From 276b1bc07a0532adc34eb8dcf3b6a55f79fc8585 Mon Sep 17 00:00:00 2001
From: Camilla Berglund <elmindreda@elmindreda.org>
Date: Sun, 31 Jan 2016 19:17:18 +0100
Subject: [PATCH] Add check for EGL specific buffer swap issue

Fixes #675.
---
 README.md            | 2 ++
 include/GLFW/glfw3.h | 3 +++
 src/egl_context.c    | 7 +++++++
 3 files changed, 12 insertions(+)

diff --git a/README.md b/README.md
index fcf4bf34..43c1abca 100644
--- a/README.md
+++ b/README.md
@@ -96,6 +96,8 @@ used by the tests and examples and are not required to build the library.
  - [GLX] Bugfix: NetBSD does not provide `libGL.so.1`
  - [EGL] Added `_GLFW_USE_EGLPLATFORM_H` configuration macro for controlling
          whether to use an existing `EGL/eglplatform.h` header
+ - [EGL] Added and documented test for if the context is current on the calling
+         thread during buffer swap
  - [EGL] Removed dependency on external EGL headers
 
 
diff --git a/include/GLFW/glfw3.h b/include/GLFW/glfw3.h
index 5201faf6..a1f058f8 100644
--- a/include/GLFW/glfw3.h
+++ b/include/GLFW/glfw3.h
@@ -3429,6 +3429,9 @@ GLFWAPI GLFWwindow* glfwGetCurrentContext(void);
  *
  *  @param[in] window The window whose buffers to swap.
  *
+ *  @remarks __EGL:__ The context of the specified window must be current on the
+ *  calling thread.
+ *
  *  @par Thread Safety
  *  This function may be called from any thread.
  *
diff --git a/src/egl_context.c b/src/egl_context.c
index 0eb0aa41..579e17f1 100644
--- a/src/egl_context.c
+++ b/src/egl_context.c
@@ -584,6 +584,13 @@ void _glfwPlatformMakeContextCurrent(_GLFWwindow* window)
 
 void _glfwPlatformSwapBuffers(_GLFWwindow* window)
 {
+    if (window != _glfwPlatformGetCurrentContext())
+    {
+        _glfwInputError(GLFW_PLATFORM_ERROR,
+                        "EGL: The context must be current on the calling thread when swapping buffers");
+        return;
+    }
+
     eglSwapBuffers(_glfw.egl.display, window->context.egl.surface);
 }