#include<windows.h>
LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
int APIENTRY WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int nShowCmd)
{
    MSG msg;
    WNDCLASS wndclass;
    HWND hwnd;
    wndclass.cbClsExtra=0;
    wndclass.cbWndExtra=0;
    wndclass.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRUSH);
    wndclass.hCursor=LoadCursor(NULL,IDC_ARROW);
    wndclass.hIcon=LoadIcon(NULL,IDI_APPLICATION);
    wndclass.hInstance=hInstance;
    wndclass.lpfnWndProc=WndProc;
    wndclass.lpszClassName=TEXT("hi");
    wndclass.lpszMenuName=NULL;
    wndclass.style=CS_HREDRAW|CS_VREDRAW;
    if(!RegisterClass(&wndclass))
    {
        MessageBox(NULL,TEXT("错误"),TEXT("警告"),MB_ICONERROR);
    }
    hwnd=CreateWindow(TEXT("hi"),TEXT("画图"),WS_OVERLAPPEDWINDOW,100,100,500,500,NULL,NULL,hInstance,NULL);
    ShowWindow(hwnd,nShowCmd);
    UpdateWindow(hwnd);
    while(GetMessage(&msg,NULL,0,0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return msg.wParam;

}
LRESULT CALLBACK WndProc(HWND hwnd,UINT message,WPARAM wParam,LPARAM lParam)
{   HDC hdc;
    PAINTSTRUCT ps;
    RECT rect;
    HPEN gpen,rpen;
    gpen=CreatePen(PS_SOLID,7,RGB(34,139,34));
    rpen=CreatePen(PS_SOLID,7,RGB(250,128,114));
    HBRUSH gbrush,rbrush;
    gbrush=CreateSolidBrush(RGB(46,139,87 ));
    rbrush=CreateSolidBrush(RGB(250,128,114));
    GetClientRect(hwnd,&rect);
    switch(message)
    {
    case WM_PAINT:
          hdc=BeginPaint(hwnd,&ps);
          SelectObject(hdc,gpen);
          FillRect(hdc,&rect,gbrush);
          Rectangle(hdc,0,0,200,900);
         
                  return 0;
    case WM_DESTROY:
        PostQuitMessage(0);
        DeleteObject(gpen);
        DeleteObject(gbrush);
        EndPaint(hwnd,&ps);
        return 0;
    }
    return DefWindowProc(hwnd,message,wParam,lParam);
}
为什么那个FillRect（）函数不可以填充Rectangle()这个矩形，如果放在Rectangle()上面就会只剩下这个矩形没填充，如果放在Rectangle()下面就全部覆盖，难道这个函数只是可以填充背景？

你想达到什么效果啊

GetClientRect(hwnd,&rect);
是这一句 决定了这一局 rect 得到的是整个显示区域
 FillRect(hdc,&rect,gbrush);
so 这个函数填充的是整个显示区域
再 so Rectangle(hdc,0,0,200,900);
这个函数与上个函数的位置 会影响你的视觉

用FillRect（）填充所画的那个矩形

但是我这样定义也不行啊，RECT rect={0,0,200,900}