MyClass a1 {a}; // clearer and less error-prone than the other three MyClass a2 = {a}; MyClass a3 = a; MyClass a4(a); Why? I couldn't find an answer on SO, so let me answer my own question. Basically copying and pasting from Bjarne Stroustrup's "The C++ Programming Language 4th Edition": List initialization does not allow narrowing (§iso.8.5.4). That is: An integer
MyClass a1 {a}; // clearer and less error-prone than the other three MyClass a2 = {a}; MyClass a3 = a; MyClass a4(a); 为什么？ 我无法找到答案，所以让我回答我自己的问题。 基本上从Bjarne Stroustrup的“The C ++ Programming Language 4th Edition”复制和粘贴： 列表初始化不允许缩小（第8.5.4节）。 那是： 一个整数不能转换为另一个不能保存其值的整数。 例如，char到int是允许的，但不是int到char。
In C++ there are few compelling reasons to use a C array over std::vector . One of those few compelling reasons, at least with C++03, was the fact that it is impossible to use a vector to allocate an uninitialized array of objects. The "fill" constructor for std::vector is: vector(size_type count, const T& value = T()) Meaning that... int* array = new array[1000000]; is like
在C ++中，通过std::vector使用C数组几乎没有令人信服的理由。 至少在C ++ 03中，这些少数令人信服的理由之一就是事实上不可能使用向量来分配未初始化的对象数组。 std::vector的“fill”构造函数是： vector(size_type count, const T& value = T()) 意思是... int* array = new array[1000000]; 可能比以下更有效率： std::vector<int> v(1000000); ...因为矢量构造函数将不得不初始化整数数组。 因此，在
I have scanned through a few C++ books but none of them describe this in detail: With VC++ 2010, I created a struct with constructors deliberately added for testing: struct BufferElement { size_t currentAllocationSize; BufferElement() { currentAllocationSize=50; } BufferElement(size_t size) { if (size==0) currentAllocationSize=20; else
我已经通过一些C ++书籍进行了扫描，但没有一篇详细描述这一点： 在VC ++ 2010中，我创建了一个结构体，并有意添加了用于测试的构造函数： struct BufferElement { size_t currentAllocationSize; BufferElement() { currentAllocationSize=50; } BufferElement(size_t size) { if (size==0) currentAllocationSize=20; else currentAllocationSize=1;
I was trying to create a vector of lambda, but failed: auto ignore = [&]() { return 10; }; //1 std::vector<decltype(ignore)> v; //2 v.push_back([&]() { return 100; }); //3 Up to line #2, it compiles fine. But the line#3 gives compilation error: error: no matching function for call to 'std::vector<main()::<lambda()>>::push_back(main()::<lambda()>)'
我试图创建一个lambda矢量，但失败了： auto ignore = [&]() { return 10; }; //1 std::vector<decltype(ignore)> v; //2 v.push_back([&]() { return 100; }); //3 直到第二行，它编译得很好。 但＃3行给出编译错误： 错误：没有用于调用'std :: vector <main（）:: lambda（）>> :: push_back（main（）:: <lambda（）>）的匹配函数' 我不想要函数指针向量或函数对象向量。
I'm am learning SDL2, but I am also using the imgui library that is using OpenGL calls. From what I read on various blogs online, I can't easily mix SDL2 renderer and opengl calls; I either use one or the other. Most of the tutorials I've read use the renderer, so I do not quite understand how to use SDL2 without the renderer for drawing primitives, or drawing sprites. Take this
我正在学习SDL2，但我也在使用使用OpenGL调用的imgui库。 从我在网上阅读的各种博客中，我无法轻松混合使用SDL2渲染器和opengl调用; 我要么使用一个或另一个。 我读过的大多数教程都使用渲染器，所以我不太了解如何在没有渲染器的情况下使用SDL2来绘制基元或绘制精灵。 以此为例：http://lazyfoo.net/tutorials/SDL/11_clip_rendering_and_sprite_sheets/index.php 他创建了sdl渲染器： gRenderer = SDL_CreateRenderer(
I'm testing supporting multiple resolutions in an application using SDL2 with OpenGL. To create my "letterbox" functionality I set my glViewport to an appropriate value and everything works perfectly. However, if I create my window with the SDL_WINDOW_ALLOW_HIGHDPI flag set, whenever I move my window (after receiving the SDL_WINDOWEVENT_MOVED event) SDL modifies the viewport to t
我在使用OpenGL的SDL2应用程序中测试支持多种分辨率。 为了创建我的“信箱”功能，我将我的glViewport设置为适当的值，并且一切正常。 但是，如果我创建了设置了SDL_WINDOW_ALLOW_HIGHDPI标志的窗口，则无论何时移动我的窗口（在接收到SDL_WINDOWEVENT_MOVED事件后），SDL都会将视口修改为窗口的全部大小，可以通过在事件期间调用SDL_GL_GetDrawableSize进行验证。 如果在创建窗口时未设置SDL_WINDOW_ALLOW_HIGHDPI ，则视口
I am on Mac OS (10.9.3). I can create a window + context which is a 3.3 Context as requested. But once I create the renderer SDL tells me that the renderer is invalid. Apart from that I can use the renderer to draw and copy textures. But creating the renderer also seems to change the OpenGL context to a 2.1 profile :( Is there a way to prevent that? [EDIT] SDL2 and glew are linked as a
我在Mac OS（10.9.3）上。 我可以根据请求创建一个窗口+上下文，它是一个3.3上下文。 但是一旦我创建了渲染器，SDL告诉我渲染器无效。 除此之外，我可以使用渲染器来绘制和复制纹理。 但创建渲染器似乎也将OpenGL上下文更改为2.1个配置文件:( 有没有办法阻止？ [编辑] SDL2和glew作为静态库链接。 glewExperimental未设置为GL_TRUE。 C ++源码： SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3); SDL_GL_Set
I've been trying to get GLew 1.10 to play nicely with SDL 2.0.3 , but GLew won't initialize. The problem I'm having is that GLew 1.10 requires a function GLEWContext* glewGetContext(). I've tried to use a the same solution used for GLew 1.10 with GLFW3, where you use a struct to handle the window and GLew context, but that method doesn't work with SDL2. The 2 errors I'
我一直试图让GLew 1.10与SDL 2.0.3很好地配合，但GLew不会初始化。 我遇到的问题是GLew 1.10需要函数GLEWContext* glewGetContext(). 我试着使用与GLFW3一样的GLew 1.10使用的相同解决方案，其中使用struct来处理窗口和GLew上下文，但该方法不适用于SDL2。 我收到的2个错误是指向glewInit（）的这个错误： C3861: 'glewGetContext': identifier not found Intellisense: identifier "glewGetContext is und
只使用给定的SDL_Window *和SDL_Renderer *，如何在SDL 2.0中创建和保存屏幕截图？ Below is a function for saving a screenshot in SDL 2 taken from a library I'm currently writing. bool saveScreenshotBMP(std::string filepath, SDL_Window* SDLWindow, SDL_Renderer* SDLRenderer) { SDL_Surface* saveSurface = NULL; SDL_Surface* infoSurface = NULL; infoSurface = SDL_GetWindowSurface(SDLWindow
只使用给定的SDL_Window *和SDL_Renderer *，如何在SDL 2.0中创建和保存屏幕截图？ 下面是一个用于从我正在编写的库中保存SDL 2屏幕截图的功能。 bool saveScreenshotBMP(std::string filepath, SDL_Window* SDLWindow, SDL_Renderer* SDLRenderer) { SDL_Surface* saveSurface = NULL; SDL_Surface* infoSurface = NULL; infoSurface = SDL_GetWindowSurface(SDLWindow); if (infoSurface == NULL) { s
I am writing an application that decodes a single video stream from an input file (any codec, any container), does a bunch of image processing, and encodes the results to an output file (single video stream, Quicktime RLE, MOV). I am using ffmpeg's libav 3.1.5 (Windows build for now, but the application will be cross-platform). There is a 1:1 correspondence between input and output frames
我正在编写一个应用程序，用于解码来自输入文件（任何编解码器，任何容器）的单个视频流，执行一堆图像处理，并将结果编码为输出文件（单视频流，Quicktime RLE，MOV）。 我正在使用ffmpeg的libav 3.1.5（Windows现在构建，但应用程序将是跨平台的）。 输入和输出帧之间有1：1的对应关系，我希望输出中的帧定时与输入相同。 我真的很难完成这个任务。 所以我的一般问题是： 我如何可靠地（如在所有输入情况下）将输出帧定时