}.
+
     \sa themeName(), setThemeName(), themeSearchPaths()
 */
-QIcon QIcon::fromTheme(const QString &name, const QIcon &fallback)
+QIcon QIcon::fromTheme(const QString &name)
 {
     QIcon icon;
 
@@ -1179,7 +1180,26 @@ QIcon QIcon::fromTheme(const QString &name, const QIcon &fallback)
         qtIconCache()->insert(name, cachedIcon);
     }
 
-    if (qApp && icon.availableSizes().isEmpty())
+    return icon;
+}
+
+/*!
+    \overload
+
+    Returns the QIcon corresponding to \a name in the current
+    icon theme. If no such icon is found in the current theme
+    \a fallback is returned instead.
+
+    If you want to provide a guaranteed fallback for platforms that
+    do not support theme icons, you can use the second argument:
+
+    \snippet code/src_gui_image_qicon.cpp 4
+*/
+QIcon QIcon::fromTheme(const QString &name, const QIcon &fallback)
+{
+    QIcon icon = fromTheme(name);
+
+    if (icon.isNull() || icon.availableSizes().isEmpty())
         return fallback;
 
     return icon;