[Bug 59602] New: Nested `UserControl` is not properly rescaled on font change

[WineHQ Bugzilla]

http://bugs.winehq.org/show_bug.cgi?id=59602

            Bug ID: 59602
           Summary: Nested `UserControl` is not properly rescaled on font
                    change
           Product: Framework Mono
           Version: 6.12.0
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: System.Windows.Forms
          Assignee: [e-mail]
          Reporter: [e-mail]
                CC: [e-mail]
      Distribution: ---

Created attachment 80671
  --> http://bugs.winehq.org/attachment.cgi?id=80671
Screenshots + Logs [Windows 11 Textscale 125% = all fine], [Mono Debian WSL =
user control not properly scaled],

Simplified situation:

TestForm
> TestButton
> TestControl
>     > SubControl
>        > SubButton

(see attached screenshots for complete sitation)

When applying a new font to the form, e.g. `Font = SystemFonts.IconTitleFont`,
form and controls are expected to get rescaled, as the form is set to
`AutoScaleMode.Font`.

Rescaling does happen, and works fine for e.g the `TestButton`
(button_Form_SizeChanged to {Width=390, Height=32}), as well as for
`TestButton` (TestControl_SizeChanged to {Width=390, Height=32}), but
`SubControl` does not get scaled in respect to Size! It only gets scaled in
respect to Location!

The attached .zip contains screenshots demonstrating the issue:
- Windows 11 .NET Framework 4.8 text scaled to 125% => all fine.
- Debian 12 with Mono 6.12.0 => user control not properly scaled.

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[Bug 59602] Nested `UserControl` is not properly rescaled on font change

[WineHQ Bugzilla]

http://bugs.winehq.org/show_bug.cgi?id=59602

--- Comment #1 from [e-mail] <[e-mail]> ---
I think the root cause is `else if (IsContainerAutoScaling (this.Parent))` at
https://gitlab.winehq.org/mono/mono/-/blob/main/mcs/class/System.Windows.For...:

The container of `TestControl` is `TestForm`, which is about auto-scaling
(https://gitlab.winehq.org/mono/mono/-/blob/main/mcs/class/System.Windows.For...)
when the above piece of code is being called. Consequently, `TestControl` will
not perform scaling in respect to the size
(https://gitlab.winehq.org/mono/mono/-/blob/main/mcs/class/System.Windows.For...).

If this analysis is correct, the implementation will have to be refined such it
performs scaling children even with nested controls.

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[Bug 59602] Nested `UserControl` is not properly rescaled on font change

[WineHQ Bugzilla]

http://bugs.winehq.org/show_bug.cgi?id=59602

--- Comment #2 from [e-mail] <[e-mail]> ---
Note that issue also applies to MDI child forms, i.e. forms that have a parent.
Depending on `Dock`, controls of an MDI child form may not get scaled for the
reason described earlier.

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[Bug 59602] Nested `UserControl` is not properly rescaled on font change

[WineHQ Bugzilla]

http://bugs.winehq.org/show_bug.cgi?id=59602

--- Comment #3 from [e-mail] <[e-mail]> ---
Workaround good enough to handle composite/nested controls:
```
/// <remarks>
/// Works around https://bugs.winehq.org/show_bug.cgi?id=59602 by scaling
nested children
/// in case of <see cref="BoundsSpecified.Location"/>, rather than skipping:
///
https://gitlab.winehq.org/mono/mono/-/blob/main/mcs/class/System.Windows.For...
/// </remarks>
[Conditional("MONO")]
public static void ApplyMonoScaleChildrenWorkaround(Control.ControlCollection
controls, SizeF factor, BoundsSpecified specified, bool scaleChildren)
{
    if ((specified == BoundsSpecified.Location) && scaleChildren)
    {
        foreach (Control c in controls)
            c.Scale(factor);
    }
}
```
Workaround has to be applied to the top-level composite control:
```
#if (MONO)
protected override void ScaleControl(SizeF factor, BoundsSpecified specified)
{
    base.ScaleControl(factor, specified);

    SuspendLayout();
    ControlEx.ApplyMonoScaleChildrenWorkaround(Controls, factor, specified,
ScaleChildren);
    ResumeLayout();
}
#endif
```
The workaround does not work for forms, e.g. MDI child forms. For such, call
`Scale()` on all composite controls:
```
#if (MONO)
protected override void ScaleControl(SizeF factor, BoundsSpecified specified)
{
    base.ScaleControl(factor, specified);

    SuspendLayout();
    someControl.Scale(factor);
    ResumeLayout();
}
#endif
```

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