Steam is not able to minimize at all . The window stays there but glitches out, drawing on top of other windows occasionally.

Alright. i "downgraded" my nvidia-drivers. I was using 337.12 while this happened. Downgraded to 331.67 and the issues resovled.

I see that in Opensuse + NVIDIA 331.xx or 334.xx + MATE 1.6 with Steam and Flash Player. If I start MATE + Compiz there are no glitches. In other DE there are no glitches too.

the glitches appear with 337.12 if you can confirm that it would be me more useful.

It might be an issue with chromium not steam.

So did you narrow this down to nvidia drivers, steam, chromium, your compositor or Flash? Would you provide more details of your system setup please. https://github.com/ValveSoftware/steam-for-linux#reporting-issues

I think it only happens when i am running flash in chromium or when i am running a game. Then the steam window seems to glitch out (draw while its minimized).

Processor Information:
Vendor:  GenuineIntel
CPU Family:  0x6
CPU Model:  0x3c
CPU Stepping:  0x3
CPU Type:  0x0
Speed:  3800 Mhz
4 logical processors
4 physical processors
HyperThreading:  Unsupported
FCMOV:  Supported
SSE2:  Supported
SSE3:  Supported
SSSE3:  Supported
SSE4a:  Unsupported
SSE41:  Supported
SSE42:  Supported

Network Information:
Network Speed:  

Operating System Version:
"NAME=Gentoo" (64 bit)
Kernel Name:  Linux
Kernel Version:  3.15.0
X Server Vendor:  The X.Org Foundation
X Server Release:  11501000
X Window Manager:  KWin
Steam Runtime Version:  steam-runtime-release_2014-04-15

Video Card:
Driver:  NVIDIA Corporation GeForce GTX 650 Ti BOOST/PCIe/SSE2

Driver Version:  4.4.0 NVIDIA 340.17
OpenGL Version: 4.4
Desktop Color Depth: 24 bits per pixel
Monitor Refresh Rate: 60 Hz
VendorID:  0x10de
DeviceID:  0x11c2
Number of Monitors:  1
Number of Video Cards Not Detected
Primary Display Resolution:  1920 x 1080
Desktop Resolution: 1920 x 1080
Primary Display Size: 18.78" x 10.55"  (21.54" diag)
                    47.7cm x 26.8cm  (54.7cm diag)
Primary Bus: PCI Express 16x
Primary VRAM: 2048 MB
Supported MSAA Modes:  2x 4x 8x 16x 

Sound card:
Audio device: Realtek ALC1150

Memory:
RAM:  32079 Mb

Miscellaneous:
UI Language:  English
LANG:  en_GB.utf8
Microphone:  Not set
Total Hard Disk Space Available:  300321 Mb
Largest Free Hard Disk Block:  248768 Mb

Installed software:

Recent Failure Reports:

Has this issue been fixed in the steam beta? The issue has disappeared for me.
A lot has changed though.

new driver versions (340.x)
new gfx card(gtx 770)
kde updates.
steam beta updates..

Now when i minimize the steam client it doesnt want to draw on top of other windows anymore .. correctly.

This issue was fixed some time ago by Nvidia (in the v340.24 driver update).

This issue seems to be back now on 340.65

# glxinfo | grep version
server glx version string: 1.4
client glx version string: 1.4
GLX version: 1.4
OpenGL core profile version string: 3.3.0 NVIDIA 340.65
OpenGL core profile shading language version string: 3.30 NVIDIA via Cg compiler
OpenGL version string: 3.3.0 NVIDIA 340.65
OpenGL shading language version string: 3.30 NVIDIA via Cg compiler
OpenGL ES profile version string: OpenGL ES 2.0 NVIDIA 340.65 340.65
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 1.00

Example of the glitches I'm receiving

Further testing indicates these glitches happen when launching steam cold while a flash player applet is running in a browser like chrome or firefox. Flash player uses overlays so it looks like a driver issue failing to clear the overlay buffer. Closing any flash applets before launching steam fixes the issue.