From 07571da98ccad2fd2c360c4b73ba989a902f184b Mon Sep 17 00:00:00 2001
From: Magnus Norddahl <dpjudas@users.noreply.github.com>
Date: Fri, 10 Jun 2016 18:43:49 +0200
Subject: [PATCH] Improved how threaded rendering is handled

---
 src/r_draw.h         | 16 ++++++++++++----
 src/r_draw_rgba.cpp  | 24 ++++++++++++++++++++++--
 src/r_main.cpp       |  4 +++-
 src/r_swrenderer.cpp |  3 ++-
 4 files changed, 39 insertions(+), 8 deletions(-)

diff --git a/src/r_draw.h b/src/r_draw.h
index 37a0e67788..d192dc5e49 100644
--- a/src/r_draw.h
+++ b/src/r_draw.h
@@ -443,8 +443,11 @@ void R_SetDSColorMapLight(FColormap *base_colormap, float light, int shade);
 
 void R_SetTranslationMap(lighttable_t *translation);
 
+// Redirect drawer commands to worker threads
+void R_BeginDrawerCommands();
+
 // Wait until all drawers finished executing
-void R_FinishDrawerCommands();
+void R_EndDrawerCommands();
 
 class DrawerCommandQueue;
 
@@ -530,13 +533,14 @@ class DrawerCommandQueue
 	std::condition_variable end_condition;
 	size_t finished_threads = 0;
 
-	bool no_threading = false;
+	int threaded_render = 0;
 	DrawerThread single_core_thread;
 	int num_passes = 2;
 	int rows_in_pass = 540;
 
 	void StartThreads();
 	void StopThreads();
+	void Finish();
 
 	static DrawerCommandQueue *Instance();
 
@@ -551,7 +555,7 @@ public:
 	static void QueueCommand(Types &&... args)
 	{
 		auto queue = Instance();
-		if (queue->no_threading)
+		if (queue->threaded_render == 0)
 		{
 			T command(std::forward<Types>(args)...);
 			command.Execute(&queue->single_core_thread);
@@ -565,9 +569,13 @@ public:
 			queue->commands.push_back(command);
 		}
 	}
+	
+	// Redirects all drawing commands to worker threads until Finish is called
+	// Begin/End blocks can be nested.
+	static void Begin();
 
 	// Wait until all worker threads finished executing commands
-	static void Finish();
+	static void End();
 };
 
 #endif
diff --git a/src/r_draw_rgba.cpp b/src/r_draw_rgba.cpp
index e2dbd443ab..23ab106a65 100644
--- a/src/r_draw_rgba.cpp
+++ b/src/r_draw_rgba.cpp
@@ -82,6 +82,21 @@ void* DrawerCommandQueue::AllocMemory(size_t size)
 	return data;
 }
 
+void DrawerCommandQueue::Begin()
+{
+	auto queue = Instance();
+	queue->Finish();
+	queue->threaded_render++;
+}
+
+void DrawerCommandQueue::End()
+{
+	auto queue = Instance();
+	queue->Finish();
+	if (queue->threaded_render > 0)
+		queue->threaded_render--;
+}
+
 void DrawerCommandQueue::Finish()
 {
 	auto queue = Instance();
@@ -3515,9 +3530,14 @@ public:
 
 /////////////////////////////////////////////////////////////////////////////
 
-void R_FinishDrawerCommands()
+void R_BeginDrawerCommands()
 {
-	DrawerCommandQueue::Finish();
+	DrawerCommandQueue::Begin();
+}
+
+void R_EndDrawerCommands()
+{
+	DrawerCommandQueue::End();
 }
 
 void R_DrawColumnP_RGBA_C()
diff --git a/src/r_main.cpp b/src/r_main.cpp
index 348c701204..c1b78303b3 100644
--- a/src/r_main.cpp
+++ b/src/r_main.cpp
@@ -960,6 +960,8 @@ void R_RenderViewToCanvas (AActor *actor, DCanvas *canvas,
 		r_swtruecolor = canvas->IsBgra();
 		R_InitColumnDrawers();
 	}
+	
+	R_BeginDrawerCommands();
 
 	viewwidth = width;
 	RenderTarget = canvas;
@@ -979,7 +981,7 @@ void R_RenderViewToCanvas (AActor *actor, DCanvas *canvas,
 	R_SetupBuffer ();
 	screen->Unlock ();
 
-	R_FinishDrawerCommands();
+	R_EndDrawerCommands();
 
 	viewactive = savedviewactive;
 	r_swtruecolor = savedoutputformat;
diff --git a/src/r_swrenderer.cpp b/src/r_swrenderer.cpp
index 62190b6064..11f879c38c 100644
--- a/src/r_swrenderer.cpp
+++ b/src/r_swrenderer.cpp
@@ -162,10 +162,11 @@ void FSoftwareRenderer::RenderView(player_t *player)
 		R_InitColumnDrawers();
 	}
 
+	R_BeginDrawerCommands();
 	R_RenderActorView (player->mo);
 	// [RH] Let cameras draw onto textures that were visible this frame.
 	FCanvasTextureInfo::UpdateAll ();
-	R_FinishDrawerCommands();
+	R_EndDrawerCommands();
 }
 
 //==========================================================================