// What does this file solves? // - Since Dear ImGui 1.00 we took pride that most of our examples applications had their entire // main-loop inside the main() function. That's because: // - It makes the examples easier to read, keeping the code sequential. // - It permit the use of local variables, making it easier to try things and perform quick // changes when someone needs to quickly test something (vs having to structure the example // in order to pass data around). This is very important because people use those examples // to craft easy-to-past repro when they want to discuss features or report issues. // - It conveys at a glance that this is a no-BS framework, it won't take your main loop away from you. // - It is generally nice and elegant. // - However, comes Emscripten... it is a wonderful and magical tech but it requires a "main loop" function. // - Only some of our examples would run on Emscripten. Typically the ones rendering with GL or WGPU ones. // - I tried to refactor those examples but felt it was problematic that other examples didn't follow the // same layout. Why would the SDL+GL example be structured one way and the SGL+DX11 be structured differently? // Especially as we are trying hard to convey that using a Dear ImGui backend in an *existing application* // should requires only a few dozens lines of code, and this should be consistent and symmetrical for all backends. // - So the next logical step was to refactor all examples to follow that layout of using a "main loop" function. // This worked, but it made us lose all the nice things we had... // Since only about 3 examples really need to run with Emscripten, here's our solution: // - Use some weird macros and capturing lambda to turn a loop in main() into a function. // - Hide all that crap in this file so it doesn't make our examples unusually ugly. // As a stance and principle of Dear ImGui development we don't use C++ headers and we don't // want to suggest to the newcomer that we would ever use C++ headers as this would affect // the initial judgment of many of our target audience. // - Technique is based on this idea: https://github.com/ocornut/imgui/pull/2492/ #ifdef __EMSCRIPTEN__ #include <emscripten.h> #include <functional> static std::function<void()> MainLoopForEmscriptenP; static void MainLoopForEmscripten() { MainLoopForEmscriptenP(); } #define EMSCRIPTEN_MAINLOOP_BEGIN MainLoopForEmscriptenP = [&]() #define EMSCRIPTEN_MAINLOOP_END ; emscripten_set_main_loop(MainLoopForEmscripten, 0, true) #else #define EMSCRIPTEN_MAINLOOP_BEGIN #define EMSCRIPTEN_MAINLOOP_END #endif