From ec075165809c8830fe2672a7af1cb4e8a64820e9 Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Sat, 14 Jan 2017 01:43:11 +0000
Subject: [PATCH] GTK: work around a gtkmm<3.22 bug.

---
 README.md                |  5 ++---
 src/platform/gtkmain.cpp | 11 +++++++++++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index ee43aca4..d421eb4c 100644
--- a/README.md
+++ b/README.md
@@ -26,9 +26,8 @@ Building on Linux
 ### Building for Linux
 
 You will need CMake, zlib, libpng, cairo, freetype. To build the GUI, you will need
-fontconfig, gtkmm 3.0, pangomm 1.4, OpenGL and OpenGL GLU, and optionally,
-the Space Navigator client library
-.
+fontconfig, gtkmm 3.0 (version 3.16 or later), pangomm 1.4, OpenGL and OpenGL GLU, and
+optionally, the Space Navigator client library.
 On a Debian derivative (e.g. Ubuntu) these can be installed with:
 
     apt-get install cmake zlib1-dev libpng-dev libcairo2-dev libfreetype6-dev
diff --git a/src/platform/gtkmain.cpp b/src/platform/gtkmain.cpp
index faa2ac13..2ba3c8f5 100644
--- a/src/platform/gtkmain.cpp
+++ b/src/platform/gtkmain.cpp
@@ -341,6 +341,12 @@ public:
     }
 
 protected:
+    // Work around a bug fixed in GTKMM 3.22:
+    // https://mail.gnome.org/archives/gtkmm-list/2016-April/msg00020.html
+    Glib::RefPtr<Gdk::GLContext> on_create_context() override {
+        return get_window()->create_gl_context();
+    }
+
     void on_resize(int width, int height) override {
         _w = width;
         _h = height;
@@ -1119,6 +1125,11 @@ public:
     }
 
 protected:
+    // See GraphicsWidget::on_create_context.
+    Glib::RefPtr<Gdk::GLContext> on_create_context() override {
+        return get_window()->create_gl_context();
+    }
+
     bool on_render(const Glib::RefPtr<Gdk::GLContext> &context) override {
         SS.TW.Paint();
         return true;