(get_phys_cursor_geometry): New function to calculate

phys cursor position and size for hollow cursor.  Position is
aligned with get_glyph_string_clip_rect and ensures that a hollow
cursor is shown, even when the actual glyph is not visible.

src/xdisp.c

@@ -1876,6 +1876,64 @@ get_glyph_string_clip_rect (s, nr)
 #endif
 }
+
+/* EXPORT:
+   Return the position and height of the phys cursor in window W.
+   Set w->phys_cursor_width to width of phys cursor.
+*/
+
+int
+get_phys_cursor_geometry (w, row, glyph, heightp)
+     struct window *w;
+     struct glyph_row *row;
+     struct glyph *glyph;
+     int *heightp;
+{
+  struct frame *f = XFRAME (WINDOW_FRAME (w));
+  int x, y, wd, h, h0, y0;
+
+  /* Compute the width of the rectangle to draw.  If on a stretch
+     glyph, and `x-stretch-block-cursor' is nil, don't draw a
+     rectangle as wide as the glyph, but use a canonical character
+     width instead.  */
+  wd = glyph->pixel_width - 1;
+#ifdef HAVE_NTGUI
+  wd++; /* Why? */
+#endif
+  if (glyph->type == STRETCH_GLYPH
+      && !x_stretch_cursor_p)
+    wd = min (FRAME_COLUMN_WIDTH (f), wd);
+  w->phys_cursor_width = wd;
+
+  y = w->phys_cursor.y + row->ascent - glyph->ascent;
+
+  /* If y is below window bottom, ensure that we still see a cursor.  */
+  h0 = min (FRAME_LINE_HEIGHT (f), row->visible_height);
+
+  h = max (h0, glyph->ascent + glyph->descent);
+  h0 = min (h0, glyph->ascent + glyph->descent);
+
+  y0 = WINDOW_HEADER_LINE_HEIGHT (w);
+  if (y < y0)
+    {
+      h = max (h - (y0 - y) + 1, h0);
+      y = y0 - 1;
+    }
+  else
+    {
+      y0 = window_text_bottom_y (w) - h0;
+      if (y > y0)
+	{
+	  h += y - y0;
+	  y = y0;
+	}
+    }
+
+  *heightp = h - 1;
+  return WINDOW_TO_FRAME_PIXEL_Y (w, y);
+}
+
+
 #endif /* HAVE_WINDOW_SYSTEM */