DPI scaling is broken if font of the form set in designer

[kirsan31]

• .NET Core Version: 3.1.3

• Have you experienced this same bug with .NET Framework?: Yes

Problem description:

DPI scaling (AutoScaleMode.Font) is broken if font of the form set in designer. Or you can read it as: DPI scaling is broken if font of the form set after DPI scaling logic code, even in SuspendLayout and before very first PerformLayout.

If you put yellow code in front of pink, or in constructor before InitializeComponent(); - all will be ok.

The bug appear only if this font is different from current system font.
Win10 pro 1809/1909.

Related old stackoverflow post.
My personal opinion is that this is not designer problem, this is the problem of DPI scaling logic that depends on instructions order even in SuspendLayout...

Expected behavior:
Form must be scaled correctly.

Minimal repro:
This test project was created in VS 16.6 preview 5 with using of new core designer: WindowsFormsAppDesignerDPI.zip

[merriemcgaw]

We want to tackle this when we address DPI scaling holistically. Will bring it up in a designer meeting to see what we might be able to do there. Since this is not a regression and there are workaround we probably won't get DPI across the board working, I'm moving to the future bucket. But I want to continue the design discussion about how we might address this.

[kirsan31]

@merriemcgaw thank you. Сan you share estimated plan when / in which version will be DPI scaling overhaul?

[merriemcgaw]

We're working on our longer term roadmap in the coming weeks. I'm starting to see more and more requests for a DPI overhaul from multiple channels, so I'm certain it will be one of the next big things once we get the designer work completed.

[kirsan31]

@dreddy-work
Here you mentioned that:

this is designer issue and is slated for VS 2022 release and will be tracked out side of .NET release.

If so, I think it's must be documented somewhere that correct DPI scaling logic depend on order of these Form's properties setters:

AutoScaleDimensions
AutoSizeMode
Font