Teach 'current-column' to account for images

* src/indent.c (check_display_width): Handle 'image' and 'slice'
display specs, instead of using the width of the underlying text.
Accept 2 additional arguments: WINDOW and SCAN_BYTE.  (Bug#76107)

(cherry picked from commit 52e7a71e3f90fede27864e366977e23bfc193891)

diff --git a/src/indent.c b/src/indent.c
index 01cea2213687d71b1057d75cf0a25b086e44820c..b4f3c349dc534e9c4ccd9d3863dd73dbf54180da 100644 (file)
--- a/src/indent.c
+++ b/src/indent.c
@@ -466,13 +466,21 @@ current_column (void)
 }
 \f
 
+static void restore_window_buffer (Lisp_Object);
+
 /* Check the presence of a display property and compute its width.
+   POS and POS_BYTE are the character and byte positions of the
+   display property and COL is the column number at POS.
    If a property was found and its width was found as well, return
    its width (>= 0) and set the position of the end of the property
    in ENDPOS.
-   Otherwise just return -1.  */
+   Otherwise just return -1.
+   WINDOW is the window to use when it is important; nil stands for
+   the selected window.  */
 static int
-check_display_width (ptrdiff_t pos, ptrdiff_t col, ptrdiff_t *endpos)
+check_display_width (Lisp_Object window,
+                    ptrdiff_t pos, ptrdiff_t pos_byte, ptrdiff_t col,
+                    ptrdiff_t *endpos)
 {
   Lisp_Object val, overlay;
 
@@ -482,30 +490,80 @@ check_display_width (ptrdiff_t pos, ptrdiff_t col, ptrdiff_t *endpos)
       int width = -1;
       Lisp_Object plist = Qnil;
 
-      /* Handle '(space ...)' display specs.  */
-      if (CONSP (val) && EQ (Qspace, XCAR (val)))
-       { /* FIXME: Use calc_pixel_width_or_height.  */
-         Lisp_Object prop;
-         EMACS_INT align_to_max =
-           (col < MOST_POSITIVE_FIXNUM - INT_MAX
-            ? (EMACS_INT) INT_MAX + col
-            : MOST_POSITIVE_FIXNUM);
-
-         plist = XCDR (val);
-         if ((prop = plist_get (plist, QCwidth),
-              RANGED_FIXNUMP (0, prop, INT_MAX))
-             || (prop = plist_get (plist, QCrelative_width),
-                 RANGED_FIXNUMP (0, prop, INT_MAX)))
-           width = XFIXNUM (prop);
-         else if (FLOATP (prop) && 0 <= XFLOAT_DATA (prop)
-                  && XFLOAT_DATA (prop) <= INT_MAX)
-           width = (int)(XFLOAT_DATA (prop) + 0.5);
-         else if ((prop = plist_get (plist, QCalign_to),
-                   RANGED_FIXNUMP (col, prop, align_to_max)))
-           width = XFIXNUM (prop) - col;
-         else if (FLOATP (prop) && col <= XFLOAT_DATA (prop)
-                  && (XFLOAT_DATA (prop) <= align_to_max))
-           width = (int)(XFLOAT_DATA (prop) + 0.5) - col;
+      if (CONSP (val))
+       {
+         Lisp_Object xcar = XCAR (val);
+
+         /* Handle '(space ...)' display specs.  */
+         if (EQ (Qspace, xcar))
+           { /* FIXME: Use calc_pixel_width_or_height.  */
+             Lisp_Object prop;
+             EMACS_INT align_to_max =
+               (col < MOST_POSITIVE_FIXNUM - INT_MAX
+                ? (EMACS_INT) INT_MAX + col
+                : MOST_POSITIVE_FIXNUM);
+
+             plist = XCDR (val);
+             if ((prop = plist_get (plist, QCwidth),
+                  RANGED_FIXNUMP (0, prop, INT_MAX))
+                 || (prop = plist_get (plist, QCrelative_width),
+                     RANGED_FIXNUMP (0, prop, INT_MAX)))
+               width = XFIXNUM (prop);
+             else if (FLOATP (prop) && 0 <= XFLOAT_DATA (prop)
+                      && XFLOAT_DATA (prop) <= INT_MAX)
+               width = (int)(XFLOAT_DATA (prop) + 0.5);
+             else if ((prop = plist_get (plist, QCalign_to),
+                       RANGED_FIXNUMP (col, prop, align_to_max)))
+               width = XFIXNUM (prop) - col;
+             else if (FLOATP (prop) && col <= XFLOAT_DATA (prop)
+                      && (XFLOAT_DATA (prop) <= align_to_max))
+               width = (int)(XFLOAT_DATA (prop) + 0.5) - col;
+           }
+           /* Handle images.  */
+         else if (EQ (Qimage, xcar)
+                  || EQ (Qslice, xcar)
+                  /* 'insert-sliced-image' creates property of the form
+                      ((slice ...) image ...) */
+                  || (CONSP (xcar) && EQ (Qslice, XCAR (xcar))))
+           {
+             specpdl_ref count = SPECPDL_INDEX ();
+             struct window *w = decode_live_window (window);
+
+             /* If needed, set the window's buffer temporarily to the
+                 current buffer and its window-point to POS.  */
+             if (XBUFFER (w->contents) != current_buffer)
+               {
+                 Lisp_Object oldbuf
+                   = list4 (window, w->contents,
+                            make_fixnum (marker_position (w->pointm)),
+                            make_fixnum (marker_byte_position (w->pointm)));
+                 record_unwind_protect (restore_window_buffer, oldbuf);
+                 wset_buffer (w, Fcurrent_buffer ());
+                 set_marker_both (w->pointm, w->contents, pos, pos_byte);
+               }
+
+             struct text_pos startpos;
+             struct it it;
+             SET_TEXT_POS (startpos, pos, pos_byte);
+             void *itdata = bidi_shelve_cache ();
+             record_unwind_protect_void (unwind_display_working_on_window);
+             display_working_on_window_p = true;
+             start_display (&it, w, startpos);
+             it.last_visible_x = 1000000; /* prevent image clipping */
+             /* Forcing HPOS non-zero prevents the display code from
+                 generating line/wrap-prefix and line numbers, which
+                 would otherwise skew the X coordinate we obtain below.  */
+             it.hpos = 1;
+             /* The POS+1 value is a trick: move_it_in_display_line
+                 will not return until it finished processing the entire
+                 image, even if it covers more than one buffer position.  */
+             move_it_in_display_line (&it, pos + 1, -1, MOVE_TO_POS);
+             /* The caller wants the width in units of the frame's
+                 canonical character width.  */
+             width = ((double)it.current_x / FRAME_COLUMN_WIDTH (it.f)) + 0.5;
+             bidi_unshelve_cache (itdata, 0);
+             unbind_to (count, Qnil);
+           }
        }
       /* Handle 'display' strings.   */
       else if (STRINGP (val))
@@ -652,7 +710,7 @@ scan_for_column (ptrdiff_t *endpos, EMACS_INT *goalcol,
 
       { /* Check display property.  */
        ptrdiff_t endp;
-       int width = check_display_width (scan, col, &endp);
+       int width = check_display_width (window, scan, scan_byte, col, &endp);
        if (width >= 0)
          {
            col += width;