[gtksourceview/wip/chergert/glyph-alignment: 13/13] map: use new textview API to fix glyph alignment

[Christian Hergert <chergert src gnome org>]

commit becafce05af48452680e231d69a17c7bbdc7f33f
Author: Christian Hergert <chergert redhat com>
Date:   Sat Jun 19 12:38:48 2021 -0700

    map: use new textview API to fix glyph alignment
    
    This helps reduce the amount of grid lines we see across the font from
    pixel alignment in text rendering. Our font is a bit special, in that we
    know how it needs to be rendered to give the effect we're looking for.
    
    Depends on https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/3690

 gtksourceview/gtksourcemap.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)
---
diff --git a/gtksourceview/gtksourcemap.c b/gtksourceview/gtksourcemap.c
index 3350a0c3..6af138cd 100644
--- a/gtksourceview/gtksourcemap.c
+++ b/gtksourceview/gtksourcemap.c
@@ -1097,6 +1097,32 @@ gtk_source_map_hide (GtkWidget *widget)
        }
 }
 
+static void
+gtk_source_map_css_changed (GtkWidget         *widget,
+                            GtkCssStyleChange *change)
+{
+       g_assert (GTK_IS_WIDGET (widget));
+
+       GTK_WIDGET_CLASS (gtk_source_map_parent_class)->css_changed (widget, change);
+
+#if GTK_CHECK_VERSION(4,3,1)
+       {
+               PangoContext *rtl_context;
+               PangoContext *ltr_context;
+
+               /* Ensure rounding so that BuilderBlocks aligns properly within
+                * rounding errors between glyphs.
+                */
+
+               rtl_context = gtk_text_view_get_rtl_context (GTK_TEXT_VIEW (widget));
+               ltr_context = gtk_text_view_get_ltr_context (GTK_TEXT_VIEW (widget));
+
+               pango_context_set_round_glyph_positions (rtl_context, TRUE);
+               pango_context_set_round_glyph_positions (ltr_context, TRUE);
+       }
+#endif
+}
+
 static void
 gtk_source_map_constructed (GObject *object)
 {
@@ -1124,6 +1150,7 @@ gtk_source_map_class_init (GtkSourceMapClass *klass)
        widget_class->show = gtk_source_map_show;
        widget_class->state_flags_changed = gtk_source_map_state_flags_changed;
        widget_class->realize = gtk_source_map_realize;
+       widget_class->css_changed = gtk_source_map_css_changed;
 
        text_view_class->snapshot_layer = gtk_source_map_snapshot_layer;