[gtk/pango-glyph-positions: 4389/4390] widget: Use subpixel positioning

[Matthias Clasen <matthiasc src gnome org>]

commit da59c77ae271f564762abf18daa551dfdc31fee1
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Jan 28 18:17:22 2021 -0500

    widget: Use subpixel positioning
    
    Before turning off pangos rounding of glyph positions,
    we must check if the cairo we are using is new enough
    to have working subpixel positioning (the relevant
    cairo commit is 52a7c79fd4ff96bb5fac175f0199819b0f8c18fc).

 gtk/gtkwidget.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index 3168091367..cddb261e47 100644
--- a/gtk/gtkwidget.c
+++ b/gtk/gtkwidget.c
@@ -6305,9 +6305,11 @@ update_pango_context (GtkWidget    *widget,
 
   font_desc = gtk_css_style_get_pango_font (style);
   pango_context_set_font_description (context, font_desc);
-
   pango_font_description_free (font_desc);
 
+  if (cairo_version () >= CAIRO_VERSION_ENCODE (1, 17, 4))
+    pango_context_set_round_glyph_positions (context, FALSE);
+
   pango_context_set_base_dir (context,
                               _gtk_widget_get_direction (widget) == GTK_TEXT_DIR_LTR ?
                               PANGO_DIRECTION_LTR : PANGO_DIRECTION_RTL);