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

[martin rudalics]

>> IIUC Emacs usually [...] rounds the height to the nearest integer
>> multiple of the canonical line height instead.
>
> That's not really relevant, since the height includes the tool bar and
> the menu bar, whose sizes aren't multiples of the canonical font
> height.  So the windows end up with non-integral number of text lines
> anyway.

My frame.h has

/* Number of lines of frame F used for menu bar.
   This is relevant on terminal frames and on
   X Windows when not using the X toolkit.
   These lines are counted in FRAME_LINES.  */
#define FRAME_MENU_BAR_LINES(f) (f)->menu_bar_lines

/* Number of lines of frame F used for the tool-bar.  */
#define FRAME_TOOL_BAR_LINES(f) (f)->tool_bar_lines

so AFAICT these are measured in canonical line heights too.

> If all of this is true, then how do we succeed to display partial
> lines with the existing ``pixel-challenged'' display engine?  What am
> I missing?

The problem I have tried to sketch was not concerned with "how do we
succeed to display ..." but rather with "how to we succeed not to break
the behavior of Emacs when we succeed to display ....".

martin