master dbcb4cedd0a: Properly compute overhangs for overstruck text

[Po Lu]

branch: master
commit dbcb4cedd0a78b7ea8447c84c3da104edc2d4b14
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Properly compute overhangs for overstruck text
    
    * src/xdisp.c (get_glyph_face_and_encoding): Account for
    non-character glyphs by not attempting to translate them to
    characters.
    (gui_get_glyph_overhangs, gui_produce_glyphs): If the face is
    overstruck, increase the right side bearing by 1 pixel.
---
 src/xdisp.c | 87 +++++++++++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 71 insertions(+), 16 deletions(-)

diff --git a/src/xdisp.c b/src/xdisp.c
index 20c7634fc3e..9e8b4b130b9 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -29638,9 +29638,9 @@ get_char_face_and_encoding (struct frame *f, int c, int 
face_id,
 }
 
 
-/* Get face and two-byte form of character glyph GLYPH on frame F.
-   The encoding of GLYPH->u.ch is returned in *CHAR2B.  Value is
-   a pointer to a realized face that is ready for display.  */
+/* Get face glyph GLYPH on frame F, and if a character glyph, its
+   multi-byte character form in *CHAR2B.  Value is a pointer to a
+   realized face that is ready for display.  */
 
 static struct face *
 get_glyph_face_and_encoding (struct frame *f, struct glyph *glyph,
@@ -29655,19 +29655,23 @@ get_glyph_face_and_encoding (struct frame *f, struct 
glyph *glyph,
   /* Make sure X resources of the face are allocated.  */
   prepare_face_for_display (f, face);
 
-  if (face->font)
+  if (glyph->type == CHAR_GLYPH)
     {
-      if (CHAR_BYTE8_P (glyph->u.ch))
-       code = CHAR_TO_BYTE8 (glyph->u.ch);
-      else
-       code = face->font->driver->encode_char (face->font, glyph->u.ch);
+      if (face->font)
+       {
+         if (CHAR_BYTE8_P (glyph->u.ch))
+           code = CHAR_TO_BYTE8 (glyph->u.ch);
+         else
+           code = face->font->driver->encode_char (face->font, glyph->u.ch);
 
-      if (code == FONT_INVALID_CODE)
-       code = 0;
+         if (code == FONT_INVALID_CODE)
+           code = 0;
+       }
+
+      /* Ensure that the code is only 2 bytes wide.  */
+      *char2b = code & 0xFFFF;
     }
 
-  /* Ensure that the code is only 2 bytes wide.  */
-  *char2b = code & 0xFFFF;
   return face;
 }
 
@@ -30167,17 +30171,28 @@ normal_char_height (struct font *font, int c)
 void
 gui_get_glyph_overhangs (struct glyph *glyph, struct frame *f, int *left, int 
*right)
 {
+  unsigned char2b;
+  struct face *face;
+
   *left = *right = 0;
+  face = get_glyph_face_and_encoding (f, glyph, &char2b);
 
   if (glyph->type == CHAR_GLYPH)
     {
-      unsigned char2b;
-      struct face *face = get_glyph_face_and_encoding (f, glyph, &char2b);
       if (face->font)
        {
-         struct font_metrics *pcm = get_per_char_metric (face->font, &char2b);
+         struct font_metrics *pcm
+           = get_per_char_metric (face->font, &char2b);
+
          if (pcm)
            {
+             /* Overstruck text is displayed twice, the second time
+                one pixel to the right.  Increase the right-side
+                bearing to match.  */
+
+             if (face->overstrike)
+               pcm->rbearing++;
+
              if (pcm->rbearing > pcm->width)
                *right = pcm->rbearing - pcm->width;
              if (pcm->lbearing < 0)
@@ -30190,8 +30205,18 @@ gui_get_glyph_overhangs (struct glyph *glyph, struct 
frame *f, int *left, int *r
       if (! glyph->u.cmp.automatic)
        {
          struct composition *cmp = composition_table[glyph->u.cmp.id];
+         int rbearing;
+
+         rbearing = cmp->rbearing;
 
-         if (cmp->rbearing > cmp->pixel_width)
+         /* Overstruck text is displayed twice, the second time one
+            pixel to the right.  Increase the right-side bearing to
+            match.  */
+
+         if (face->overstrike)
+           rbearing++;
+
+         if (rbearing > cmp->pixel_width)
            *right = cmp->rbearing - cmp->pixel_width;
          if (cmp->lbearing < 0)
            *left = - cmp->lbearing;
@@ -30203,6 +30228,14 @@ gui_get_glyph_overhangs (struct glyph *glyph, struct 
frame *f, int *left, int *r
 
          composition_gstring_width (gstring, glyph->slice.cmp.from,
                                     glyph->slice.cmp.to + 1, &metrics);
+
+         /* Overstruck text is displayed twice, the second time one
+            pixel to the right.  Increase the right-side bearing to
+            match.  */
+
+         if (face->overstrike)
+           metrics.rbearing++;
+
          if (metrics.rbearing > metrics.width)
            *right = metrics.rbearing - metrics.width;
          if (metrics.lbearing < 0)
@@ -32311,6 +32344,14 @@ gui_produce_glyphs (struct it *it)
          if (get_char_glyph_code (it->char_to_display, font, &char2b))
            {
              pcm = get_per_char_metric (font, &char2b);
+
+             /* Overstruck text is displayed twice, the second time
+                one pixel to the right.  Increase the right-side
+                bearing to match.  */
+
+             if (pcm && face->overstrike)
+               pcm->rbearing++;
+
              if (pcm->width == 0
                  && pcm->rbearing == 0 && pcm->lbearing == 0)
                pcm = NULL;
@@ -32703,6 +32744,13 @@ gui_produce_glyphs (struct it *it)
          /* Initialize the bounding box.  */
          if (pcm)
            {
+             /* Overstruck text is displayed twice, the second time
+                one pixel to the right.  Increase the right-side
+                bearing to match.  */
+
+             if (face->overstrike)
+               pcm->rbearing++;
+
              width = cmp->glyph_len > 0 ? pcm->width : 0;
              ascent = pcm->ascent;
              descent = pcm->descent;
@@ -32764,6 +32812,13 @@ gui_produce_glyphs (struct it *it)
                cmp->offsets[i * 2] = cmp->offsets[i * 2 + 1] = 0;
              else
                {
+                 /* Overstruck text is displayed twice, the second
+                    time one pixel to the right.  Increase the
+                    right-side bearing to match.  */
+
+                 if (face->overstrike)
+                   pcm->rbearing++;
+
                  width = pcm->width;
                  ascent = pcm->ascent;
                  descent = pcm->descent;