``
```
case WM_PAINT:
{
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd, &ps);
// TODO: 在此处添加使用 hdc 的任何绘图代码...
//
double slope = 0.6;// 0.75;// 当斜率大于1的时候,绘图要反转,即以y和 DeltaY为循环变量!
//1.75;// 0.75;// deltY/deltX=1.45 即斜率(y2-y1)/(x2-x1)=1.75
int x100 = 1000;// 100;
int x500 = 5000;// 500;
int y100 = 1000;// 100;
int y400 = 4000;// 400;
MoveToEx(hdc, 50, 10, NULL); Rectangle(hdc, x100, y100, x500, y400);
INT64 maxY; maxY = 2 ^ 63 - 1;
INT64 x1 = 100; double dx1 = (double)x1;
INT64 x2 = x1; double dx2 = (double)x2;
INT64 y1 = 100; double dy1 = (double)y1;
INT64 y2 = y1; double dy2 = (double)y2;
int flagx = 1; int flagy = 1; int flagy0 = 0;// -1;
//flagy0比较晦涩难懂, 有时精密计算的结果是 y2多次等于边界 y400等,当是第一次的时候 就反转
//
for (INT64 ii = 100; ii < 99999; ++ii) {//for110
//x1 = ixi;// / 10; //精密到 0.1
//dx1 = (double)x1;
aboutFlag:
//x1 = (int)dx1;
if (x100 >= (x1/1) ) { //if (100 == (x1/10) ) {
flagx = 1;
}
if (x500 <= (x1/1)) {//if (x500 == (x1/10)) {
flagx = -1;
}
y1 = (int)dy1;//把y的坐标找出来变成整数
if (y100 >= y1) {//if (y100 == y1) {
flagy = 1;
}
//if (0==flagy0 && y400 == (int)(y1/1) ) { //if (y400 == (int)(y1/10) || (4000==(int)y1 ) ) {
if ( y400 <= (int)y1) { //(int)(y1 / 1)) {
flagy = -1; flagy0 = 2;
}
if (100 == x1 && 100 == y1) { flagx = 1; flagy = 1; } //这个点特殊,这是光源,或笛卡尔坐标原点
//aboutFlag-End;
label_Y_as_aVar:
x2 = x1 + (flagx) * 1;
dx2 = dx1 + (flagx) * 1;
INT64 deltaX = labs(long(x2 - x1));
dy2 = (flagy)*deltaX*slope + dy1;
// SetPixel(hdc, (x2/1), (int)(dy2/1), RGB(1, 200, 0)); //
SetPixel(hdc, (x2/10), (int)(dy2/10), RGB(1, 200, 0));
//
labelEnd990:
x1 = x2;
dx1 = dx2;
if (y1 != y2) { flagy0 = 0; }//此举回复反转开关
y1 = y2;
dy1 = dy2;
}//for110
//
//
EndPaint(hWnd, &ps);
}//case WM_PAINT:
break;
//......省略
//
case WM_DESTROY:
```
