Improve scaling for HighDPI displays

[matty0ung]

Currently semi-manual scaling applies only to the main window (excluding elements in its title bar). In particular, the window where you can manually override the scaling factor is itself not scaled. Also, although the 150% scaling is a slight improvement, it's not enough for all High-DPI displays. This change switches to fully-automatic scaling for the full application, based on the DPI returned for the main display. It makes all the text of the whole application readable for the first time on my laptop display (where I needed 220% scaling).

[asb2m10]

Thanks for this, but don't remove the possibility to the user to change the scale the ui. I need this feature to test scaling on different platforms.

[matty0ung]

Ah, OK.
Could go in a couple of different directions here. One would be to allow the user to override the scaling with a % value. (Currently, selecting between 100% and 150% is not enough range for all displays.) Another would be to have the window resizeable (rather than fixed size) and just scale to the size of the window. (IIRC, this is what, eg, ZynAddSubFX does for instance.)
What's your preference?

[mkruselj]

Override the scaling with % value, upscaling from lower sized assets halfways through upwards, downscaling from higher sized assets halfways through downwards.

Example: We have 100%, 150% and 200% assets. Zoom level of 120% would upscale 100% assets. Zoom level of 130% would downscale 150% assets, etc.

[matty0ung]

Wouldn't it be better to have the assets as SVGs and just let the framework handle the scaling?

[asb2m10]

Yes... if somebody can provides those "8-bit" SVGs assets I'll be happy to implement them. Otherwise we have to use static assets. I am planning to stick to 200% for the next version. I have to check if that doesn't tax too much on the cpu.

[asb2m10]

I'm closing this since this has been addressed with #356