From 3b19ae2bbd7654fe0bd0108b2c22506280f76ae8 Mon Sep 17 00:00:00 2001
From: Zeno Rogue <zeno@attnam.com>
Date: Tue, 20 Feb 2018 11:41:55 +0100
Subject: [PATCH] a commandline option to disable vsync

---
 basegraph.cpp   | 7 +++++++
 commandline.cpp | 4 ++++
 2 files changed, 11 insertions(+)

diff --git a/basegraph.cpp b/basegraph.cpp
index 6e4c70ad..b40fe24b 100644
--- a/basegraph.cpp
+++ b/basegraph.cpp
@@ -1063,10 +1063,16 @@ void saveHighQualityShot(const char *fname, const char *caption, int fade) {
 
 bool setfsize = true;
 
+bool vsync_off;
+
 void do_setfsize() {
   vid.fsize = min(vid.yres * fontscale/ 3200, vid.xres * fontscale/ 4800), setfsize = false;
   }
 
+void disable_vsync() {
+  SDL_GL_SetAttribute( SDL_GL_SWAP_CONTROL, 0 ); 
+  }
+  
 #if CAP_SDL
 void setvideomode() {
 
@@ -1085,6 +1091,7 @@ void setvideomode() {
   if(vid.usingGL) {
     flags = SDL_OPENGL | SDL_HWSURFACE | SDL_GL_DOUBLEBUFFER;
     SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 1);
+    if(vsync_off) disable_vsync();
 #if !ISWEB
     if(vid.antialias & AA_MULTI) {
       SDL_GL_SetAttribute(SDL_GL_MULTISAMPLEBUFFERS, 1);
diff --git a/commandline.cpp b/commandline.cpp
index 5950ab7f..7328e6f8 100644
--- a/commandline.cpp
+++ b/commandline.cpp
@@ -74,6 +74,10 @@ int arg::readCommon() {
   else if(argis("-font")) { PHASE(1); shift(); fontpath = args(); }
   else if(argis("-picload")) { PHASE(3); shift(); mapeditor::loadPicFile(args()); }
 #endif
+  else if(argis("-vsync_off")) {
+    vsync_off = true;
+    if(curphase == 3) setvideomode();
+    }
   else if(argis("-canvas")) {
     PHASE(2);
     firstland = specialland = laCanvas;