From fd7b833ad568386086d2101f7f8403dda405d919 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <c.oelckers@zdoom.fake>
Date: Sat, 6 Aug 2016 19:20:41 +0200
Subject: [PATCH] - added some helper code mainly designed to help GZDoom
 maintain the vertex buffer for the textured automap.

---
 src/am_map.cpp |  2 ++
 src/v_draw.cpp | 13 +++++++++++++
 src/v_video.h  |  3 +++
 3 files changed, 18 insertions(+)

diff --git a/src/am_map.cpp b/src/am_map.cpp
index 3a4e0aaa14..7e346843b0 100644
--- a/src/am_map.cpp
+++ b/src/am_map.cpp
@@ -1897,6 +1897,7 @@ void AM_drawSubsectors()
 	FDynamicColormap *colormap;
 	mpoint_t originpt;
 
+	screen->StartSimplePolys();
 	for (int i = 0; i < numsubsectors; ++i)
 	{
 		if (subsectors[i].flags & SSECF_POLYORG)
@@ -2049,6 +2050,7 @@ void AM_drawSubsectors()
 				);
 		}
 	}
+	screen->FinishSimplePolys();
 }
 
 //=============================================================================
diff --git a/src/v_draw.cpp b/src/v_draw.cpp
index c7b62b0a66..89023d4bda 100644
--- a/src/v_draw.cpp
+++ b/src/v_draw.cpp
@@ -1244,6 +1244,19 @@ void DCanvas::Clear (int left, int top, int right, int bottom, int palcolor, uin
 	}
 }
 
+//==========================================================================
+//
+// no-ops. This is so that renderer backends can better manage the
+// processing of the subsector drawing in the automap
+//
+//==========================================================================
+
+void DCanvas::StartSimplePolys()
+{}
+
+void DCanvas::FinishSimplePolys()
+{}
+
 //==========================================================================
 //
 // DCanvas :: FillSimplePoly
diff --git a/src/v_video.h b/src/v_video.h
index fa1ce83df0..7091c518d4 100644
--- a/src/v_video.h
+++ b/src/v_video.h
@@ -216,6 +216,9 @@ public:
 	// Fill an area with a texture
 	virtual void FlatFill (int left, int top, int right, int bottom, FTexture *src, bool local_origin=false);
 
+	virtual void StartSimplePolys();
+	virtual void FinishSimplePolys();
+
 	// Fill a simple polygon with a texture
 	virtual void FillSimplePoly(FTexture *tex, FVector2 *points, int npoints,
 		double originx, double originy, double scalex, double scaley, DAngle rotation,