(x_draw_glyph_string): Treat XA_UNDERLINE_POSITION as a

signed value, and use a default value computed from the font's
maximum descent.

2 files changed, 28 insertions, 12 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index e118a0041a4..cd4de4991b3 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2000-10-27  Gerd Moellmann  <gerd@gnu.org>
+
+        * xterm.c (x_draw_glyph_string): Treat XA_UNDERLINE_POSITION as a
+        signed value, and use a default value computed from the font's
+        maximum descent.
+
 2000-10-27  Miles Bader  <miles@lsi.nec.co.jp>
 
         * xterm.c (x_draw_glyph_string): Add a workaround so that fonts
diff --git a/src/xterm.c b/src/xterm.c
index 3539d8123af..2d818a1e4ff 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -4217,28 +4217,38 @@ x_draw_glyph_string (s)
       /* Draw underline.  */
       if (s->face->underline_p)
         {
-          unsigned long dy, h;
+          unsigned long tem, h;
+          int y;
 
+          /* Get the underline thickness.  Default is 1 pixel.  */
           if (!XGetFontProperty (s->font, XA_UNDERLINE_THICKNESS, &h))
             h = 1;
-          if (!XGetFontProperty (s->font, XA_UNDERLINE_POSITION, &dy)
-              /* If the font specifies a negative underline position,
-                 we'll get a huge positive number, because dy is
-                 unsigned.  This comparison is a workaround that just
-                 ignores the font's underline position in that case.  XXX */
-              || dy > s->height)
-            dy = s->height - h;
+
+          /* Get the underline position.  This is the recommended
+             vertical offset in pixels from the baseline to the top of
+             the underline.  This is a signed value according to the
+             specs, and its default is
+
+             ROUND ((maximum descent) / 2), with
+             ROUND(x) = floor (x + 0.5)  */
+          
+          if (XGetFontProperty (s->font, XA_UNDERLINE_POSITION, &tem))
+            y = s->ybase + (long) tem;
+          else if (s->face->font)
+            y = s->ybase + (s->face->font->max_bounds.descent + 1) / 2;
+          else
+            y = s->height - h;
       
           if (s->face->underline_defaulted_p)
-            XFillRectangle (s->display, s->window, s->gc, s->x, s->y + dy,
-                            s->width, h);
+            XFillRectangle (s->display, s->window, s->gc,
+                            s->x, y, s->width, h);
           else
             {
               XGCValues xgcv;
               XGetGCValues (s->display, s->gc, GCForeground, &xgcv);
               XSetForeground (s->display, s->gc, s->face->underline_color);
-              XFillRectangle (s->display, s->window, s->gc, s->x, s->y + dy,
-                              s->width, h);
+              XFillRectangle (s->display, s->window, s->gc,
+                              s->x, y, s->width, h);
               XSetForeground (s->display, s->gc, xgcv.foreground);
             }
         }