Honor 'line-spacing' for empty lines

* src/xdisp.c (append_space_for_newline): Honor 'line-height'
property and 'line-spacing' frame parameter or variable or
property for empty lines, by doing the same processing as in
x_produce_glyph for newline characters.  (Bug#21165)

diff --git a/src/xdisp.c b/src/xdisp.c
index 5a89f4c988b373a40d3f362e524711e31c9bcaaf..03b03d06b3e49340293e136dbb9daf3678c2d9c3 100644 (file)
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -839,6 +839,9 @@ static void normal_char_ascent_descent (struct font *, int, int *, int *);
 static void append_stretch_glyph (struct it *, Lisp_Object,
                                   int, int, int);
 
+static Lisp_Object get_it_property (struct it *, Lisp_Object);
+static Lisp_Object calc_line_height_property (struct it *, Lisp_Object,
+                                             struct font *, int, bool);
 
 #endif /* HAVE_WINDOW_SYSTEM */
 
@@ -19205,12 +19208,74 @@ append_space_for_newline (struct it *it, bool default_face_p)
 #ifdef HAVE_WINDOW_SYSTEM
          /* Make sure this space glyph has the right ascent and
             descent values, or else cursor at end of line will look
-            funny.  */
+            funny, and height of empty lines will be incorrect.  */
          g = it->glyph_row->glyphs[TEXT_AREA] + n;
          struct font *font = face->font ? face->font : FRAME_FONT (it->f);
          if (n == 0 || it->glyph_row->height < font->pixel_size)
            {
+             Lisp_Object height, total_height;
+             int extra_line_spacing = it->extra_line_spacing;
+             int boff = font->baseline_offset;
+
+             if (font->vertical_centering)
+               boff = VCENTER_BASELINE_OFFSET (font, it->f) - boff;
+
+             it->object = saved_object; /* get_it_property needs this */
              normal_char_ascent_descent (font, -1, &it->ascent, &it->descent);
+             /* Must do a subset of line height processing from
+                x_produce_glyph for newline characters.  */
+             height = get_it_property (it, Qline_height);
+             if (CONSP (height)
+                 && CONSP (XCDR (height))
+                 && NILP (XCDR (XCDR (height))))
+               {
+                 total_height = XCAR (XCDR (height));
+                 height = XCAR (height);
+               }
+             else
+               total_height = Qnil;
+             height = calc_line_height_property (it, height, font, boff, true);
+
+             if (it->override_ascent >= 0)
+               {
+                 it->ascent = it->override_ascent;
+                 it->descent = it->override_descent;
+                 boff = it->override_boff;
+               }
+             if (EQ (height, Qt))
+               extra_line_spacing = 0;
+             else
+               {
+                 Lisp_Object spacing;
+
+                 it->phys_ascent = it->ascent;
+                 it->phys_descent = it->descent;
+                 if (!NILP (height)
+                     && XINT (height) > it->ascent + it->descent)
+                   it->ascent = XINT (height) - it->descent;
+
+                 if (!NILP (total_height))
+                   spacing = calc_line_height_property (it, total_height, font,
+                                                        boff, false);
+                 else
+                   {
+                     spacing = get_it_property (it, Qline_spacing);
+                     spacing = calc_line_height_property (it, spacing, font,
+                                                          boff, false);
+                   }
+                 if (INTEGERP (spacing))
+                   {
+                     extra_line_spacing = XINT (spacing);
+                     if (!NILP (total_height))
+                       extra_line_spacing -= (it->phys_ascent + it->phys_descent);
+                   }
+               }
+             if (extra_line_spacing > 0)
+               {
+                 it->descent += extra_line_spacing;
+                 if (extra_line_spacing > it->max_extra_line_spacing)
+                   it->max_extra_line_spacing = extra_line_spacing;
+               }
              it->max_ascent = it->ascent;
              it->max_descent = it->descent;
              /* Make sure compute_line_metrics recomputes the row height.  */