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SDL源代碼分析系列文章列表:
SDL2源代碼分析5:更新紋理(SDL_UpdateTexture())
SDL2源代碼分析6:複製到渲染器(SDL_RenderCopy())
SDL2源代碼分析7:顯示(SDL_RenderPresent())
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上一篇文章分析了SDL中創建窗口的函數SDL_CreateWindow()。這篇文章繼續分析SDL的源代碼。本文分析SDL的渲染器(SDL_Renderer)。
SDL播放視頻的代碼流程如下所示。
初始化:SDL_Init(): 初始化SDL。循環渲染數據:
SDL_CreateWindow(): 創建窗口(Window)。
SDL_CreateRenderer(): 基於窗口創建渲染器(Render)。
SDL_CreateTexture(): 創建紋理(Texture)。
SDL_UpdateTexture(): 設置紋理的數據。
SDL_RenderCopy(): 紋理複製給渲染器。SDL_RenderPresent(): 顯示。
上篇文章分析了該流程中的第2個函數SDL_CreateWindow()。本文繼續分析該流程中的第3個函數SDL_CreateRenderer()。
SDL_Renderer
SDL_Renderer結構體定義了一個SDL2中的渲染器。如果直接使用SDL2編譯好的SDK的話,是看不到它的內部結構的。有關它的定義在頭文件中只有一行代碼,如下所示。
- /**
- * \brief A structure representing rendering state
- */
- struct SDL_Renderer;
- typedef struct SDL_Renderer SDL_Renderer;
在源代碼工程中可以看到SDL_Renderer的定義,位於render\SDL_sysrender.h文件中。它的定義如下。
- /* Define the SDL renderer structure */
- struct SDL_Renderer
- {
- const void *magic;
- void (*WindowEvent) (SDL_Renderer * renderer, const SDL_WindowEvent *event);
- int (*GetOutputSize) (SDL_Renderer * renderer, int *w, int *h);
- int (*CreateTexture) (SDL_Renderer * renderer, SDL_Texture * texture);
- int (*SetTextureColorMod) (SDL_Renderer * renderer,
- SDL_Texture * texture);
- int (*SetTextureAlphaMod) (SDL_Renderer * renderer,
- SDL_Texture * texture);
- int (*SetTextureBlendMode) (SDL_Renderer * renderer,
- SDL_Texture * texture);
- int (*UpdateTexture) (SDL_Renderer * renderer, SDL_Texture * texture,
- const SDL_Rect * rect, const void *pixels,
- int pitch);
- int (*UpdateTextureYUV) (SDL_Renderer * renderer, SDL_Texture * texture,
- const SDL_Rect * rect,
- const Uint8 *Yplane, int Ypitch,
- const Uint8 *Uplane, int Upitch,
- const Uint8 *Vplane, int Vpitch);
- int (*LockTexture) (SDL_Renderer * renderer, SDL_Texture * texture,
- const SDL_Rect * rect, void **pixels, int *pitch);
- void (*UnlockTexture) (SDL_Renderer * renderer, SDL_Texture * texture);
- int (*SetRenderTarget) (SDL_Renderer * renderer, SDL_Texture * texture);
- int (*UpdateViewport) (SDL_Renderer * renderer);
- int (*UpdateClipRect) (SDL_Renderer * renderer);
- int (*RenderClear) (SDL_Renderer * renderer);
- int (*RenderDrawPoints) (SDL_Renderer * renderer, const SDL_FPoint * points,
- int count);
- int (*RenderDrawLines) (SDL_Renderer * renderer, const SDL_FPoint * points,
- int count);
- int (*RenderFillRects) (SDL_Renderer * renderer, const SDL_FRect * rects,
- int count);
- int (*RenderCopy) (SDL_Renderer * renderer, SDL_Texture * texture,
- const SDL_Rect * srcrect, const SDL_FRect * dstrect);
- int (*RenderCopyEx) (SDL_Renderer * renderer, SDL_Texture * texture,
- const SDL_Rect * srcquad, const SDL_FRect * dstrect,
- const double angle, const SDL_FPoint *center, const SDL_RendererFlip flip);
- int (*RenderReadPixels) (SDL_Renderer * renderer, const SDL_Rect * rect,
- Uint32 format, void * pixels, int pitch);
- void (*RenderPresent) (SDL_Renderer * renderer);
- void (*DestroyTexture) (SDL_Renderer * renderer, SDL_Texture * texture);
- void (*DestroyRenderer) (SDL_Renderer * renderer);
- int (*GL_BindTexture) (SDL_Renderer * renderer, SDL_Texture *texture, float *texw, float *texh);
- int (*GL_UnbindTexture) (SDL_Renderer * renderer, SDL_Texture *texture);
- /* The current renderer info */
- SDL_RendererInfo info;
- /* The window associated with the renderer */
- SDL_Window *window;
- SDL_bool hidden;
- /* The logical resolution for rendering */
- int logical_w;
- int logical_h;
- int logical_w_backup;
- int logical_h_backup;
- /* The drawable area within the window */
- SDL_Rect viewport;
- SDL_Rect viewport_backup;
- /* The clip rectangle within the window */
- SDL_Rect clip_rect;
- SDL_Rect clip_rect_backup;
- /* The render output coordinate scale */
- SDL_FPoint scale;
- SDL_FPoint scale_backup;
- /* The list of textures */
- SDL_Texture *textures;
- SDL_Texture *target;
- Uint8 r, g, b, a; /**< Color for drawing operations values */
- SDL_BlendMode blendMode; /**< The drawing blend mode */
- void *driverdata;
- };
通過代碼可以看出其中包含了一個“渲染器”應該包含的各種屬性。這個結構體中的各個變量還沒有深入研究,暫不詳細分析。下面來看看如何創建這個SDL_Renderer。
SDL_CreateRenderer()
函數簡介
SDL中使用SDL_CreateRenderer()基於窗口創建渲染器。SDL_CreateRenderer()原型如下。- SDL_Renderer * SDLCALL SDL_CreateRenderer(SDL_Window * window,
- int index, Uint32 flags);
參數含義如下。
window : 渲染的目標窗口。
index :打算初始化的渲染設備的索引。設置“-1”則初始化默認的渲染設備。
flags :支持以下值(位於SDL_RendererFlags定義中)
SDL_RENDERER_SOFTWARE :使用軟件渲染SDL_RENDERER_ACCELERATED :使用硬件加速
SDL_RENDERER_PRESENTVSYNC:和顯示器的刷新率同步SDL_RENDERER_TARGETTEXTURE :不太懂
返回創建完成的渲染器的ID。如果創建失敗則返回NULL。
函數調用關係圖
SDL_CreateRenderer()關鍵函數的調用關係可以用下圖表示。
上述圖片不太清晰,相冊裏面上傳了一份原始的大圖片:
http://my.csdn.net/leixiaohua1020/album/detail/1793385
源碼分析
SDL_CreateRenderer()的源代碼位於render\SDL_render.c中,如下所示。
- SDL_Renderer * SDL_CreateRenderer(SDL_Window * window, int index, Uint32 flags)
- {
- #if !SDL_RENDER_DISABLED
- SDL_Renderer *renderer = NULL;
- int n = SDL_GetNumRenderDrivers();
- const char *hint;
- if (!window) {
- SDL_SetError("Invalid window");
- return NULL;
- }
- if (SDL_GetRenderer(window)) {
- SDL_SetError("Renderer already associated with window");
- return NULL;
- }
- hint = SDL_GetHint(SDL_HINT_RENDER_VSYNC);
- if (hint) {
- if (*hint == '0') {
- flags &= ~SDL_RENDERER_PRESENTVSYNC;
- } else {
- flags |= SDL_RENDERER_PRESENTVSYNC;
- }
- }
- if (index < 0) {
- hint = SDL_GetHint(SDL_HINT_RENDER_DRIVER);
- if (hint) {
- for (index = 0; index < n; ++index) {
- const SDL_RenderDriver *driver = render_drivers[index];
- if (SDL_strcasecmp(hint, driver->info.name) == 0) {
- /* Create a new renderer instance */
- renderer = driver->CreateRenderer(window, flags);
- break;
- }
- }
- }
- if (!renderer) {
- for (index = 0; index < n; ++index) {
- const SDL_RenderDriver *driver = render_drivers[index];
- if ((driver->info.flags & flags) == flags) {
- /* Create a new renderer instance */
- renderer = driver->CreateRenderer(window, flags);
- if (renderer) {
- /* Yay, we got one! */
- break;
- }
- }
- }
- }
- if (index == n) {
- SDL_SetError("Couldn't find matching render driver");
- return NULL;
- }
- } else {
- if (index >= SDL_GetNumRenderDrivers()) {
- SDL_SetError("index must be -1 or in the range of 0 - %d",
- SDL_GetNumRenderDrivers() - 1);
- return NULL;
- }
- /* Create a new renderer instance */
- renderer = render_drivers[index]->CreateRenderer(window, flags);
- }
- if (renderer) {
- renderer->magic = &renderer_magic;
- renderer->window = window;
- renderer->scale.x = 1.0f;
- renderer->scale.y = 1.0f;
- if (SDL_GetWindowFlags(window) & (SDL_WINDOW_HIDDEN|SDL_WINDOW_MINIMIZED)) {
- renderer->hidden = SDL_TRUE;
- } else {
- renderer->hidden = SDL_FALSE;
- }
- SDL_SetWindowData(window, SDL_WINDOWRENDERDATA, renderer);
- SDL_RenderSetViewport(renderer, NULL);
- SDL_AddEventWatch(SDL_RendererEventWatch, renderer);
- SDL_LogInfo(SDL_LOG_CATEGORY_RENDER,
- "Created renderer: %s", renderer->info.name);
- }
- return renderer;
- #else
- SDL_SetError("SDL not built with rendering support");
- return NULL;
- #endif
- }
SDL_CreateRenderer()中最重要的一個函數就是它調用了SDL_RenderDriver的CreateRenderer()方法。通過該方法可以創建一個渲染器。圍繞着這個方法,包含了一些初始化工作以及一些收尾工作。下面針對這個最核心的函數進行分析。
我們首先來看一下SDL_RenderDriver這個結構體。從字面的意思可以看出它代表了“渲染器的驅動程序”。這個結構體的定義如下。
- /* Define the SDL render driver structure */
- struct SDL_RenderDriver
- {
- SDL_Renderer *(*CreateRenderer) (SDL_Window * window, Uint32 flags);
- /* Info about the renderer capabilities */
- SDL_RendererInfo info;
- };
從代碼中可以看出,這個結構體的成員比較簡單,包含了一個函數指針CreateRenderer()和一個存儲信息的SDL_RendererInfo類型的結構體info。CreateRenderer()是用於創建渲染器的函數,而SDL_RendererInfo則包含了該結構體的一些信息,可以看一下SDL_RendererInfo的定義。
- /**
- * \brief Information on the capabilities of a render driver or context.
- */
- typedef struct SDL_RendererInfo
- {
- const char *name; /**< The name of the renderer */
- Uint32 flags; /**< Supported ::SDL_RendererFlags */
- Uint32 num_texture_formats; /**< The number of available texture formats */
- Uint32 texture_formats[16]; /**< The available texture formats */
- int max_texture_width; /**< The maximimum texture width */
- int max_texture_height; /**< The maximimum texture height */
- } SDL_RendererInfo;
在SDL中有一個全局的SDL_RenderDriver類型的靜態數組render_drivers,其中存儲了SDL支持的所有渲染器。該數組定義如下。
- static const SDL_RenderDriver *render_drivers[] = {
- #if SDL_VIDEO_RENDER_D3D
- &D3D_RenderDriver,
- #endif
- #if SDL_VIDEO_RENDER_D3D11
- &D3D11_RenderDriver,
- #endif
- #if SDL_VIDEO_RENDER_OGL
- &GL_RenderDriver,
- #endif
- #if SDL_VIDEO_RENDER_OGL_ES2
- &GLES2_RenderDriver,
- #endif
- #if SDL_VIDEO_RENDER_OGL_ES
- &GLES_RenderDriver,
- #endif
- #if SDL_VIDEO_RENDER_DIRECTFB
- &DirectFB_RenderDriver,
- #endif
- #if SDL_VIDEO_RENDER_PSP
- &PSP_RenderDriver,
- #endif
- &SW_RenderDriver
- };
從render_drivers數組的定義可以看出,其中包含了Direct3D,OpenGL,OpenGL ES等各種渲染器的驅動程序。我們可以選擇幾個看一下。
例如Direct3D的渲染器驅動程序D3D_RenderDriver的定義如下(位於render\direct3d\SDL_render_d3d.c)。
- SDL_RenderDriver D3D_RenderDriver = {
- D3D_CreateRenderer,
- {
- "direct3d",
- (SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC | SDL_RENDERER_TARGETTEXTURE),
- 1,
- {SDL_PIXELFORMAT_ARGB8888},
- 0,
- 0}
- };
可以看出創建Direct3D渲染器的函數是D3D_CreateRenderer()。
OpenGL的渲染器驅動程序GL_RenderDriver的定義如下(位於render\opengl\SDL_render_gl.c)。
- SDL_RenderDriver GL_RenderDriver = {
- GL_CreateRenderer,
- {
- "opengl",
- (SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC | SDL_RENDERER_TARGETTEXTURE),
- 1,
- {SDL_PIXELFORMAT_ARGB8888},
- 0,
- 0}
- };
可以看出創建OpenGL渲染器的函數是GL_CreateRenderer()。
軟件渲染器驅動程序SW_RenderDriver的定義如下(位於render\software\SDL_render_sw.c)。
- SDL_RenderDriver SW_RenderDriver = {
- SW_CreateRenderer,
- {
- "software",
- SDL_RENDERER_SOFTWARE | SDL_RENDERER_TARGETTEXTURE,
- 8,
- {
- SDL_PIXELFORMAT_RGB555,
- SDL_PIXELFORMAT_RGB565,
- SDL_PIXELFORMAT_RGB888,
- SDL_PIXELFORMAT_BGR888,
- SDL_PIXELFORMAT_ARGB8888,
- SDL_PIXELFORMAT_RGBA8888,
- SDL_PIXELFORMAT_ABGR8888,
- SDL_PIXELFORMAT_BGRA8888
- },
- 0,
- 0}
- };
可以看出創建軟件渲染器的函數是SW_CreateRenderer ()。
有關SDL_RenderDriver這個結構體就不再多說了。下面分別看一下Direct3D,OpenGL,Software這三種最常見的渲染器的創建方法。
1. Direct3D
Direct3D 的渲染器在創建函數是D3D_CreateRenderer()。該函數位於render\direct3d\SDL_render_d3d.c文件中。首先看一下它的代碼。
- SDL_Renderer * D3D_CreateRenderer(SDL_Window * window, Uint32 flags)
- {
- SDL_Renderer *renderer;
- D3D_RenderData *data;
- SDL_SysWMinfo windowinfo;
- HRESULT result;
- const char *hint;
- D3DPRESENT_PARAMETERS pparams;
- IDirect3DSwapChain9 *chain;
- D3DCAPS9 caps;
- DWORD device_flags;
- Uint32 window_flags;
- int w, h;
- SDL_DisplayMode fullscreen_mode;
- int displayIndex;
- renderer = (SDL_Renderer *) SDL_calloc(1, sizeof(*renderer));
- if (!renderer) {
- SDL_OutOfMemory();
- return NULL;
- }
- data = (D3D_RenderData *) SDL_calloc(1, sizeof(*data));
- if (!data) {
- SDL_free(renderer);
- SDL_OutOfMemory();
- return NULL;
- }
- if (!D3D_LoadDLL(&data->d3dDLL, &data->d3d)) {
- SDL_free(renderer);
- SDL_free(data);
- SDL_SetError("Unable to create Direct3D interface");
- return NULL;
- }
- renderer->WindowEvent = D3D_WindowEvent;
- renderer->CreateTexture = D3D_CreateTexture;
- renderer->UpdateTexture = D3D_UpdateTexture;
- renderer->UpdateTextureYUV = D3D_UpdateTextureYUV;
- renderer->LockTexture = D3D_LockTexture;
- renderer->UnlockTexture = D3D_UnlockTexture;
- renderer->SetRenderTarget = D3D_SetRenderTarget;
- renderer->UpdateViewport = D3D_UpdateViewport;
- renderer->UpdateClipRect = D3D_UpdateClipRect;
- renderer->RenderClear = D3D_RenderClear;
- renderer->RenderDrawPoints = D3D_RenderDrawPoints;
- renderer->RenderDrawLines = D3D_RenderDrawLines;
- renderer->RenderFillRects = D3D_RenderFillRects;
- renderer->RenderCopy = D3D_RenderCopy;
- renderer->RenderCopyEx = D3D_RenderCopyEx;
- renderer->RenderReadPixels = D3D_RenderReadPixels;
- renderer->RenderPresent = D3D_RenderPresent;
- renderer->DestroyTexture = D3D_DestroyTexture;
- renderer->DestroyRenderer = D3D_DestroyRenderer;
- renderer->info = D3D_RenderDriver.info;
- renderer->info.flags = (SDL_RENDERER_ACCELERATED | SDL_RENDERER_TARGETTEXTURE);
- renderer->driverdata = data;
- SDL_VERSION(&windowinfo.version);
- SDL_GetWindowWMInfo(window, &windowinfo);
- window_flags = SDL_GetWindowFlags(window);
- SDL_GetWindowSize(window, &w, &h);
- SDL_GetWindowDisplayMode(window, &fullscreen_mode);
- SDL_zero(pparams);
- pparams.hDeviceWindow = windowinfo.info.win.window;
- pparams.BackBufferWidth = w;
- pparams.BackBufferHeight = h;
- if (window_flags & SDL_WINDOW_FULLSCREEN) {
- pparams.BackBufferFormat =
- PixelFormatToD3DFMT(fullscreen_mode.format);
- } else {
- pparams.BackBufferFormat = D3DFMT_UNKNOWN;
- }
- pparams.BackBufferCount = 1;
- pparams.SwapEffect = D3DSWAPEFFECT_DISCARD;
- if (window_flags & SDL_WINDOW_FULLSCREEN) {
- if ((window_flags & SDL_WINDOW_FULLSCREEN_DESKTOP) == SDL_WINDOW_FULLSCREEN_DESKTOP) {
- pparams.Windowed = TRUE;
- pparams.FullScreen_RefreshRateInHz = 0;
- } else {
- pparams.Windowed = FALSE;
- pparams.FullScreen_RefreshRateInHz = fullscreen_mode.refresh_rate;
- }
- } else {
- pparams.Windowed = TRUE;
- pparams.FullScreen_RefreshRateInHz = 0;
- }
- if (flags & SDL_RENDERER_PRESENTVSYNC) {
- pparams.PresentationInterval = D3DPRESENT_INTERVAL_ONE;
- } else {
- pparams.PresentationInterval = D3DPRESENT_INTERVAL_IMMEDIATE;
- }
- /* Get the adapter for the display that the window is on */
- displayIndex = SDL_GetWindowDisplayIndex(window);
- data->adapter = SDL_Direct3D9GetAdapterIndex(displayIndex);
- IDirect3D9_GetDeviceCaps(data->d3d, data->adapter, D3DDEVTYPE_HAL, &caps);
- device_flags = D3DCREATE_FPU_PRESERVE;
- if (caps.DevCaps & D3DDEVCAPS_HWTRANSFORMANDLIGHT) {
- device_flags |= D3DCREATE_HARDWARE_VERTEXPROCESSING;
- } else {
- device_flags |= D3DCREATE_SOFTWARE_VERTEXPROCESSING;
- }
- hint = SDL_GetHint(SDL_HINT_RENDER_DIRECT3D_THREADSAFE);
- if (hint && SDL_atoi(hint)) {
- device_flags |= D3DCREATE_MULTITHREADED;
- }
- result = IDirect3D9_CreateDevice(data->d3d, data->adapter,
- D3DDEVTYPE_HAL,
- pparams.hDeviceWindow,
- device_flags,
- &pparams, &data->device);
- if (FAILED(result)) {
- D3D_DestroyRenderer(renderer);
- D3D_SetError("CreateDevice()", result);
- return NULL;
- }
- /* Get presentation parameters to fill info */
- result = IDirect3DDevice9_GetSwapChain(data->device, 0, &chain);
- if (FAILED(result)) {
- D3D_DestroyRenderer(renderer);
- D3D_SetError("GetSwapChain()", result);
- return NULL;
- }
- result = IDirect3DSwapChain9_GetPresentParameters(chain, &pparams);
- if (FAILED(result)) {
- IDirect3DSwapChain9_Release(chain);
- D3D_DestroyRenderer(renderer);
- D3D_SetError("GetPresentParameters()", result);
- return NULL;
- }
- IDirect3DSwapChain9_Release(chain);
- if (pparams.PresentationInterval == D3DPRESENT_INTERVAL_ONE) {
- renderer->info.flags |= SDL_RENDERER_PRESENTVSYNC;
- }
- data->pparams = pparams;
- IDirect3DDevice9_GetDeviceCaps(data->device, &caps);
- renderer->info.max_texture_width = caps.MaxTextureWidth;
- renderer->info.max_texture_height = caps.MaxTextureHeight;
- if (caps.NumSimultaneousRTs >= 2) {
- renderer->info.flags |= SDL_RENDERER_TARGETTEXTURE;
- }
- if (caps.PrimitiveMiscCaps & D3DPMISCCAPS_SEPARATEALPHABLEND) {
- data->enableSeparateAlphaBlend = SDL_TRUE;
- }
- /* Store the default render target */
- IDirect3DDevice9_GetRenderTarget(data->device, 0, &data->defaultRenderTarget );
- data->currentRenderTarget = NULL;
- /* Set up parameters for rendering */
- D3D_InitRenderState(data);
- if (caps.MaxSimultaneousTextures >= 3)
- {
- #ifdef ASSEMBLE_SHADER
- /* This shader was created by running the following HLSL through the fxc compiler
- and then tuning the generated assembly.
- fxc /T fx_4_0 /O3 /Gfa /Fc yuv.fxc yuv.fx
- --- yuv.fx ---
- Texture2D g_txY;
- Texture2D g_txU;
- Texture2D g_txV;
- SamplerState samLinear
- {
- Filter = ANISOTROPIC;
- AddressU = Clamp;
- AddressV = Clamp;
- MaxAnisotropy = 1;
- };
- struct VS_OUTPUT
- {
- float2 TextureUV : TEXCOORD0;
- };
- struct PS_OUTPUT
- {
- float4 RGBAColor : SV_Target;
- };
- PS_OUTPUT YUV420( VS_OUTPUT In )
- {
- const float3 offset = {-0.0625, -0.5, -0.5};
- const float3 Rcoeff = {1.164, 0.000, 1.596};
- const float3 Gcoeff = {1.164, -0.391, -0.813};
- const float3 Bcoeff = {1.164, 2.018, 0.000};
- PS_OUTPUT Output;
- float2 TextureUV = In.TextureUV;
- float3 yuv;
- yuv.x = g_txY.Sample( samLinear, TextureUV ).r;
- yuv.y = g_txU.Sample( samLinear, TextureUV ).r;
- yuv.z = g_txV.Sample( samLinear, TextureUV ).r;
- yuv += offset;
- Output.RGBAColor.r = dot(yuv, Rcoeff);
- Output.RGBAColor.g = dot(yuv, Gcoeff);
- Output.RGBAColor.b = dot(yuv, Bcoeff);
- Output.RGBAColor.a = 1.0f;
- return Output;
- }
- technique10 RenderYUV420
- {
- pass P0
- {
- SetPixelShader( CompileShader( ps_4_0_level_9_0, YUV420() ) );
- }
- }
- */
- const char *shader_text =
- "ps_2_0\n"
- "def c0, -0.0625, -0.5, -0.5, 1\n"
- "def c1, 1.16400003, 0, 1.59599996, 0\n"
- "def c2, 1.16400003, -0.391000003, -0.813000023, 0\n"
- "def c3, 1.16400003, 2.01799989, 0, 0\n"
- "dcl t0.xy\n"
- "dcl v0.xyzw\n"
- "dcl_2d s0\n"
- "dcl_2d s1\n"
- "dcl_2d s2\n"
- "texld r0, t0, s0\n"
- "texld r1, t0, s1\n"
- "texld r2, t0, s2\n"
- "mov r0.y, r1.x\n"
- "mov r0.z, r2.x\n"
- "add r0.xyz, r0, c0\n"
- "dp3 r1.x, r0, c1\n"
- "dp3 r1.y, r0, c2\n"
- "dp2add r1.z, r0, c3, c3.z\n" /* Logically this is "dp3 r1.z, r0, c3" but the optimizer did its magic */
- "mov r1.w, c0.w\n"
- "mul r0, r1, v0\n" /* Not in the HLSL, multiply by vertex color */
- "mov oC0, r0\n"
- ;
- LPD3DXBUFFER pCode;
- LPD3DXBUFFER pErrorMsgs;
- LPDWORD shader_data = NULL;
- DWORD shader_size = 0;
- result = D3DXAssembleShader(shader_text, SDL_strlen(shader_text), NULL, NULL, 0, &pCode, &pErrorMsgs);
- if (!FAILED(result)) {
- shader_data = (DWORD*)pCode->lpVtbl->GetBufferPointer(pCode);
- shader_size = pCode->lpVtbl->GetBufferSize(pCode);
- PrintShaderData(shader_data, shader_size);
- } else {
- const char *error = (const char *)pErrorMsgs->lpVtbl->GetBufferPointer(pErrorMsgs);
- SDL_SetError("Couldn't assemble shader: %s", error);
- }
- #else
- const DWORD shader_data[] = {
- 0xffff0200, 0x05000051, 0xa00f0000, 0xbd800000, 0xbf000000, 0xbf000000,
- 0x3f800000, 0x05000051, 0xa00f0001, 0x3f94fdf4, 0x00000000, 0x3fcc49ba,
- 0x00000000, 0x05000051, 0xa00f0002, 0x3f94fdf4, 0xbec83127, 0xbf5020c5,
- 0x00000000, 0x05000051, 0xa00f0003, 0x3f94fdf4, 0x400126e9, 0x00000000,
- 0x00000000, 0x0200001f, 0x80000000, 0xb0030000, 0x0200001f, 0x80000000,
- 0x900f0000, 0x0200001f, 0x90000000, 0xa00f0800, 0x0200001f, 0x90000000,
- 0xa00f0801, 0x0200001f, 0x90000000, 0xa00f0802, 0x03000042, 0x800f0000,
- 0xb0e40000, 0xa0e40800, 0x03000042, 0x800f0001, 0xb0e40000, 0xa0e40801,
- 0x03000042, 0x800f0002, 0xb0e40000, 0xa0e40802, 0x02000001, 0x80020000,
- 0x80000001, 0x02000001, 0x80040000, 0x80000002, 0x03000002, 0x80070000,
- 0x80e40000, 0xa0e40000, 0x03000008, 0x80010001, 0x80e40000, 0xa0e40001,
- 0x03000008, 0x80020001, 0x80e40000, 0xa0e40002, 0x0400005a, 0x80040001,
- 0x80e40000, 0xa0e40003, 0xa0aa0003, 0x02000001, 0x80080001, 0xa0ff0000,
- 0x03000005, 0x800f0000, 0x80e40001, 0x90e40000, 0x02000001, 0x800f0800,
- 0x80e40000, 0x0000ffff
- };
- #endif
- if (shader_data != NULL) {
- result = IDirect3DDevice9_CreatePixelShader(data->device, shader_data, &data->ps_yuv);
- if (!FAILED(result)) {
- renderer->info.texture_formats[renderer->info.num_texture_formats++] = SDL_PIXELFORMAT_YV12;
- renderer->info.texture_formats[renderer->info.num_texture_formats++] = SDL_PIXELFORMAT_IYUV;
- } else {
- D3D_SetError("CreatePixelShader()", result);
- }
- }
- }
- return renderer;
- }
D3D_CreateRenderer()這個函數的代碼很長。在這裏提取它最重點的幾個進行簡單的分析。
PS:由於這個函數中包含了大量的Direct3D的API,這方面如果不熟悉的話,可以參考以下兩篇文章:
《最簡單的視音頻播放示例3:Direct3D播放YUV,RGB(通過Surface)》
《最簡單的視音頻播放示例4:Direct3D播放RGB(通過Texture)》
(1) 爲SDL_Renderer分配內存這一步比較簡單。直接使用SDL_calloc()分配內存就可以了。SDL_calloc()實際上就是calloc(),這一點在前面的文章中已經敘述,在這裏不再重複。
(2) 加載Direct3D
加載Direct3D通過函數D3D_LoadDLL()完成。調用該函數可以得到一個IDirect3D9類型的接口。IDirect3D9接口可以用於完成D3D後續的初始化工作。D3D_LoadDLL()函數的代碼如下。
- SDL_bool D3D_LoadDLL( void **pD3DDLL, IDirect3D9 **pDirect3D9Interface )
- {
- *pD3DDLL = SDL_LoadObject("D3D9.DLL");
- if (*pD3DDLL) {
- IDirect3D9 *(WINAPI * D3DCreate) (UINT SDKVersion);
- D3DCreate =
- (IDirect3D9 * (WINAPI *) (UINT)) SDL_LoadFunction(*pD3DDLL,
- "Direct3DCreate9");
- if (D3DCreate) {
- *pDirect3D9Interface = D3DCreate(D3D_SDK_VERSION);
- }
- if (!*pDirect3D9Interface) {
- SDL_UnloadObject(*pD3DDLL);
- *pD3DDLL = NULL;
- return SDL_FALSE;
- }
- return SDL_TRUE;
- } else {
- *pDirect3D9Interface = NULL;
- return SDL_FALSE;
- }
- }
從代碼中可以看出,該函數加載了一個“D3D9.DLL”的Dll,並且調用了其中的Direct3DCreate9()方法。
(3) 渲染器接口函數賦值
SDL_Render結構體中有一系列的函數指針,包含了有關渲染器的各種功能。SDL通過調用這些函數指針就可以調用渲染器相應的功能。這是SDL支持多種渲染器的一個重要特點。代碼如下所示。
- renderer->WindowEvent = D3D_WindowEvent;
- renderer->CreateTexture = D3D_CreateTexture;
- renderer->UpdateTexture = D3D_UpdateTexture;
- renderer->UpdateTextureYUV = D3D_UpdateTextureYUV;
- renderer->LockTexture = D3D_LockTexture;
- renderer->UnlockTexture = D3D_UnlockTexture;
- renderer->SetRenderTarget = D3D_SetRenderTarget;
- renderer->UpdateViewport = D3D_UpdateViewport;
- renderer->UpdateClipRect = D3D_UpdateClipRect;
- renderer->RenderClear = D3D_RenderClear;
- renderer->RenderDrawPoints = D3D_RenderDrawPoints;
- renderer->RenderDrawLines = D3D_RenderDrawLines;
- renderer->RenderFillRects = D3D_RenderFillRects;
- renderer->RenderCopy = D3D_RenderCopy;
- renderer->RenderCopyEx = D3D_RenderCopyEx;
- renderer->RenderReadPixels = D3D_RenderReadPixels;
- renderer->RenderPresent = D3D_RenderPresent;
- renderer->DestroyTexture = D3D_DestroyTexture;
- renderer->DestroyRenderer = D3D_DestroyRenderer;
(4) 創建Device
創建Direct3D的Device通過IDirect3D9_CreateDevice()函數來實現。這一方面的知識不再敘述,可以參考Direct3D創建Device的相關的文章。
(5) 設置渲染狀態
設置渲染狀態在函數D3D_InitRenderState()中完成。該部分的知識也不再詳述,可以參考Direct3D相關的渲染教程。貼出D3D_InitRenderState()的代碼。- static void D3D_InitRenderState(D3D_RenderData *data)
- {
- D3DMATRIX matrix;
- IDirect3DDevice9 *device = data->device;
- IDirect3DDevice9_SetVertexShader(device, NULL);
- IDirect3DDevice9_SetFVF(device, D3DFVF_XYZ | D3DFVF_DIFFUSE | D3DFVF_TEX1);
- IDirect3DDevice9_SetRenderState(device, D3DRS_ZENABLE, D3DZB_FALSE);
- IDirect3DDevice9_SetRenderState(device, D3DRS_CULLMODE, D3DCULL_NONE);
- IDirect3DDevice9_SetRenderState(device, D3DRS_LIGHTING, FALSE);
- /* Enable color modulation by diffuse color */
- IDirect3DDevice9_SetTextureStageState(device, 0, D3DTSS_COLOROP,
- D3DTOP_MODULATE);
- IDirect3DDevice9_SetTextureStageState(device, 0, D3DTSS_COLORARG1,
- D3DTA_TEXTURE);
- IDirect3DDevice9_SetTextureStageState(device, 0, D3DTSS_COLORARG2,
- D3DTA_DIFFUSE);
- /* Enable alpha modulation by diffuse alpha */
- IDirect3DDevice9_SetTextureStageState(device, 0, D3DTSS_ALPHAOP,
- D3DTOP_MODULATE);
- IDirect3DDevice9_SetTextureStageState(device, 0, D3DTSS_ALPHAARG1,
- D3DTA_TEXTURE);
- IDirect3DDevice9_SetTextureStageState(device, 0, D3DTSS_ALPHAARG2,
- D3DTA_DIFFUSE);
- /* Enable separate alpha blend function, if possible */
- if (data->enableSeparateAlphaBlend) {
- IDirect3DDevice9_SetRenderState(device, D3DRS_SEPARATEALPHABLENDENABLE, TRUE);
- }
- /* Disable second texture stage, since we're done */
- IDirect3DDevice9_SetTextureStageState(device, 1, D3DTSS_COLOROP,
- D3DTOP_DISABLE);
- IDirect3DDevice9_SetTextureStageState(device, 1, D3DTSS_ALPHAOP,
- D3DTOP_DISABLE);
- /* Set an identity world and view matrix */
- matrix.m[0][0] = 1.0f;
- matrix.m[0][1] = 0.0f;
- matrix.m[0][2] = 0.0f;
- matrix.m[0][3] = 0.0f;
- matrix.m[1][0] = 0.0f;
- matrix.m[1][1] = 1.0f;
- matrix.m[1][2] = 0.0f;
- matrix.m[1][3] = 0.0f;
- matrix.m[2][0] = 0.0f;
- matrix.m[2][1] = 0.0f;
- matrix.m[2][2] = 1.0f;
- matrix.m[2][3] = 0.0f;
- matrix.m[3][0] = 0.0f;
- matrix.m[3][1] = 0.0f;
- matrix.m[3][2] = 0.0f;
- matrix.m[3][3] = 1.0f;
- IDirect3DDevice9_SetTransform(device, D3DTS_WORLD, &matrix);
- IDirect3DDevice9_SetTransform(device, D3DTS_VIEW, &matrix);
- /* Reset our current scale mode */
- SDL_memset(data->scaleMode, 0xFF, sizeof(data->scaleMode));
- /* Start the render with beginScene */
- data->beginScene = SDL_TRUE;
- }
(6) 創建Shader
創建Shader通過函數IDirect3DDevice9_CreatePixelShader()完成。
完成以上步驟之後,Direct3D的渲染器就創建完畢了。
2. OpenGL
OpenGL 的渲染器在創建函數是GL_CreateRenderer()。該函數位於render\opengl\SDL_render_gl.c文件中。首先看一下它的代碼。
PS:其中用到了OpenGL的很多API。如果對OpenGL的API還不熟悉的話,可以參考文章:
《最簡單的視音頻播放示例6:OpenGL播放YUV420P(通過Texture,使用Shader)》
- SDL_Renderer * GL_CreateRenderer(SDL_Window * window, Uint32 flags)
- {
- SDL_Renderer *renderer;
- GL_RenderData *data;
- const char *hint;
- GLint value;
- Uint32 window_flags;
- int profile_mask, major, minor;
- SDL_GL_GetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, &profile_mask);
- SDL_GL_GetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, &major);
- SDL_GL_GetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, &minor);
- window_flags = SDL_GetWindowFlags(window);
- if (!(window_flags & SDL_WINDOW_OPENGL) ||
- profile_mask == SDL_GL_CONTEXT_PROFILE_ES || major != RENDERER_CONTEXT_MAJOR || minor != RENDERER_CONTEXT_MINOR) {
- SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, 0);
- SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, RENDERER_CONTEXT_MAJOR);
- SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, RENDERER_CONTEXT_MINOR);
- if (SDL_RecreateWindow(window, window_flags | SDL_WINDOW_OPENGL) < 0) {
- /* Uh oh, better try to put it back... */
- SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, profile_mask);
- SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, major);
- SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, minor);
- SDL_RecreateWindow(window, window_flags);
- return NULL;
- }
- }
- renderer = (SDL_Renderer *) SDL_calloc(1, sizeof(*renderer));
- if (!renderer) {
- SDL_OutOfMemory();
- return NULL;
- }
- data = (GL_RenderData *) SDL_calloc(1, sizeof(*data));
- if (!data) {
- GL_DestroyRenderer(renderer);
- SDL_OutOfMemory();
- return NULL;
- }
- renderer->WindowEvent = GL_WindowEvent;
- renderer->GetOutputSize = GL_GetOutputSize;
- renderer->CreateTexture = GL_CreateTexture;
- renderer->UpdateTexture = GL_UpdateTexture;
- renderer->UpdateTextureYUV = GL_UpdateTextureYUV;
- renderer->LockTexture = GL_LockTexture;
- renderer->UnlockTexture = GL_UnlockTexture;
- renderer->SetRenderTarget = GL_SetRenderTarget;
- renderer->UpdateViewport = GL_UpdateViewport;
- renderer->UpdateClipRect = GL_UpdateClipRect;
- renderer->RenderClear = GL_RenderClear;
- renderer->RenderDrawPoints = GL_RenderDrawPoints;
- renderer->RenderDrawLines = GL_RenderDrawLines;
- renderer->RenderFillRects = GL_RenderFillRects;
- renderer->RenderCopy = GL_RenderCopy;
- renderer->RenderCopyEx = GL_RenderCopyEx;
- renderer->RenderReadPixels = GL_RenderReadPixels;
- renderer->RenderPresent = GL_RenderPresent;
- renderer->DestroyTexture = GL_DestroyTexture;
- renderer->DestroyRenderer = GL_DestroyRenderer;
- renderer->GL_BindTexture = GL_BindTexture;
- renderer->GL_UnbindTexture = GL_UnbindTexture;
- renderer->info = GL_RenderDriver.info;
- renderer->info.flags = (SDL_RENDERER_ACCELERATED | SDL_RENDERER_TARGETTEXTURE);
- renderer->driverdata = data;
- renderer->window = window;
- data->context = SDL_GL_CreateContext(window);
- if (!data->context) {
- GL_DestroyRenderer(renderer);
- return NULL;
- }
- if (SDL_GL_MakeCurrent(window, data->context) < 0) {
- GL_DestroyRenderer(renderer);
- return NULL;
- }
- if (GL_LoadFunctions(data) < 0) {
- GL_DestroyRenderer(renderer);
- return NULL;
- }
- #ifdef __MACOSX__
- /* Enable multi-threaded rendering */
- /* Disabled until Ryan finishes his VBO/PBO code...
- CGLEnable(CGLGetCurrentContext(), kCGLCEMPEngine);
- */
- #endif
- if (flags & SDL_RENDERER_PRESENTVSYNC) {
- SDL_GL_SetSwapInterval(1);
- } else {
- SDL_GL_SetSwapInterval(0);
- }
- if (SDL_GL_GetSwapInterval() > 0) {
- renderer->info.flags |= SDL_RENDERER_PRESENTVSYNC;
- }
- /* Check for debug output support */
- if (SDL_GL_GetAttribute(SDL_GL_CONTEXT_FLAGS, &value) == 0 &&
- (value & SDL_GL_CONTEXT_DEBUG_FLAG)) {
- data->debug_enabled = SDL_TRUE;
- }
- if (data->debug_enabled && SDL_GL_ExtensionSupported("GL_ARB_debug_output")) {
- PFNGLDEBUGMESSAGECALLBACKARBPROC glDebugMessageCallbackARBFunc = (PFNGLDEBUGMESSAGECALLBACKARBPROC) SDL_GL_GetProcAddress("glDebugMessageCallbackARB");
- data->GL_ARB_debug_output_supported = SDL_TRUE;
- data->glGetPointerv(GL_DEBUG_CALLBACK_FUNCTION_ARB, (GLvoid **)&data->next_error_callback);
- data->glGetPointerv(GL_DEBUG_CALLBACK_USER_PARAM_ARB, &data->next_error_userparam);
- glDebugMessageCallbackARBFunc(GL_HandleDebugMessage, renderer);
- /* Make sure our callback is called when errors actually happen */
- data->glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS_ARB);
- }
- if (SDL_GL_ExtensionSupported("GL_ARB_texture_rectangle")
- || SDL_GL_ExtensionSupported("GL_EXT_texture_rectangle")) {
- data->GL_ARB_texture_rectangle_supported = SDL_TRUE;
- data->glGetIntegerv(GL_MAX_RECTANGLE_TEXTURE_SIZE_ARB, &value);
- renderer->info.max_texture_width = value;
- renderer->info.max_texture_height = value;
- } else {
- data->glGetIntegerv(GL_MAX_TEXTURE_SIZE, &value);
- renderer->info.max_texture_width = value;
- renderer->info.max_texture_height = value;
- }
- /* Check for multitexture support */
- if (SDL_GL_ExtensionSupported("GL_ARB_multitexture")) {
- data->glActiveTextureARB = (PFNGLACTIVETEXTUREARBPROC) SDL_GL_GetProcAddress("glActiveTextureARB");
- if (data->glActiveTextureARB) {
- data->GL_ARB_multitexture_supported = SDL_TRUE;
- data->glGetIntegerv(GL_MAX_TEXTURE_UNITS_ARB, &data->num_texture_units);
- }
- }
- /* Check for shader support */
- hint = SDL_GetHint(SDL_HINT_RENDER_OPENGL_SHADERS);
- if (!hint || *hint != '0') {
- data->shaders = GL_CreateShaderContext();
- }
- SDL_LogInfo(SDL_LOG_CATEGORY_RENDER, "OpenGL shaders: %s",
- data->shaders ? "ENABLED" : "DISABLED");
- /* We support YV12 textures using 3 textures and a shader */
- if (data->shaders && data->num_texture_units >= 3) {
- renderer->info.texture_formats[renderer->info.num_texture_formats++] = SDL_PIXELFORMAT_YV12;
- renderer->info.texture_formats[renderer->info.num_texture_formats++] = SDL_PIXELFORMAT_IYUV;
- }
- #ifdef __MACOSX__
- renderer->info.texture_formats[renderer->info.num_texture_formats++] = SDL_PIXELFORMAT_UYVY;
- #endif
- if (SDL_GL_ExtensionSupported("GL_EXT_framebuffer_object")) {
- data->GL_EXT_framebuffer_object_supported = SDL_TRUE;
- data->glGenFramebuffersEXT = (PFNGLGENFRAMEBUFFERSEXTPROC)
- SDL_GL_GetProcAddress("glGenFramebuffersEXT");
- data->glDeleteFramebuffersEXT = (PFNGLDELETEFRAMEBUFFERSEXTPROC)
- SDL_GL_GetProcAddress("glDeleteFramebuffersEXT");
- data->glFramebufferTexture2DEXT = (PFNGLFRAMEBUFFERTEXTURE2DEXTPROC)
- SDL_GL_GetProcAddress("glFramebufferTexture2DEXT");
- data->glBindFramebufferEXT = (PFNGLBINDFRAMEBUFFEREXTPROC)
- SDL_GL_GetProcAddress("glBindFramebufferEXT");
- data->glCheckFramebufferStatusEXT = (PFNGLCHECKFRAMEBUFFERSTATUSEXTPROC)
- SDL_GL_GetProcAddress("glCheckFramebufferStatusEXT");
- renderer->info.flags |= SDL_RENDERER_TARGETTEXTURE;
- }
- data->framebuffers = NULL;
- /* Set up parameters for rendering */
- GL_ResetState(renderer);
- return renderer;
- }
GL_CreateRenderer()這個函數的代碼很長。在這裏提取它最重點的幾個進行簡單的分析。
(1) 爲SDL_Renderer分配內存
這一步比較簡單。直接使用SDL_calloc()分配內存就可以了。
(2) 渲染器接口函數賦值
SDL_Render結構體中有一系列的函數指針,包含了有關渲染器的各種功能。這一點在Direct3D的時候已經提過,不再重複。代碼如下。- renderer->WindowEvent = GL_WindowEvent;
- renderer->GetOutputSize = GL_GetOutputSize;
- renderer->CreateTexture = GL_CreateTexture;
- renderer->UpdateTexture = GL_UpdateTexture;
- renderer->UpdateTextureYUV = GL_UpdateTextureYUV;
- renderer->LockTexture = GL_LockTexture;
- renderer->UnlockTexture = GL_UnlockTexture;
- renderer->SetRenderTarget = GL_SetRenderTarget;
- renderer->UpdateViewport = GL_UpdateViewport;
- renderer->UpdateClipRect = GL_UpdateClipRect;
- renderer->RenderClear = GL_RenderClear;
- renderer->RenderDrawPoints = GL_RenderDrawPoints;
- renderer->RenderDrawLines = GL_RenderDrawLines;
- renderer->RenderFillRects = GL_RenderFillRects;
- renderer->RenderCopy = GL_RenderCopy;
- renderer->RenderCopyEx = GL_RenderCopyEx;
- renderer->RenderReadPixels = GL_RenderReadPixels;
- renderer->RenderPresent = GL_RenderPresent;
- renderer->DestroyTexture = GL_DestroyTexture;
- renderer->DestroyRenderer = GL_DestroyRenderer;
- renderer->GL_BindTexture = GL_BindTexture;
- renderer->GL_UnbindTexture = GL_UnbindTexture;
(3) 初始化OpenGL
初始化OpenGL各種變量,包括SDL_GL_CreateContext(),SDL_GL_MakeCurrent(),GL_LoadFunctions()等函數。這一部分還沒有詳細分析。
(4) 初始化Shader
對Shader的初始化在函數GL_CreateShaderContext()中完成。GL_CreateShaderContext()的代碼如下(位於render\opengl\SDL_shaders_gl.c)。
- GL_ShaderContext * GL_CreateShaderContext()
- {
- GL_ShaderContext *ctx;
- SDL_bool shaders_supported;
- int i;
- ctx = (GL_ShaderContext *)SDL_calloc(1, sizeof(*ctx));
- if (!ctx) {
- return NULL;
- }
- if (SDL_GL_ExtensionSupported("GL_ARB_texture_rectangle")
- || SDL_GL_ExtensionSupported("GL_EXT_texture_rectangle")) {
- ctx->GL_ARB_texture_rectangle_supported = SDL_TRUE;
- }
- /* Check for shader support */
- shaders_supported = SDL_FALSE;
- if (SDL_GL_ExtensionSupported("GL_ARB_shader_objects") &&
- SDL_GL_ExtensionSupported("GL_ARB_shading_language_100") &&
- SDL_GL_ExtensionSupported("GL_ARB_vertex_shader") &&
- SDL_GL_ExtensionSupported("GL_ARB_fragment_shader")) {
- ctx->glGetError = (GLenum (*)(void)) SDL_GL_GetProcAddress("glGetError");
- ctx->glAttachObjectARB = (PFNGLATTACHOBJECTARBPROC) SDL_GL_GetProcAddress("glAttachObjectARB");
- ctx->glCompileShaderARB = (PFNGLCOMPILESHADERARBPROC) SDL_GL_GetProcAddress("glCompileShaderARB");
- ctx->glCreateProgramObjectARB = (PFNGLCREATEPROGRAMOBJECTARBPROC) SDL_GL_GetProcAddress("glCreateProgramObjectARB");
- ctx->glCreateShaderObjectARB = (PFNGLCREATESHADEROBJECTARBPROC) SDL_GL_GetProcAddress("glCreateShaderObjectARB");
- ctx->glDeleteObjectARB = (PFNGLDELETEOBJECTARBPROC) SDL_GL_GetProcAddress("glDeleteObjectARB");
- ctx->glGetInfoLogARB = (PFNGLGETINFOLOGARBPROC) SDL_GL_GetProcAddress("glGetInfoLogARB");
- ctx->glGetObjectParameterivARB = (PFNGLGETOBJECTPARAMETERIVARBPROC) SDL_GL_GetProcAddress("glGetObjectParameterivARB");
- ctx->glGetUniformLocationARB = (PFNGLGETUNIFORMLOCATIONARBPROC) SDL_GL_GetProcAddress("glGetUniformLocationARB");
- ctx->glLinkProgramARB = (PFNGLLINKPROGRAMARBPROC) SDL_GL_GetProcAddress("glLinkProgramARB");
- ctx->glShaderSourceARB = (PFNGLSHADERSOURCEARBPROC) SDL_GL_GetProcAddress("glShaderSourceARB");
- ctx->glUniform1iARB = (PFNGLUNIFORM1IARBPROC) SDL_GL_GetProcAddress("glUniform1iARB");
- ctx->glUniform1fARB = (PFNGLUNIFORM1FARBPROC) SDL_GL_GetProcAddress("glUniform1fARB");
- ctx->glUseProgramObjectARB = (PFNGLUSEPROGRAMOBJECTARBPROC) SDL_GL_GetProcAddress("glUseProgramObjectARB");
- if (ctx->glGetError &&
- ctx->glAttachObjectARB &&
- ctx->glCompileShaderARB &&
- ctx->glCreateProgramObjectARB &&
- ctx->glCreateShaderObjectARB &&
- ctx->glDeleteObjectARB &&
- ctx->glGetInfoLogARB &&
- ctx->glGetObjectParameterivARB &&
- ctx->glGetUniformLocationARB &&
- ctx->glLinkProgramARB &&
- ctx->glShaderSourceARB &&
- ctx->glUniform1iARB &&
- ctx->glUniform1fARB &&
- ctx->glUseProgramObjectARB) {
- shaders_supported = SDL_TRUE;
- }
- }
- if (!shaders_supported) {
- SDL_free(ctx);
- return NULL;
- }
- /* Compile all the shaders */
- for (i = 0; i < NUM_SHADERS; ++i) {
- if (!CompileShaderProgram(ctx, i, &ctx->shaders[i])) {
- GL_DestroyShaderContext(ctx);
- return NULL;
- }
- }
- /* We're done! */
- return ctx;
- }
上述代碼主要完成了以下兩步:
第一步,初始化GL_ShaderContext。GL_ShaderContext中包含了OpenGL的Shader方面用到的各種接口函數。GL_ShaderContext定義如下。
- struct GL_ShaderContext
- {
- GLenum (*glGetError)(void);
- PFNGLATTACHOBJECTARBPROC glAttachObjectARB;
- PFNGLCOMPILESHADERARBPROC glCompileShaderARB;
- PFNGLCREATEPROGRAMOBJECTARBPROC glCreateProgramObjectARB;
- PFNGLCREATESHADEROBJECTARBPROC glCreateShaderObjectARB;
- PFNGLDELETEOBJECTARBPROC glDeleteObjectARB;
- PFNGLGETINFOLOGARBPROC glGetInfoLogARB;
- PFNGLGETOBJECTPARAMETERIVARBPROC glGetObjectParameterivARB;
- PFNGLGETUNIFORMLOCATIONARBPROC glGetUniformLocationARB;
- PFNGLLINKPROGRAMARBPROC glLinkProgramARB;
- PFNGLSHADERSOURCEARBPROC glShaderSourceARB;
- PFNGLUNIFORM1IARBPROC glUniform1iARB;
- PFNGLUNIFORM1FARBPROC glUniform1fARB;
- PFNGLUSEPROGRAMOBJECTARBPROC glUseProgramObjectARB;
- SDL_bool GL_ARB_texture_rectangle_supported;
- GL_ShaderData shaders[NUM_SHADERS];
- };
看這個結構體的定義會給人一種很混亂的感覺。不用去理會那些大串的大寫字母,只要知道這個結構體是函數的接口的“合集”就可以了。從函數的名稱中我們可以看出有編譯Shader的glCreateShaderObject(),glShaderSource(),glCompileShader()等;以及編譯Program的glCreateProgramObject(),glAttachObject (),glLinkProgram(),glUseProgramObject ()等等。
GL_CreateShaderContext()函數中創建了一個GL_ShaderContext並對其中的接口函數進行了賦值。
第二步,編譯Shader程序。該功能在CompileShaderProgram()函數中完成。CompileShaderProgram()的函數代碼如下所示。
- static SDL_bool CompileShaderProgram(GL_ShaderContext *ctx, int index, GL_ShaderData *data)
- {
- const int num_tmus_bound = 4;
- const char *vert_defines = "";
- const char *frag_defines = "";
- int i;
- GLint location;
- if (index == SHADER_NONE) {
- return SDL_TRUE;
- }
- ctx->glGetError();
- /* Make sure we use the correct sampler type for our texture type */
- if (ctx->GL_ARB_texture_rectangle_supported) {
- frag_defines =
- "#define sampler2D sampler2DRect\n"
- "#define texture2D texture2DRect\n";
- }
- /* Create one program object to rule them all */
- data->program = ctx->glCreateProgramObjectARB();
- /* Create the vertex shader */
- data->vert_shader = ctx->glCreateShaderObjectARB(GL_VERTEX_SHADER_ARB);
- if (!CompileShader(ctx, data->vert_shader, vert_defines, shader_source[index][0])) {
- return SDL_FALSE;
- }
- /* Create the fragment shader */
- data->frag_shader = ctx->glCreateShaderObjectARB(GL_FRAGMENT_SHADER_ARB);
- if (!CompileShader(ctx, data->frag_shader, frag_defines, shader_source[index][1])) {
- return SDL_FALSE;
- }
- /* ... and in the darkness bind them */
- ctx->glAttachObjectARB(data->program, data->vert_shader);
- ctx->glAttachObjectARB(data->program, data->frag_shader);
- ctx->glLinkProgramARB(data->program);
- /* Set up some uniform variables */
- ctx->glUseProgramObjectARB(data->program);
- for (i = 0; i < num_tmus_bound; ++i) {
- char tex_name[10];
- SDL_snprintf(tex_name, SDL_arraysize(tex_name), "tex%d", i);
- location = ctx->glGetUniformLocationARB(data->program, tex_name);
- if (location >= 0) {
- ctx->glUniform1iARB(location, i);
- }
- }
- ctx->glUseProgramObjectARB(0);
- return (ctx->glGetError() == GL_NO_ERROR);
- }
從代碼中可以看出,這個函數調用了GL_ShaderContext中用於初始化Shader以及Program的各個函數。有關初始化的流程不再細說,可以參考相關的文章。
在該函數中,調用了CompileShader()專門用於初始化Shader。該函數被調用了兩次,分別用於初始化vertex shader和fragment shader。CompileShader()的代碼如下。
- static SDL_bool CompileShader(GL_ShaderContext *ctx, GLhandleARB shader, const char *defines, const char *source)
- {
- GLint status;
- const char *sources[2];
- sources[0] = defines;
- sources[1] = source;
- ctx->glShaderSourceARB(shader, SDL_arraysize(sources), sources, NULL);
- ctx->glCompileShaderARB(shader);
- ctx->glGetObjectParameterivARB(shader, GL_OBJECT_COMPILE_STATUS_ARB, &status);
- if (status == 0) {
- GLint length;
- char *info;
- ctx->glGetObjectParameterivARB(shader, GL_OBJECT_INFO_LOG_LENGTH_ARB, &length);
- info = SDL_stack_alloc(char, length+1);
- ctx->glGetInfoLogARB(shader, length, NULL, info);
- SDL_LogError(SDL_LOG_CATEGORY_RENDER,
- "Failed to compile shader:\n%s%s\n%s", defines, source, info);
- #ifdef DEBUG_SHADERS
- fprintf(stderr,
- "Failed to compile shader:\n%s%s\n%s", defines, source, info);
- #endif
- SDL_stack_free(info);
- return SDL_FALSE;
- } else {
- return SDL_TRUE;
- }
- }
從代碼中可以看出,該函數調用glShaderSource(),glCompileShader(),glGetObjectParameteriv()這幾個函數初始化一個Shader。
Shader的代碼位於一個名稱爲shader_source的char型二維數組裏,源代碼如下所示。數組中每個元素代表一個Shader的代碼,每個Shader的代碼包含兩個部分:vertex shader代碼(對應元素[0])以及fragment shader代碼(對應元素[1])。
- /*
- * NOTE: Always use sampler2D, etc here. We'll #define them to the
- * texture_rectangle versions if we choose to use that extension.
- */
- static const char *shader_source[NUM_SHADERS][2] =
- {
- /* SHADER_NONE */
- { NULL, NULL },
- /* SHADER_SOLID */
- {
- /* vertex shader */
- "varying vec4 v_color;\n"
- "\n"
- "void main()\n"
- "{\n"
- " gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
- " v_color = gl_Color;\n"
- "}",
- /* fragment shader */
- "varying vec4 v_color;\n"
- "\n"
- "void main()\n"
- "{\n"
- " gl_FragColor = v_color;\n"
- "}"
- },
- /* SHADER_RGB */
- {
- /* vertex shader */
- "varying vec4 v_color;\n"
- "varying vec2 v_texCoord;\n"
- "\n"
- "void main()\n"
- "{\n"
- " gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
- " v_color = gl_Color;\n"
- " v_texCoord = vec2(gl_MultiTexCoord0);\n"
- "}",
- /* fragment shader */
- "varying vec4 v_color;\n"
- "varying vec2 v_texCoord;\n"
- "uniform sampler2D tex0;\n"
- "\n"
- "void main()\n"
- "{\n"
- " gl_FragColor = texture2D(tex0, v_texCoord) * v_color;\n"
- "}"
- },
- /* SHADER_YV12 */
- {
- /* vertex shader */
- "varying vec4 v_color;\n"
- "varying vec2 v_texCoord;\n"
- "\n"
- "void main()\n"
- "{\n"
- " gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
- " v_color = gl_Color;\n"
- " v_texCoord = vec2(gl_MultiTexCoord0);\n"
- "}",
- /* fragment shader */
- "varying vec4 v_color;\n"
- "varying vec2 v_texCoord;\n"
- "uniform sampler2D tex0; // Y \n"
- "uniform sampler2D tex1; // U \n"
- "uniform sampler2D tex2; // V \n"
- "\n"
- "// YUV offset \n"
- "const vec3 offset = vec3(-0.0625, -0.5, -0.5);\n"
- "\n"
- "// RGB coefficients \n"
- "const vec3 Rcoeff = vec3(1.164, 0.000, 1.596);\n"
- "const vec3 Gcoeff = vec3(1.164, -0.391, -0.813);\n"
- "const vec3 Bcoeff = vec3(1.164, 2.018, 0.000);\n"
- "\n"
- "void main()\n"
- "{\n"
- " vec2 tcoord;\n"
- " vec3 yuv, rgb;\n"
- "\n"
- " // Get the Y value \n"
- " tcoord = v_texCoord;\n"
- " yuv.x = texture2D(tex0, tcoord).r;\n"
- "\n"
- " // Get the U and V values \n"
- " tcoord *= 0.5;\n"
- " yuv.y = texture2D(tex1, tcoord).r;\n"
- " yuv.z = texture2D(tex2, tcoord).r;\n"
- "\n"
- " // Do the color transform \n"
- " yuv += offset;\n"
- " rgb.r = dot(yuv, Rcoeff);\n"
- " rgb.g = dot(yuv, Gcoeff);\n"
- " rgb.b = dot(yuv, Bcoeff);\n"
- "\n"
- " // That was easy. :) \n"
- " gl_FragColor = vec4(rgb, 1.0) * v_color;\n"
- "}"
- },
- };
有關OpenGL的渲染器的初始化代碼暫時分析到這裏。
3. Software
Software的渲染器在創建函數是SW_CreateRenderer()。該函數位於render\software\SDL_render_sw.c文件中。首先看一下它的代碼。
- SDL_Renderer * SW_CreateRenderer(SDL_Window * window, Uint32 flags)
- {
- SDL_Surface *surface;
- surface = SDL_GetWindowSurface(window);
- if (!surface) {
- return NULL;
- }
- return SW_CreateRendererForSurface(surface);
- }
從代碼中可以看出,SW_CreateRenderer()調用了2個函數:SDL_GetWindowSurface()和SW_CreateRendererForSurface()。SDL_GetWindowSurface()用於創建一個Surface;SW_CreateRendererForSurface()基於Surface創建一個Renderer。
下面分別看一下這2個函數的代碼。
SDL_GetWindowSurface()的代碼如下所示(位於video\SDL_video.c)。
- SDL_Surface * SDL_GetWindowSurface(SDL_Window * window)
- {
- CHECK_WINDOW_MAGIC(window, NULL);
- if (!window->surface_valid) {
- if (window->surface) {
- window->surface->flags &= ~SDL_DONTFREE;
- SDL_FreeSurface(window->surface);
- }
- window->surface = SDL_CreateWindowFramebuffer(window);
- if (window->surface) {
- window->surface_valid = SDL_TRUE;
- window->surface->flags |= SDL_DONTFREE;
- }
- }
- return window->surface;
- }
其中調用了一個函數SDL_CreateWindowFramebuffer(),看一下該函數的代碼。
- static SDL_Surface * SDL_CreateWindowFramebuffer(SDL_Window * window)
- {
- Uint32 format;
- void *pixels;
- int pitch;
- int bpp;
- Uint32 Rmask, Gmask, Bmask, Amask;
- if (!_this->CreateWindowFramebuffer || !_this->UpdateWindowFramebuffer) {
- return NULL;
- }
- if (_this->CreateWindowFramebuffer(_this, window, &format, &pixels, &pitch) < 0) {
- return NULL;
- }
- if (!SDL_PixelFormatEnumToMasks(format, &bpp, &Rmask, &Gmask, &Bmask, &Amask)) {
- return NULL;
- }
- return SDL_CreateRGBSurfaceFrom(pixels, window->w, window->h, bpp, pitch, Rmask, Gmask, Bmask, Amask);
- }
該函數中調用了SDL_VideoDevice中的一個函數CreateWindowFramebuffer()。我們以“Windows視頻驅動”爲例,看看CreateWindowFramebuffer()中的代碼。在“Windows視頻驅動”下,CreateWindowFramebuffer()對應的函數是WIN_CreateWindowFramebuffer()。下面看一下該函數的代碼。
- int WIN_CreateWindowFramebuffer(_THIS, SDL_Window * window, Uint32 * format, void ** pixels, int *pitch)
- {
- SDL_WindowData *data = (SDL_WindowData *) window->driverdata;
- size_t size;
- LPBITMAPINFO info;
- HBITMAP hbm;
- /* Free the old framebuffer surface */
- if (data->mdc) {
- DeleteDC(data->mdc);
- }
- if (data->hbm) {
- DeleteObject(data->hbm);
- }
- /* Find out the format of the screen */
- size = sizeof(BITMAPINFOHEADER) + 256 * sizeof (RGBQUAD);
- info = (LPBITMAPINFO)SDL_stack_alloc(Uint8, size);
- SDL_memset(info, 0, size);
- info->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
- /* The second call to GetDIBits() fills in the bitfields */
- hbm = CreateCompatibleBitmap(data->hdc, 1, 1);
- GetDIBits(data->hdc, hbm, 0, 0, NULL, info, DIB_RGB_COLORS);
- GetDIBits(data->hdc, hbm, 0, 0, NULL, info, DIB_RGB_COLORS);
- DeleteObject(hbm);
- *format = SDL_PIXELFORMAT_UNKNOWN;
- if (info->bmiHeader.biCompression == BI_BITFIELDS) {
- int bpp;
- Uint32 *masks;
- bpp = info->bmiHeader.biPlanes * info->bmiHeader.biBitCount;
- masks = (Uint32*)((Uint8*)info + info->bmiHeader.biSize);
- *format = SDL_MasksToPixelFormatEnum(bpp, masks[0], masks[1], masks[2], 0);
- }
- if (*format == SDL_PIXELFORMAT_UNKNOWN)
- {
- /* We'll use RGB format for now */
- *format = SDL_PIXELFORMAT_RGB888;
- /* Create a new one */
- SDL_memset(info, 0, size);
- info->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
- info->bmiHeader.biPlanes = 1;
- info->bmiHeader.biBitCount = 32;
- info->bmiHeader.biCompression = BI_RGB;
- }
- /* Fill in the size information */
- *pitch = (((window->w * SDL_BYTESPERPIXEL(*format)) + 3) & ~3);
- info->bmiHeader.biWidth = window->w;
- info->bmiHeader.biHeight = -window->h; /* negative for topdown bitmap */
- info->bmiHeader.biSizeImage = window->h * (*pitch);
- data->mdc = CreateCompatibleDC(data->hdc);
- data->hbm = CreateDIBSection(data->hdc, info, DIB_RGB_COLORS, pixels, NULL, 0);
- SDL_stack_free(info);
- if (!data->hbm) {
- return WIN_SetError("Unable to create DIB");
- }
- SelectObject(data->mdc, data->hbm);
- return 0;
- }
從代碼中可以看出,該函數調用了Win32的API函數CreateCompatibleBitmap(),CreateCompatibleDC()等一系列方法創建了“Surface”。
SDL_GetWindowSurface()函數到此分析完畢,現在回過頭來再看SW_CreateRenderer ()的另一個函數SW_CreateRendererForSurface()。該函數的代碼如下。
- SDL_Renderer * SW_CreateRendererForSurface(SDL_Surface * surface)
- {
- SDL_Renderer *renderer;
- SW_RenderData *data;
- if (!surface) {
- SDL_SetError("Can't create renderer for NULL surface");
- return NULL;
- }
- renderer = (SDL_Renderer *) SDL_calloc(1, sizeof(*renderer));
- if (!renderer) {
- SDL_OutOfMemory();
- return NULL;
- }
- data = (SW_RenderData *) SDL_calloc(1, sizeof(*data));
- if (!data) {
- SW_DestroyRenderer(renderer);
- SDL_OutOfMemory();
- return NULL;
- }
- data->surface = surface;
- renderer->WindowEvent = SW_WindowEvent;
- renderer->GetOutputSize = SW_GetOutputSize;
- renderer->CreateTexture = SW_CreateTexture;
- renderer->SetTextureColorMod = SW_SetTextureColorMod;
- renderer->SetTextureAlphaMod = SW_SetTextureAlphaMod;
- renderer->SetTextureBlendMode = SW_SetTextureBlendMode;
- renderer->UpdateTexture = SW_UpdateTexture;
- renderer->LockTexture = SW_LockTexture;
- renderer->UnlockTexture = SW_UnlockTexture;
- renderer->SetRenderTarget = SW_SetRenderTarget;
- renderer->UpdateViewport = SW_UpdateViewport;
- renderer->UpdateClipRect = SW_UpdateClipRect;
- renderer->RenderClear = SW_RenderClear;
- renderer->RenderDrawPoints = SW_RenderDrawPoints;
- renderer->RenderDrawLines = SW_RenderDrawLines;
- renderer->RenderFillRects = SW_RenderFillRects;
- renderer->RenderCopy = SW_RenderCopy;
- renderer->RenderCopyEx = SW_RenderCopyEx;
- renderer->RenderReadPixels = SW_RenderReadPixels;
- renderer->RenderPresent = SW_RenderPresent;
- renderer->DestroyTexture = SW_DestroyTexture;
- renderer->DestroyRenderer = SW_DestroyRenderer;
- renderer->info = SW_RenderDriver.info;
- renderer->driverdata = data;
- SW_ActivateRenderer(renderer);
- return renderer;
- }
與前面的函數一樣,該函數完成了SDL_Renderer結構體中函數指針的賦值。