You've changed some of the pre-existing defines for the DPAD, which could cause issues (for example if someone serializes out their input assignment and updates GLFW). I'd recommend moving the new defines to after the end of the existing ones.

Extending the number of buttons effectively changes the API (see #2423 for a similar discussion) and so may need a new input mode with glfwSetInputMode, but I'll have to check with @elmindreda. This would mean that the defines would be something like:

#define GLFW_GAMEPAD_BUTTON_DPAD_UP         11
#define GLFW_GAMEPAD_BUTTON_DPAD_RIGHT      12
#define GLFW_GAMEPAD_BUTTON_DPAD_DOWN       13
#define GLFW_GAMEPAD_BUTTON_DPAD_LEFT       14
#define GLFW_GAMEPAD_BUTTON_LAST            GLFW_GAMEPAD_BUTTON_DPAD_LEFT
#define GLFW_GAMEPAD_BUTTON_MISC1           15
#define GLFW_GAMEPAD_BUTTON_TOUCHPAD        16
#define GLFW_GAMEPAD_BUTTON_LAST_EXT1       GLFW_GAMEPAD_BUTTON_TOUCHPAD        

I get your point. The reason why I added the misc1 and touchpad before dpad is exactly, because I saw that some of the code parts used the assumption GLFW_GAMEPAD_BUTTON_LAST - 4 for dpad hat impl and didn't want to mess with it. I'm not familiar with glfwSetInputMode I'll check it out.

@elmindreda any update on this?