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关于Windows更新窗口内容的问题(作为一个实验,效果很明显)
Windows中的窗口在特定情况下会由系统进行重绘,如无效区域重新显现时,,会向窗口的处理过程发送VM_PAINT消息,但是,可能还有Windows自己的更新窗口处理,如在下面的代码中,将击键显式地转换为VM_PAINT消息,让窗口过程处理,但是运行的结果却是,击键后窗口没有马上重绘(显示字体没有改变),而是在下次重绘时才改变字体,但是如果改变为一个UpdateWindow()函数时,就会马上改变字体。猜想UpdateWindow(),InvaliddateRect()和Windows系统调用都有更新窗口处理。
#include<windows.h>
//LRESULT CALLBACK WndProc(HWND hwnd,UINT message,WPARAM wParam,LPARAM lParam);
LRESULT CALLBACK WndProc(HWND hwnd,UINT message,WPARAM wParam,LPARAM lParam)
{
HDC hdc;
PAINTSTRUCT ps;
RECT rect;
static int a=0;
switch(message)
{
case WM_CREATE:
return 0;
case WM_PAINT:
hdc=BeginPaint(hwnd,&ps);
GetClientRect(hwnd,&rect);
int c;
if(a==0)
DrawText(hdc,TEXT("Liu Wangsheng !"),-1,&rect,DT_SINGLELINE|DT_CENTER|DT_VCENTER);
else
c=DrawText(hdc,TEXT("HELLO HELLO!"),-1,&rect,DT_SINGLELINE);
EndPaint(hwnd,&ps);
return 0;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
case WM_KEYDOWN:
switch(wParam)
{
case VK_UP:
a=1;
//SendMessage(hwnd,WM_PAINT,0,0);
InvalidateRect(hwnd,NULL,TRUE);
return 0;
case VK_DOWN:
PostQuitMessage(0);
return 0;
}
return 0;
}
return DefWindowProc(hwnd,message,wParam,lParam);
//return 0;
}
int APIENTRY WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance, LPSTR lpCmdLine,int nCmdShow)
{
// TODO: Place code here.
static TCHAR szAppName[]=TEXT("LWS");
HWND hwnd;
MSG msg;
WNDCLASS wndclass;
wndclass.style=CS_HREDRAW | CS_VREDRAW;
wndclass.lpfnWndProc=WndProc;
wndclass.cbClsExtra=0;
wndclass.cbWndExtra=0;
wndclass.hInstance=hInstance;
wndclass.hIcon=LoadIcon(NULL,IDI_APPLICATION);
wndclass.hCursor=LoadCursor(NULL,IDC_ARROW);
wndclass.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRUSH);
wndclass.lpszMenuName=NULL;
wndclass.lpszClassName=szAppName;
RegisterClass(&wndclass);
hwnd=CreateWindow(szAppName,
TEXT("hello!"),
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
CW_USEDEFAULT,
NULL,
NULL,
hInstance,
NULL);
ShowWindow(hwnd,nCmdShow);
UpdateWindow(hwnd);
while(GetMessage(&msg,NULL,0,0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return msg.wParam;
}
http://blog.csdn.net/tobacco5648/article/details/7422803
关于Windows更新窗口内容的问题(作为一个实验,效果很明显)