JoyMega.cc

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#include "JoyMega.hh"
#include "PluggingController.hh"
#include "MSXEventDistributor.hh"
#include "StateChangeDistributor.hh"
#include "InputEvents.hh"
#include "InputEventGenerator.hh"
#include "StateChange.hh"
#include "checked_cast.hh"
#include "serialize.hh"
#include "serialize_meta.hh"
#include "unreachable.hh"
#include "build-info.hh"
#include <memory>

using std::string;
using std::shared_ptr;

namespace openmsx {

#if PLATFORM_ANDROID
static const int THRESHOLD = 32768 / 4;
#else
static const int THRESHOLD = 32768 / 10;
#endif

void JoyMega::registerAll(MSXEventDistributor& eventDistributor,
                           StateChangeDistributor& stateChangeDistributor,
                           PluggingController& controller)
{
#ifdef SDL_JOYSTICK_DISABLED
        (void)eventDistributor;
        (void)stateChangeDistributor;
        (void)controller;
#else
        unsigned numJoysticks = SDL_NumJoysticks();
        for (unsigned i = 0; i < numJoysticks; i++) {
                if (SDL_Joystick* joystick = SDL_JoystickOpen(i)) {
                        // Avoid devices that have axes but no buttons, like accelerometers.
                        // SDL 1.2.14 in Linux has an issue where it rejects a device from
                        // /dev/input/event* if it has no buttons but does not reject a
                        // device from /dev/input/js* if it has no buttons, while
                        // accelerometers do end up being symlinked as a joystick in
                        // practice.
                        if (InputEventGenerator::joystickNumButtons(joystick) != 0) {
                                controller.registerPluggable(
                                        std::make_unique<JoyMega>(
                                                eventDistributor,
                                                stateChangeDistributor,
                                                joystick));
                        }
                }
        }
#endif
}

class JoyMegaState final : public StateChange
{
public:
        JoyMegaState() = default; // for serialize
        JoyMegaState(EmuTime::param time_, unsigned joyNum_,
                     unsigned press_, unsigned release_)
                : StateChange(time_)
                , joyNum(joyNum_), press(press_), release(release_)
        {
                assert((press != 0) || (release != 0));
                assert((press & release) == 0);
        }
        unsigned getJoystick() const { return joyNum; }
        unsigned getPress()    const { return press; }
        unsigned getRelease()  const { return release; }

        template<typename Archive> void serialize(Archive& ar, unsigned /*version*/)
        {
                ar.template serializeBase<StateChange>(*this);
                ar.serialize("joyNum",  joyNum,
                             "press",   press,
                             "release", release);
        }
private:
        unsigned joyNum;
        unsigned press, release;
};
REGISTER_POLYMORPHIC_CLASS(StateChange, JoyMegaState, "JoyMegaState");

#ifndef SDL_JOYSTICK_DISABLED
// Note: It's OK to open/close the same SDL_Joystick multiple times (we open it
// once per MSX machine). The SDL documentation doesn't state this, but I
// checked the implementation and a SDL_Joystick uses a 'reference count' on
// the open/close calls.
JoyMega::JoyMega(MSXEventDistributor& eventDistributor_,
                 StateChangeDistributor& stateChangeDistributor_,
                 SDL_Joystick* joystick_)
        : eventDistributor(eventDistributor_)
        , stateChangeDistributor(stateChangeDistributor_)
        , joystick(joystick_)
        , joyNum(SDL_JoystickInstanceID(joystick_))
        , name("joymegaX") // 'X' is filled in below
        , desc(string(SDL_JoystickName(joystick_)))
        , lastTime(EmuTime::zero)
{
        const_cast<string&>(name)[7] = char('1' + joyNum);
}

JoyMega::~JoyMega()
{
        if (isPluggedIn()) {
                JoyMega::unplugHelper(EmuTime::dummy());
        }
        SDL_JoystickClose(joystick);
}

// Pluggable
const string& JoyMega::getName() const
{
        return name;
}

string_view JoyMega::getDescription() const
{
        return desc;
}

void JoyMega::plugHelper(Connector& /*connector*/, EmuTime::param /*time*/)
{
        plugHelper2();
        status = calcInitialState();
        cycle = 0;
        // when mode button is pressed when joystick is plugged in, then
        // act as a 3-button joypad (otherwise 6-button)
        cycleMask = (status & 0x800) ? 7 : 1;
}

void JoyMega::plugHelper2()
{
        eventDistributor.registerEventListener(*this);
        stateChangeDistributor.registerListener(*this);
}

void JoyMega::unplugHelper(EmuTime::param /*time*/)
{
        stateChangeDistributor.unregisterListener(*this);
        eventDistributor.unregisterEventListener(*this);
}


// JoystickDevice
byte JoyMega::read(EmuTime::param time)
{
        // See http://segaretro.org/Control_Pad_(Mega_Drive)
        // and http://frs.badcoffee.info/hardware/joymega-en.html
        // for a detailed description of the MegaDrive joystick.
        checkTime(time);
        switch (cycle) {
        case 0: case 2: case 4:
                // up/down/left/right/b/c
                return (status & 0x00f) | ((status & 0x060) >> 1);
        case 1: case 3:
                // up/down/0/0/a/start
                return (status & 0x013) | ((status & 0x080) >> 2);
        case 5:
                // 0/0/0/0/a/start
                return (status & 0x010) | ((status & 0x080) >> 2);
        case 6:
                // z/y/x/mode/b/c
                return ((status & 0x400) >> 10) | // z
                       ((status & 0xA00) >>  8) | // start+y
                       ((status & 0x100) >>  6) | // x
                       ((status & 0x060) >>  1);  // c+b
        case 7:
                // 1/1/1/1/a/start
                return (status & 0x010) | ((status & 0x080) >> 2) | 0x0f;
        default:
                UNREACHABLE; return 0;
        }
}

void JoyMega::write(byte value, EmuTime::param time)
{
        checkTime(time);
        lastTime = time;
        if (((value >> 2) & 1) != (cycle & 1)) {
                cycle = (cycle + 1) & cycleMask;
        }
        assert(((value >> 2) & 1) == (cycle & 1));
}

void JoyMega::checkTime(EmuTime::param time)
{
        if ((time - lastTime) > EmuDuration::usec(1500)) {
                // longer than 1.5ms since last write -> reset cycle
                cycle = 0;
        }
}

static unsigned encodeButton(unsigned button, byte cycleMask)
{
        unsigned n = (cycleMask == 7) ? 7 : 3; // 6- or 3-button mode
        return 1 << (4 + (button & n));
}

unsigned JoyMega::calcInitialState()
{
        unsigned result = 0xfff;
        int xAxis = SDL_JoystickGetAxis(joystick, 0);
        if (xAxis < -THRESHOLD) {
                result &= ~JOY_LEFT;
        } else if (xAxis > THRESHOLD) {
                result &= ~JOY_RIGHT;
        }

        int yAxis = SDL_JoystickGetAxis(joystick, 1);
        if (yAxis < -THRESHOLD) {
                result &= ~JOY_UP;
        } else if (yAxis > THRESHOLD) {
                result &= ~JOY_DOWN;
        }

        int numButtons = InputEventGenerator::joystickNumButtons(joystick);
        for (int button = 0; button < numButtons; ++button) {
                if (InputEventGenerator::joystickGetButton(joystick, button)) {
                        result &= ~encodeButton(button, 7);
                }
        }
        return result;
}

// MSXEventListener
void JoyMega::signalMSXEvent(const shared_ptr<const Event>& event, EmuTime::param time)
{
        auto joyEvent = dynamic_cast<const JoystickEvent*>(event.get());
        if (!joyEvent) return;

        // TODO: It would be more efficient to make a dispatcher instead of
        //       sending the event to all joysticks.
        if (joyEvent->getJoystick() != joyNum) return;

        switch (event->getType()) {
        case OPENMSX_JOY_AXIS_MOTION_EVENT: {
                auto& mev = checked_cast<const JoystickAxisMotionEvent&>(*event);
                int value = mev.getValue();
                switch (mev.getAxis() & 1) {
                case JoystickAxisMotionEvent::X_AXIS: // Horizontal
                        if (value < -THRESHOLD) {
                                // left, not right
                                createEvent(time, JOY_LEFT, JOY_RIGHT);
                        } else if (value > THRESHOLD) {
                                // not left, right
                                createEvent(time, JOY_RIGHT, JOY_LEFT);
                        } else {
                                // not left, not right
                                createEvent(time, 0, JOY_LEFT | JOY_RIGHT);
                        }
                        break;
                case JoystickAxisMotionEvent::Y_AXIS: // Vertical
                        if (value < -THRESHOLD) {
                                // up, not down
                                createEvent(time, JOY_UP, JOY_DOWN);
                        } else if (value > THRESHOLD) {
                                // not up, down
                                createEvent(time, JOY_DOWN, JOY_UP);
                        } else {
                                // not up, not down
                                createEvent(time, 0, JOY_UP | JOY_DOWN);
                        }
                        break;
                default:
                        // ignore other axis
                        break;
                }
                break;
        }
        case OPENMSX_JOY_BUTTON_DOWN_EVENT: {
                auto& butEv = checked_cast<const JoystickButtonEvent&>(*event);
                createEvent(time, encodeButton(butEv.getButton(), cycleMask), 0);
                break;
        }
        case OPENMSX_JOY_BUTTON_UP_EVENT: {
                auto& butEv = checked_cast<const JoystickButtonEvent&>(*event);
                createEvent(time, 0, encodeButton(butEv.getButton(), cycleMask));
                break;
        }
        default:
                UNREACHABLE;
        }
}

void JoyMega::createEvent(EmuTime::param time, unsigned press, unsigned release)
{
        unsigned newStatus = (status & ~press) | release;
        createEvent(time, newStatus);
}

void JoyMega::createEvent(EmuTime::param time, unsigned newStatus)
{
        unsigned diff = status ^ newStatus;
        if (!diff) {
                // event won't actually change the status, so ignore it
                return;
        }
        // make sure we create an event with minimal changes
        unsigned press   =    status & diff;
        unsigned release = newStatus & diff;
        stateChangeDistributor.distributeNew(std::make_shared<JoyMegaState>(
                time, joyNum, press, release));
}

// StateChangeListener
void JoyMega::signalStateChange(const shared_ptr<StateChange>& event)
{
        auto js = dynamic_cast<const JoyMegaState*>(event.get());
        if (!js) return;

        // TODO: It would be more efficient to make a dispatcher instead of
        //       sending the event to all joysticks.
        // TODO an alternative is to log events based on the connector instead
        //      of the joystick. That would make it possible to replay on a
        //      different host without an actual SDL joystick connected.
        if (js->getJoystick() != joyNum) return;

        status = (status & ~js->getPress()) | js->getRelease();
}

void JoyMega::stopReplay(EmuTime::param time)
{
        createEvent(time, calcInitialState());
}

template<typename Archive>
void JoyMega::serialize(Archive& ar, unsigned /*version*/)
{
        ar.serialize("lastTime",  lastTime,
                     "status",    status,
                     "cycle",     cycle,
                     "cycleMask", cycleMask);
        if (ar.isLoader()) {
                if (isPluggedIn()) {
                        plugHelper2();
                }
        }
}
INSTANTIATE_SERIALIZE_METHODS(JoyMega);
REGISTER_POLYMORPHIC_INITIALIZER(Pluggable, JoyMega, "JoyMega");

#endif // SDL_JOYSTICK_DISABLED

} // namespace openmsx