add png sprite support using SDL_Image

Author: cskyzi

Makefile

@@ -1,4 +1,4 @@
-PKGS=sdl SDL_gfx
+PKGS=sdl SDL_gfx SDL_image
 CFLAGS=-O2 -Wall -W -Ilua/src `pkg-config --cflags $(PKGS)`
 LDLIBS=lua/src/liblua.a -lm `pkg-config --libs $(PKGS)`
 

examples/sprite.lua

@@ -0,0 +1,19 @@
+
+local t, x = 0, 0
+
+function draw()
+	background(0, 0, 0, 0)
+
+	local c = math.abs(math.cos(2*3.14*t));
+	local y = 0.5*HEIGHT*c/math.exp(0.8*t);
+
+	sprite("examples/sprite.png", x, y);
+
+	x = x + 3
+	t = t + 0.01
+
+	if (x > WIDTH) then 
+		t, x = 0, 0
+	end
+end
+

examples/sprite.png

@@ -118,6 +118,94 @@ void programError(const char *e) {
     l81.luaerr = 1;
 }
 
+/* =============================== Sprites ================================== */
+
+#include <SDL_image.h>
+
+#define SPRITE_MT "l81.sprite_mt"
+
+void spriteBlit(SDL_Surface *s, int x, int y)
+{
+    if (s == NULL) return;
+    SDL_Rect dst = {x, l81.fb->height-1-y - s->h, s->w, s->h};
+    SDL_BlitSurface(s, NULL, l81.fb->screen, &dst);
+}
+
+/* Load sprite.  Return surface pointer and object on top of stack */
+SDL_Surface * spriteLoad(const char *filename)
+{
+    SDL_Surface **pps;
+
+    /* check if image was already loaded and cached */
+    lua_getglobal(l81.L, "sprites");
+    lua_getfield(l81.L, -1, filename);
+    if (lua_isnil(l81.L, -1))
+    {
+        /* load image into surface */
+        SDL_Surface *ps = IMG_Load(filename);
+        if (ps == NULL)
+        {   
+            luaL_error(l81.L, "failed to load sprite %s", filename);
+            return NULL;
+        }
+
+        /* box the surface pointer in a userdata */
+        pps = (SDL_Surface **)lua_newuserdata(l81.L, sizeof(SDL_Surface *));
+        *pps = ps;
+
+        /* set sprite metatable */
+        luaL_getmetatable(l81.L, SPRITE_MT);
+        lua_setmetatable(l81.L, -2);
+
+        /* cache loaded surface in sprite table */
+        lua_pushvalue(l81.L, -1); 
+        lua_setfield(l81.L, -4, filename);
+    }
+    else
+    {
+        /* unbox surface pointer */
+        pps = (SDL_Surface **)luaL_checkudata(l81.L, -1, SPRITE_MT);
+    }
+
+    return *pps;
+}
+
+int spriteGC(lua_State *L) {
+    SDL_Surface **pps = (SDL_Surface **)luaL_checkudata(L, 1, SPRITE_MT);
+    if (pps) SDL_FreeSurface(*pps);
+    return 0;
+}
+
+int spriteGetHeight(lua_State *L) {
+    SDL_Surface **pps = (SDL_Surface **)luaL_checkudata(L, 1, SPRITE_MT);
+    lua_pushnumber(L, (*pps)->h);
+    return 1;
+}
+
+int spriteGetWidth(lua_State *L) {
+    SDL_Surface **pps = (SDL_Surface **)luaL_checkudata(L, 1, SPRITE_MT);
+    lua_pushnumber(L, (*pps)->w);
+    return 1;
+}
+
+static const struct luaL_Reg sprite_m[] = {
+    { "__gc",      spriteGC        },
+    { "getHeight", spriteGetHeight },
+    { "getWidth",  spriteGetWidth  },
+    { NULL,        NULL            }
+};
+
+int spriteBinding(lua_State *L) {
+    const char *filename;
+    int x, y;
+
+    filename = lua_tostring(L, 1);
+    x = lua_tonumber(L, 2);
+    y = lua_tonumber(L, 3);
+    spriteBlit(spriteLoad(filename), x, y);
+    return 1;
+}
+
 /* ============================= Lua bindings ============================== */
 int fillBinding(lua_State *L) {
     l81.r = lua_tonumber(L,-4);
@@ -431,7 +519,8 @@ void initScreen(void) {
 void resetProgram(void) {
     char *initscript =
         "keyboard={}; keyboard['pressed']={};"
-        "mouse={}; mouse['pressed']={};";
+        "mouse={}; mouse['pressed']={};"
+        "sprites={}";
 
     l81.epoch = 0;
     if (l81.L) lua_close(l81.L);
@@ -472,6 +561,14 @@ void resetProgram(void) {
     lua_setglobal(l81.L,"setFPS");
     lua_pushcfunction(l81.L,getpixelBinding);
     lua_setglobal(l81.L,"getpixel");
+    lua_pushcfunction(l81.L,spriteBinding);
+    lua_setglobal(l81.L,"sprite");
+
+    luaL_newmetatable(l81.L, SPRITE_MT);
+    lua_pushvalue(l81.L, -1);
+    lua_setfield(l81.L, -2, "__index");
+
+    luaL_register(l81.L, NULL, sprite_m);
 
     /* Start with a black screen */
     fillBackground(l81.fb,0,0,0);