From b4893840eb51573f53620e087b2cd77a9d08bf2e Mon Sep 17 00:00:00 2001
From: "Pierre-Loup A. Griffais" <git@plagman.net>
Date: Sun, 26 Jan 2020 16:28:35 -0800
Subject: [PATCH] vblank: more tweaks, align to DRM vblank.

---
 src/drm.cpp           |  5 +++++
 src/steamcompmgr.cpp  | 11 +++++------
 src/vblankmanager.cpp | 40 ++++++++++++++++++++++++++++++++++++----
 3 files changed, 46 insertions(+), 10 deletions(-)

diff --git a/src/drm.cpp b/src/drm.cpp
index 1248f3e..2c07a42 100644
--- a/src/drm.cpp
+++ b/src/drm.cpp
@@ -15,6 +15,7 @@
 
 #include "drm.hpp"
 #include "main.hpp"
+#include "vblankmanager.hpp"
 
 #include "gpuvis_trace_utils.h"
 
@@ -191,6 +192,8 @@ static int get_plane_id(struct drm_t *drm)
 static void page_flip_handler(int fd, unsigned int frame,
 							  unsigned int sec, unsigned int usec, void *data)
 {
+	vblank_mark_possible_vblank();
+
 	// TODO: get the fbids_in_req instance from data if we ever have more than one in flight
 	
 	if ( s_drm_log != 0 )
@@ -444,6 +447,8 @@ int init_drm(struct drm_t *drm, const char *device, const char *mode_str, unsign
 	
 	g_nOutputWidth = drm->mode->hdisplay;
 	g_nOutputHeight = drm->mode->vdisplay;
+	
+	g_nOutputRefresh = drm->mode->vrefresh;
 
 	if ( g_nOutputWidth < g_nOutputHeight )
 	{
diff --git a/src/steamcompmgr.cpp b/src/steamcompmgr.cpp
index dece0c3..1d8ce38 100644
--- a/src/steamcompmgr.cpp
+++ b/src/steamcompmgr.cpp
@@ -2371,6 +2371,7 @@ steamcompmgr_main (int argc, char **argv)
 						if ( ev.xclient.data.l[0] == 24 && ev.xclient.data.l[1] == 8 )
 						{
 							// Message from vblankmanager
+							gpuvis_trace_printf( "got vblank\n" );
 							vblank = true;
 						}
 						
@@ -2456,12 +2457,11 @@ steamcompmgr_main (int argc, char **argv)
 
 			check_new_wayland_res();
 			
-			bool bDidRepaint = false;
-			
 			if ( hasRepaint == true && vblank == true )
 			{
 				paint_all(dpy);
-				bDidRepaint = true;
+				
+				// Consumed the need to repaint here
 				hasRepaint = false;
 			}
 			
@@ -2511,9 +2511,8 @@ steamcompmgr_main (int argc, char **argv)
 				}
 			}
 			
-			// Send frame done event to all Wayland surfaces
-			
-			if ( bDidRepaint == true )
+			// Ask for a new surface every vblank
+			if ( vblank == true )
 			{
 				for (win *w = list; w; w = w->next)
 				{
diff --git a/src/vblankmanager.cpp b/src/vblankmanager.cpp
index 18ee4cc..d7e12e5 100644
--- a/src/vblankmanager.cpp
+++ b/src/vblankmanager.cpp
@@ -3,10 +3,13 @@
 #include <thread>
 #include <vector>
 #include <chrono>
+#include <atomic>
 
 #include "X11/Xlib.h"
 #include "assert.h"
 
+#include "gpuvis_trace_utils.h"
+
 #include "vblankmanager.hpp"
 #include "steamcompmgr.hpp"
 #include "wlserver.h"
@@ -15,18 +18,42 @@
 static Display *g_nestedDpy;
 static XEvent repaintMsg;
 
+std::mutex g_vblankLock;
+std::chrono::time_point< std::chrono::system_clock > g_lastVblank;
+
+float g_flVblankDrawBufferMS = 5.0;
+
 void vblankThreadRun( void )
 {
 	while ( true )
 	{
-		int usec = 1.0 / g_nOutputRefresh * 1000.0 * 1000.0;
-		std::chrono::system_clock::time_point timePoint =
-		std::chrono::system_clock::now() + std::chrono::microseconds( usec );
+		std::chrono::time_point< std::chrono::system_clock > lastVblank;
+		int usecInterval = 1.0 / g_nOutputRefresh * 1000.0 * 1000.0;
 		
-		std::this_thread::sleep_until( timePoint );
+		{
+			std::unique_lock<std::mutex> lock( g_vblankLock );
+			lastVblank = g_lastVblank;
+		}
+		
+		lastVblank -= std::chrono::microseconds( (int)(g_flVblankDrawBufferMS * 1000) );
+
+		std::chrono::system_clock::time_point now = std::chrono::system_clock::now();
+		std::chrono::system_clock::time_point targetPoint = lastVblank + std::chrono::microseconds( usecInterval );
+		
+		while ( targetPoint < now )
+		{
+			targetPoint += std::chrono::microseconds( usecInterval );
+		}
+		
+		std::this_thread::sleep_until( targetPoint );
 		
 		XSendEvent( g_nestedDpy , DefaultRootWindow( g_nestedDpy ), True, SubstructureRedirectMask, &repaintMsg);
 		XFlush( g_nestedDpy );
+		
+		gpuvis_trace_printf( "sent vblank\n" );
+		
+		// Get on the other side of it now
+		std::this_thread::sleep_for( std::chrono::microseconds( (int)((g_flVblankDrawBufferMS + 1.0) * 1000) ) );
 	}
 }
 
@@ -40,6 +67,8 @@ void vblank_init( void )
 	repaintMsg.xclient.format = 32;
 	repaintMsg.xclient.data.l[0] = 24;
 	repaintMsg.xclient.data.l[1] = 8;
+	
+	g_lastVblank = std::chrono::system_clock::now();
 
 	std::thread vblankThread( vblankThreadRun );
 	vblankThread.detach();
@@ -47,4 +76,7 @@ void vblank_init( void )
 
 void vblank_mark_possible_vblank( void )
 {
+	std::unique_lock<std::mutex> lock( g_vblankLock );
+
+	g_lastVblank = std::chrono::system_clock::now();
 }