Programming 2D Games 读书笔记(第四章)

 

示例一:Game Engine Part 1

更加完善游戏的基本流程

Graphics添加了以下几个方法,beginScene和endScene提高绘图,showBackbuffer去掉了clear方法

    // Reset the graphics device.
    HRESULT reset();

    // get functions
    // Return direct3d.
    LP_3D   get3D()             { return direct3d; }

    // Return device3d.
    LP_3DDEVICE get3Ddevice()   { return device3d; }

    // Return handle to device context (window).
    HDC     getDC()             { return GetDC(hwnd); }

    // Test for lost device
    HRESULT getDeviceState();

    //=============================================================================
    // Inline functions for speed. How much more speed? It depends on the game and
    // computer. Improvements of 3 or 4 percent have been observed.
    //=============================================================================

    // Set color used to clear screen
    void setBackColor(COLOR_ARGB c) {backColor = c;}

    //=============================================================================
    // Clear backbuffer and BeginScene()
    //=============================================================================
    HRESULT beginScene() 
    {
        result = E_FAIL;
        if(device3d == NULL)
            return result;
        // clear backbuffer to backColor
        device3d->Clear(0, NULL, D3DCLEAR_TARGET, backColor, 1.0F, 0);
        result = device3d->BeginScene();          // begin scene for drawing
        return result;
    }

    //=============================================================================
    // EndScene()
    //=============================================================================
    HRESULT endScene() 
    {
        result = E_FAIL;
        if(device3d)
            result = device3d->EndScene();
        return result;
    }

IDirect3DDevice9::TestCooperativeLevel。因此在设备丢失之后，你应该停止整个游戏循环，而通过反复调用

IDirect3DDevice9::TestCooperativeLevel判断设备是否可用。

//=============================================================================
// Test for lost device
//=============================================================================
HRESULT Graphics::getDeviceState()
{ 
    result = E_FAIL;    // default to fail, replace on success
    if (device3d == NULL)
        return  result;
    result = device3d->TestCooperativeLevel(); 
    return result;
}

Game类

现在Graphics类属于Game类包装

Game类主要流程:

1.初始化

//=============================================================================
// Initializes the game
// throws GameError on error
//=============================================================================
void Game::initialize(HWND hw)
{
    hwnd = hw;                                  // save window handle

    // initialize graphics
    graphics = new Graphics();
    // throws GameError
    graphics->initialize(hwnd, GAME_WIDTH, GAME_HEIGHT, FULLSCREEN);

    // initialize input, do not capture mouse
    input->initialize(hwnd, false);             // throws GameError

    // attempt to set up high resolution timer
    if(QueryPerformanceFrequency(&timerFreq) == false)
        throw(GameError(gameErrorNS::FATAL_ERROR, "Error initializing high resolution timer"));

    QueryPerformanceCounter(&timeStart);        // get starting time

    initialized = true;
}

2.messageHandler方法处理消息流程,由Input类接入

3.renderGame

属于Game呈现的主流程,子类重写render方法

//=============================================================================
// Render game items
//=============================================================================
void Game::renderGame()
{
    //start rendering
    if (SUCCEEDED(graphics->beginScene()))
    {
        // render is a pure virtual function that must be provided in the
        // inheriting class.
        render();               // call render in derived class

        //stop rendering
        graphics->endScene();
    }
    handleLostGraphicsDevice();

    //display the back buffer on the screen
    graphics->showBackbuffer();
}

4.子类Spacewar继承自Game

// Programming 2D Games
// Copyright (c) 2011 by: 
// Charles Kelly
// Game Engine Part 1
// Chapter 4 spacewar.cpp v1.0
// Spacewar is the class we create.

#include "spaceWar.h"

//=============================================================================
// Constructor
//=============================================================================
Spacewar::Spacewar()
{}

//=============================================================================
// Destructor
//=============================================================================
Spacewar::~Spacewar()
{
    releaseAll();           // call onLostDevice() for every graphics item
}

//=============================================================================
// Initializes the game
// Throws GameError on error
//=============================================================================
void Spacewar::initialize(HWND hwnd)
{
    Game::initialize(hwnd); // throws GameError

    return;
}

//=============================================================================
// Update all game items
//=============================================================================
void Spacewar::update()
{}

//=============================================================================
// Artificial Intelligence
//=============================================================================
void Spacewar::ai()
{}

//=============================================================================
// Handle collisions
//=============================================================================
void Spacewar::collisions()
{}

//=============================================================================
// Render game items
//=============================================================================
void Spacewar::render()
{}

//=============================================================================
// The graphics device was lost.
// Release all reserved video memory so graphics device may be reset.
//=============================================================================
void Spacewar::releaseAll()
{
    Game::releaseAll();
    return;
}

//=============================================================================
// The grahics device has been reset.
// Recreate all surfaces.
//=============================================================================
void Spacewar::resetAll()
{
    Game::resetAll();
    return;
}

以上是一个基本游戏的一个主流程

// Game pointer
Spacewar *game = NULL;
HWND hwnd = NULL;

//=============================================================================
// Starting point for a Windows application
//=============================================================================
int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    LPSTR lpCmdLine, int nCmdShow)
{
    // Check for memory leak if debug build
    #if defined(DEBUG) | defined(_DEBUG)
        _CrtSetDbgFlag( _CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF );
    #endif

    MSG msg;

    // Create the game, sets up message handler
    game = new Spacewar;

    // Create the window
    if (!CreateMainWindow(hwnd, hInstance, nCmdShow))
        return 1;

    try{
        game->initialize(hwnd);     // throws GameError

        // main message loop
        int done = 0;
        while (!done)
        {
            if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) 
            {
                // look for quit message
                if (msg.message == WM_QUIT)
                    done = 1;

                // decode and pass messages on to WinProc
                TranslateMessage(&msg);
                DispatchMessage(&msg);
            } else
                game->run(hwnd);    // run the game loop
        }
        SAFE_DELETE (game);     // free memory before exit
        return msg.wParam;
    }
    catch(const GameError &err)
    {
        game->deleteAll();
        DestroyWindow(hwnd);
        MessageBox(NULL, err.getMessage(), "Error", MB_OK);
    }
    catch(...)
    {
        game->deleteAll();
        DestroyWindow(hwnd);
        MessageBox(NULL, "Unknown error occured in game.", "Error", MB_OK);
    }

    SAFE_DELETE (game);     // free memory before exit
    return 0;
}

//=============================================================================
// window event callback function
//=============================================================================
LRESULT WINAPI WinProc( HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam )
{
    return (game->messageHandler(hwnd, msg, wParam, lParam));
}