Outsource chart pixbuf creation to ag_chart_get_pixbuf()

src/ag-chart.h

@@ -22,6 +22,7 @@
 #include <glib-object.h>
 #include <gtk/gtk.h>
 #include <swe-glib.h>
+#include <gdk-pixbuf/gdk-pixbuf.h>
 
 #include "ag-db.h"
 #include "ag-display-theme.h"
@@ -140,6 +141,12 @@ const gchar *ag_chart_get_note(AgChart *chart);
 
 AgDbChartSave *ag_chart_get_db_save(AgChart *chart, gint db_id);
 
+GdkPixbuf *ag_chart_get_pixbuf(AgChart        *chart,
+                               guint          image_size,
+                               guint          icon_size,
+                               AgDisplayTheme *theme,
+                               GError         **err);
+
 #define AG_CHART_ERROR (ag_chart_error_quark())
 GQuark ag_chart_error_quark(void);