From 8ae641952f4e17c62af26697d6d808711d47de0d Mon Sep 17 00:00:00 2001
From: Alberto Griggio <agriggio@users.noreply.github.com>
Date: Fri, 5 May 2017 16:43:08 +0200
Subject: [PATCH] properly notify Cairo when drawing a gradient to a
 ThresholdAdjuster

Candidate fix for #3769
---
 rtgui/coloredbar.cc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/rtgui/coloredbar.cc b/rtgui/coloredbar.cc
index 9ec966d30..7d623949e 100644
--- a/rtgui/coloredbar.cc
+++ b/rtgui/coloredbar.cc
@@ -131,6 +131,8 @@ void ColoredBar::updateBackBuffer(Gtk::DrawingArea &drawingArea)
         } else {
             // ask the ColorProvider to provide colors :) for each pixels
             if (colorProvider) {
+                surface->flush();
+                
                 unsigned char *surfaceData = surface->get_data();
 
                 cr->set_antialias(Cairo::ANTIALIAS_NONE);
@@ -202,6 +204,8 @@ void ColoredBar::updateBackBuffer(Gtk::DrawingArea &drawingArea)
 
                     break;
                 }
+
+                surface->mark_dirty();
             }
         }