From 9bb961f63f3e14e84878adfe3057a7ca51de7f81 Mon Sep 17 00:00:00 2001
From: Fierelier <fierelier@gmail.com>
Date: Fri, 19 May 2023 01:01:02 +0200
Subject: [PATCH] Fix engine_texture_render_2d

---
 src/engine/frontend/generic/textures.c | 52 +++++++++++++++++---------
 src/engine/lua.c                       |  6 +--
 src/engine/values/functions.toml       |  2 +-
 3 files changed, 38 insertions(+), 22 deletions(-)

diff --git a/src/engine/frontend/generic/textures.c b/src/engine/frontend/generic/textures.c
index 637e421..d1dc1fd 100644
--- a/src/engine/frontend/generic/textures.c
+++ b/src/engine/frontend/generic/textures.c
@@ -46,27 +46,43 @@ void engine_texture_destroy(struct ENGINE_TEXTURE * texture) {
 	engine_free(texture);
 }
 
-void engine_texture_render_2d(struct ENGINE_TEXTURE * texture,int sx,int sy) {
-	char * pixels = ((struct ENGINE_GENERIC_TEXTURE *)(texture->fe_texture))->pixels;
-	int ex = sx + texture->width;
-	if (ex > engine_width) { ex = engine_width; }
-	int ey = sy + texture->height;
-	if (ey > engine_height) { ey = engine_height; }
-	int x = sx;
-	if (x < 0) { x = 0; }
-	int y = sy;
-	if (y < 0) { y = 0; }
-	long pixelIndex = 0;
+void engine_texture_render_2d(struct ENGINE_TEXTURE * texture,int x,int y) {
+	int sx = 0;
+	if (x < 0) {
+		sx -= x;
+	}
+	if (sx > texture->width) { return; } // unnecessary? maybe faster with a lot of offscreen textures?
 	
-	while (y < ey) {
-		while (x < ex) {
-			pixelIndex = ((x - sx) + (y - sy) * texture->width)*4;
+	int sy = 0;
+	if (y < 0) {
+		sy -= y;
+	}
+	if (sy > texture->height) { return; } // unnecessary? maybe faster with a lot of offscreen textures?
+	
+	int ex = texture->width;
+	if (x + ex > engine_width) {
+		ex -= (x + ex) - engine_width;
+		if (ex < 0) { return; } // unnecessary? maybe faster with a lot of offscreen textures?
+	}
+	
+	int ey = texture->height;
+	if (y + ey > engine_height) {
+		ey -= (y + ey) - engine_height;
+		if (ey < 0) { return; } // unnecessary? maybe faster with a lot of offscreen textures?
+	}
+	
+	char * pixels = ((struct ENGINE_GENERIC_TEXTURE *)(texture->fe_texture))->pixels;
+	int pixelIndex;
+	int tx = sx;
+	while (sy < ey) {
+		while (tx < ex) {
+			pixelIndex = (tx + sy * texture->width)*4;
 			engine_surface_color_set(pixels[pixelIndex],pixels[pixelIndex + 1],pixels[pixelIndex + 2],pixels[pixelIndex + 3]);
-			engine_surface_draw_pixel(x,y);
-			++x;
+			engine_surface_draw_pixel(x + tx,y + sy);
+			++tx;
 		}
-		x = sx;
-		++y;
+		tx = sx;
+		++sy;
 	}
 }
 
diff --git a/src/engine/lua.c b/src/engine/lua.c
index 59bdd32..ab716f9 100644
--- a/src/engine/lua.c
+++ b/src/engine/lua.c
@@ -96,9 +96,9 @@ int engine_luaf_texture_destroy(lua_State *L) {
 
 int engine_luaf_texture_render_2d(lua_State *L) {
 	struct ENGINE_TEXTURE * texture = lua_touserdata(L,1);
-	int sx = luaL_checkinteger(L,2);
-	int sy = luaL_checkinteger(L,3);
-	engine_texture_render_2d(texture,sx,sy);
+	int x = luaL_checkinteger(L,2);
+	int y = luaL_checkinteger(L,3);
+	engine_texture_render_2d(texture,x,y);
 	return 0;
 }
 
diff --git a/src/engine/values/functions.toml b/src/engine/values/functions.toml
index 8bbdcc6..3f499fd 100644
--- a/src/engine/values/functions.toml
+++ b/src/engine/values/functions.toml
@@ -91,7 +91,7 @@ description = "Destroy a texture, freeing up memory."
 [engine_texture_render_2d]
 type = "void"
 arguments =   ["struct ENGINE_TEXTURE *","int","int"]
-argNames =    ["texture",                "sx", "sy"]
+argNames =    ["texture",                "x",  "y"]
 description = "Render texture to the window surface."
 
 [engine_texture_from_file]