Support transparency in qt5 system tray icons, regardless of tray visual

This ports the Qt4 method of supporting the system tray
window visual that has an alpha channel as well as ones
that do not. We detect whether or not we have a 32-bit
format and either use a Qt::transparent background, or
call xcb_clear_region before painting the icon.

[ChangeLog][Linux/XCB] Fix transparency of tray icons in cases where
there is no alpha channel or system tray visual.

Task-number: QTBUG-35832
Change-Id: I43d500c39846d2916dd39f8c47c8d85e59b49cae
Reviewed-by: Uli Schlachter <psychon@znc.in>
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@digia.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/src/plugins/platforms/xcb/qxcbscreen.cpp b/src/plugins/platforms/xcb/qxcbscreen.cpp
index 01e78465b6..85f4dfbd43 100644
--- a/src/plugins/platforms/xcb/qxcbscreen.cpp
+++ b/src/plugins/platforms/xcb/qxcbscreen.cpp
@@ -200,6 +200,7 @@ QXcbScreen::QXcbScreen(QXcbConnection *connection, xcb_screen_t *scr,
         while (visualtype_iterator.rem) {
             xcb_visualtype_t *visualtype = visualtype_iterator.data;
             m_visuals.insert(visualtype->visual_id, *visualtype);
+            m_visualDepths.insert(visualtype->visual_id, depth->depth);
             xcb_visualtype_next(&visualtype_iterator);
         }
 
@@ -296,6 +297,14 @@ const xcb_visualtype_t *QXcbScreen::visualForId(xcb_visualid_t visualid) const
     return &*it;
 }
 
+quint8 QXcbScreen::depthOfVisual(xcb_visualid_t visualid) const
+{
+    QMap<xcb_visualid_t, quint8>::const_iterator it = m_visualDepths.find(visualid);
+    if (it == m_visualDepths.constEnd())
+        return 0;
+    return *it;
+}
+
 QImage::Format QXcbScreen::format() const
 {
     return QImage::Format_RGB32;