From 14ef59d8e791fc8a0d52978873555dc36d2d5ee0 Mon Sep 17 00:00:00 2001
From: Holger Schemel <info@artsoft.org>
Date: Wed, 7 Sep 2022 17:07:33 +0200
Subject: [PATCH] added command line option to select display to open program
 window

---
 src/libgame/misc.c   | 19 +++++++++++++++++++
 src/libgame/sdl.c    |  8 +++++---
 src/libgame/system.h |  2 ++
 src/main.c           |  1 +
 4 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/src/libgame/misc.c b/src/libgame/misc.c
index 7c3e04fc..f0858f4a 100644
--- a/src/libgame/misc.c
+++ b/src/libgame/misc.c
@@ -1350,6 +1350,8 @@ void GetOptions(int argc, char *argv[],
   options.identifier = NULL;
   options.level_nr = NULL;
 
+  options.display_nr = 0;
+
   options.mytapes = FALSE;
   options.serveronly = FALSE;
   options.network = FALSE;
@@ -1549,6 +1551,23 @@ void GetOptions(int argc, char *argv[],
       if (option_arg == next_option)
 	options_left++;
     }
+    else if (strncmp(option, "-display", option_len) == 0)
+    {
+      if (option_arg == NULL)
+	FailWithHelp("option '%s' requires an argument", option_str);
+
+      if (option_arg == next_option)
+	options_left++;
+
+      int display_nr = atoi(option_arg);
+
+      options.display_nr =
+	MAX(0, MIN(display_nr, SDL_GetNumVideoDisplays() - 1));
+
+      if (display_nr != options.display_nr)
+	Warn("invalid display %d -- using display %d",
+	     display_nr, options.display_nr);
+    }
 #if defined(PLATFORM_MAC)
     else if (strPrefix(option, "-psn"))
     {
diff --git a/src/libgame/sdl.c b/src/libgame/sdl.c
index f586bd8b..fe859452 100644
--- a/src/libgame/sdl.c
+++ b/src/libgame/sdl.c
@@ -553,6 +553,7 @@ static boolean SDLCreateScreen(boolean fullscreen)
   int screen_height = video.screen_height;
   int surface_flags = (fullscreen ? surface_flags_fullscreen :
 		       surface_flags_window);
+  int display_nr = options.display_nr;
 
   // default window size is unscaled
   video.window_width  = screen_width;
@@ -595,8 +596,8 @@ static boolean SDLCreateScreen(boolean fullscreen)
 
   if (sdl_window == NULL)
     sdl_window = SDL_CreateWindow(program.window_title,
-				  SDL_WINDOWPOS_CENTERED,
-				  SDL_WINDOWPOS_CENTERED,
+				  SDL_WINDOWPOS_CENTERED_DISPLAY(display_nr),
+				  SDL_WINDOWPOS_CENTERED_DISPLAY(display_nr),
 				  video.window_width,
 				  video.window_height,
 				  surface_flags);
@@ -796,7 +797,8 @@ void SDLSetWindowFullscreen(boolean fullscreen)
   {
     SDLSetWindowScaling(setup.window_scaling_percent);
     SDL_SetWindowPosition(sdl_window,
-			  SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED);
+			  SDL_WINDOWPOS_CENTERED_DISPLAY(options.display_nr),
+			  SDL_WINDOWPOS_CENTERED_DISPLAY(options.display_nr));
 
     video.fullscreen_initial = FALSE;
   }
diff --git a/src/libgame/system.h b/src/libgame/system.h
index cf2b0ca6..301e9fac 100644
--- a/src/libgame/system.h
+++ b/src/libgame/system.h
@@ -1098,6 +1098,8 @@ struct OptionInfo
   char *identifier;
   char *level_nr;
 
+  int display_nr;
+
   boolean mytapes;
   boolean serveronly;
   boolean network;
diff --git a/src/main.c b/src/main.c
index b72a521c..e03681c7 100644
--- a/src/main.c
+++ b/src/main.c
@@ -7714,6 +7714,7 @@ static void print_usage(void)
 	"  -g, --graphics DIRECTORY         alternative graphics DIRECTORY\n"
 	"  -s, --sounds DIRECTORY           alternative sounds DIRECTORY\n"
 	"  -m, --music DIRECTORY            alternative music DIRECTORY\n"
+	"      --display NR                 open program window on display NR\n"
 	"      --mytapes                    use private tapes for tape tests\n"
 	"  -n, --network                    network multiplayer game\n"
 	"      --serveronly                 only start network server\n"
-- 
2.34.1