Question

请VC++高手帮个忙，用TextOut（）每隔一秒在窗口同一位置输出背景透明文字，会产生叠加，请问如何刷新

//以下代码在VC6.0中编译通过，要求输出文字时，能擦除之前的文字，不要前后叠加
//不知如何实现，最好在下面代码基础上修改，完成后能发到本人邮箱更好，不胜感谢
//邮箱地址：78381315@qq.com

#include "windows.h"
#include "stdio.h"

LRESULT CALLBACK LcyProc(HWND, UINT, WPARAM, LPARAM);

int tim=48;
int tima;
char timch[2]="A";
int testtimer(HWND hwnd);
int WINAPI WinMain(
HINSTANCE hInstance,

HINSTANCE hPrevInstance,

LPSTR lpCmdLine,

int nCmdShow
)

{
WNDCLASS wcex;

wcex.style= CS_HREDRAW | CS_VREDRAW;

wcex.lpfnWndProc= (WNDPROC)LcyProc;

wcex.cbClsExtra = 0;

wcex.cbWndExtra = 0;

wcex.hInstance= hInstance;

wcex.hIcon= LoadIcon(NULL,IDI_QUESTION);

wcex.hCursor=LoadCursor(NULL,IDC_CROSS);

wcex.hbrBackground=(HBRUSH)(COLOR_WINDOW-1);//可以用NULL试一种通明背景效果
wcex.lpszMenuName= NULL;//不显示菜单栏

wcex.lpszClassName="MyWindowTest";

RegisterClass(&wcex);
HWND hwnd;
hwnd=CreateWindow("MyWindowTest", "请大虾帮个忙啊", WS_OVERLAPPEDWINDOW,CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInstance, NULL);//"快速高效自学教程"被改1,如果将WS_OVERLAPPEDWINDOW改为WS_DLGFRAME,将禁用右击关闭

ShowWindow(hwnd,SW_SHOWNORMAL);
UpdateWindow(hwnd);
testtimer(hwnd);
MSG msg;
while(GetMessage(&msg,NULL,0,0))
{
TranslateMessage(&msg);

DispatchMessage(&msg);

}

return 0;
}

LRESULT CALLBACK LcyProc(HWND hwnd, UINT message,
WPARAM wParam, LPARAM lParam)

{
switch (message)

{

case WM_LBUTTONDOWN:
MessageBox(hwnd,"点击才可以刷新一次红色数字 ","我想自动刷新",0);
InvalidateRect(hwnd,NULL,TRUE);//把这句放到case WM_TIMER中会闪烁
break;
case WM_PAINT:
HDC hDc;
PAINTSTRUCT ps;
hDc=BeginPaint(hwnd,&ps);
SetBkMode(hDc, TRANSPARENT);
SetTextColor(hDc, RGB(0, 255, 0));
TextOut(hDc,0,10,"我希望能刷新,且不闪烁",strlen("我希望能刷新,且不闪烁"));
EndPaint(hwnd,&ps);
break;
case WM_TIMER:
if (1 == wParam)
{
tim +=1;
if(tim>99)
tim=10;
HDC hdc;
hdc=GetDC(hwnd);
_itoa(tim, timch, 10 );
SetBkMode(hdc, TRANSPARENT);
SetTextColor(hdc, RGB(255, 0, 0));
TextOut(hdc,55,30,timch,2);
ReleaseDC(hwnd,hdc);
}
break;

case WM_DESTROY:

PostQuitMessage(0);
break;

default:
return DefWindowProc(hwnd,message,wParam,lParam);
}
return 0;
}

testtimer(HWND hwnd)
{tima=SetTimer(hwnd,1,1000,0 );
return NULL;
}
谢谢回答！用你的方法还是有点闪烁，听说双缓冲方法效果最好，不知代码如何写，如何加进去？

Answer 1

WM_TIMER消息的处理方式改下；
case WM_TIMER: ::InvalidateRect(hwnd, NULL); break;

然后在WM_PAINT里调TextOut()

双缓冲是OpenGL/D3D里的方案，只有当你画的东西非常耗时的时候才需要。
解决闪烁的办法：创建一个memory DC，把你要画的东西都画到memory DC上。之后再bitblit到窗口DC上。