Redrawing when minimized

[CptPotato]

I recently saw that psst has noticable GPU usage when minimized. Taking a look with RenderDoc shows that, even if minimized, psst draws new frames while the UI is being updated (when playing for example).

Edit: OS is Win10 x64

[CptPotato]

After updating it seems that psst only refreshes the UI once every second when idle / during playback now. This reduces the background GPU usage to practically zero for me, so this might not be very relevant anymore.

[jpochyla]

I'd be still interested in any CPU/GPU optimizations, so if you'd be interested to work on this anyway, we could pause the rendering when the window is hidden.