Re: mouse-drag-and-drop-region

[Stefan Monnier]

>> A more general solution could be to add two more glyph matrices (one for
>> overlay thingies like menus and tooltips, and another that combines the
>> "normal" glyph matrix with the one for overlay thingies (and it's this
>> one which is then sent to be displayed)).
> I don't see how this solves the problem, because the display engine
> will still know nothing about that "second" matrix.

As mentioned: "it's this one which is then sent to be displayed", so
this assumes we'd change the display engine to use the combined matrix:

    render buffer text to desired-glyph-matrix
    combine desired-glyph-matrix with overlay-matrix into combined-matrix
    send combined-matrix to screen


-- Stefan