master b377080c: Add notification about xelatex in preview-latex doc

[Ikumi Keita]

branch: master
commit b377080c809e688cce895def7b95fc0bc33eaa39
Author: Ikumi Keita <ikumi@ikumi.que.jp>
Commit: Ikumi Keita <ikumi@ikumi.que.jp>

    Add notification about xelatex in preview-latex doc
    
    * doc/preview-problems.texi (Black texts are too hard to read on dark
    background): New node explaining that preview-latex with xelatex
    cannot adjust foreground color.
---
 doc/preview-problems.texi | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/doc/preview-problems.texi b/doc/preview-problems.texi
index e40ff42d..0f1518bf 100644
--- a/doc/preview-problems.texi
+++ b/doc/preview-problems.texi
@@ -20,6 +20,7 @@ newer versions of the problematic software or by simple 
patches.
 * x-symbol interoperation::     
 * Middle-clicks paste instead of toggling::  
 * No images are displayed with gs 9.27 and earlier::
+* Black texts are too hard to read on dark background::
 @end menu
 
 If you find something not mentioned here, please send a bug report using
@@ -194,3 +195,12 @@ well.
 The default value used to be @code{compatible} for short period before
 Ghostscript 9.50 was released but now is @code{t}.
 @end defopt
+
+@node Black texts are too hard to read on dark background
+@section Black texts are too hard to read on dark background
+Unfortunately, foreground color adjustment discussed in the previous node
+doesn't work for Xe@LaTeX{} for technical reason.  The texts are always
+rendered as black in the preview images, so it's almost impossible to read
+them on dark background.  Hence Xe@LaTeX{} users who like dark background
+in Emacs frame should customize @code{preview-pdf-adjust-color-method} to
+@code{nil}.