QGtk3Theme: Fix QGtk3Interface::fileIcon

By failing to set the G_FILE_ATTRIBUTE_STANDARD_ICON attribute, the
"icon" returned by g_file_info_get_icon was always null and a
GLib-GIO-CRITICAL warning was output to the console (at least since glib
2.76.0)[1].

After adding the necessary attribute, the code was crashing, because now
a valid icon was returned, however the icon should not be freed[2],
which is why I removed the "g_object_unref(icon)".

Now it was no longer crashing, but the size of the icons was off. It was
passing GTK_ICON_SIZE_BUTTON (4) to gtk_icon_theme_lookup_by_gicon where
a size in pixels was expected. I chose 16 because that's the pixel size
associated with GTK_ICON_SIZE_BUTTON[3].

Finally I noticed the returned icons had the wrong color. It seems that
a GdkPixbuf uses RGBA8888 format[4]. Adding an explicit conversion to
ARGB32 made the icons look correct for me.

[1] https://gitlab.gnome.org/GNOME/glib/-/commit/ed8e86a7d41a0900d8fa57edc64264d04cf8135b
[2] https://docs.gtk.org/gio/method.FileInfo.get_icon.html
[3] https://docs.gtk.org/gtk3/enum.IconSize.html#button
[4] https://docs.gtk.org/gdk-pixbuf/class.Pixbuf.html#image-data

[ChangeLog][Platform Specific Changes][Linux] Fixed file icons provided by QFileIconProvider when using the gtk3 platform theme.

Pick-to: 6.5 6.6 6.7
Change-Id: I312ef76ac28bc28435b756d299998485db122906
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

1 files changed, 6 insertions, 6 deletions

diff --git a/src/plugins/platformthemes/gtk3/qgtk3interface.cpp b/src/plugins/platformthemes/gtk3/qgtk3interface.cpp
index 33d0182521..a35e211fbf 100644
--- a/src/plugins/platformthemes/gtk3/qgtk3interface.cpp
+++ b/src/plugins/platformthemes/gtk3/qgtk3interface.cpp
@@ -296,8 +296,10 @@ QImage QGtk3Interface::qt_convert_gdk_pixbuf(GdkPixbuf *buf) const
     const int width = gdk_pixbuf_get_width(buf);
     const int height = gdk_pixbuf_get_height(buf);
     const int bpl = gdk_pixbuf_get_rowstride(buf);
-    QImage converted(data, width, height, bpl, QImage::Format_ARGB32);
-    return converted.copy(); // detatch to survive lifetime of buf
+    QImage converted(data, width, height, bpl, QImage::Format_RGBA8888);
+
+    // convert to more optimal format and detach to survive lifetime of buf
+    return converted.convertToFormat(QImage::Format_ARGB32_Premultiplied);
 }
 
 /*!
@@ -666,7 +668,7 @@ QIcon QGtk3Interface::fileIcon(const QFileInfo &fileInfo) const
     if (!file)
         return QIcon();
 
-    GFileInfo *info = g_file_query_info (file, G_FILE_ATTRIBUTE_STANDARD_CONTENT_TYPE,
+    GFileInfo *info = g_file_query_info (file, G_FILE_ATTRIBUTE_STANDARD_ICON,
                                          G_FILE_QUERY_INFO_NONE, nullptr, nullptr);
     if (!info) {
         g_object_unref(file);
@@ -681,12 +683,11 @@ QIcon QGtk3Interface::fileIcon(const QFileInfo &fileInfo) const
     }
 
     GtkIconTheme *theme = gtk_icon_theme_get_default();
-    GtkIconInfo *iconInfo = gtk_icon_theme_lookup_by_gicon(theme, icon, GTK_ICON_SIZE_BUTTON,
+    GtkIconInfo *iconInfo = gtk_icon_theme_lookup_by_gicon(theme, icon, 16,
                                                                   GTK_ICON_LOOKUP_FORCE_SIZE);
     if (!iconInfo) {
         g_object_unref(file);
         g_object_unref(info);
-        g_object_unref(icon);
         return QIcon();
     }
 
@@ -694,7 +695,6 @@ QIcon QGtk3Interface::fileIcon(const QFileInfo &fileInfo) const
     QImage image = qt_convert_gdk_pixbuf(buf);
     g_object_unref(file);
     g_object_unref(info);
-    g_object_unref(icon);
     g_object_unref(buf);
     return QIcon(QPixmap::fromImage(image));
 }