Respect mouse-face on SVG image glyphs (bug#67794)

* src/dispextern.h:
* src/image.c (image_spec_value): Export 'image_spec_value'.
* src/xdisp.c (draw_glyphs): Maybe update SVG image glyphs with
mouse face features before drawing.

src/dispextern.h

@@ -3618,6 +3618,7 @@ void image_prune_animation_caches (bool);
 bool valid_image_p (Lisp_Object);
 void prepare_image_for_display (struct frame *, struct image *);
 ptrdiff_t lookup_image (struct frame *, Lisp_Object, int);
+Lisp_Object image_spec_value (Lisp_Object, Lisp_Object, bool *);
 
 #if defined HAVE_X_WINDOWS || defined USE_CAIRO || defined HAVE_NS \
   || defined HAVE_HAIKU || defined HAVE_ANDROID

src/image.c

@@ -1543,7 +1543,7 @@ parse_image_spec (Lisp_Object spec, struct image_keyword *keywords,
    if KEY is not present in SPEC.  Set *FOUND depending on whether KEY
    was found in SPEC.  */
 
-static Lisp_Object
+Lisp_Object
 image_spec_value (Lisp_Object spec, Lisp_Object key, bool *found)
 {
   Lisp_Object tail;

src/xdisp.c

@@ -30940,6 +30940,26 @@ draw_glyphs (struct window *w, int x, struct glyph_row *row,
 	  }
     }
+#ifdef HAVE_RSVG
+  /* Update SVG image glyphs with mouse face features.  FIXME: it
+     should be possible to have this behaviour with transparent
+     background PNG.  */
+  if (hl == DRAW_MOUSE_FACE)
+    {
+      Mouse_HLInfo *hlinfo = MOUSE_HL_INFO (f);
+      for (s = head; s; s = s->next)
+	if (s->first_glyph->type == IMAGE_GLYPH)
+	  if (s->img
+	      && (EQ (image_spec_value (s->img->spec, QCtype, NULL), Qsvg)))
+	    {
+	      ptrdiff_t id;
+	      id = lookup_image (f, s->img->spec, hlinfo->mouse_face_face_id);
+	      s->img = IMAGE_FROM_ID (f, id);
+	      prepare_image_for_display(f, s->img);
+	    }
+    }
+#endif
+
   /* Draw all strings.  */
   for (s = head; s; s = s->next)
     FRAME_RIF (f)->draw_glyph_string (s);