From 3d8a3e581c5c2c0359df309b7e2ede57447e74fd Mon Sep 17 00:00:00 2001
From: Lach <lachsrb2@gmail.com>
Date: Sat, 18 May 2024 23:55:19 +1000
Subject: [PATCH] Remember the last used window display

---
 src/cvars.cpp       |  2 ++
 src/screen.h        |  1 +
 src/sdl/i_video.cpp | 34 ++++++++++++++++++++++++++++++----
 3 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/src/cvars.cpp b/src/cvars.cpp
index 83c360eb2..73dbde390 100644
--- a/src/cvars.cpp
+++ b/src/cvars.cpp
@@ -446,6 +446,8 @@ consvar_t cv_scr_scale = Player("scr_scale", "1.0").floating_point();
 consvar_t cv_scr_x = Player("scr_x", "0.0").floating_point();
 consvar_t cv_scr_y = Player("scr_y", "0.0").floating_point();
 
+consvar_t cv_display = Player("display", "0").values(CV_Unsigned).save();
+
 consvar_t cv_seenames = Player("seenames", "On").on_off();
 consvar_t cv_shadow = Player("shadow", "On").on_off();
 consvar_t cv_showfocuslost = Player("showfocuslost", "Yes").yes_no();
diff --git a/src/screen.h b/src/screen.h
index 341edba9a..39828a03a 100644
--- a/src/screen.h
+++ b/src/screen.h
@@ -138,6 +138,7 @@ extern UINT8 *scr_borderpatch; // patch used to fill the view borders
 extern consvar_t cv_scr_width, cv_scr_height, cv_scr_depth, cv_renderview, cv_renderer, cv_renderhitbox, cv_fullscreen;
 extern consvar_t cv_scr_effect;
 extern consvar_t cv_parallelsoftware;
+extern consvar_t cv_display;
 
 // wait for page flipping to end or not
 extern consvar_t cv_vidwait;
diff --git a/src/sdl/i_video.cpp b/src/sdl/i_video.cpp
index 065ee3958..70d70e3c7 100644
--- a/src/sdl/i_video.cpp
+++ b/src/sdl/i_video.cpp
@@ -171,6 +171,23 @@ static SDL_bool Impl_CreateWindow(SDL_bool fullscreen);
 //static void Impl_SetWindowName(const char *title);
 static void Impl_SetWindowIcon(void);
 
+static void ValidateDisplay(void)
+{
+	// Validate display index, otherwise use main display
+	if (cv_display.value >= SDL_GetNumVideoDisplays())
+	{
+		CV_SetValue(&cv_display, 0);
+	}
+}
+
+static void CenterWindow(void)
+{
+	SDL_SetWindowPosition(window,
+		SDL_WINDOWPOS_CENTERED_DISPLAY(cv_display.value),
+		SDL_WINDOWPOS_CENTERED_DISPLAY(cv_display.value)
+	);
+}
+
 static void SDLSetMode(int width, int height, SDL_bool fullscreen, SDL_bool reposition)
 {
 	static SDL_bool wasfullscreen = SDL_FALSE;
@@ -182,6 +199,14 @@ static void SDLSetMode(int width, int height, SDL_bool fullscreen, SDL_bool repo
 	{
 		if (fullscreen)
 		{
+			if (reposition)
+			{
+				ValidateDisplay();
+				if (SDL_GetWindowDisplayIndex(window) != cv_display.value)
+				{
+					CenterWindow();
+				}
+			}
 			wasfullscreen = SDL_TRUE;
 			SDL_SetWindowFullscreen(window, SDL_WINDOW_FULLSCREEN_DESKTOP);
 		}
@@ -196,10 +221,8 @@ static void SDLSetMode(int width, int height, SDL_bool fullscreen, SDL_bool repo
 			SDL_SetWindowSize(window, width, height);
 			if (reposition)
 			{
-				SDL_SetWindowPosition(window,
-					SDL_WINDOWPOS_CENTERED_DISPLAY(SDL_GetWindowDisplayIndex(window)),
-					SDL_WINDOWPOS_CENTERED_DISPLAY(SDL_GetWindowDisplayIndex(window))
-				);
+				ValidateDisplay();
+				CenterWindow();
 			}
 		}
 	}
@@ -504,6 +527,9 @@ static void Impl_HandleWindowEvent(SDL_WindowEvent evt)
 			vid.realwidth = evt.data1;
 			vid.realheight = evt.data2;
 			break;
+		case SDL_WINDOWEVENT_DISPLAY_CHANGED:
+			CV_SetValue(&cv_display, evt.data1);
+			break;
 	}
 
 	if (FOCUSUNION == oldfocus) // No state change