2d shadowmap pspgu

#include "glib2d.h"
#include <pspkernel.h>
#include <pspgu.h>
#include <pspctrl.h>
#include <math.h>

#define SM_SIZE 0.25f // A _low_ resolution must be enough.

PSP_MODULE_INFO("App",0,1,1);
PSP_MAIN_THREAD_ATTR(THREAD_ATTR_USER | THREAD_ATTR_VFPU);

/* Callbacks */
int exit_callback(int arg1, int arg2, void *common) {
  sceKernelExitGame();
  return 0; }
int CallbackThread(SceSize args, void *argp) {
  int cbid;
  cbid = sceKernelCreateCallback("Exit Callback", exit_callback, NULL);
  sceKernelRegisterExitCallback(cbid);
  sceKernelSleepThreadCB();
  return 0; }
int SetupCallbacks() {
  int thid = 0;
  thid = sceKernelCreateThread("update_thread", CallbackThread, 0x11, 0xFA0, 0, 0);
  if(thid >= 0) sceKernelStartThread(thid, 0, 0);
  return thid; }

int main()
{
    g2dImage *t1, *t2, *sm;
    int x[4] = {50, 200, -130, 80};
    int y[4] = {70, 20, -50, 100};
    int s[4] = {6, 8, 10, 15};
    int a[4] = {60, 100, 150, 200};
    g2dColor c[4] = {CYAN, WHITE, RED, GREEN};
    int i, r=0, mode=0;
    SceCtrlData pad, oldPad;

    SetupCallbacks();

    g2dInit();
    t1 = g2dTexLoad("t1.png", G2D_SWIZZLE); // Background
    t2 = g2dTexLoad("t2.png", G2D_SWIZZLE); // Point light
    sm = g2dTexCreate(G2D_SCR_W*SM_SIZE, G2D_SCR_H*SM_SIZE, true); // Shadowmap

    while (1)
    {
        // Update controls
        oldPad = pad;
        sceCtrlPeekBufferPositive(&pad, 1);
        if ( (pad.Buttons & PSP_CTRL_CROSS) &&
            !(oldPad.Buttons & PSP_CTRL_CROSS))
        {
            mode = (mode+1) % 3;
        }
        // Rotation step
        r = (r+1) % 360;

        /* First pass : construct the shadow map into the framebuffer */

        if (mode > 0)
        {
            g2dClear(BLACK);

            // Limit the draw zone
            g2dSetScissor(0, 0, G2D_SCR_W*SM_SIZE, G2D_SCR_H*SM_SIZE);
            // Scale
            g2dSetGlobalScale(SM_SIZE);
            // Color add
            sceGuBlendFunc(GU_ADD, GU_SRC_ALPHA, GU_FIX, 0, WHITE);

            // Some coloured point lights
            g2dBeginRects(t2);
            for (i=0; i<4; i++)
            {
                g2dSetCoordXYRelative(x[i], y[i]);
                g2dSetRotationRelative(i%3 ? r : -r); // Random rotations
                g2dSetAlpha(a[i]);
                g2dSetColor(c[i]);
                g2dSetScale(s[i], s[i]);
                g2dAdd();
            }
            g2dEnd();

            // Copy the framebuffer back to the shadowmap texture
            sceGuCopyImage(GU_PSM_8888, 0, 0,
                           g2d_draw_buffer.w*SM_SIZE+1,
                           g2d_draw_buffer.h*SM_SIZE+1,
                           g2d_draw_buffer.tw, g2d_draw_buffer.data,
                           0, 0, sm->tw, sm->data);

            // Restore
            g2dResetScissor();
            g2dResetGlobalScale();
            sceGuBlendFunc(GU_ADD, GU_SRC_ALPHA, GU_ONE_MINUS_SRC_ALPHA, 0, 0);
        }

        if (mode != 1)
        {
            g2dClear(BLACK);

            /* Draw dafuq you want here */

            g2dBeginRects(t1);
            g2dAdd();
            g2dEnd();
        }

        /* Second pass : draw the shadowmap */

        if (mode == 2)
        {
            // Color multiply
            sceGuBlendFunc(GU_ADD, GU_DST_COLOR, GU_FIX, 0, 0);
            // Ignore alpha
            sceGuTexFunc(GU_TFX_REPLACE, GU_TCC_RGB);

            // Draw the shadowmap texture
            g2dBeginRects(sm);
            g2dSetScaleWH(G2D_SCR_W+1, G2D_SCR_H+1);
            g2dAdd();
            g2dEnd();

            // Restore
            sceGuBlendFunc(GU_ADD, GU_SRC_ALPHA, GU_ONE_MINUS_SRC_ALPHA, 0, 0);
            sceGuTexFunc(GU_TFX_MODULATE, GU_TCC_RGBA);
        }

        /* Framebuffer flip */

        g2dFlip(G2D_VSYNC);
    }

    g2dTerm();
    return 0;
}