[vte] widget: Avoid double painting of letters

[Egmont Koblinger <egmontkob src gnome org>]

commit 1867af10ea314dc3ab4fb7f7093a8882a2fd3f77
Author: Egmont Koblinger <egmont gmail com>
Date:   Mon May 6 19:57:35 2019 +0200

    widget: Avoid double painting of letters
    
    In some cases a piece of text was overstriked with itself,
    resulting in bolder look at antialiased edges.
    
    https://gitlab.gnome.org/GNOME/vte/issues/4

 src/vte.cc | 10 ++++++++++
 1 file changed, 10 insertions(+)
---
diff --git a/src/vte.cc b/src/vte.cc
index 55cab374..0e799cef 100644
--- a/src/vte.cc
+++ b/src/vte.cc
@@ -9365,7 +9365,17 @@ Terminal::widget_draw(cairo_t *cr)
 
         /* and now paint them */
         for (n = 0; n < n_rectangles; n++) {
+                /* paint_area() paints more than asked to (entire rows). Without an individual
+                 * cropping rectangle around each invocation we might end up with text getting
+                 * overstriked with itself, thus appearing bolder. See vte#4.
+                 * TODO: refactor so that paint_area() is called at most once for each row, see vte#56. */
+                cairo_save(cr);
+                cairo_rectangle(cr, rectangles[n].x, rectangles[n].y, rectangles[n].width, 
rectangles[n].height);
+                cairo_clip(cr);
+
                 paint_area(&rectangles[n]);
+
+                cairo_restore(cr);
         }
         g_free (rectangles);