Graphics/Backgrounds/Double_Buffer/source/main.cpp

//---------------------------------------------------------------------------------
// Simple double buffering demo
// -- dovoto
//---------------------------------------------------------------------------------

#include <nds.h>

#include <stdlib.h>
#include <stdio.h>


//---------------------------------------------------------------------------------
int main(void) {
//---------------------------------------------------------------------------------
    //set the mode for 2 text layers and two extended background layers
    videoSetMode(MODE_5_2D); 

    //set the first two banks as background memory and the third as sub background memory
    //D is not used..if you need a bigger background then you will need to map
    //more vram banks consecutivly (VRAM A-D are all 0x20000 bytes in size)
    vramSetMainBanks(   VRAM_A_MAIN_BG_0x06000000, VRAM_B_MAIN_BG_0x06020000, 
        VRAM_C_SUB_BG , VRAM_D_LCD); 

    consoleDemoInit();

    iprintf("\n\n\tHello DS devers\n");
    iprintf("\twww.drunkencoders.com\n");
    iprintf("\tdouble buffer demo");


    int bg = bgInit(3, BgType_Bmp16, BgSize_B16_256x256, 0,0);

    u16 colorMask = 0x1F;

    u16* backBuffer = (u16*)bgGetGfxPtr(bg) + 256*256;

    while(1) 
    {
        //draw a box (60,60,196,136)
        for(int iy = 60; iy < 196 - 60; iy++)
            for(int ix = 60; ix < 256 - 60; ix++) 
                backBuffer[iy * 256 + ix] = (rand() & colorMask) | BIT(15);

        swiWaitForVBlank();

        //swap the back buffer to the current buffer
        backBuffer = (u16*)bgGetGfxPtr(bg);

        //swap the current buffer by changing the base. Each base
        //represents 16KB of offset and each screen is 256x256x2 (128KB)
        //this requires a map base seperation of 8 (could get away with smaller
        //as the screen is really only showing 256x192 (96KB or map base 6)
        if(bgGetMapBase(bg) == 8)
        {
            bgSetMapBase(bg, 0);
        }
        else
        {
            bgSetMapBase(bg, 8);
        }

        colorMask ^= 0x3FF;
    }
}