bug#7004: 23.2; In fullscreen mode, the echo area takes too much vertical space

[martin rudalics]

> You also have to fix distribution of window sizes so that in a layout
> like this:
>
>  -----------------------------
>  |               |           |
>  |               |           |
>  ----------------            |
>  |         |     |           |
>  |   1     | 2   |     3     |
>  |         |     |           |
>  -----------------------------
>
> it is 1, 2 and 3 that gets the leftoer pixels.

Moreover, if 1 or 2 are fixed-size I should give the pixels to the
unnamed window above.

> Handling split and delete
> of windows correctly can be hard.

Splitting works line based and the number of lines of a window is not
affected by pixels.  In particular, answering the question whether a
window can be split in the first place is unaffected by pixels.

Now the parent window of the split window has a pixel-height and I have
to reapply the same procedure as for frame resizing recursively to each
of its child windows.

For deleting I add the leftover pixels to the window(s) that get the
lines of the window deleted.

Finally the display-engine must be able to deal with window
top-lines/left-columns and height/width given in pixels.  So the window
structure will probably have four additional slots like pixel-top,
pixel-left, pixel-height, and pixel-width and the display engine must be
able to interpret these.

martin