From c1101191964768cc48c1be38991d40ad4a2b8b0d Mon Sep 17 00:00:00 2001
From: Bill Currie <bill@taniwha.org>
Date: Sat, 25 Nov 2023 21:05:37 +0900
Subject: [PATCH] [win] Track mouse leaving the window

This fixes the incorrect mouse deltas experienced when looping the mouse
cursor through and around the window.
---
 libs/video/targets/context_win.c |  3 ---
 libs/video/targets/in_win.c      | 29 +++++++++++++++++++++++++----
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/libs/video/targets/context_win.c b/libs/video/targets/context_win.c
index 101d035b5..71a8dde42 100644
--- a/libs/video/targets/context_win.c
+++ b/libs/video/targets/context_win.c
@@ -321,9 +321,6 @@ Win_RemoveEvent (UINT event)
 static LONG WINAPI
 Win_EventHandler (HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
 {
-	if (uMsg == uiWheelMessage) {
-		uMsg = WM_MOUSEWHEEL;
-	}
 	if (uMsg < WM_USER && event_handlers[uMsg]) {
 		return event_handlers[uMsg] (hWnd, uMsg, wParam, lParam);
 	}
diff --git a/libs/video/targets/in_win.c b/libs/video/targets/in_win.c
index ba983ec87..bb0850266 100644
--- a/libs/video/targets/in_win.c
+++ b/libs/video/targets/in_win.c
@@ -100,6 +100,7 @@ static int in_mouse_avail;
 static int win_driver_handle = -1;
 static in_buttoninfo_t win_key_buttons[512];
 static int win_key_scancode;
+static bool win_mouse_enter = true;
 static in_axisinfo_t win_mouse_axes[2];
 static in_buttoninfo_t win_mouse_buttons[WIN_MOUSE_BUTTONS];
 static const char *win_mouse_axis_names[] = {"M_X", "M_Y"};
@@ -525,8 +526,6 @@ win_add_device (win_device_t *dev)
 static void
 in_win_init (void *data)
 {
-	uiWheelMessage = RegisterWindowMessage ("MSWHEEL_ROLLMSG");
-
 	win_add_device (&win_keyboard_device);
 	win_add_device (&win_mouse_device);
 
@@ -943,6 +942,13 @@ in_win_send_focus_event (int gain)
 	IE_Send_Event (&event);
 }
 
+static LONG
+event_leave (HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
+{
+	win_mouse_enter = true;
+	return 0;
+}
+
 static LONG
 event_focusin (HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
 {
@@ -1030,8 +1036,21 @@ event_mouse (HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
 	// this is complicated because Win32 seems to pack multiple mouse
 	// events into one update sometimes, so we always check all states and
 	// look for events
-	int         x = (int) LOWORD (lParam);
-	int         y = (int) HIWORD (lParam);
+	int         x = (short) LOWORD (lParam);
+	int         y = (short) HIWORD (lParam);
+
+	if (win_mouse_enter) {
+		win_mouse_enter = false;
+		TRACKMOUSEEVENT track = {
+			.cbSize = sizeof (track),
+			.dwFlags = TME_LEAVE,
+			.hwndTrack = win_mainwindow,
+		};
+		TrackMouseEvent (&track);
+
+		win_mouse.x = x;
+		win_mouse.y = y;
+	}
 
 	win_mouse_axes[0].value = x - win_mouse.x;
 	win_mouse_axes[1].value = y - win_mouse.y;
@@ -1085,6 +1104,8 @@ event_activate (HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
 void
 IN_Win_Preinit (void)
 {
+	Win_AddEvent (WM_MOUSELEAVE, event_leave);
+
 	Win_AddEvent (WM_SETFOCUS, event_focusin);
 	Win_AddEvent (WM_SETFOCUS, event_focusout);