Toolbars: ToolbarItem.when field is evaluated and respected

[jonah-iden]

ToolbarItem.when field is evaluated and respected
by toolbar and tab-bar-toolbar +
when clause can be set in toolbar.json

Signed-off-by: Jonah Iden [email protected]

What it does

Implements/fixes #11705

This PR implements the funcitionality for toolbars to evaluate and respect the when field/clause of ConditionalToolbarItem.
Also allows setting the when field in toolbar.json.

How to test

easiest way to test is probably through the toolbar.json file:

1. press Alt+T to open the toolbar
2. right click it and click Customize Toolbar (open JSON)
3. either add a new toolbar item or edit an existing one. Add "when": "inDebugMode" and save the file
4. see the icon gets grayed out and does not react to clicks
5. start a debug session
6. see icon is white again and reacts to clicks
7. stop debug session
8. icon disabled again

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[msujew]

The changes look good to me 👍

• Registering a when context correctly updates the toolbar item (disables/enables it)
• When the context changes, the item is also updated as expected
• A disabled toolbar item will not trigger its command when pressed (though it still allows to remove/move the item)
• The string type for the when property is correctly reflected when editing the JSON file

[vince-fugnitto]

For transparency the pull-request has caused regressions with other toolbar items such as #12314.

[alvsan09]

Another regression is described at:
#12314 (comment)