bug#29627: 25.3; x-show-tip does not display text when x-gtk-use-tooltips is nil and left/right-margin-width is set

[martin rudalics]

> First, I didn't make the window a pseudo-window; it was always a
> pseudo-window.  The line
>
>    w->pseudo_window_p = true;
>
> existed in x-show-tip ever since Emacs 21.

Ah, sorry.  I misread both ChangeLog entry and diffs (and was probably
mislead by this change

-       Currently only used for menu bar windows of frames.  */
+       Currently only used for menu bar windows, for tool bar windows,
+       and for tooltips.  */
)

> I didn't feel comfortable
> with changing that now, certainly not on the release branch.

Sure so.

> And you will see that window_box_left does this for pseudo-windows:
>
>    if (w->pseudo_window_p)
>      return FRAME_INTERNAL_BORDER_WIDTH (f);
>
> which is just another example of the above-mentioned assumption about
> pseudo-windows being margin-less.

Right.

> So from_x remained (almost) zero, unlike in normal windows, and the
> already displayed text was deleted.
>
> For some reason that I cannot identify, and don't really care about,
> the original recipe did work until Emacs 24.3.  But it could only work
> by sheer luck, or maybe something else was preventing the window of
> the tooltip frame to acquire display margins.  I just made this
> official with my changes, that's all.
>
> As for why I forced the tip buffer have zero margins, instead of doing
> the same with the window in which that buffer is displayed, then:
>
>    . why does it matter? the buffer is a temporary buffer generated
>      specifically for showing the tip text;
>    . I thought doing that with the window is more complex, what with
>      all the different ways one can affect a window's parameters
>
> Having said all that, if you see problem(s) caused by my change,
> please describe them; I'm not married to the fix I pushed.

It's OK.  My concern was that turning tooltip windows into
pseudo-windows would have meant a quite substantial change for the
release branch.

Thanks for the explanations, martin