Sdl2 source analysis 7: performance (sdl_renderpresent())

Hello everyone , I meet you again , I'm the king of the whole stack .

=====================================================

SDL Source code analysis series articles on the market ：

SDL2 Source code analysis 1： initialization （SDL_Init()）

SDL2 Source code analysis 2： forms （SDL_Window）

SDL2 Source code analysis 3： Renderers （SDL_Renderer）

SDL2 Source code analysis 4： texture （SDL_Texture）

SDL2 Source code analysis 5： Update texture （SDL_UpdateTexture()）

SDL2 Source code analysis 6： Copy to the render （SDL_RenderCopy()）

SDL2 Source code analysis 7： Show （SDL_RenderPresent()）

SDL2 Source code analysis 8： Video display summary

=====================================================

The last article analyzed SDL Texture assignment function to render target SDL_RenderCopy().

This article analyzes SDL Show the last function of the video ：SDL_RenderPresent().

SDL The code flow of playing video, such as the following . initialization :

SDL_Init(): initialization SDL. SDL_CreateWindow(): Create a form （Window）. SDL_CreateRenderer(): Create a renderer based on the form （Render）. SDL_CreateTexture(): Create texture （Texture）.

Loop render data :

SDL_UpdateTexture(): Set texture data . SDL_RenderCopy(): Texture copy to renderer . SDL_RenderPresent(): Show .

The last article analyzed the... In this process 6 A function SDL_RenderCopy(). This article continues to analyze the last function in the process SDL_RenderPresent().

SDL_RenderPresent()

Function introduction

SDL Use SDL_RenderPresent() display frame .

SDL_RenderPresent() The prototype of is as follows .

void SDLCALL SDL_RenderPresent(SDL_Renderer * renderer);

Copy

Parameters renderer Lets you specify the renderer .

Function call graph

SDL_RenderPresent() The calling relationship of key functions can be represented by the following figure .

The picture above is not very clear , Clearer pictures are uploaded to the album ：

http://my.csdn.net/leixiaohua1020/album/detail/1794103

Save the pictures in the album to get clear pictures .

Source code analysis

SDL_RenderPresent() The source code of is located in render\SDL_render.c in .

As you can see below .

void SDL_RenderPresent(SDL_Renderer * renderer)
{
    CHECK_RENDERER_MAGIC(renderer, );


    /* Don't draw while we're hidden */
    if (renderer->hidden) {
        return;
    }
    renderer->RenderPresent(renderer);
}

Copy

From the source code, we can see ,SDL_RenderPresent() Called SDL_Render Of RenderPresent() Method to display the image .

Let's take a look at several different renderers RenderPresent() Methods .

1. Direct3D

Direct3D Corresponding in the renderer RenderPresent() The function of is D3D_RenderPresent(). Its source code, such as the following （ be located render\direct3d\SDL_render_d3d.c）.

static void D3D_RenderPresent(SDL_Renderer * renderer)
{
    D3D_RenderData *data = (D3D_RenderData *) renderer->driverdata;
    HRESULT result;


    if (!data->beginScene) {
        IDirect3DDevice9_EndScene(data->device);
        data->beginScene = SDL_TRUE;
    }


    result = IDirect3DDevice9_TestCooperativeLevel(data->device);
    if (result == D3DERR_DEVICELOST) {
        /* We'll reset later */
        return;
    }
    if (result == D3DERR_DEVICENOTRESET) {
        D3D_Reset(renderer);
    }
    result = IDirect3DDevice9_Present(data->device, NULL, NULL, NULL, NULL);
    if (FAILED(result)) {
        D3D_SetError("Present()", result);
    }
}

Copy

As you can see from the code , This function calls 2 The key Direct3D Of API： IDirect3DDevice9_EndScene()： End a scene . IDirect3DDevice9_Present()： Show .

2. OpenGL

OpenGL Corresponding in the renderer RenderPresent() The function of is GL_RenderPresent(), Its source code, such as the following （ be located render\opengl\SDL_render_gl.c）.

static void GL_RenderPresent(SDL_Renderer * renderer)
{
GL_ActivateRenderer(renderer);


    SDL_GL_SwapWindow(renderer->window);
}

Copy

The code is relatively simple , There are only two lines . The key display functions are located in SDL_GL_SwapWindow() Function . Let's take a look at SDL_GL_SwapWindow() Code for （ be located video\SDL_video.c. I feel that the calling relationship here is a little messy …）.

void SDL_GL_SwapWindow(SDL_Window * window)
{
    CHECK_WINDOW_MAGIC(window, );


    if (!(window->flags & SDL_WINDOW_OPENGL)) {
        SDL_SetError("The specified window isn't an OpenGL window");
        return;
    }


    if (SDL_GL_GetCurrentWindow() != window) {
        SDL_SetError("The specified window has not been made current");
        return;
    }


    _this->GL_SwapWindow(_this, window);
}

Copy

From the above code, we can see .SDL_GL_SwapWindow() Called SDL_VideoDevice Of GL_SwapWindow() function .

Let's see “Windows Video drive ” Under the circumstances , The code for this function . stay “Windows Video drive ” Under the circumstances , call GL_SwapWindow() It's actually called WIN_GL_SwapWindow() function . to glance at WIN_GL_SwapWindow() Function code （ be located video\windows\SDL_windowsopengl.c）.

void WIN_GL_SwapWindow(_THIS, SDL_Window * window)
{
    HDC hdc = ((SDL_WindowData *) window->driverdata)->hdc;


    SwapBuffers(hdc);
}

Copy

A simple function is called in the code SwapBuffers(), Finished the display function .

3. Software

Software Corresponding in the renderer RenderPresent() The function of is SW_RenderPresent(), Its source code, such as the following （ be located render\software\SDL_render_sw.c）.

static void SW_RenderPresent(SDL_Renderer * renderer)
{
    SDL_Window *window = renderer->window;


    if (window) {
        SDL_UpdateWindowSurface(window);
    }
}

Copy

As you can see from the code .SW_RenderPresent() A function was called SDL_UpdateWindowSurface(). Let's see SDL_UpdateWindowSurface() Code for （ be located video\SDL_video.c）.

int SDL_UpdateWindowSurface(SDL_Window * window)
{
    SDL_Rect full_rect;


    CHECK_WINDOW_MAGIC(window, -1);


    full_rect.x = 0;
    full_rect.y = 0;
    full_rect.w = window->w;
    full_rect.h = window->h;
    return SDL_UpdateWindowSurfaceRects(window, &full_rect, 1);
}

Copy

SDL_UpdateWindowSurface() Another function is called SDL_UpdateWindowSurfaceRects(). Continue to look at SDL_UpdateWindowSurfaceRects() Code for .

int SDL_UpdateWindowSurfaceRects(SDL_Window * window, const SDL_Rect * rects,
                             int numrects)
{
    CHECK_WINDOW_MAGIC(window, -1);


    if (!window->surface_valid) {
        return SDL_SetError("Window surface is invalid, please call SDL_GetWindowSurface() to get a new surface");
    }


    return _this->UpdateWindowFramebuffer(_this, window, rects, numrects);
}

Copy

SDL_UpdateWindowSurfaceRects() Called SDL_VideoDevice Of UpdateWindowFramebuffer() function . stay “Windows Video drive ” Under the circumstances . Equivalent to calling WIN_UpdateWindowFramebuffer().

Let's take a look at the code of this function （ be located video\windows\SDL_windowsframebuffer.c）

int WIN_UpdateWindowFramebuffer(_THIS, SDL_Window * window, const SDL_Rect * rects, int numrects)
{
    SDL_WindowData *data = (SDL_WindowData *) window->driverdata;


    BitBlt(data->hdc, 0, 0, window->w, window->h, data->mdc, 0, 0, SRCCOPY);
    return 0;
}

Copy

After a series of searching , Finally found Software Render the video show “ resources ”：BitBlt() performance .

Copyright notice ： This article is the original article of the blogger . Blog , Do not reprint without permission .

Publisher ： Full stack programmer stack length , Reprint please indicate the source ：https://javaforall.cn/117099.html Link to the original text ：https://javaforall.cn