ELS square display principle

#include"els_h.h"
// Background array
int g_arrBackGroud[20][10] = {0};

void OnPaint(HDC hDc)
{
    // Create compatibility DC.
    HDC hMemDC = CreateCompatibleDC(hDc);// Memory id by ：HMemDc, window id hDc.

    // Create compatibility bitmap .
    HBITMAP hBitmapBack= CreateCompatibleBitmap(hDc, 500, 600);

    // Connect .
    SelectObject(hMemDC, hBitmapBack);

    PaintSqare(hMemDC);
    
    // Pass on ：
    // Return value ： Failure to return 0, Successfully returned non-zero .
    // Parameters 1： The goal is DC, window DC
    // Parameters 2,3： The starting position of the target , Attention is based on our window .
    // Parameters 4,5： The size of the area .
    // Parameters 6： Source DC, That is, our memory DC.
    // Parameters 7,8： The starting position of the memory picture .
    // Parameters 9： delivery .
    //
    BitBlt(hDc, 0, 0, 300, 600, hMemDC, 0, 0, SRCCOPY);

    // Release DC
    DeleteObject(hBitmapBack);
    DeleteDC(hMemDC);
    
}
void Oncreate()
{

}
void PaintSqare(HDC hMemDC)
{
    int i = 0,
        j = 0;

    // Draw a big square .
    Rectangle(hMemDC, 0, 0, 300, 600);// The coordinates of the starting position and the ending position of the rectangular box from the running window .
    
    // Specify a square . test .
    g_arrBackGroud[2][4] = 1;
    g_arrBackGroud[3][3] = 1;
    g_arrBackGroud[3][4] = 1;
    g_arrBackGroud[3][5] = 1;

    // Traverse
    for (i =0; i < 20; i++)
    {
        for (j=0 ; j < 10; j++)
        {
            if (1 == g_arrBackGroud[i][j])
            {
                // Draw squares .
                Rectangle(hMemDC, j*30, i*30, j * 30+30, i * 30+30);// The coordinates of the starting position and the ending position of the rectangular box from the running window .

            }
        }
    }
}