在DirectX程序中当设备工作在全屏模式下时, 程序用到的很多资源(纹理, 缓冲区等)都保存在一定的显存中, 当我们改变显示模式或切换到其他程序时, 显存可能会被其他程序占用造成原来的数据丢失, 函数可能仍然返回成功但是将无法渲染任何东西, 这种情况也叫做设备丢失. 通常D3D设备在创建成功后是处于可操作状态的, 这种状态下程序可以正常的渲染物体, 但是当窗口程序改变大小时或是全屏程序最小化时, 设备将转变到丢失状态, 丢失状态表现为所有渲染操作的悄然失败, 这意味着即使渲染操作失败所有的渲染方法仍可以返回成功码. 在这种情况下, IDirect3DDevice9::Present 返回错误码 D3DERR_DEVICELOST.
当然会造成设备丢失还有很多的情况, 如切换到其他程序等. 在很多程序中通过禁止ALT+TAB切换程序, 禁止使用Windows健等. 但这样并不能有效解决丢失设备的问题, 而且还会让玩家感觉很郁闷! 当设备丢失以后, 其实函数将可能会返回 D3DERR_DEVICELOST 告诉你设备已丢失, 也可能返回一个响应设备丢失的值, 或者仍返回S_OK, 这种情况也叫悄然失败, 程序不知道是否执行成功. 在D3D中大部分被频繁调用的方法都不会返回任何关于设备丢失的信息. 你可以继续调用那些函数, 但是在D3D内部这些操作将被抛弃, 直到设备被重置到可以操作的状态为止. 以下是一般情况下检测和处理丢失设备的代码:
//********************************************************************
// Filename: Main.cpp
// Author: Chinafish
// Modifier: Chinafish
// Created: 2008-5-13 20:52
// Updated: 2008-5-13 20:52
// QQ: 149200849
// MSN: china_fish@msn.com
// Purpose: Recover from a lost device.
//====================================================================
// Copyright(C) 2004-2008 by Chinafish. All Rights Reserved.
//********************************************************************
#define STRICT
#define WIN32_LEAN_AND_MEAN
#include "windows.h"
// Link D3D
#include "d3d9.h"
#pragma comment(lib, "d3d9.lib")
#define Release_Safe(p){if(p!=NULL) p->Release();}
#define WINDOW_TITLE "www.csinx.org - Lost Device (DX9+VC7)"
#define WINDOW_WIDTH 800
#define WINDOW_HEIGHT 600
//-----------------------------------------------------------------------------
// GLOBALS
//-----------------------------------------------------------------------------
HWND g_hWnd = NULL;
LPDIRECT3D9 g_pD3D = NULL;
LPDIRECT3DDEVICE9 g_pd3dDevice = NULL;
D3DPRESENT_PARAMETERS g_d3dpp;
bool g_bDeviceLost = false;
//-----------------------------------------------------------------------------
// PROTOTYPES
//-----------------------------------------------------------------------------
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,LPSTR lpCmdLine, int nCmdShow);
LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
void ReInitD3D();
HRESULT RestoreDeviceObjects();
HRESULT InvalidateDeviceObjects();
void ShutDown(void);
void Render(void);
//-----------------------------------------------------------------------------
// Name: WinMain()
// Desc: The application's entry point
//-----------------------------------------------------------------------------
int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow )
{
WNDCLASSEX winClass;
MSG uMsg;
memset(&uMsg,0,sizeof(uMsg));
winClass.lpszClassName = "CLASS_LOSTDEVICE";
winClass.cbSize = sizeof(WNDCLASSEX);
winClass.style = CS_HREDRAW | CS_VREDRAW;
winClass.lpfnWndProc = WindowProc;
winClass.hInstance = hInstance;
winClass.hIcon = LoadIcon(hInstance, (LPCTSTR)NULL);
winClass.hIconSm = LoadIcon(hInstance, (LPCTSTR)NULL);
winClass.hCursor = LoadCursor(NULL, IDC_ARROW);
winClass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
winClass.lpszMenuName = NULL;
winClass.cbClsExtra = 0;
winClass.cbWndExtra = 0;
if( !RegisterClassEx(&winClass) )
return E_FAIL;
g_hWnd = CreateWindowEx( NULL, "CLASS_LOSTDEVICE",
WINDOW_TITLE,
WS_EX_TOPMOST, 0, 0,
WINDOW_WIDTH, WINDOW_HEIGHT, NULL, NULL,
hInstance, NULL );
if( g_hWnd == NULL )
return E_FAIL;
// Adjust window
RECT rect = { 0, 0, WINDOW_WIDTH, WINDOW_HEIGHT };
AdjustWindowRect( &rect, GetWindowLong( g_hWnd, GWL_STYLE ), FALSE );
SetWindowPos( g_hWnd, 0, 0, 0, rect.right - rect.left, rect.bottom - rect.top,
SWP_NOZORDER | SWP_NOMOVE );
ShowWindow( g_hWnd, nCmdShow );
UpdateWindow( g_hWnd );
// Init or reset D3D
ReInitD3D();
while( uMsg.message != WM_QUIT )
{
if( PeekMessage( &uMsg, NULL, 0, 0, PM_REMOVE ) )
{
TranslateMessage( &uMsg );
DispatchMessage( &uMsg );
}
else
{
// Render a frame
Render();
}
}
ShutDown();
UnregisterClass( "CLASS_LOSTDEVICE", winClass.hInstance );
return uMsg.wParam;
}
//-----------------------------------------------------------------------------
// Name: WindowProc()
// Desc: The window's message handler
//-----------------------------------------------------------------------------
LRESULT CALLBACK WindowProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam )
{
switch( msg )
{
case WM_KEYDOWN:
{
switch( wParam )
{
case VK_ESCAPE:
PostQuitMessage(0);
break;
}
}
break;
case WM_CLOSE:
{
PostQuitMessage(0);
}
case WM_DESTROY:
{
PostQuitMessage(0);
}
break;
default:
{
return DefWindowProc( hWnd, msg, wParam, lParam );
}
break;
}
return 0;
}
//-----------------------------------------------------------------------------
// Name: ReInitD3D()
// Desc: This function will only be called once during the application's
// initialization phase. Therefore, it can't contain any resources that
// need to be restored every time the Direct3D device is lost or the
// window is resized.
//-----------------------------------------------------------------------------
void ReInitD3D()
{
// Create D3D
g_pD3D = Direct3DCreate9(D3D_SDK_VERSION);
if(!g_pD3D)
{
MessageBox(NULL, "Direct3DCreate9() - Failed!", "Error", NULL);
return;
}
D3DDISPLAYMODE d3ddm;
g_pD3D->GetAdapterDisplayMode( D3DADAPTER_DEFAULT, &d3ddm );
ZeroMemory( &g_d3dpp, sizeof(g_d3dpp) );
g_d3dpp.Windowed = TRUE;
g_d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
g_d3dpp.BackBufferFormat = d3ddm.Format;
g_d3dpp.EnableAutoDepthStencil = TRUE;
g_d3dpp.AutoDepthStencilFormat = D3DFMT_D16;
g_d3dpp.PresentationInterval = D3DPRESENT_INTERVAL_IMMEDIATE;
g_pD3D->CreateDevice( D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL,
g_hWnd, D3DCREATE_SOFTWARE_VERTEXPROCESSING,
&g_d3dpp, &g_pd3dDevice );
if(!g_pd3dDevice)
{
return;
}
// Any resources or settings that need to be restored after losing the
// DirectX device should probably be grouped together into one function so
// they can be re-created or reset in one call.
RestoreDeviceObjects();
}
//-----------------------------------------------------------------------------
// Name: RestoreDeviceObjects()
// Desc: You are encouraged to develop applications with a single code path to
// respond to device loss. This code path is likely to be similar, if not
// identical, to the code path taken to initialize the device at startup.
//-----------------------------------------------------------------------------
HRESULT RestoreDeviceObjects()
{
// Set some important state settings...
// Set Transform
// Create a texture object, mesh object, buffer etc.
return S_OK;
}
//-----------------------------------------------------------------------------
// Name: InvalidateDeviceObjects()
// Desc: If the lost device can be restored, the application prepares the
// device by destroying all video-memory resources and any
// swap chains. This is typically accomplished by using the SAFE_RELEASE
// macro.
//-----------------------------------------------------------------------------
HRESULT InvalidateDeviceObjects()
{
// Invalidate the texture object, mesh object, buffer etc.
return S_OK;
}
//-----------------------------------------------------------------------------
// Name: ShutDown()
// Desc: Release all
//-----------------------------------------------------------------------------
void ShutDown( void )
{
InvalidateDeviceObjects();
Release_Safe(g_pd3dDevice);
Release_Safe(g_pD3D);
}
//-----------------------------------------------------------------------------
// Name: Render()
// Desc: Render something you want
//-----------------------------------------------------------------------------
void Render( void )
{
HRESULT hr;
if( g_bDeviceLost == true )
{
// Yield some CPU time to other processes
Sleep( 100 ); // 100 milliseconds
// Check for lost device
hr = g_pd3dDevice->TestCooperativeLevel();
if( FAILED( hr ) )
{
// The device has been lost but cannot be reset at this time.
// Therefore, rendering is not possible and we'll have to return
// and try again at a later time.
if( hr == D3DERR_DEVICELOST )
return;
// The device has been lost but it can be reset at this time.
if( hr == D3DERR_DEVICENOTRESET )
{
// If the device can be restored, the application prepares the
// device by destroying all video-memory resources and any swap chains.
InvalidateDeviceObjects();
// Reset is the only method that has an effect when a device
// is lost, and is the only method by which an application can
// change the device from a lost to an operational state.
// Reset will fail unless the application releases all
// resources that are allocated in D3DPOOL_DEFAULT, including
// those created by the IDirect3DDevice9::CreateRenderTarget
// and IDirect3DDevice9::CreateDepthStencilSurface methods.
hr = g_pd3dDevice->Reset( &g_d3dpp );
if( FAILED(hr ) )
return;
//
// Finally, a lost device must re-create resources (including
// video memory resources) after it has been reset.
//
RestoreDeviceObjects();
}
return;
}
g_bDeviceLost = false;
}
// Clear screen with D3DCOLOR_XRGB(255, 0, 255)
g_pd3dDevice->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(255, 0, 255), 1.0f, 0);
g_pd3dDevice->BeginScene();
// Render geometry here...
g_pd3dDevice->EndScene();
//
// If Present fails with D3DERR_DEVICELOST the application needs to be
// notified so it cleanup resources and reset the device.
//
hr = g_pd3dDevice->Present( NULL, NULL, NULL, NULL );
if( hr == D3DERR_DEVICELOST )
{
g_bDeviceLost = true;
}
}
在以代码中我们定义恢复和销毁程序的函数, 只是在 IDirect3DDevice9::Present 返回错误码 D3DERR_DEVICELOST 时才去检测和恢复丢失的设备及重建程序资源. 我们可以通过 IDirect3DDevice9::TestCooperativeLevel 的返回值来确定是否设备已丢失, 如果设备已丢失并且无法重置, 我们就要等待设备可以重置时, 销毁所有已调用的显存资源和交换链. 然后再调用 IDirect3DDevice9::Reset 方法, 这个方法也是设备丢失以后唯一可以有效的方法, 并且也是用于把丢失的设备重置到可操作状态的唯一方法. 要注意的是你必须释放所有使用 D3DPOOL_DEFAULT 创建的资源, 包括使用 IDirect3DDevice9::CreateRenderTarget 和 IDirect3DDevice9::CreateDepthStencilSurface 方法创建的资源以后才可能成功的重置设备. 最后你必须重新创建所用到的资源包括顶点, 纹理, 状态和变换等. 另外在设备丢失以后除 IDirect3DDevice9::Reset 外, IDirect3DDevice9::ValidateDevice 方法也可以对照单次渲染用硬件验证纹理和渲染状态, 返回D3DERR_DEVICELOST. 当设备丢失时,因为不存在主表面,所以复制操作IDirect3DDevice9::GetFrontBufferData 会失败,返回值为D3DERR_DEVICELOST. 当设备丢失时, IDirect3DDevice9::CreateAdditionalSwapChain 也会因为无法创建后缓存而失败,并返回D3DERR_DEVICELOST. 当设备丢失时, IDirect3DDevice9::Present 因为无法渲染而失败, 返回D3DERR_DEVICELOST.