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动画程序编写——DirectDraw之旅(3)

下面我们开始分析源程序:

下载源程序  (编辑者:链接丢失)

属于Win32程序的基本框架的我们用蓝色标出,而用红色表出的是我们要重点学习的。下面的所有程序都是 FullScreenMode.cpp 文件中的内容,其中“IDB_DIRECTX”和“IDB_WinXP”都是图片资源的ID号,我想如何向程序中添加资源应该不用我多说了吧:)

工程文件:FullScreenMode.cpp

#define STRICT
#include <windows.h>
#include <ddraw.h>
#include <mmsystem.h>
#include "resource.h"
#include "ddutil.h"

//定义删除指针和释放对象的宏

#define SAFE_DELETE(p)
{
 if(p)
 {
  delete (p);
  (p)=NULL;
  }
}

#define SAFE_RELEASE(p)
{
  if(p)
  {
   (p)->Release();
   (p)=NULL;
  }
}

#define SCREEN_WIDTH 1024
//定义屏幕宽度

#define SCREEN_HEIGHT 768
//定义屏幕高度

#define SCREEN_BPP 8
//定义调色板位数

#define SPRITE_DIAMETER 32
//定义飘动的子画面 的直径(宽度和高度一样)

#define NUM_SPRITES 10
//定义飘动的子画面 的个数

#define HELPTEXT TEXT("Press Escape to quit.")
//定义文本住表面

上面出现的这个 TEXT( ) 是一个系统头文件里定义的宏,起作用是检查程序中是否定义了 Unicode ,如果有,就将括号中的文本转化成宽自负,如果没有,则转化成ASCLL 码。以下定义的是子画面飘动时的属性:

struct SPRITE_STRUCT

{
 FLOAT fPosX;
//sprite当前坐标的x值,如果在初始化时,即为初始坐标x值
 FLOAT fPosY;
//sprite当前坐标的y值,如果在初始化时,即为初始坐标y值
 FLOAT fVelX;
//sprite在x轴上的速度
 FLOAT fVelY;
//sprite在y轴上的速度
};

CDisplay* g_pDisplay = NULL;
/*CDisplay就是ddutil.h(我们又新加入的目录中的)中定义的类,用于处理表面之间的拷贝翻页等操作的类,再次定义一个全局变量,用于以后对指向的表面之间进行操作*/

CSurface* g_pBackSurface = NULL;
/* CSurface也是ddutil.h头文件中定义的类,用于对表面本身进行操作,如设置色彩键码,在此定义的是背景图画指针*/

CSurface* g_pLogoSurface = NULL;
/*子画面图画指针*/

CSurface* g_pTextSurface = NULL;
/*背景文本指针*/

BOOL g_bActive = FALSE;
/*定义一个bool形变量,起到一个开关的作用,对程序流程进行控制*/

DWORD g_dwLastTick;
/*用于记录最后一次的系统时间*/

SPRITE_STRUCT g_Sprite[NUM_SPRITES];
/*定义多个子画面,其中包括多个 运动时的属性*/

Function-prototypes

LRESULT CALLBACK MainWndProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam );//主窗口消息处理函数

HRESULT WinInit( HINSTANCE hInst, int nCmdShow, HWND* phWnd, HACCEL* phAccel );
//窗口类设置,注册,并创建窗口

HRESULT InitDirectDraw( HWND hWnd );

VOID FreeDirectDraw();

HRESULT ProcessNextFrame();

VOID UpdateSprite( SPRITE_STRUCT* pSprite, FLOAT fTimeDelta );

HRESULT DisplayFrame();

HRESULT RestoreSurfaces();

WinMain()

Desc: Entry point to the program. Initializes everything and calls

UpdateFrame() when idle from the message pump.

int APIENTRY WinMain( HINSTANCE hInst, HINSTANCE hPrevInst, LPSTR pCmdLine, int nCmdShow )
{
  MSG msg;
 
  HWND hWnd;
 
  HACCEL hAccel;

  ZeroMemory( &g_Sprite, sizeof(SPRITE_STRUCT) * NUM_SPRITES );
//清空内存
 
  srand( GetTickCount()
/*用于获取自windows启动以来经历的时间长度(毫秒)*/ ); //设置随机数随时间变化而变化

  if( FAILED( WinInit( hInst, nCmdShow, &hWnd, &hAccel ) ) )
   return FALSE;

  if( FAILED( InitDirectDraw( hWnd ) ) )
  {
   MessageBox( hWnd, TEXT("DirectDraw init failed. ")
  
   TEXT("The sample will now exit. "), TEXT("DirectDraw Sample"),
  
   MB_ICONERROR | MB_OK );

   return FALSE;
  }

  g_dwLastTick = timeGetTime();
//获得当前系统时间

  while( TRUE )
  {

// Look for messages, if none are found then
// update the state and display it


   if( PeekMessage( &msg, NULL, 0, 0, PM_NOREMOVE ) )
   {
    if( 0 == GetMessage(&msg, NULL, 0, 0 ) )
    {

// WM_QUIT was posted, so exit

     return (int)msg.wParam;
    }

// Translate and dispatch the message

    if( 0 == TranslateAccelerator( hWnd, hAccel, &msg ) )
    {
     TranslateMessage( &msg );
     DispatchMessage( &msg );
    }
   }
   else
   {
    if( g_bActive )
    {

// Move the sprites, blt them to the back buffer, then
// flip or blt the back buffer to the primary buffer

    if( FAILED( ProcessNextFrame() ) /*设置下张页面的子画面的位置*/)
    {
      SAFE_DELETE( g_pDisplay );
     
      MessageBox( hWnd, TEXT("Displaying the next frame failed. ")
     
      TEXT("The sample will now exit. "), TEXT("DirectDraw Sample"),

      MB_ICONERROR | MB_OK );
     
      return FALSE;
     }
    }
    else
    {

// Make sure we go to sleep if we have nothing else to do

     WaitMessage();

// Ignore time spent inactive

     g_dwLastTick = timeGetTime();//获得当前系统时间
    }
   }
  }
}

WinInit()

Desc: Init the window

HRESULT WinInit( HINSTANCE hInst, int nCmdShow, HWND* phWnd, HACCEL* phAccel )
{
  WNDCLASS wc;
  HWND hWnd;
  HACCEL hAccel;

// Register the Window Class 设置窗口类

  wc.lpszClassName = TEXT("FullScreenMode");

  wc.lpfnWndProc = MainWndProc;

  wc.style = CS_VREDRAW | CS_HREDRAW;

  wc.hInstance = hInst;

  wc.hIcon = LoadIcon( hInst, MAKEINTRESOURCE(IDI_MAIN) );

  wc.hCursor = LoadCursor( NULL, IDC_ARROW );

  wc.hbrBackground = (HBRUSH) (COLOR_WINDOW + 1);

  wc.lpszMenuName = NULL;

  wc.cbClsExtra = 0;

  wc.cbWndExtra = 0;

  if( RegisterClass( &wc ) == 0
/*注册窗口类*/ )
   return E_FAIL;

// Load keyboard accelerators

  hAccel = LoadAccelerators( hInst, MAKEINTRESOURCE(IDR_MAIN_ACCEL) );

// Create and show the main window

  hWnd = CreateWindowEx( 0, TEXT("FullScreenMode"), TEXT("DirectDraw FullScreenMode Sample"),

  WS_POPUP, CW_USEDEFAULT, CW_USEDEFAULT,

  CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInst, NULL );

  if( hWnd == NULL )
   return E_FAIL;

  ShowWindow( hWnd, nCmdShow );

  UpdateWindow( hWnd );

  *phWnd = hWnd;

  *phAccel = hAccel;

  return S_OK;
}

InitDirectDraw()

Desc: Create the DirectDraw object, and init the surfaces

HRESULT InitDirectDraw( HWND hWnd )
{
  HRESULT hr;
//接受返回值,其实是long型变量

  LPDIRECTDRAWPALETTE pDDPal = NULL;
//定义程序中的调色板

  int iSprite;
//定义与sprite个数有关的计数器

  g_pDisplay = new CDisplay();
//动态开辟一个CDisplay类

  if( FAILED( hr = g_pDisplay->CreateFullScreenDisplay( hWnd, SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP ) ) )
//设置程序为全屏,并且g_pDisplay就为后备缓冲区表面的句柄,即指向后备缓冲区表面的指针。
  {
   MessageBox( hWnd, TEXT("This display card does not support 1024x768x8. "),
  
   TEXT("DirectDraw Sample"), MB_ICONERROR | MB_OK );
  
   return hr;
  }

// Create and set the palette when in palettized color

  if( FAILED( hr = g_pDisplay->CreatePaletteFromBitmap( &pDDPal, MAKEINTRESOURCE( IDB_DIRECTX ) ) ) )
//顾名思义,就是从bmp图片中获得调色板值,并赋值在pDDPal结构指针中。
   return hr;
 
  if( FAILED( hr = g_pDisplay->SetPalette( pDDPal ) ) )
//用刚才从IDB_DIRECTX中获得的调色板制来设置程序调色板
   return hr;

  SAFE_RELEASE( pDDPal );
//释放指针

// Create a surface, and draw a bitmap resource on it.
// 用IDB_DIRECTX图片创建一个表面,并用g_pLogoSurface指向这个表面

 
  if( FAILED( hr = g_pDisplay->CreateSurfaceFromBitmap( &g_pLogoSurface, MAKEINTRESOURCE( IDB_DIRECTX ), SPRITE_DIAMETER, SPRITE_DIAMETER ) ) )
   return hr;

  if( FAILED( hr = g_pDisplay->CreateSurfaceFromBitmap( &g_pBackSurface, MAKEINTRESOURCE( IDB_WINXP ), SCREEN_WIDTH, SCREEN_HEIGHT ) ) )
   return hr;

// Create a surface, and draw text to it.
//创建文本表面

  if( FAILED( hr = g_pDisplay->CreateSurfaceFromText( &g_pTextSurface, NULL, HELPTEXT, RGB(0,0,0), RGB(255, 255, 0) ) ) )
   return hr;

// Set the color key for the logo sprite to black
//设置色彩键码为黑色,0代表黑色,这样在表面的拷贝过程中黑色像素的点将不会被拷贝


  if( FAILED( hr = g_pLogoSurface->SetColorKey( 0 ) ) )
   return hr;

  if( FAILED( hr = g_pTextSurface->SetColorKey( 0 ) ) )
   return hr;

// Init all the sprites. All of these sprites look the same,
// using the g_pDDSLogo surface.


  for( iSprite = 0; iSprite < NUM_SPRITES; iSprite++ )
  {

// Set the sprite's position and velocity
// 设置这些 sprite(小怪物)的初始坐标随机产生
 

   g_Sprite[iSprite].fPosX = (float) (rand() % SCREEN_WIDTH);
   g_Sprite[iSprite].fPosY = (float) (rand() % SCREEN_HEIGHT);

// 速度也随机产生

   g_Sprite[iSprite].fVelX = 500.0f * rand() / RAND_MAX - 250.0f;
   g_Sprite[iSprite].fVelY = 500.0f * rand() / RAND_MAX - 250.0f;
  }
  return S_OK;
}

FreeDirectDraw()

Release all the DirectDraw objects 释放所有指针。

VOID FreeDirectDraw()
{
  SAFE_DELETE( g_pBackSurface );
  SAFE_DELETE( g_pLogoSurface );
  SAFE_DELETE( g_pTextSurface );
  SAFE_DELETE( g_pDisplay );
}

MainWndProc()

Desc: The main window procedure

LRESULT CALLBACK MainWndProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam )
{
  switch (msg)
  {
   case WM_COMMAND:
   switch( LOWORD(wParam) )
   {
    case IDM_EXIT:

// Received key/menu command to exit app
 
    PostMessage( hWnd, WM_CLOSE, 0, 0 );
 
    return 0L;
   }
   break; // Continue with default processing

   case WM_SETCURSOR:

// Hide the cursor in fullscreen
 
   SetCursor( NULL );

   return TRUE;

   case WM_SIZE:

// Check to see if we are losing our window...

   if( SIZE_MAXHIDE==wParam || SIZE_MINIMIZED==wParam )
    g_bActive = FALSE;
   else
    g_bActive = TRUE;
  
   if( g_pDisplay )
    g_pDisplay->UpdateBounds();

   break;

   case WM_EXITMENULOOP:

// Ignore time spent in menu

   g_dwLastTick = timeGetTime();

   break;

   case WM_EXITSIZEMOVE:

// Ignore time spent resizing

   g_dwLastTick = timeGetTime();

   break;

   case WM_MOVE:

   if( g_pDisplay )
    g_pDisplay->UpdateBounds();

   break;

   case WM_SYSCOMMAND:

// Prevent moving/sizing and power loss in fullscreen mode

   switch( wParam )
   {
    case SC_MOVE:

    case SC_SIZE:

    case SC_MAXIMIZE:

    case SC_MONITORPOWER:

    return TRUE;
   }

   break;

   case WM_DESTROY:

// Cleanup and close the app

   FreeDirectDraw();

   PostQuitMessage( 0 );

   return 0L;
  }
 
  return DefWindowProc(hWnd, msg, wParam, lParam);
}

ProcessNextFrame()

Desc: Move the sprites, blt them to the back buffer, then

flips the back buffer to the primary buffer

HRESULT ProcessNextFrame()
{
  HRESULT hr;

// Figure how much time has passed since the last time

  DWORD dwCurrTick = timeGetTime();
//get current time 获得当前时间
  DWORD dwTickDiff = dwCurrTick - g_dwLastTick;
//the difference between current-time (dwCurrTick) and last time (g_dwLastTick)

//计算当前时间 (dwCurrTick) 与最后一次时间 (g_dwLastTick) 的差值
// Don't update if no time has passed


  if( dwTickDiff == 0 )
//如果时间差值为0,即时间没有变化,则不更新屏幕,而返回
   return S_OK;

//如果程序运行到这里,而没有在前面返回,则说明时间有变化,则下面将要更新屏幕

  g_dwLastTick = dwCurrTick;
//使最后时间=当前时间

// Move the sprites according to how much time has passed
//根据时间的变化来移动子画面,即移动sprites

  for( int iSprite = 0; iSprite < NUM_SPRITES; iSprite++ )
   UpdateSprite( &g_Sprite[ iSprite ], dwTickDiff / 1000.0f );

// Display the sprites on the screen

  if( FAILED( hr = DisplayFrame() ) )
  {
   if( hr != DDERR_SURFACELOST )
    return hr;

// The surfaces were lost so restore them

   RestoreSurfaces();
  }

  return S_OK;
}

UpdateSprite()

Desc: Move the sprite around and make it bounce based on how much time has passed ,此函数属于动画的关键算法,就是控制spirte如何移动

VOID UpdateSprite( SPRITE_STRUCT* pSprite, FLOAT fTimeDelta )
{

// Update the sprite position

  pSprite->fPosX += pSprite->fVelX * fTimeDelta;
  pSprite->fPosY += pSprite->fVelY * fTimeDelta;

// Clip the position, and bounce if it hits the edge

  if( pSprite->fPosX < 0.0f )
  {
   pSprite->fPosX = 0;
   pSprite->fVelX = -pSprite->fVelX;
  }
 
  if( pSprite->fPosX >= SCREEN_WIDTH - SPRITE_DIAMETER )
  {
   pSprite->fPosX = SCREEN_WIDTH - 1 - SPRITE_DIAMETER;
   pSprite->fVelX = -pSprite->fVelX;
  }
 
  if( pSprite->fPosY < 0 )
  {
   pSprite->fPosY = 0;
   pSprite->fVelY = -pSprite->fVelY;
  }

  if( pSprite->fPosY > SCREEN_HEIGHT - SPRITE_DIAMETER )
  {
   pSprite->fPosY = SCREEN_HEIGHT - 1 - SPRITE_DIAMETER;
   pSprite->fVelY = -pSprite->fVelY;
  }
}

DisplayFrame()

Desc: Blts a the sprites to the back buffer, then flips the back buffer onto the primary buffer.

HRESULT DisplayFrame()
{
  HRESULT hr;

// Fill the back buffer with black, ignoring errors until the flip

  g_pDisplay->Clear( 0 );
//清空后备缓冲区表面

// Blt the help text on the backbuffer, ignoring errors until the flip
//将g_pBackSurface所指向的图片拷贝到后备缓冲区表面


  g_pDisplay->Blt( 0, 0, g_pBackSurface, NULL );

//将g_pTextSurface所指向的文本拷贝到后备缓冲区表面

  g_pDisplay->Blt( 10, 10, g_pTextSurface, NULL );

// Blt all the sprites onto the back buffer using color keying,
// ignoring errors until the flip. Note that all of these sprites
// use the same DirectDraw surface.
//将所有的spirits拷贝到后备缓冲区表面,这里要注意拷贝顺序,后拷贝上的画面会压盖在先拷贝的画面上


  for( int iSprite = 0; iSprite < NUM_SPRITES; iSprite++ )
  {
   g_pDisplay->Blt( (DWORD)g_Sprite[iSprite].fPosX,(DWORD)g_Sprite[iSprite].fPosY,g_pLogoSurface, NULL );
  }

// We are in fullscreen mode, so perform a flip and return
// any errors like DDERR_SURFACELOST
//最关键的地方在这里,请看下面的语句,只要我们一执行翻页操作,就可以将改动了的图像了显示在屏幕上了


  if( FAILED( hr = g_pDisplay->Present()
/*翻页操作*/) )
   return hr;

  return S_OK;
}

RestoreSurfaces()

Desc: Restore all the surfaces, and redraw the sprite surfaces.

HRESULT RestoreSurfaces()
{
  HRESULT hr;

  LPDIRECTDRAWPALETTE pDDPal = NULL;

  if( FAILED( hr = g_pDisplay->GetDirectDraw()->RestoreAllSurfaces() ) )
   return hr;

// No need to re-create the surface, just re-draw it.

  if( FAILED( hr = g_pTextSurface->DrawText( NULL, HELPTEXT, 0, 0, RGB(0,0,0), RGB(255, 255, 0) ) ) )
   return hr;

// We need to release and re-load, and set the palette again to
// redraw the bitmap on the surface. Otherwise, GDI will not
// draw the bitmap on the surface with the right palette


  if( FAILED( hr = g_pDisplay->CreatePaletteFromBitmap( &pDDPal, MAKEINTRESOURCE( IDB_DIRECTX ) ) ) )
   return hr;

  if( FAILED( hr = g_pDisplay->SetPalette( pDDPal ) ) )
   return hr;

  SAFE_RELEASE( pDDPal );

// No need to re-create the surface, just re-draw it.

  if( FAILED( hr = g_pLogoSurface->DrawBitmap( MAKEINTRESOURCE( IDB_DIRECTX ),SPRITE_DIAMETER, SPRITE_DIAMETER ) ) )
   return hr;
  return S_OK;
}

好了,我们的程序分析就到这了,我想您现在应该大概了解了DirectDraw程序的大概流程了吧,就是先创建DDraw对象,然后进行相关的设置,然后绘制后备缓冲区页,然后执行翻页操作,这样循环,就会产生很好的动画效果了,其实用DirectDraw编程很简单,说白了其实就是:“几个表面之间拷来拷去”。只不过这其间可是大有文章可作的哟!

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