WM_PAINT消息触发程序重新绘制界面,过程如下:
PAINTSTRUCT ps; // used in WM_PAINT
HDC hdc; // handle to a device context
case WM_PAINT:
{
hdc = BeginPaint(hwnd,&ps);
EndPaint(hwnd,&ps);
return(0);
} break;
beginpaint将需要重绘的区域存入ps的rcpaint中,ps定义结构如下:
typedef struct tagPAINTSTRUCT
{
HDC hdc; // graphics device context
BOOL fErase; // if TRUE then you must draw background
RECT rcPaint; // the RECT containing invalid region
BOOL fRestore; // internal
BOOL fIncUpdate; // internal
BYTE rgbReserved[32]; // internal
} PAINTSTRUCT;
其中RECT结构如下:
typedef struct _RECT
{
LONG left; // left edge if rectangle
LONG top; // upper edge of rectangle
LONG right; // right edge of rectangle
LONG bottom; // bottom edge of rectangle
} RECT;
GDI文字输出依靠DrawText和TextOut两个函数
例子:
#define WIN32_LEAN_AND_MEAN // just say no to MFC #include <windows.h> // include all the windows headers
#include <windowsx.h> // include useful macros
#include <mmsystem.h> // very important and include WINMM.LIB too!
#include <stdio.h>
#include <stdlib.h>
#include <math.h> // DEFINES //////////////////////////////////////////////// // defines for windows
#define WINDOW_CLASS_NAME "WINCLASS1" // GLOBALS ////////////////////////////////////////////////
HWND main_window_handle = NULL; // globally track main window
HINSTANCE hinstance_app = NULL; // globally track hinstance // FUNCTIONS //////////////////////////////////////////////
LRESULT CALLBACK WindowProc(HWND hwnd,
UINT msg,
WPARAM wparam,
LPARAM lparam)
{
// this is the main message handler of the system
PAINTSTRUCT ps; // used in WM_PAINT
HDC hdc; // handle to a device context // what is the message
switch(msg)
{
case WM_CREATE:
{
// do initialization stuff here
// return success
return(0);
} break; case WM_PAINT:
{
// simply validate the window
hdc = BeginPaint(hwnd,&ps);
// you would do all your painting here
EndPaint(hwnd,&ps); // return success
return(0);
} break; case WM_DESTROY:
{ // kill the application, this sends a WM_QUIT message
PostQuitMessage(0); // return success
return(0);
} break; default:break; } // end switch // process any messages that we didn't take care of
return (DefWindowProc(hwnd, msg, wparam, lparam)); } // end WinProc // WINMAIN ////////////////////////////////////////////////
int WINAPI WinMain( HINSTANCE hinstance,
HINSTANCE hprevinstance,
LPSTR lpcmdline,
int ncmdshow)
{ WNDCLASSEX winclass; // this will hold the class we create
HWND hwnd; // generic window handle
MSG msg; // generic message // first fill in the window class stucture
winclass.cbSize = sizeof(WNDCLASSEX);
winclass.style = CS_DBLCLKS | CS_OWNDC |
CS_HREDRAW | CS_VREDRAW;
winclass.lpfnWndProc = WindowProc;
winclass.cbClsExtra = 0;
winclass.cbWndExtra = 0;
winclass.hInstance = hinstance;
winclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
winclass.hCursor = LoadCursor(NULL, IDC_ARROW);
winclass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
winclass.lpszMenuName = NULL;
winclass.lpszClassName = WINDOW_CLASS_NAME;
winclass.hIconSm = LoadIcon(NULL, IDI_APPLICATION); // save hinstance in global
hinstance_app = hinstance; // register the window class
if (!RegisterClassEx(&winclass))
return(0); // create the window
if (!(hwnd = CreateWindowEx(NULL, // extended style
WINDOW_CLASS_NAME, // class
"GDI Text Printing Demo", // title
WS_OVERLAPPEDWINDOW | WS_VISIBLE,
0,0, // initial x,y
400,400, // initial width, height
NULL, // handle to parent
NULL, // handle to menu
hinstance,// instance of this application
NULL))) // extra creation parms
return(0); // save main window handle
main_window_handle = hwnd; // get the dc and hold it
HDC hdc = GetDC(hwnd); // enter main event loop, but this time we use PeekMessage()
// instead of GetMessage() to retrieve messages
while(TRUE)
{
// test if there is a message in queue, if so get it
if (PeekMessage(&msg,NULL,0,0,PM_REMOVE))
{
// test if this is a quit
if (msg.message == WM_QUIT)
break; // translate any accelerator keys
TranslateMessage(&msg); // send the message to the window proc
DispatchMessage(&msg);
} // end if // main game processing goes here // set the foreground color to random
SetTextColor(hdc, RGB(rand()%256,rand()%256,rand()%256)); // set the background color to black
SetBkColor(hdc, RGB(11,11,11)); // finally set the transparency mode to transparent
SetBkMode(hdc, TRANSPARENT); // draw some text at a random location
TextOut(hdc,rand()%400,rand()%400, "GDI Text Demo!", strlen("GDI Text Demo!")); Sleep(10); } // end while // release the dc
ReleaseDC(hwnd,hdc); // return to Windows like this
return(msg.wParam); } // end WinMain ///////////////////////////////////////////////////////////