[OE-core] Strange issue with symbolic icons for adwaita-icon-theme

[Andreas Müller]

Hi,

I first noticed this with update of XFCE's thunar: From thunar 1.6 ->
1.8 the icons in toolbar changed to 'symbolic' variants and there are
some icons missing since the upgrade. I opened an issue at XFCE but it
turned out that it is not an issue of thunar [1].

To debug a thud based XFCE image was created with:
* adwaita-icon-theme / adwaita-icon-theme-symbolic /
adwaita-icon-theme-symbolic-hires installed
* KDE's breeze-icons installed
* gtk+3-demo installed (it contains gtk3-icon-browser)

Without further modifications starting gtk3-icon-browser and move to
'Symbolic' results in:
* no icons displayed for adwaita-icons selected in XFCE
* icons displayed properly for breeze/breeze-dark selected in XFCE

And now the strange parts:
1. After deleting '/usr/share/icons/Adwaita/icon-theme.cache' symbolic
icons are displayed properly in gtk3-icon-browser! Recreating cache by
'gtk-update-icon-cache-3.0 /usr/share/icons/Adwaita' makes symbolic
icons dissapear again.
2. (With caches) Starting gtk3-icon-browser with breeze-icons selected
in XFCE and changing icon theme to Adwaita while gtk3-icon-browser is
running, shows symbolic icons properly!
3. Starting thunar with Adwaita (missing icons) and selecting
'View/Configure Columns' opens a dialog in which 'Move up' button uses
go-up-symbolic and it is displayed although missing in toolbar!
4. Googling for this issue does not lead to any hits - seems PC world
does not have this issue - on my Fedora PC gtk3-icon-browser works
without issues.

Some guesswork:
Looking at symptoms 1-4 this 'smells' like some race on icon preparations:
* For 1.: Icon loading is slower without cache
* For 2.: Breeze icons are svg - they might load slower
* For 3.: The dialog is much later in application's timing
* For 4.: PC have a much different timing than RaspberryPi

Sorry for volubility... - GNOME experts wanted :)

Cheers

Andreas

[1] https://bugzilla.xfce.org/show_bug.cgi?id=14443