Null: Add non-functional EGL support

This is done in preparation for runtime platform selection, to make sure
every platform can build with EGL enabled.

It may be possible to add support for things like the ANGLE null
platform later.

src/CMakeLists.txt

@@ -48,7 +48,8 @@ elseif (_GLFW_OSMESA)
     target_sources(glfw PRIVATE null_platform.h null_joystick.h posix_time.h
                                 posix_thread.h osmesa_context.h null_init.c
                                 null_monitor.c null_window.c null_joystick.c
-                                posix_time.c posix_thread.c osmesa_context.c)
+                                posix_time.c posix_thread.c egl_context.c
+                                osmesa_context.c)
 endif()
 
 if (_GLFW_X11 OR _GLFW_WAYLAND)

src/null_init.c

@@ -48,10 +48,11 @@ void _glfwPlatformTerminate(void)
 {
     _glfw_free(_glfw.null.clipboardString);
     _glfwTerminateOSMesa();
+    _glfwTerminateEGL();
 }
 
 const char* _glfwPlatformGetVersionString(void)
 {
-    return _GLFW_VERSION_NUMBER " null OSMesa";
+    return _GLFW_VERSION_NUMBER " null OSMesa EGL";
 }
 

src/null_window.c

@@ -121,9 +121,11 @@ int _glfwPlatformCreateWindow(_GLFWwindow* window,
             if (!_glfwCreateContextOSMesa(window, ctxconfig, fbconfig))
                 return GLFW_FALSE;
         }
-        else
+        else if (ctxconfig->source == GLFW_EGL_CONTEXT_API)
         {
-            _glfwInputError(GLFW_API_UNAVAILABLE, "Null: EGL not available");
+            if (!_glfwInitEGL())
+                return GLFW_FALSE;
+            if (!_glfwCreateContextEGL(window, ctxconfig, fbconfig))
                 return GLFW_FALSE;
         }
     }
@@ -522,6 +524,21 @@ const char* _glfwPlatformGetClipboardString(void)
     return _glfw.null.clipboardString;
 }
 
+EGLenum _glfwPlatformGetEGLPlatform(EGLint** attribs)
+{
+    return 0;
+}
+
+EGLNativeDisplayType _glfwPlatformGetEGLNativeDisplay(void)
+{
+    return 0;
+}
+
+EGLNativeWindowType _glfwPlatformGetEGLNativeWindow(_GLFWwindow* window)
+{
+    return 0;
+}
+
 const char* _glfwPlatformGetScancodeName(int scancode)
 {
     if (scancode < GLFW_KEY_SPACE || scancode > GLFW_KEY_LAST)