Method FetchFilesAsync

Sources/Shared/IO/EmscriptenFileStream.cpp:222–263

	}

	void EmscriptenFilePicker::FetchFilesAsync(Containers::StringView fileFilter, bool multiple, Containers::Function<void(Containers::ArrayView<EmscriptenFileStream>)>&& callback)
	{
		if (_activeCallback) {
			// Another callback is already active, cancel this one
			callback({});
			return;
		}

		_activeCallback = Death::move(callback);

		// Create file input element which will display a native file dialog
		auto document = emscripten::val::global("document");
		auto input = document.call<emscripten::val>("createElement", std::string("input"));
		input.set("type", "file");
		input.set("style", "display:none");
		if (!fileFilter.empty()) {
			input.set("accept", emscripten::val(fileFilter.data()));
		}
		if (multiple) {
			input.set("multiple", "multiple");
		}

		// http://perfectionkills.com/detecting-event-support-without-browser-sniffing
		_supportsCancel = false;
		if (emscripten::val("oncancel").in(input)) {
			_supportsCancel = true;
		} else {
			input.set("oncancel", emscripten::val("return;"));
			if (input["oncancel"].typeOf().as<std::string>() == "function") {
				_supportsCancel = true;
			}
		}

		input.set("onchange", emscripten::val::module_property("jsReadFiles"));
		input.set("oncancel", emscripten::val::module_property("jsCancelReadFiles"));
		input.set("data-callbackContext", emscripten::val(std::size_t(this)));

		auto body = document["body"];
		body.call<void>("appendChild", input);
		input.call<void>("click");
		body.call<void>("removeChild", input);
	}

	void EmscriptenFilePicker::FetchDirectoryAsync(Containers::Function<void(Containers::ArrayView<EmscriptenFileStream>)>&& callback)
	{