Live change of theme from Preferences dropdown

[francescospissu]

Motivation

The theme must be updated immediately if the user selects it from the Preferences drop-down menu. In this way it's possible to preview the appearance of the various themes available.

By pressing the Cancel button the initial theme must be restored.

Change description

Restore the previous theme when the dialog is closed by pressing the Cancel button.

Other information

This is an ad hoc solution for themes, in the long run this behavior should be generalized because other elements of the Preferences, such as the Editor font size or the Interface scale, may also require a live update to give immediate feedback to the user. In this case maybe a big rework of settings is needed.

Closes #1048.

Reviewer checklist

• PR addresses a single concern.
• The PR has no duplicates (please search among the Pull Requests before creating one)
• PR title and description are properly filled.
• Docs have been added / updated (for bug fixes / features)

[per1234]

I gave it a try on Windows and it works perfectly for me. Very cool enhancement to the IDE.

Thanks Francesco!

[kittaakos]

It worked for me. I have verified it from the IDE2 started from the sources. 👍

[davegarthsimpson]

@kittaakos is the method .setCurrentTheme also called by Theia code after we click apply on the settings dialog?

[kittaakos]

Yes.

[davegarthsimpson]

considering the proposed changes maybe we should consequently mod this also:

 <select className="theia-select" value={ ThemeService.get() .getThemes() .find(({ id }) => id === this.state.themeId)?.label || nls.localize('arduino/common/unknown', 'Unknown') } onChange={this.themeDidChange} > 

could be:

 <select className="theia-select" value={ ThemeService.get().getCurrentTheme().label } onChange={this.themeDidChange} > 

I don't see a reason to now reference the state prop themeId in the JSX (though maybe I'm missing something).

p.s. I don't know if || nls.localize('arduino/common/unknown', 'Unknown') is really required, here I've assumed not.

[francescospissu]

I agree @davegarthsimpson. I applied the change here, I tested it and it works fine.