Fix the expand icon calculation logic to the function Button::get_minimum_size

[Rindbee]

Fix the expand icon calculation logic which belongs to the function Button::get_minimum_size

Type	Before	After
Button
OptionButton

If enable the expand_icon, the icon may be hidden when the width of the button is not wide enough. This is where I mainly want to fix in this patch.

Note:
The last thing worth noting is that the minimum achievable scale size is highly correlated with the font size, even if the text is empty. So, if you want a small texture size, you need to make the font size small enough. I'm not sure the specific design requirements, just adjusted some logic.

Should we make the texture keep aspect, or follow other rules?

Other matters

I'm glad it partially resolves #59202, but if the height of the button is too large, it will still appear.

I checked the source code of OptionButton, it overrides this method, maybe this problem needs to be fixed there. It is very likely that this property theme_override_constants/arrow_margin was not considered.

[Chaosus]

Maybe you should explain what this PR does in details and how it works (for example by providing some video to show)?

[EricEzaM]

Is this fixing an existing issue? #59202 Perhaps? You can indicate that a PR will close a certain issue by writing, for example.

Fixes #issue number

There are a number of these keywords, see here: https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue

Explaining a bit about what you did in the PR and perhaps an image or GIF showing the fixed behaviour also goes a long way, as Chaosus said.

[Rindbee]

@Chaosus @EricEzaM Yes, the GIF can make the description more intuitive. Do you have any good tools to recommend on the Linux platform.

[Chaosus]

Do you have any good tools to recommend on the Linux platform.

Probably one of the recorders listed in here: https://itsfoss.com/best-gif-recorder-linux. On Windows (which I'm using), the screentogif serves me the best.

[Rindbee]

Do you have any good tools to recommend on the Linux platform.

Probably one of the recorders listed in here: https://itsfoss.com/best-gif-recorder-linux. On Windows (which I'm using), the screentogif serves me the best.

Thanks, I will try it.

[Rindbee]

Thanks again to @Chaosus for the recommended tool, peek. Now it behaves like in the GIF image above.

[Rindbee]

@Chaosus @EricEzaM OK, now I think it would illustrate the main purpose of this patch. Please review. I feel like I found the cause of the problem in #59202 . Should I fix it in this PR, or open a new one?

[Rindbee]

Before	After

When the size is the smallest, modifying the property theme_override_constants/arrow_margin, now the arrow icon will not appear outside the button.

[Rindbee]

Now, it fixes #59202 by adding a callback method.

The method will return the width caused by the properties beside those in Button.

Edited:

I found that there is a property _internal_margin already defined in Button. This property seems to have a similar effect to get the size of inner icons, but I'm not clear on its specific purpose.

[Rindbee]

Superseded by #64351.