In the first dialog picture is that your regular window manager decoration? It doesn't seem to be Steam's.
Yes, this is regular window manager decoration (metacity-2.30.3). This dialog have this as long as I can remember Steam for Linux. Steam runtime is enabled.
Steam must be providing the string data for the window title incorrectly.
It probably did.
What about second issue with text overflowing? is it correctable?
I think the source of that problem is in fact that Steam window elements was never been resizable, so if text would be longer, then it will not fit. That is common problem with DPI and fixed size elements, for example in web design.
The second issue is fixable but low priority.
Make sure that you set _NET_WM_NAME using full UTF-8 data using the UTF8_STRING property type, and do not use the deprecated WM_NAME with any kind of localized data. This will make sure that the WM can read your title string.
The second issue isn't related to nonstandard DPI; it's present in the vanilla Windows client as well, though it'll probably be hard to catch now that the client updates during startup as well. I think the text box's contents are set to a fixed width that's wider than the actual box.
Here we go. A picture of the self-updater in Windows 7, no custom text scaling:
Ok, first problem (wrong title encoding) is fixed in latest update.
Closing as this was fixed some time ago.
Nothing extracted yet.
I have Gentoo on AMD64. My Xorg DPI setting is 106. System locale is "ru_RU.UTF8".
This is not a Cyrillic: