[gtk/gtk-3-24] treeview: respect expander-size style property

[Matthias Clasen <matthiasc src gnome org>]

commit d6a29e1b8cb815a2dfc00cd17681ef13e0487a27
Author: Christian Hergert <chergert redhat com>
Date:   Fri May 6 16:12:29 2016 +0300

    treeview: respect expander-size style property
    
    Without enforcement to the expander-size, we can end up rendering icons
    rather fuzzy. This uses the expander-size style property to determine
    the square for the icon, centered on what was the calculated space for
    the expander.

 gtk/gtktreeview.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
---
diff --git a/gtk/gtktreeview.c b/gtk/gtktreeview.c
index 758e3e2168..44ae4fad91 100644
--- a/gtk/gtktreeview.c
+++ b/gtk/gtktreeview.c
@@ -10296,11 +10296,13 @@ gtk_tree_view_draw_arrow (GtkTreeView *tree_view,
   gint x2;
   gint vertical_separator;
   GtkCellRendererState flags = 0;
+  gint expander_size;
 
   widget = GTK_WIDGET (tree_view);
   context = gtk_widget_get_style_context (widget);
 
   gtk_widget_style_get (widget,
+                        "expander-size", &expander_size,
                         "vertical-separator", &vertical_separator,
                         NULL);
 
@@ -10335,6 +10337,21 @@ gtk_tree_view_draw_arrow (GtkTreeView *tree_view,
   gtk_style_context_set_state (context, state);
   gtk_style_context_add_class (context, GTK_STYLE_CLASS_EXPANDER);
 
+  if (expander_size > 0)
+    {
+      if (expander_size < area.width && area.width % expander_size != 0)
+        {
+          area.x += (area.width % expander_size) / 2;
+          area.width = expander_size;
+        }
+
+      if (expander_size < area.height && area.height % expander_size != 0)
+        {
+          area.y += (area.height % expander_size) / 2;
+          area.height = expander_size;
+        }
+    }
+
   gtk_render_expander (context, cr,
                        area.x, area.y,
                        area.width, area.height);