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113 lines
3.3 KiB
C++
113 lines
3.3 KiB
C++
//
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// Joystick.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 16/02/2021.
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// Copyright © 2021 Thomas Harte. All rights reserved.
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//
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#ifndef AppleII_Joystick_hpp
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#define AppleII_Joystick_hpp
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#include "../../../Inputs/Joystick.hpp"
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#include <memory>
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#include <vector>
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namespace Apple {
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namespace II {
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class JoystickPair {
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public:
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JoystickPair() {
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// Add a couple of joysticks.
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joysticks_.emplace_back(new Joystick);
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joysticks_.emplace_back(new Joystick);
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}
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class Joystick: public Inputs::ConcreteJoystick {
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public:
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Joystick() :
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ConcreteJoystick({
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Input(Input::Horizontal),
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Input(Input::Vertical),
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// The Apple II offers three buttons between two joysticks;
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// this emulator puts three buttons on each joystick and
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// combines them.
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Input(Input::Fire, 0),
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Input(Input::Fire, 1),
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Input(Input::Fire, 2),
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}) {}
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void did_set_input(const Input &input, float value) final {
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if(!input.info.control.index && (input.type == Input::Type::Horizontal || input.type == Input::Type::Vertical))
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axes[(input.type == Input::Type::Horizontal) ? 0 : 1] = 1.0f - value;
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}
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void did_set_input(const Input &input, bool value) final {
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if(input.type == Input::Type::Fire && input.info.control.index < 3) {
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buttons[input.info.control.index] = value;
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}
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}
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bool buttons[3] = {false, false, false};
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float axes[2] = {0.5f, 0.5f};
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};
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inline bool button(size_t index) {
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return joystick(0)->buttons[index] || joystick(1)->buttons[2-index];
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}
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inline bool analogue_channel_is_discharged(size_t channel) {
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return (1.0f - static_cast<Joystick *>(joysticks_[channel >> 1].get())->axes[channel & 1]) < analogue_charge_ + analogue_biases_[channel];
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}
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inline void update_charge(float one_mhz_cycles = 1.0f) {
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analogue_charge_ = std::min(analogue_charge_ + one_mhz_cycles * (1.0f / 2820.0f), 1.1f);
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}
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inline void access_c070() {
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// Permit analogue inputs that are currently discharged to begin a charge cycle.
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// Ensure those that were still charging retain that state.
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for(size_t c = 0; c < 4; ++c) {
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if(analogue_channel_is_discharged(c)) {
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analogue_biases_[c] = 0.0f;
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} else {
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analogue_biases_[c] += analogue_charge_;
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}
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}
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analogue_charge_ = 0.0f;
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}
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const std::vector<std::unique_ptr<Inputs::Joystick>> &get_joysticks() {
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return joysticks_;
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}
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private:
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// On an Apple II, the programmer strobes 0xc070 and that causes each analogue input
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// to begin a charge and discharge cycle **if they are not already charging**.
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// The greater the analogue input, the faster they will charge and therefore the sooner
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// they will discharge.
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//
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// This emulator models that with analogue_charge_ being essentially the amount of time,
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// in charge threshold units, since 0xc070 was last strobed. But if any of the analogue
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// inputs were already partially charged then they gain a bias in analogue_biases_.
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//
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// It's a little indirect, but it means only having to increment the one value in the
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// main loop.
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float analogue_charge_ = 0.0f;
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float analogue_biases_[4] = {0.0f, 0.0f, 0.0f, 0.0f};
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std::vector<std::unique_ptr<Inputs::Joystick>> joysticks_;
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inline Joystick *joystick(size_t index) {
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return static_cast<Joystick *>(joysticks_[index].get());
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}
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};
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}
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}
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#endif /* AppleII_Joystick_hpp */
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