Introduce QIcon::fallbackSearchPaths()

... that will be used if an icon can't be found in the
current theme.

The Icon Theme Specification
https://standards.freedesktop.org/icon-theme-spec/latest/ar01s05.html
states that unthemed icons must be searched in the base directories,
i.e. /usr/share/icons, ... But in practice unthemed icons are
installed into /usr/share/pixmaps and this dir is not used as
a base dir for icon themes. So it's better to explicitly specify
fallback dirs to avoid needless access to the filesystem.

Also some KDE application install their own unthemed icons
(into /usr/share/<appname>/pics), that can't be found by
QIconLoader. With this change it would be possible for them
to specify dirs with unthemed icons and thus be displayed
correctly in non-KDE environments.

[ChangeLog][QtGui][QIcon] Added fallbackSearchPaths() that
will be used to find icons missing in the current icon theme.

Change-Id: I0dc55ba958b29356a3b0a2123d6b8faa24d4c91e
Task-number: QTBUG-33123
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/src/gui/kernel/qplatformtheme.h b/src/gui/kernel/qplatformtheme.h
index f4ff418db6..87873d446f 100644
--- a/src/gui/kernel/qplatformtheme.h
+++ b/src/gui/kernel/qplatformtheme.h
@@ -116,7 +116,8 @@ public:
         MouseDoubleClickDistance,
         WheelScrollLines,
         TouchDoubleTapDistance,
-        ShowShortcutsInContextMenus
+        ShowShortcutsInContextMenus,
+        IconFallbackSearchPaths
     };
 
     enum DialogType {