From 8f80dbab7753ea54ff5013f35ed861dd8fc97969 Mon Sep 17 00:00:00 2001
From: Nolan Nicholson <NolanNicholson@users.noreply.github.com>
Date: Mon, 9 May 2022 00:00:28 -0700
Subject: [PATCH] CRT lightguns: 50 ms offscreen grace period (#599)

When a CRT lightgun starts reporting out-of-screen coordinates,
the last good on-screen coordinates are retained and passed through
for 50 ms. This improves GunCon 2 performance on NES, and generally
makes CRT-based guns a bit more reliable in games with a lot of dark
areas.
---
 input.cpp | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 57 insertions(+), 1 deletion(-)

diff --git a/input.cpp b/input.cpp
index ba8feda..6a6d096 100644
--- a/input.cpp
+++ b/input.cpp
@@ -1586,6 +1586,8 @@ static uint32_t autofire[NUMPLAYERS] = {};
 static uint32_t autofirecodes[NUMPLAYERS][BTN_NUM] = {};
 static int af_delay[NUMPLAYERS] = {};
 
+static uint32_t crtgun_timeout[NUMDEV] = {};
+
 static unsigned char mouse_btn = 0; //emulated mouse
 static unsigned char mice_btn = 0;
 static int mouse_req = 0;
@@ -4865,7 +4867,7 @@ int input_test(int getchar)
 									}
 								}
 
-								if (ev.type == EV_ABS && (input[i].quirk == QUIRK_LIGHTGUN_CRT || input[i].quirk == QUIRK_LIGHTGUN))
+								if (ev.type == EV_ABS && input[i].quirk == QUIRK_LIGHTGUN)
 								{
 									menu_lightgun_cb(i, ev.type, ev.code, ev.value);
 
@@ -4881,6 +4883,60 @@ int input_test(int getchar)
 									}
 								}
 
+								if (ev.type == EV_ABS && input[i].quirk == QUIRK_LIGHTGUN_CRT)
+								{
+									menu_lightgun_cb(i, ev.type, ev.code, ev.value);
+
+									if (ev.code == ABS_X)
+									{
+										absinfo.minimum = input[i].guncal[2];
+										absinfo.maximum = input[i].guncal[3];
+
+										// When the gun loses tracking, give it a short grace period
+										// before passing through the off-screen coordinates.
+										// The GunCon 1 and 2 both report out-of-screen x values
+										// more reliably than Y values, so X is used here.
+										if (ev.value < absinfo.minimum || ev.value > absinfo.maximum)
+										{
+											// Grace period of 50 ms. Longer times here make guns a bit
+											// more reliable on dark screens, but introduce lag to any mechanics
+											// where you want to shoot offscreen (e.g., to reload.)
+											if (!crtgun_timeout[i]) crtgun_timeout[i] = GetTimer(50);
+										}
+										else
+										{
+											crtgun_timeout[i] = 0;
+											input[i].lastx = ev.value;
+										}
+										// For the window between losing the gun signal and the timer
+										// running out, report the last on-screen coordinate
+										if (crtgun_timeout[i] && !CheckTimer(crtgun_timeout[i]))
+										{
+											ev.value = input[i].lastx;
+										}
+									}
+									else if (ev.code == ABS_Y)
+									{
+										absinfo.minimum = input[i].guncal[0];
+										absinfo.maximum = input[i].guncal[1];
+
+										// Handle gun going off-screen
+										if (crtgun_timeout[i])
+										{
+											// For the window between losing the gun signal and the timer
+											// running out, report the last on-screen coordinate
+											if (!CheckTimer(crtgun_timeout[i]))
+											{
+												ev.value = input[i].lasty;
+											}
+										}
+										else
+										{
+											input[i].lasty = ev.value;
+										}
+									}
+								}
+
 								if (ev.type == EV_KEY && user_io_osd_is_visible())
 								{
 									if (input[i].quirk == QUIRK_WIIMOTE || input[i].quirk == QUIRK_LIGHTGUN_CRT || input[i].quirk == QUIRK_LIGHTGUN)