(x_underline_at_descent_line): New variable.

(syms_of_xterm): DEFVAR_BOOL it.
(x_draw_glyph_string): Use it.
Draw underline and overline up to the end of line if the face
extends to the end of line.

3 files changed, 64 insertions, 31 deletions

diff --git a/src/macterm.c b/src/macterm.c
index 97e3b743469..04b55d9fa80 100644
--- a/src/macterm.c
+++ b/src/macterm.c
@@ -3679,14 +3679,14 @@ x_draw_glyph_string (s)
 
           if (s->face->underline_defaulted_p)
             mac_fill_rectangle (s->f, s->gc, s->x, s->y + dy,
-                                s->width, h);
+                                s->background_width, h);
           else
             {
               XGCValues xgcv;
               XGetGCValues (s->display, s->gc, GCForeground, &xgcv);
               XSetForeground (s->display, s->gc, s->face->underline_color);
               mac_fill_rectangle (s->f, s->gc, s->x, s->y + dy,
-                                  s->width, h);
+                                  s->background_width, h);
               XSetForeground (s->display, s->gc, xgcv.foreground);
             }
         }
@@ -3698,14 +3698,14 @@ x_draw_glyph_string (s)
 
           if (s->face->overline_color_defaulted_p)
             mac_fill_rectangle (s->f, s->gc, s->x, s->y + dy,
-                                s->width, h);
+                                s->background_width, h);
           else
             {
               XGCValues xgcv;
               XGetGCValues (s->display, s->gc, GCForeground, &xgcv);
               XSetForeground (s->display, s->gc, s->face->overline_color);
               mac_fill_rectangle (s->f, s->gc, s->x, s->y + dy,
-                                  s->width, h);
+                                  s->background_width, h);
               XSetForeground (s->display, s->gc, xgcv.foreground);
             }
         }
diff --git a/src/w32term.c b/src/w32term.c
index 5e33c3af7b9..93a697bbd8c 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -91,6 +91,10 @@ static Lisp_Object last_window;
    (Not yet supported, see TODO in x_draw_glyph_string.)  */
 int x_use_underline_position_properties;
 
+/* Non-zero means to draw the underline at the same place as the descent line.  */
+
+int x_underline_at_descent_line;
+
 extern unsigned int msh_mousewheel;
 
 extern void free_frame_menubar ();
@@ -2509,21 +2513,27 @@ x_draw_glyph_string (s)
           && (s->font->bdf || !s->font->tm.tmUnderlined))
         {
           unsigned long h = 1;
-          unsigned long dy = s->height - h;
+          unsigned long dy = 0;
 
-          /* TODO: Use font information for positioning and thickness
-             of underline.  See OUTLINETEXTMETRIC, and xterm.c.
-             Note: If you make this work, don't forget to change the
-             doc string of x-use-underline-position-properties below.  */
+          if (x_underline_at_descent_line)
+            dy = s->height - h;
+          else
+            {
+              /* TODO: Use font information for positioning and thickness of
+                 underline.  See OUTLINETEXTMETRIC, and xterm.c.  Note: If
+                 you make this work, don't forget to change the doc string of
+                 x-use-underline-position-properties below.  */
+              dy = s->height - h;
+            }
           if (s->face->underline_defaulted_p)
             {
               w32_fill_area (s->f, s->hdc, s->gc->foreground, s->x,
-                             s->y + dy, s->width, 1);
+                             s->y + dy, s->background_width, 1);
             }
           else
             {
               w32_fill_area (s->f, s->hdc, s->face->underline_color, s->x,
-                             s->y + dy, s->width, 1);
+                             s->y + dy, s->background_width, 1);
             }
         }
 
@@ -2535,12 +2545,12 @@ x_draw_glyph_string (s)
           if (s->face->overline_color_defaulted_p)
         {
           w32_fill_area (s->f, s->hdc, s->gc->foreground, s->x,
-                         s->y + dy, s->width, h);
+                         s->y + dy, s->background_width, h);
         }
           else
             {
               w32_fill_area (s->f, s->hdc, s->face->overline_color, s->x,
-                             s->y + dy, s->width, h);
+                             s->y + dy, s->background_width, h);
             }
         }
 
@@ -6510,6 +6520,14 @@ to 4.1, set this to nil.
 NOTE: Not supported on MS-Windows yet.  */);
   x_use_underline_position_properties = 0;
 
+  DEFVAR_BOOL ("x-underline-at-descent-line",
+               &x_underline_at_descent_line,
+     doc: /* *Non-nil means to draw the underline at the same place as the descent line.
+nil means to draw the underline according to the value of the variable
+`x-use-underline-position-properties', which is usually at the baseline
+level.  The default value is nil.  */);
+  x_underline_at_descent_line = 0;
+
   DEFVAR_LISP ("x-toolkit-scroll-bars", &Vx_toolkit_scroll_bars,
                doc: /* If not nil, Emacs uses toolkit scroll bars.  */);
   Vx_toolkit_scroll_bars = Qt;
diff --git a/src/xterm.c b/src/xterm.c
index 9cea615ca1e..c2cf2721881 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -182,6 +182,10 @@ static Lisp_Object last_window;
 
 int x_use_underline_position_properties;
 
+/* Non-zero means to draw the underline at the same place as the descent line.  */
+
+int x_underline_at_descent_line;
+
 /* This is a chain of structures for all the X displays currently in
    use.  */
 
@@ -2685,32 +2689,35 @@ x_draw_glyph_string (s)
           if (!XGetFontProperty (s->font, XA_UNDERLINE_THICKNESS, &h))
             h = 1;
 
-          /* 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 (x_use_underline_position_properties
-              && 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
+          if (x_underline_at_descent_line)
             y = s->y + s->height - h;
+          else
+            {
+              /* 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 (x_use_underline_position_properties
+                  && 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;
+            }
 
           if (s->face->underline_defaulted_p)
             XFillRectangle (s->display, s->window, s->gc,
-                            s->x, y, s->width, h);
+                            s->x, y, s->background_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, y, s->width, h);
+                              s->x, y, s->background_width, h);
               XSetForeground (s->display, s->gc, xgcv.foreground);
             }
         }
@@ -2722,14 +2729,14 @@ x_draw_glyph_string (s)
 
           if (s->face->overline_color_defaulted_p)
             XFillRectangle (s->display, s->window, s->gc, s->x, s->y + dy,
-                            s->width, h);
+                            s->background_width, h);
           else
             {
               XGCValues xgcv;
               XGetGCValues (s->display, s->gc, GCForeground, &xgcv);
               XSetForeground (s->display, s->gc, s->face->overline_color);
               XFillRectangle (s->display, s->window, s->gc, s->x, s->y + dy,
-                              s->width, h);
+                              s->background_width, h);
               XSetForeground (s->display, s->gc, xgcv.foreground);
             }
         }
@@ -10979,6 +10986,14 @@ UNDERLINE_POSITION font properties, for example 7x13 on XFree prior
 to 4.1, set this to nil.  */);
   x_use_underline_position_properties = 1;
 
+  DEFVAR_BOOL ("x-underline-at-descent-line",
+               &x_underline_at_descent_line,
+     doc: /* *Non-nil means to draw the underline at the same place as the descent line.
+nil means to draw the underline according to the value of the variable
+`x-use-underline-position-properties', which is usually at the baseline
+level.  The default value is nil.  */);
+  x_underline_at_descent_line = 0;
+
   DEFVAR_BOOL ("x-mouse-click-focus-ignore-position",
                &x_mouse_click_focus_ignore_position,
     doc: /* Non-nil means that a mouse click to focus a frame does not move point.