From 375fcdeadb6ae1e870777505b1925e34caff5899 Mon Sep 17 00:00:00 2001
From: Doug Binks <doug@enkisoftware.com>
Date: Thu, 16 Jul 2020 15:20:25 +0100
Subject: [PATCH] Added GLFW_NO_API check to glfwCreateUserContext and error
 documentation.

---
 include/GLFW/glfw3.h |  5 +++++
 src/context.c        | 15 +++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/include/GLFW/glfw3.h b/include/GLFW/glfw3.h
index e8626932..a25f4144 100644
--- a/include/GLFW/glfw3.h
+++ b/include/GLFW/glfw3.h
@@ -5834,6 +5834,11 @@ GLFWAPI GLFWglproc glfwGetProcAddress(const char* procname);
  *  Contexts share resources with the window context and with any other
  *  user context created for that window.
  *
+ *  @errors Possible errors include @ref GLFW_NOT_INITIALIZED,
+ *  @ref GLFW_INVALID_VALUE the window parameter is `NULL`,
+ *  @ref GLFW_NO_WINDOW_CONTEXT if the window has no OpenGL or
+ *  OpenGL US context, and @ref GLFW_PLATFORM_ERROR.
+ *
  *  @param[in] window The Window for which the user context is to be
  *  created.
  *  @return The handle of the user context created, or `NULL` if an
diff --git a/src/context.c b/src/context.c
index d12ba991..a3057e92 100644
--- a/src/context.c
+++ b/src/context.c
@@ -767,6 +767,21 @@ GLFWAPI GLFWusercontext* glfwCreateUserContext(GLFWwindow* handle)
 
     _GLFW_REQUIRE_INIT_OR_RETURN(NULL);
 
+    if (!window)
+    {
+        _glfwInputError(GLFW_INVALID_VALUE,
+                        "Cannot create a user context without a valid window handle");
+        return NULL;
+    }
+
+    if (window->context.client == GLFW_NO_API)
+    {
+        _glfwInputError(GLFW_NO_WINDOW_CONTEXT,
+                        "Cannot create a user context for a window that has no OpenGL or OpenGL ES context");
+        return NULL;
+    }
+
+
     context = _glfwPlatformCreateUserContext(window);
 
     return (GLFWusercontext*)context;