SDL: Document the range of trigger axes for virtual joysticks

From e4b85091fd0eea25a149af2dd3c2a24f99128baa Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Thu, 25 Aug 2022 10:15:45 -0700
Subject: [PATCH] Document the range of trigger axes for virtual joysticks

Fixes https://github.com/libsdl-org/SDL/issues/6130
---
 include/SDL_joystick.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/SDL_joystick.h b/include/SDL_joystick.h
index 1a7c66ee2b1..cb7be29afc9 100644
--- a/include/SDL_joystick.h
+++ b/include/SDL_joystick.h
@@ -425,6 +425,8 @@ extern DECLSPEC SDL_bool SDLCALL SDL_JoystickIsVirtual(int device_index);
  * the following: SDL_PollEvent, SDL_PumpEvents, SDL_WaitEventTimeout,
  * SDL_WaitEvent.
  *
+ * Note that when sending trigger axes, you should scale the value to the full range of Sint16. For example, a trigger at rest would have the value of `SDL_JOYSTICK_AXIS_MIN`.
+ *
  * \param joystick the virtual joystick on which to set state.
  * \param axis the specific axis on the virtual joystick to set.
  * \param value the new value for the specified axis.