Your system information

• Steam client version (build number or date): 8 Jun 2018, at 22:22:39
• Distribution (e.g. Ubuntu): Multiple
• Opted into Steam client beta?: [Yes/No] no
• Have you checked for system updates?: [Yes/No] yes (Fresh install)

Please describe your issue in as much detail as possible:

Describe what you expected should happen and what did happen. Please link any large code pastes as a Github Gist

Steam seems to be using an out of date or incomplete version of the GTK2 framework which leads to theming being broken in about 99% of all themes I've tried since most modern themes make use of the "direction" attribute. When steam attempts to load this attribute it fails and reverts back to a fallback theme which often looks unpleasant.

This causes the following error:
"/usr/share/themes/deepen-dark/get-2.0/main.rc:1090: error: unexpected identifier 'direction', expected character '}'"

The main side effect of this is the broken menu theming found when you click on the steam system tray icon. Even if the rest of your system looks modern, that menu will look asif it were ripped strait from an OS from 2 decades ago

Steps for reproducing this issue:

1. Download a them that contains the "direction attribute"
   e.g. the deepen dark theme I am using has it at line 1090

image {
function = SHADOW
setail = "entry"
state = NORMAL
shadow = IN
file = "assets/combo-entry.png"
border = { 4, 4, 5, 4 }
stretch = TRUE
direction = LTR
}

1. Install steam
2. run "steam" via terminal and look for the error I've described above