(原)关于sdl在部分机器上做视频显示，改变显示窗口大小会崩溃

今天测试人员反应,之前做的视频绘图显示，会在她机器上，会出现崩溃现象，最后我在她机器上对代码进行跟踪，发现在某种情况，确实会崩溃。

最主要的原因是，视频显示窗口变成非活动窗口的时候，sdl内部会循环消息处理，当处理WM_WINDOWPOSCHANGED消息的时候，就会出现崩溃，崩溃的代码在,D3D_UpdateViewport函数内部的IDirect3DDevice9_SetViewport函数。

当初我为了解决这个问题，觉得是sdl内部接管了窗口的消息处理函数引起的，因为实际上我们这里也没用到sdl的事件处理消息函数，所以我最初是打算把消息接管函数给屏蔽掉，就饿可以解决这个问题，当时也免得消息函数里面出现其他异常情况。

#ifdef GWLP_WNDPROC
data->wndproc = (WNDPROC) GetWindowLongPtr(hwnd, GWLP_WNDPROC);
if (data->wndproc == WIN_WindowProc) {
data->wndproc = NULL;
} else {
//SetWindowLongPtr(hwnd, GWLP_WNDPROC, (LONG_PTR) WIN_WindowProc);//以为屏蔽掉这里的消息处理函数，就可以解决问题了。
}
#else
data->wndproc = (WNDPROC) GetWindowLong(hwnd, GWL_WNDPROC);
if (data->wndproc == WIN_WindowProc) {
data->wndproc = NULL;
} else {
//SetWindowLong(hwnd, GWL_WNDPROC, (LONG_PTR) WIN_WindowProc);
}
#endif

结果是,崩溃的问题看似解决了,在她那台机器和其他机器上也不会出现崩溃,但有一个其他的问题引入了，就是sdl内部不能响应事件处理函数，这样当我们从视频显示画面变为全屏的时候，出现了一个问题，全屏的时候，画面质量很差，线条和边界画面出现明显的锯齿现象。所以最后此方法没行通，只能再找解决办法：

分析sdl内部消息的源码：

///////////////SDL消息分析//////////////////////////
WIN_WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)//这个函数是SDL接管windows窗口消息的函数
{
...
        case WM_WINDOWPOSCHANGED://会触发这个消息
        {
            RECT rect;
            int x, y;
            int w, h;

            if (!GetClientRect(hwnd, &rect) || IsRectEmpty(&rect)) {
                break;
            }
            ClientToScreen(hwnd, (LPPOINT) & rect);
            ClientToScreen(hwnd, (LPPOINT) & rect + 1);

            WIN_UpdateClipCursor(data->window);

            x = rect.left;
            y = rect.top;
            //这里先发送窗口移动消息,移动x,y的坐标位置
            SDL_SendWindowEvent(data->window, SDL_WINDOWEVENT_MOVED, x, y);

            w = rect.right - rect.left;
            h = rect.bottom - rect.top;
            //然后这里发送尺寸修改消息,修改显示窗口的w,h
            //屏蔽掉这个消息之后,全屏会出现锯齿，视频渲染效果很差
            SDL_SendWindowEvent(data->window, SDL_WINDOWEVENT_RESIZED, w,h);//发送这个事件
        }
        break;
...
}
    
////////////////////////////////////////////////////
int SDL_SendWindowEvent(SDL_Window * window, Uint8 windowevent, int data1,int data2)
{
    case SDL_WINDOWEVENT_MOVED:        //处理
        if (SDL_WINDOWPOS_ISUNDEFINED(data1) ||
            SDL_WINDOWPOS_ISUNDEFINED(data2)) {
            return 0;
        }
        if (!(window->flags & SDL_WINDOW_FULLSCREEN)) {
            window->windowed.x = data1;
            window->windowed.y = data2;
        }
        if (data1 == window->x && data2 == window->y) {
            return 0;
        }
        window->x = data1;
        window->y = data2;
        break;
    case SDL_WINDOWEVENT_RESIZED://处理
        if (!(window->flags & SDL_WINDOW_FULLSCREEN)) {
            window->windowed.w = data1;
            window->windowed.h = data2;
        }
        if (data1 == window->w && data2 == window->h) {
            return 0;
        }
        window->w = data1;
        window->h = data2;
        SDL_OnWindowResized(window);//进入这个事件处理会崩溃-lhp
            {//注意这个函数里面也是发送一个窗口大小改变的消息
                SDL_SendWindowEvent(window, SDL_WINDOWEVENT_SIZE_CHANGED, window->w, window->h);//发送改变消息-LHP
            }
        break;
        /////////////////Break出来以后////////////////////////
    if (SDL_GetEventState(SDL_WINDOWEVENT) == SDL_ENABLE) {
        SDL_Event event;
        event.type = SDL_WINDOWEVENT;
        event.window.event = windowevent;
        event.window.data1 = data1;
        event.window.data2 = data2;
        event.window.windowID = window->id;

        /* Fixes queue overflow with resize events that aren't processed */
        if (windowevent == SDL_WINDOWEVENT_RESIZED) {//2)然后触发这个消息事件
            SDL_FilterEvents(RemovePendingResizedEvents, &event);
        }
        if (windowevent == SDL_WINDOWEVENT_SIZE_CHANGED) {//3)最后触发这个消息事件
            SDL_FilterEvents(RemovePendingSizeChangedEvents, &event);
        }
        if (windowevent == SDL_WINDOWEVENT_MOVED) {//1)首先触发这个消息事件
            SDL_FilterEvents(RemovePendingMoveEvents, &event);
        }

        posted = (SDL_PushEvent(&event) > 0);
    }
}    

//////////////////////////////////////
//上面的分析是消息的触发，下面看看消息捕捉以后消息的处理分析    
//SDL的渲染事件watch函数用于捕捉事件
static int SDL_RendererEventWatch(void *userdata, SDL_Event *event)
{
    SDL_Renderer *renderer = (SDL_Renderer *)userdata;
        if (event->type == SDL_WINDOWEVENT) {
        SDL_Window *window = SDL_GetWindowFromID(event->window.windowID);
        if (window == renderer->window) {
            if (renderer->WindowEvent) {
                renderer->WindowEvent(renderer, &event->window);
                //这个函数的内部实现源码如下:
                        static void D3D_WindowEvent(SDL_Renderer * renderer, const SDL_WindowEvent *event)
                        {
                            D3D_RenderData *data = (D3D_RenderData *) renderer->driverdata;

                            if (event->event == SDL_WINDOWEVENT_SIZE_CHANGED) {
                                data->updateSize = SDL_TRUE;
                            }
                        }
            }

            if (event->window.event == SDL_WINDOWEVENT_SIZE_CHANGED) {
                if (renderer->logical_w) {
                    UpdateLogicalSize(renderer);
                } else {
                    /* Window was resized, reset viewport */
                    int w, h;

                    if (renderer->GetOutputSize) {
                        renderer->GetOutputSize(renderer, &w, &h);
                    } else {
                        SDL_GetWindowSize(renderer->window, &w, &h);
                    }

                    if (renderer->target) {
                        renderer->viewport_backup.x = 0;
                        renderer->viewport_backup.y = 0;
                        renderer->viewport_backup.w = w;
                        renderer->viewport_backup.h = h;
                    } else {
                        renderer->viewport.x = 0;
                        renderer->viewport.y = 0;
                        renderer->viewport.w = w;
                        renderer->viewport.h = h;
                        //这个函数会导致崩溃,在部分机器上，设置视区区域
                        //最后我把这个地方的这个函数给注释掉了。
                        //modefy by lhp -20150805
                        //renderer->UpdateViewport(renderer);//崩溃的地方-LHP
                    }
                }
            } 
        }
        }

}
//updateViewport
static int D3D_UpdateViewport(SDL_Renderer * renderer)
{
    D3D_RenderData *data = (D3D_RenderData *) renderer->driverdata;

    viewport.X = renderer->viewport.x;
    viewport.Y = renderer->viewport.y;
    viewport.Width = renderer->viewport.w;
    viewport.Height = renderer->viewport.h;
    viewport.MinZ = 0.0f;
    viewport.MaxZ = 1.0f;
    //这里是跟踪的时候,调用崩溃的函数,在部分机器上,当窗口视区改变大小的时候,这个函数会崩溃
    IDirect3DDevice9_SetViewport(data->device, &viewport);

}
    







    

当时想从D3D_UpdateViewport函数入手，但发现我改的几个版本出来的效果，依然会崩溃，例如加clear，getviewport函数看会失败不，等等操作函数，都无用，没办法，只有在消息函数里面处理，把更新显示视区的函数给屏蔽掉。(这个地方做修改也是影响最小的屏蔽，因为这个地方是针对SDL_WINDOWEVENT_SIZE_CHANGED这个事件。)

 

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