[gtkmm] Gdk::Texture: Add create_for_gl() and release_gl()

[Kjell Ahlstedt <kjellahl src gnome org>]

commit cf84c3a55153fb51853306a18174c5b2ad5d4de1
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Wed Feb 7 19:01:31 2018 +0100

    Gdk::Texture: Add create_for_gl() and release_gl()

 gdk/src/texture.ccg |   19 +++++++++++++++++++
 gdk/src/texture.hg  |   12 ++++++++++++
 2 files changed, 31 insertions(+), 0 deletions(-)
---
diff --git a/gdk/src/texture.ccg b/gdk/src/texture.ccg
index 96109a8..e5ba9de 100644
--- a/gdk/src/texture.ccg
+++ b/gdk/src/texture.ccg
@@ -15,4 +15,23 @@
  */
 
 #include <giomm/file.h>
+#include <gdkmm/glcontext.h>
 #include <gdkmm/pixbuf.h>
+
+namespace
+{
+void Texture_GL_destroy_callback(void* data)
+{
+  auto the_slot = static_cast<Gdk::Texture::SlotGLReleased*>(data);
+  try
+  {
+    (*the_slot)();
+  }
+  catch (...)
+  {
+    Glib::exception_handlers_invoke();
+  }
+  delete the_slot;
+}
+
+} // anonymous namespace
diff --git a/gdk/src/texture.hg b/gdk/src/texture.hg
index 8451162..117d290 100644
--- a/gdk/src/texture.hg
+++ b/gdk/src/texture.hg
@@ -26,6 +26,7 @@ class File;
 
 namespace Gdk
 {
+class GLContext;
 class Pixbuf;
 
 /** Pixel data.
@@ -59,6 +60,17 @@ public:
   _WRAP_METHOD(static Glib::RefPtr<Texture> create_from_file(
     const Glib::RefPtr<Gio::File>& file), gdk_texture_new_from_file, errthrow)
 
+  /** For instance,
+   * void on_gl_resources_released();
+   */
+  using SlotGLReleased = sigc::slot<void()>;
+
+  _WRAP_METHOD(static Glib::RefPtr<Texture> create_for_gl(
+    const Glib::RefPtr<GLContext>& context,
+    guint id, int width, int height, const SlotGLReleased& slot{destroy} = {}),
+    gdk_texture_new_for_gl, slot_name slot, slot_callback Texture_GL_destroy_callback)
+  _WRAP_METHOD(void release_gl(), gdk_texture_release_gl)
+
   _WRAP_METHOD(int get_width() const, gdk_texture_get_width)
   _WRAP_METHOD(int get_height() const, gdk_texture_get_height)
   _WRAP_METHOD(void download(guchar* data, gsize stride) const, gdk_texture_download)