UI Scaling for Dual Monitor Setup

[rav7en]

Describe the bug

Dual monitor setup with separate scaling settings creates discrepancy in how Open-Shell applies its UI overlay.
I am specifically referring to the Start Menu Windows button overlay. View the image below to see what I mean.

Area of issue

Start menu, Taskbar

To reproduce

Not applicable

Expected behavior

Custom UI scaling options for the dual monitor setup

Open-Shell version

4.4.196

Windows version

Windows 11 24H2

Additional context

No response

[ge0rdi]

It seems that custom Start button doesn't apply DPI at all.

There is LoadImageFile called to load image in CStartButton::LoadBitmap, but it doesn't do anything with DPI.
For Aero button style we are loading appropriate (scaled) built-in image according to DPI.

I think we need to pass DPI (of actual button window) to LoadImageFile so it will scale loaded image accordingly.
Then the rest should work nicely.

However, this may be kind of breaking change as right now some users may have set custom Button size to adjust for their DPI. For those users the button size value will get scaled, so they will have to adapt their settings.

[ge0rdi]

You can try build from #2248 PR.
Custom start button should be scaled according to monitor's DPI.