src/joystick/emscripten/SDL_sysjoystick.c

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2020 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/

#include "../../SDL_internal.h"

#ifdef SDL_JOYSTICK_EMSCRIPTEN

#include <stdio.h>              /* For the definition of NULL */
#include "SDL_error.h"
#include "SDL_events.h"

#include "SDL_joystick.h"
#include "SDL_assert.h"
#include "SDL_timer.h"
#include "SDL_sysjoystick_c.h"
#include "../SDL_joystick_c.h"

static SDL_joylist_item * JoystickByIndex(int index);

static SDL_joylist_item *SDL_joylist = NULL;
static SDL_joylist_item *SDL_joylist_tail = NULL;
static int numjoysticks = 0;
static int instance_counter = 0;

static EM_BOOL
Emscripten_JoyStickConnected(int eventType, const EmscriptenGamepadEvent *gamepadEvent, void *userData)
{
    int i;

    SDL_joylist_item *item;

    if (JoystickByIndex(gamepadEvent->index) != NULL) {
      return 1;
    }

    item = (SDL_joylist_item *) SDL_malloc(sizeof (SDL_joylist_item));
    if (item == NULL) {
        return 1;
    }

    SDL_zerop(item);
    item->index = gamepadEvent->index;

    item->name = SDL_CreateJoystickName(0, 0, NULL, gamepadEvent->id);
    if ( item->name == NULL ) {
        SDL_free(item);
        return 1;
    }

    item->mapping = SDL_strdup(gamepadEvent->mapping);
    if ( item->mapping == NULL ) {
        SDL_free(item->name);
        SDL_free(item);
        return 1;
    }

    item->naxes = gamepadEvent->numAxes;
    item->nbuttons = gamepadEvent->numButtons;
    item->device_instance = instance_counter++;

    item->timestamp = gamepadEvent->timestamp;

    for( i = 0; i < item->naxes; i++) {
        item->axis[i] = gamepadEvent->axis[i];
    }

    for( i = 0; i < item->nbuttons; i++) {
        item->analogButton[i] = gamepadEvent->analogButton[i];
        item->digitalButton[i] = gamepadEvent->digitalButton[i];
    }

    if (SDL_joylist_tail == NULL) {
        SDL_joylist = SDL_joylist_tail = item;
    } else {
        SDL_joylist_tail->next = item;
        SDL_joylist_tail = item;
    }

    ++numjoysticks;

    SDL_PrivateJoystickAdded(item->device_instance);

#ifdef DEBUG_JOYSTICK
    SDL_Log("Number of joysticks is %d", numjoysticks);
#endif

#ifdef DEBUG_JOYSTICK
    SDL_Log("Added joystick with index %d", item->index);
#endif

    return 1;
}

static EM_BOOL
Emscripten_JoyStickDisconnected(int eventType, const EmscriptenGamepadEvent *gamepadEvent, void *userData)
{
    SDL_joylist_item *item = SDL_joylist;
    SDL_joylist_item *prev = NULL;

    while (item != NULL) {
        if (item->index == gamepadEvent->index) {
            break;
        }
        prev = item;
        item = item->next;
    }

    if (item == NULL) {
        return 1;
    }

    if (item->joystick) {
        item->joystick->hwdata = NULL;
    }

    if (prev != NULL) {
        prev->next = item->next;
    } else {
        SDL_assert(SDL_joylist == item);
        SDL_joylist = item->next;
    }
    if (item == SDL_joylist_tail) {
        SDL_joylist_tail = prev;
    }

    /* Need to decrement the joystick count before we post the event */
    --numjoysticks;

    SDL_PrivateJoystickRemoved(item->device_instance);

#ifdef DEBUG_JOYSTICK
    SDL_Log("Removed joystick with id %d", item->device_instance);
#endif
    SDL_free(item->name);
    SDL_free(item->mapping);
    SDL_free(item);
    return 1;
}

/* Function to perform any system-specific joystick related cleanup */
static void
EMSCRIPTEN_JoystickQuit(void)
{
    SDL_joylist_item *item = NULL;
    SDL_joylist_item *next = NULL;

    for (item = SDL_joylist; item; item = next) {
        next = item->next;
        SDL_free(item->mapping);
        SDL_free(item->name);
        SDL_free(item);
    }

    SDL_joylist = SDL_joylist_tail = NULL;

    numjoysticks = 0;
    instance_counter = 0;

    emscripten_set_gamepadconnected_callback(NULL, 0, NULL);
    emscripten_set_gamepaddisconnected_callback(NULL, 0, NULL);
}

/* Function to scan the system for joysticks.
 * It should return 0, or -1 on an unrecoverable fatal error.
 */
static int
EMSCRIPTEN_JoystickInit(void)
{
    int retval, i, numjs;
    EmscriptenGamepadEvent gamepadState;

    numjoysticks = 0;

    retval = emscripten_sample_gamepad_data();

    /* Check if gamepad is supported by browser */
    if (retval == EMSCRIPTEN_RESULT_NOT_SUPPORTED) {
        return SDL_SetError("Gamepads not supported");
    }

    numjs = emscripten_get_num_gamepads();

    /* handle already connected gamepads */
    if (numjs > 0) {
        for(i = 0; i < numjs; i++) {
            retval = emscripten_get_gamepad_status(i, &gamepadState);
            if (retval == EMSCRIPTEN_RESULT_SUCCESS) {
                Emscripten_JoyStickConnected(EMSCRIPTEN_EVENT_GAMEPADCONNECTED,
                                             &gamepadState,
                                             NULL);
            }
        }
    }

    retval = emscripten_set_gamepadconnected_callback(NULL,
                                                      0,
                                                      Emscripten_JoyStickConnected);

    if(retval != EMSCRIPTEN_RESULT_SUCCESS) {
        EMSCRIPTEN_JoystickQuit();
        return SDL_SetError("Could not set gamepad connect callback");
    }

    retval = emscripten_set_gamepaddisconnected_callback(NULL,
                                                         0,
                                                         Emscripten_JoyStickDisconnected);
    if(retval != EMSCRIPTEN_RESULT_SUCCESS) {
        EMSCRIPTEN_JoystickQuit();
        return SDL_SetError("Could not set gamepad disconnect callback");
    }

    return 0;
}

/* Returns item matching given SDL device index. */
static SDL_joylist_item *
JoystickByDeviceIndex(int device_index)
{
    SDL_joylist_item *item = SDL_joylist;

    while (0 < device_index) {
        --device_index;
        item = item->next;
    }

    return item;
}

/* Returns item matching given HTML gamepad index. */
static SDL_joylist_item *
JoystickByIndex(int index)
{
    SDL_joylist_item *item = SDL_joylist;

    if (index < 0) {
        return NULL;
    }

    while (item != NULL) {
        if (item->index == index) {
            break;
        }
        item = item->next;
    }

    return item;
}

static int
EMSCRIPTEN_JoystickGetCount(void)
{
    return numjoysticks;
}

static void
EMSCRIPTEN_JoystickDetect(void)
{
}

static const char *
EMSCRIPTEN_JoystickGetDeviceName(int device_index)
{
    return JoystickByDeviceIndex(device_index)->name;
}

static int
EMSCRIPTEN_JoystickGetDevicePlayerIndex(int device_index)
{
    return -1;
}

static void
EMSCRIPTEN_JoystickSetDevicePlayerIndex(int device_index, int player_index)
{
}

static SDL_JoystickID
EMSCRIPTEN_JoystickGetDeviceInstanceID(int device_index)
{
    return JoystickByDeviceIndex(device_index)->device_instance;
}

/* Function to open a joystick for use.
   The joystick to open is specified by the device index.
   This should fill the nbuttons and naxes fields of the joystick structure.
   It returns 0, or -1 if there is an error.
 */
static int
EMSCRIPTEN_JoystickOpen(SDL_Joystick * joystick, int device_index)
{
    SDL_joylist_item *item = JoystickByDeviceIndex(device_index);

    if (item == NULL ) {
        return SDL_SetError("No such device");
    }

    if (item->joystick != NULL) {
        return SDL_SetError("Joystick already opened");
    }

    joystick->instance_id = item->device_instance;
    joystick->hwdata = (struct joystick_hwdata *) item;
    item->joystick = joystick;

    /* HTML5 Gamepad API doesn't say anything about these */
    joystick->nhats = 0;
    joystick->nballs = 0;

    joystick->nbuttons = item->nbuttons;
    joystick->naxes = item->naxes;

    return (0);
}

/* Function to update the state of a joystick - called as a device poll.
 * This function shouldn't update the joystick structure directly,
 * but instead should call SDL_PrivateJoystick*() to deliver events
 * and update joystick device state.
 */
static void
EMSCRIPTEN_JoystickUpdate(SDL_Joystick * joystick)
{
    EmscriptenGamepadEvent gamepadState;
    SDL_joylist_item *item = (SDL_joylist_item *) joystick->hwdata;
    int i, result, buttonState;

    emscripten_sample_gamepad_data();

    if (item) {
        result = emscripten_get_gamepad_status(item->index, &gamepadState);
        if( result == EMSCRIPTEN_RESULT_SUCCESS) {
            if(gamepadState.timestamp == 0 || gamepadState.timestamp != item->timestamp) {
                for(i = 0; i < item->nbuttons; i++) {
                    if(item->digitalButton[i] != gamepadState.digitalButton[i]) {
                        buttonState = gamepadState.digitalButton[i]? SDL_PRESSED: SDL_RELEASED;
                        SDL_PrivateJoystickButton(item->joystick, i, buttonState);
                    }

                    /* store values to compare them in the next update */
                    item->analogButton[i] = gamepadState.analogButton[i];
                    item->digitalButton[i] = gamepadState.digitalButton[i];
                }

                for(i = 0; i < item->naxes; i++) {
                    if(item->axis[i] != gamepadState.axis[i]) {
                        /* do we need to do conversion? */
                        SDL_PrivateJoystickAxis(item->joystick, i,
                                                  (Sint16) (32767.*gamepadState.axis[i]));
                    }

                    /* store to compare in next update */
                    item->axis[i] = gamepadState.axis[i];
                }

                item->timestamp = gamepadState.timestamp;
            }
        }
    }
}

/* Function to close a joystick after use */
static void
EMSCRIPTEN_JoystickClose(SDL_Joystick * joystick)
{
    SDL_joylist_item *item = (SDL_joylist_item *) joystick->hwdata;
    if (item) {
        item->joystick = NULL;
    }
}

static SDL_JoystickGUID
EMSCRIPTEN_JoystickGetDeviceGUID(int device_index)
{
    SDL_JoystickGUID guid;
    /* the GUID is just the first 16 chars of the name for now */
    const char *name = EMSCRIPTEN_JoystickGetDeviceName(device_index);
    SDL_zero(guid);
    SDL_memcpy(&guid, name, SDL_min(sizeof(guid), SDL_strlen(name)));
    return guid;
}

static int
EMSCRIPTEN_JoystickRumble(SDL_Joystick * joystick, Uint16 low_frequency_rumble, Uint16 high_frequency_rumble)
{
    return SDL_Unsupported();
}

static SDL_bool
EMSCRIPTEN_JoystickGetGamepadMapping(int device_index, SDL_GamepadMapping *out)
{
    return SDL_FALSE;
}

SDL_JoystickDriver SDL_EMSCRIPTEN_JoystickDriver =
{
    EMSCRIPTEN_JoystickInit,
    EMSCRIPTEN_JoystickGetCount,
    EMSCRIPTEN_JoystickDetect,
    EMSCRIPTEN_JoystickGetDeviceName,
    EMSCRIPTEN_JoystickGetDevicePlayerIndex,
    EMSCRIPTEN_JoystickSetDevicePlayerIndex,
    EMSCRIPTEN_JoystickGetDeviceGUID,
    EMSCRIPTEN_JoystickGetDeviceInstanceID,
    EMSCRIPTEN_JoystickOpen,
    EMSCRIPTEN_JoystickRumble,
    EMSCRIPTEN_JoystickUpdate,
    EMSCRIPTEN_JoystickClose,
    EMSCRIPTEN_JoystickQuit,
    EMSCRIPTEN_JoystickGetGamepadMapping
};

#endif /* SDL_JOYSTICK_EMSCRIPTEN */

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