From a32dc3daa0ce4f3f16674021198f194386212543 Mon Sep 17 00:00:00 2001
From: Eidolon <furyhunter600@gmail.com>
Date: Sun, 26 Feb 2023 17:57:44 -0600
Subject: [PATCH] Fix software vsync

This pre-SDL 2.0.18 hack from the interp branch is no longer needed when
building with a new enough SDL version. This makes vid_wait toggleable
at all times if SDL is at least 2.0.18.
---
 src/sdl/i_video.c | 37 ++++++++++++++++++++++++++++++-------
 1 file changed, 30 insertions(+), 7 deletions(-)

diff --git a/src/sdl/i_video.c b/src/sdl/i_video.c
index 6e971a5d8..47d41ede5 100644
--- a/src/sdl/i_video.c
+++ b/src/sdl/i_video.c
@@ -102,8 +102,10 @@ rendermode_t chosenrendermode = render_none; // set by command line arguments
 
 boolean highcolor = false;
 
+static void VidWaitChanged(void);
+
 // synchronize page flipping with screen refresh
-consvar_t cv_vidwait = CVAR_INIT ("vid_wait", "On", CV_SAVE, CV_OnOff, NULL);
+consvar_t cv_vidwait = CVAR_INIT ("vid_wait", "On", CV_SAVE | CV_CALL, CV_OnOff, VidWaitChanged);
 static consvar_t cv_stretch = CVAR_INIT ("stretch", "Off", CV_SAVE|CV_NOSHOWHELP, CV_OnOff, NULL);
 static consvar_t cv_alwaysgrabmouse = CVAR_INIT ("alwaysgrabmouse", "Off", CV_SAVE, CV_OnOff, NULL);
 
@@ -274,6 +276,22 @@ static void SDLSetMode(INT32 width, INT32 height, SDL_bool fullscreen, SDL_bool
 	}
 }
 
+static void VidWaitChanged(void)
+{
+	if (renderer && rendermode == render_soft)
+	{
+#if SDL_VERSION_ATLEAST(2, 0, 18)
+		SDL_RenderSetVSync(renderer, cv_vidwait.value ? 1 : 0);
+#endif
+	}
+#ifdef HWRENDER
+	else if (rendermode == render_opengl && sdlglcontext != NULL && SDL_GL_GetCurrentContext() == sdlglcontext)
+	{
+		SDL_GL_SetSwapInterval(cv_vidwait.value ? 1 : 0);
+	}
+#endif
+}
+
 static INT32 Impl_SDL_Scancode_To_Keycode(SDL_Scancode code)
 {
 	if (code >= SDL_SCANCODE_A && code <= SDL_SCANCODE_Z)
@@ -1476,15 +1494,19 @@ static SDL_bool Impl_CreateContext(void)
 		int flags = 0; // Use this to set SDL_RENDERER_* flags now
 		if (usesdl2soft)
 			flags |= SDL_RENDERER_SOFTWARE;
-#if 0
-		// This shit is BROKEN.
-		// - The version of SDL we're using cannot toggle VSync at runtime. We'll need a new SDL version implemented to have this work properly.
-		// - cv_vidwait is initialized before config is loaded, so it's forced to default value at runtime, and forced off when switching. The config loading code would need restructured.
-		// - With both this & frame interpolation on, I_FinishUpdate takes x10 longer. At this point, it is simpler to use a standard FPS cap.
-		// So you can probably guess why I'm kinda over this, I'm just disabling it.
 		else if (cv_vidwait.value)
+		{
+#if SDL_VERSION_ATLEAST(2, 0, 18)
+			// If SDL is new enough, we can turn off vsync later.
 			flags |= SDL_RENDERER_PRESENTVSYNC;
+#else
+			// However, if it isn't, we should just silently turn vid_wait off
+			// This is because the renderer will be created before the config
+			// is read and vid_wait is set from the user's preferences, and thus
+			// vid_wait will have no effect.
+			CV_StealthSetValue(cv_vidwait, 0);
 #endif
+		}
 
 		if (!renderer)
 			renderer = SDL_CreateRenderer(window, -1, flags);
@@ -1571,6 +1593,7 @@ boolean VID_CheckRenderer(void)
 			else if (vid.glstate == VID_GL_LIBRARY_ERROR)
 				rendererchanged = false;
 		}
+		else
 #endif
 
 		if (!contextcreated)