Implement a feature to constrict the map canvas to a specified map frame on a layout

[bkepl]

Feature description

It would be nice to be able to mask the map canvas outside the extent of a specified map frame on a layout. This view should position labels at the edges the way labels are positioned in that map frame. Features outside should still be visible with user-definable opacity (at least) and color for the mask area. The goal would be to see how labels will be placed at the edges of the map frame and allow more precise label positioning as needed. This masked view should reflect label settings applied to the map frame, such as edge distance. It would be totally cool if other items on the map frame, such as the legend and north arrow, could be emulated as additional masks. An option to show the surrounding layout would be a plus.

Additional context

No response