org-latex-preview: Improved face adaptation

* lisp/org-latex-preview.el (org-latex-preview--face-around): Instead of
only examining the face immediately before the LaTeX snippet, also look
at the face immediately after before determining the appropriate face to
use.  This is relevant when the prior face is
uninformative (e.g. org-indent) but the latter face contains the
applicable face (e.g. org-list-dt).  Determination of the applicable
face is now performed in the new function
`org-latex-preview--face-around'.
(org-latex-preview--colors-at, org-latex-preview--update-overlay):
Rename `org-latex-preview--colors-at' to
`org-latex-preview--colors-around', and use
`org-latex-preview--face-around' for better face determination.
(org-latex-preview-place, org-latex-preview-clear-cache): Update to
provide an "end" value to `org-latex-preview--colors-around'.

lisp/org-latex-preview.el

@@ -480,21 +480,38 @@ overlay face is set to `org-latex-preview-processing-face'."
       (overlay-put
        ov 'face
        (or (and errors 'error)
-           (and (> (overlay-start ov) (point-min))
+           (org-latex-preview--face-around
-                (not (eq (char-before (overlay-start ov)) ?\n))
+            (overlay-start ov) (overlay-end ov)))))
-                (let ((face (get-text-property (1- (overlay-start ov)) 'face)))
-                  (cond
-                   ((consp face)
-                    (cl-set-difference face org-latex-preview--ignored-faces))
-                   ((not (memq face org-latex-preview--ignored-faces))
-                    face))))
-           'default)))
      (errors
       (overlay-put
        ov 'before-string
        (propertize "!" 'display
                    `(left-fringe exclamation-mark error)))))))
 
+(defun org-latex-preview--face-around (start end)
+  "Return the relevant face symbol around the region START to END.
+A relevant face symbol before START is prefered, with END
+examined if none could be found, and finally the default face
+used as the final fallback.
+Faces in `org-latex-preview--ignored-faces' are ignored."
+  (or (and (> start (point-min))
+           (not (eq (char-before start) ?\n))
+           (let ((face (get-text-property (1- start) 'face)))
+             (cond
+              ((consp face)
+               (cl-set-difference face org-latex-preview--ignored-faces))
+              ((not (memq face org-latex-preview--ignored-faces))
+               face))))
+      (and (> (point-max) end)
+           (not (eq (char-after end) ?\n))
+           (let ((face (get-text-property end 'face)))
+             (cond
+              ((consp face)
+               (cl-set-difference face org-latex-preview--ignored-faces))
+              ((not (memq face org-latex-preview--ignored-faces))
+               face))))
+      'default))
+
 ;; Code for `org-latex-preview-auto-mode':
 ;;
 ;; The boundaries of latex preview image overlays are automatically
@@ -1068,7 +1085,7 @@ is either the substring between BEG and END or (when provided) VALUE."
         (pcase-let* ((`(,beg ,end ,provided-value) entry)
                      (value (or provided-value
                                 (buffer-substring-no-properties beg end)))
-                     (`(,fg ,bg) (org-latex-preview--colors-at beg))
+                     (`(,fg ,bg) (org-latex-preview--colors-around beg end))
                      (number (car (setq numbering-offsets (cdr numbering-offsets))))
                      (hash (org-latex-preview--hash
                             processing-type value imagetype fg bg number))
@@ -1100,11 +1117,9 @@ is either the substring between BEG and END or (when provided) VALUE."
        :latex-preamble latex-preamble
        :place-preview-p t))))
 
-(defun org-latex-preview--colors-at (pos)
+(defun org-latex-preview--colors-around (start end)
-  "Find colors for LaTeX previews to be inserted at POS."
+  "Find colors for LaTeX previews occuping the region START to END."
-  (let* ((face (or (and (> pos 1)
+  (let* ((face (org-latex-preview--face-around start end))
-                        (get-text-property (1- pos) 'face))
-                   'default))
          (fg (pcase (plist-get org-latex-preview-options :foreground)
                ('auto
                 (org-latex-preview--resolved-faces-attr face :foreground))
@@ -2129,7 +2144,12 @@ the *entire* preview cache will be cleared, and `org-persist-gc' run."
       (dolist (element (org-latex-preview-collect-fragments beg end))
         (pcase-let* ((begin (or (org-element-property :post-affiliated element)
                                 (org-element-property :begin element)))
-                     (`(,fg ,bg) (org-latex-preview--colors-at begin))
+                     (end (- (org-element-property :end element)
+                             (or (org-element-property :post-blank element) 0)
+                             (if (eq (char-before (org-element-property :end element))
+                                     ?\n)
+                                 1 0)))
+                     (`(,fg ,bg) (org-latex-preview--colors-around begin end))
                      (value (org-element-property :value element))
                      (number (and numbering-table
                                   (eq (org-element-type element)