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39 lines
2.7 KiB
C++
39 lines
2.7 KiB
C++
// What does this file solves?
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// - Since Dear ImGui 1.00 we took pride that most of our examples applications had their entire
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// main-loop inside the main() function. That's because:
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// - It makes the examples easier to read, keeping the code sequential.
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// - It permit the use of local variables, making it easier to try things and perform quick
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// changes when someone needs to quickly test something (vs having to structure the example
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// in order to pass data around). This is very important because people use those examples
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// to craft easy-to-past repro when they want to discuss features or report issues.
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// - It conveys at a glance that this is a no-BS framework, it won't take your main loop away from you.
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// - It is generally nice and elegant.
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// - However, comes Emscripten... it is a wonderful and magical tech but it requires a "main loop" function.
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// - Only some of our examples would run on Emscripten. Typically the ones rendering with GL or WGPU ones.
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// - I tried to refactor those examples but felt it was problematic that other examples didn't follow the
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// same layout. Why would the SDL+GL example be structured one way and the SGL+DX11 be structured differently?
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// Especially as we are trying hard to convey that using a Dear ImGui backend in an *existing application*
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// should requires only a few dozens lines of code, and this should be consistent and symmetrical for all backends.
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// - So the next logical step was to refactor all examples to follow that layout of using a "main loop" function.
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// This worked, but it made us lose all the nice things we had...
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// Since only about 4 examples really need to run with Emscripten, here's our solution:
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// - Use some weird macros and capturing lambda to turn a loop in main() into a function.
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// - Hide all that crap in this file so it doesn't make our examples unusually ugly.
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// As a stance and principle of Dear ImGui development we don't use C++ headers and we don't
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// want to suggest to the newcomer that we would ever use C++ headers as this would affect
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// the initial judgment of many of our target audience.
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// - Technique is based on this idea: https://github.com/ocornut/imgui/pull/2492/
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// - The do { } while (0) is to allow our code calling continue in the main loop.
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#ifdef __EMSCRIPTEN__
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#include <emscripten.h>
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#include <functional>
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static std::function<void()> MainLoopForEmscriptenP;
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static void MainLoopForEmscripten() { MainLoopForEmscriptenP(); }
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#define EMSCRIPTEN_MAINLOOP_BEGIN MainLoopForEmscriptenP = [&]() { do
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#define EMSCRIPTEN_MAINLOOP_END while (0); }; emscripten_set_main_loop(MainLoopForEmscripten, 0, true)
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#else
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#define EMSCRIPTEN_MAINLOOP_BEGIN
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#define EMSCRIPTEN_MAINLOOP_END
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#endif
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