This issue should probably be moved to dotnet/winforms. IsHandleCreated was added in this commit: 9b77d91

@swapso I believe what you're seeing is expected and by design due to the change in the default font (documented here). To ease the pain of the migration in .NET 6 we introduced Application.SetDefaultFont API and the application bootstrap (documented here, blogged here).
Setting the application default font to ""Microsoft Sans Serif, 8pt" should set your layouts back to the original.

I would also recommend reviewing the list of the breaking changes Windows Forms SDK accepted moving from .NET Framework to .NET.

@RussKie, you're spot on. It only functions correctly when the forms are already open, as IsHandleCreated returns true in that scenario. However, if the form is closed and we modify the font for the application from another part of the application, then open the form again, IsHandleCreated returns false, leading to improper scaling.

Difference between NET 4.8 & NET Core font scaling.pdf

Hi @RussKie @Suchiman
To support my statements, I have created two separate applications based on NET Core & NET 4.8. In Above documents I have provided github links to clone the repos and step-by-step workflow to reproduce the same error I am facing.

Please go through it once.
You will observe how IsHandleCreated comes false in case TabControl contained controls.

Thank you @swapso, that's for @dotnet/dotnet-winforms team to investigate.

This problem can be reproduced by setting a larger font size for the form and making the control layout in the Form more compact.
WinFormsApp3.zip

#11213

@RussKie @LeafShi1

In above pull request I have provided a solution to bypass this IsHandleCreated condition.
May I know how to get these changes approved ?

@swapso thank you for raising this issue. A change in this part of the code is extremely risky and can have a lot of unintended consequences. @LeafShi1 - can your team do a deep dive into a workaround, perhaps enforcing SuspendLayout when handle is created?

@merriemcgaw @LeafShi1 @ricardobossan
can you provide me an update on this issue?

@merriemcgaw @ricardobossan @Tanya-Solyanik
The reason for this problem is that PerformAutoScale is not executed, because when the Form object is created, its handle is not created immediately, this is by design.

So the way to fix this problem

1. As a workaround, force creation of Handle before font change
   
2. Update judgment here so that PerformAutoScale can be executed. Can we consider the following judgment logic?
   if (AutoScaleMode != AutoScaleMode.None && (IsHandleCreated || Font != DefaultFont))

Thanks for the workaround @LeafShi1! @swapso does this solve your issue?

@merriemcgaw I will test the changes and let you know soon

Hi @merriemcgaw , @LeafShi1 @Tanya-Solyanik
Previously I was using below document to test the changes. But now its not working, even after copying DLL to shared folder when I run my program, I am not getting modified SDK files in debug.
I also enabled in VS under Tools->Options->Environment->Preview Features->Use previews of the .Net Core SDK (Requires restart) setting.

Document: https://github.com/dotnet/winforms/blob/main/docs/debugging.md

am I missing something?

Hi @merriemcgaw , @LeafShi1 @Tanya-Solyanik Previously I was using below document to test the changes. But now its not working, even after copying DLL to shared folder when I run my program, I am not getting modified SDK files in debug. I also enabled in VS under Tools->Options->Environment->Preview Features->Use previews of the .Net Core SDK (Requires restart) setting.

Document: https://github.com/dotnet/winforms/blob/main/docs/debugging.md

am I missing something?

Is there any error? You can try to upgrade the .net SDK to latest version.

@LeafShi1
There is no specific error, it just don't switch to modified the SDK with above settings.
Also, I have already these SDK installed:

1. Windows 11 SDK (10.0.22621.0)
2. .NET Framework 4.8 SDK
3. .NET SDK

@swapso You may have misunderstood the workaround I provided. You don't need to change the Winform code. You only need to add CreateHandle(); in your Application.

@LeafShi1 oh thanks. I already tried & tested adding CreateHandle(); in my application and it works.

But to close this issue, I guess I need to change in Winform code and then submit a PR for this issue. Isn't it? Or you guys will do it?

@LeafShi1 Sorry for the confusion what I write in earlier comment. The CreateHandle(); worked in my sample application for single form only. When I tried to put it in base form, it just don't work.
Also, in my main application even after putting CreateHandle(); for a single form don't work.

@LeafShi1 Sorry for the confusion what I write in earlier comment. The CreateHandle(); worked in my sample application for single form only. When I tried to put it in base form, it just don't work. Also, in my main application even after putting CreateHandle(); for a single form don't work.

I see. Font settings may be more complicated in real applications. CreateHandle(); can only solve the problem of setting the default font when the Form is initially sized. We will revisit this issue.

There's also an issue with a specific nesting of controls that won't allow auto-scaling for some controls. When a control is placed in a SplitContainer inside a TabControl on its second page, this control isn't included in the auto-scaling until after the second page has been created (selected).
TestAutoScaleOnFontChange.zip

Hi @LeafShi1

I made the changes you provided in winform code. Built and exported DLL and tested it with my application. it works. Every contols are properly scaled according to font size.

Steps I took:

1. Set my targetFramwork to 'net9.0-windows'. because i was using .NET 9 preview version.
   net9.0-windows
2. Enabled visual studio option in Debug -> Options -> Environment -> Preview features: Use previews of the .NET SDK.
3. By following guide https://github.com/dotnet/winforms/blob/main/docs/debugging.md
   updated DLL at appropriate path, so visual studio can reference DLL while building app.

@Camel-RD even tested your application 'TestAutoScaleOnFontChange.zip' , it also work with that.

code changes in winform screenshot attached below. (updated if condition)

@LeafShi1 Let me know so we can close this issue.

estAutoScaleOnFontChange.zip' , it also work with that.

Thanks for your feedback, we need to discuss the feasibility of this fix and whether it can solve all possible situations.

@LeafShi1 if we can move faster, we want these small changes to go live in the next .NET preview version Or get added in the previous version .NET

Let me know how can I help to do it faster.

Let me know how can I help to do it faster.

For issue tracking, please see the comment below PR #11641

@LeafShi1 why PR#11641 is closed? What happened to new infrastructure that Jeremy was planning to rework.

@LeafShi1 why PR#11641 is closed? What happened to new infrastructure that Jeremy was planning to rework.

@LeafShi1 please reply

@LeafShi1 why PR#11641 is closed? What happened to new infrastructure that Jeremy was planning to rework.

@LeafShi1 please reply

I can't give a specific time for the new infrastructure, closing this PR is to avoid outdated code, which will increase merge conflicts and make review difficult. When the new infrastructure is completed, I will submit a new PR
FYI @JeremyKuhne @Tanya-Solyanik

@LeafShi1 any update?

@LeafShi1 any update?

Sorry for the late reply! I cannot provide a detailed infomation to you. @JeremyKuhne is working on creating new infrastructure, I will update you if there are any updates.

@swapso redoing layout is a very large feature which has no specific delivery date yet. We'll try to do a targeted fix for this in .NET 10.