[pango/visible-things] Render \n as synthetic glyph as well

[Matthias Clasen <matthiasc src gnome org>]

commit 941568683024a7f37bb98b3efed5a836c7d24128
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Jul 7 23:47:11 2019 -0400

    Render \n as synthetic glyph as well
    
    Like we do for tabs now, render a missing 0x0A glyph
    as an arrow, to indicate a carriage return.
    
    This makes single-paragraph mode prettier.
    
    Also tweak the rendering of tab and space slightly.

 pango/pangocairo-render.c | 32 ++++++++++++++++++++++++++++----
 1 file changed, 28 insertions(+), 4 deletions(-)
---
diff --git a/pango/pangocairo-render.c b/pango/pangocairo-render.c
index c18556c8..eb4aee95 100644
--- a/pango/pangocairo-render.c
+++ b/pango/pangocairo-render.c
@@ -400,7 +400,7 @@ _pango_cairo_renderer_draw_unknown_glyph (PangoCairoRenderer *crenderer,
       double y = cy + hbi->box_descent - 0.5 * hbi->box_height;
 
       cairo_new_sub_path (crenderer->cr);
-      cairo_arc (crenderer->cr, x, y, hbi->line_width, 0, 2 * G_PI);
+      cairo_arc (crenderer->cr, x, y, 1.5 * hbi->line_width, 0, 2 * G_PI);
       cairo_close_path (crenderer->cr);
       cairo_fill (crenderer->cr);
       goto done;
@@ -413,15 +413,15 @@ _pango_cairo_renderer_draw_unknown_glyph (PangoCairoRenderer *crenderer,
       double x = cx + arrow_offset;
       double arrow_length = width - 2 * arrow_offset;
       double tip_length = MIN (hbi->digit_width, 0.75 * arrow_length);
-      double tip_width = 3 * hbi->line_width;
+      double tip_width = 5 * hbi->line_width;
 
       cairo_move_to (crenderer->cr, x - 0.5 * hbi->line_width, y - 0.5 * tip_width);
       cairo_line_to (crenderer->cr, x + 0.5 * hbi->line_width, y - 0.5 * tip_width);
       cairo_line_to (crenderer->cr, x + 0.5 * hbi->line_width, y - 0.5 * hbi->line_width);
       cairo_line_to (crenderer->cr, x + arrow_length - tip_length, y - 0.5 * hbi->line_width);
-      cairo_line_to (crenderer->cr, x + arrow_length - tip_length, y - 0.5 * tip_width); 
+      cairo_line_to (crenderer->cr, x + arrow_length - tip_length, y - 0.5 * tip_width);
       cairo_line_to (crenderer->cr, x + arrow_length,  y);
-      cairo_line_to (crenderer->cr, x + arrow_length - tip_length, y + 0.5 * tip_width); 
+      cairo_line_to (crenderer->cr, x + arrow_length - tip_length, y + 0.5 * tip_width);
       cairo_line_to (crenderer->cr, x + arrow_length - tip_length, y + 0.5 * hbi->line_width);
       cairo_line_to (crenderer->cr, x + 0.5 * hbi->line_width, y + 0.5 * hbi->line_width);
       cairo_line_to (crenderer->cr, x + 0.5 * hbi->line_width, y + 0.5 * tip_width);
@@ -430,6 +430,30 @@ _pango_cairo_renderer_draw_unknown_glyph (PangoCairoRenderer *crenderer,
       cairo_fill (crenderer->cr);
       goto done;
     }
+  else if (ch == '\n')
+    {
+      double width = (double)gi->geometry.width / PANGO_SCALE;
+      double arrow_offset = 0.2 * width;
+      double arrow_length = width - 2 * arrow_offset;
+      double tip_length = MIN (hbi->digit_width, 0.75 * arrow_length);
+      double arrow_height = arrow_length - 0.5 * tip_length;
+      double tip_width = 5 * hbi->line_width;
+      double x = cx + arrow_offset;
+      double y = cy - (hbi->box_height - arrow_length) / 2;
+
+      cairo_move_to (crenderer->cr, x, y);
+      cairo_line_to (crenderer->cr, x + tip_length, y - 0.5 * tip_width);
+      cairo_line_to (crenderer->cr, x + tip_length, y - 0.5 * hbi->line_width);
+      cairo_line_to (crenderer->cr, x + arrow_length - 0.5 * hbi->line_width, y - 0.5 * hbi->line_width);
+      cairo_line_to (crenderer->cr, x + arrow_length - 0.5 * hbi->line_width, y - arrow_height);
+      cairo_line_to (crenderer->cr, x + arrow_length + 0.5 * hbi->line_width, y - arrow_height);
+      cairo_line_to (crenderer->cr, x + arrow_length + 0.5 * hbi->line_width, y + 0.5 * hbi->line_width);
+      cairo_line_to (crenderer->cr, x + tip_length, y + 0.5 * hbi->line_width);
+      cairo_line_to (crenderer->cr, x + tip_length, y + 0.5 * tip_width);
+      cairo_close_path (crenderer->cr);
+      cairo_fill (crenderer->cr);
+      goto done;
+    }
   else if ((name = pango_get_ignorable_size (ch, &rows, &cols)))
     {
       /* nothing else to do */