From 397856089d01f3ed80c680661a5e121161368fff Mon Sep 17 00:00:00 2001
From: Jonas Kulla <Nyocurio@gmail.com>
Date: Wed, 16 Oct 2013 19:20:36 +0200
Subject: [PATCH] Tilemap: Optimize atlas assembly from mega surface tileset

Use 'glPixelStorei()' parameters to upload sub images
directly from the same surface instead of creating
helper surfaces to upload from.
---
 src/gl-util.h   | 18 ++++++++++++++++++
 src/tilemap.cpp | 25 ++++---------------------
 2 files changed, 22 insertions(+), 21 deletions(-)

diff --git a/src/gl-util.h b/src/gl-util.h
index 0bca223..45aa0b9 100644
--- a/src/gl-util.h
+++ b/src/gl-util.h
@@ -313,6 +313,24 @@ typedef struct GenericBO<GL_ELEMENT_ARRAY_BUFFER> IBO;
 
 #undef DEF_GL_ID
 
+namespace PixelStore
+{
+	/* Setup a 'glSubTexImage2D()' call where the uploaded image
+	 * itself is part of a bigger image in client memory */
+	inline void setupSubImage(GLint imgWidth, GLint subX, GLint subY)
+	{
+		glPixelStorei(GL_UNPACK_ROW_LENGTH, imgWidth);
+		glPixelStorei(GL_UNPACK_SKIP_PIXELS, subX);
+		glPixelStorei(GL_UNPACK_SKIP_ROWS, subY);
+	}
+
+	/* Reset all states set with 'setupSubImage()' */
+	inline void reset()
+	{
+		setupSubImage(0, 0, 0);
+	}
+}
+
 /* Convenience struct wrapping a framebuffer
  * and a 2D texture as its target */
 struct TEXFBO
diff --git a/src/tilemap.cpp b/src/tilemap.cpp
index 08d9109..c9a5d83 100644
--- a/src/tilemap.cpp
+++ b/src/tilemap.cpp
@@ -654,33 +654,16 @@ struct TilemapPrivate
 
 			SDL_Surface *tsSurf = tileset->megaSurface();
 
-			int bpp;
-			Uint32 rMask, gMask, bMask, aMask;
-			SDL_PixelFormatEnumToMasks(SDL_PIXELFORMAT_ABGR8888,
-			                           &bpp, &rMask, &gMask, &bMask, &aMask);
-
 			for (int i = 0; i < blits.count(); ++i)
 			{
 				TileAtlas::Blit &blitOp = blits[i];
 
-				SDL_Surface *blitTemp =
-				        SDL_CreateRGBSurface(0, tsLaneW, blitOp.h, bpp, rMask, gMask, bMask, aMask);
+				PixelStore::setupSubImage(tsSurf->w, blitOp.src.x, blitOp.src.y);
 
-				SDL_Rect tsRect;
-				tsRect.x = blitOp.src.x;
-				tsRect.y = blitOp.src.y;
-				tsRect.w = tsLaneW;
-				tsRect.h = blitOp.h;
-
-				SDL_Rect tmpRect = tsRect;
-				tmpRect.x = tmpRect.y = 0;
-
-				SDL_BlitSurface(tsSurf, &tsRect, blitTemp, &tmpRect);
-
-				TEX::uploadSubImage(blitOp.dst.x, blitOp.dst.y, tsLaneW, blitOp.h, blitTemp->pixels, GL_RGBA);
-
-				SDL_FreeSurface(blitTemp);
+				TEX::uploadSubImage(blitOp.dst.x, blitOp.dst.y, tsLaneW, blitOp.h, tsSurf->pixels, GL_RGBA);
 			}
+
+			PixelStore::reset();
 		}
 		else
 		{