2D游戏编程3—GDI

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

///////////////////////////////////////////////////////////