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gamepad_only_once_per_frame #4292

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merged 2 commits into from
May 6, 2016
Merged

gamepad_only_once_per_frame #4292

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f13edd4
Only poll gamepad api once per application frame in order to be safe …
juj May 5, 2016
cb492d8
Test against EMSCRIPTEN_RESULT_SUCCESS in test_html5.c for gamepad st…
juj May 5, 2016
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58 changes: 32 additions & 26 deletions src/library_html5.js
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,13 @@ var LibraryJSEvents = {
visibilityChangeEvent: 0,
touchEvent: 0,

// In order to ensure most coherent Gamepad API state as possible (https://github.com/w3c/gamepad/issues/22) and
// to minimize the amount of garbage created, we sample the gamepad state at most once per frame, and not e.g. once per
// each controller or similar. To implement that, the following variables retain a cache of the most recent polled gamepad
// state.
lastGamepadState: null,
lastGamepadStateFrame: null, // The integer value of Browser.mainLoop.currentFrameNumber of when the last gamepad state was produced.

// When we transition from fullscreen to windowed mode, we remember here the element that was just in fullscreen mode
// so that we can report information about that element in the event message.
previousFullscreenElement: null,
Expand Down Expand Up @@ -1650,37 +1657,36 @@ var LibraryJSEvents = {
return {{{ cDefine('EMSCRIPTEN_RESULT_SUCCESS') }}};
},

emscripten_get_num_gamepads: function() {
if (!navigator.getGamepads && !navigator.webkitGetGamepads) return {{{ cDefine('EMSCRIPTEN_RESULT_NOT_SUPPORTED') }}};
if (navigator.getGamepads) {
return navigator.getGamepads().length;
} else if (navigator.webkitGetGamepads) {
return navigator.webkitGetGamepads().length;
_emscripten_sample_gamepad_data: function() {
// Produce a new Gamepad API sample if we are ticking a new game frame, or if not using emscripten_set_main_loop() at all to drive animation.
if (Browser.mainLoop.currentFrameNumber !== JSEvents.lastGamepadStateFrame || !Browser.mainLoop.currentFrameNumber) {
JSEvents.lastGamepadState = navigator.getGamepads ? navigator.getGamepads() : (navigator.webkitGetGamepads ? navigator.webkitGetGamepads : null);
JSEvents.lastGamepadStateFrame = Browser.mainLoop.currentFrameNumber;
}
},

emscripten_get_num_gamepads__deps: ['_emscripten_sample_gamepad_data'],
emscripten_get_num_gamepads: function() {
__emscripten_sample_gamepad_data();
if (!JSEvents.lastGamepadState) return {{{ cDefine('EMSCRIPTEN_RESULT_NOT_SUPPORTED') }}};
return JSEvents.lastGamepadState.length;
},

emscripten_get_gamepad_status__deps: ['_emscripten_sample_gamepad_data'],
emscripten_get_gamepad_status: function(index, gamepadState) {
if (!navigator.getGamepads && !navigator.webkitGetGamepads) return {{{ cDefine('EMSCRIPTEN_RESULT_NOT_SUPPORTED') }}};
var gamepads;
if (navigator.getGamepads) {
gamepads = navigator.getGamepads();
} else if (navigator.webkitGetGamepads) {
gamepads = navigator.webkitGetGamepads();
}
if (index < 0 || index >= gamepads.length) {
return {{{ cDefine('EMSCRIPTEN_RESULT_INVALID_PARAM') }}};
}
// For previously disconnected gamepads there should be a null at the index.
__emscripten_sample_gamepad_data();
if (!JSEvents.lastGamepadState) return {{{ cDefine('EMSCRIPTEN_RESULT_NOT_SUPPORTED') }}};

// INVALID_PARAM is returned on a Gamepad index that never was there.
if (index < 0 || index >= JSEvents.lastGamepadState.length) return {{{ cDefine('EMSCRIPTEN_RESULT_INVALID_PARAM') }}};

// NO_DATA is returned on a Gamepad index that was removed.
// For previously disconnected gamepads there should be an empty slot (null/undefined/false) at the index.
// This is because gamepads must keep their original position in the array.
// For example, removing the first of two gamepads produces [null, gamepad].
// Older implementations of the Gamepad API used undefined instead of null.
// The following check works because null and undefined evaluate to false.
if (!gamepads[index]) {
// There is a "false" but no gamepad at index because it was disconnected.
return {{{ cDefine('EMSCRIPTEN_RESULT_NO_DATA') }}};
}
// There should be a gamepad at index which can be queried.
JSEvents.fillGamepadEventData(gamepadState, gamepads[index]);
// For example, removing the first of two gamepads produces [null/undefined/false, gamepad].
if (!JSEvents.lastGamepadState[index]) return {{{ cDefine('EMSCRIPTEN_RESULT_NO_DATA') }}};

JSEvents.fillGamepadEventData(gamepadState, JSEvents.lastGamepadState[index]);
return {{{ cDefine('EMSCRIPTEN_RESULT_SUCCESS') }}};
},

Expand Down
4 changes: 2 additions & 2 deletions tests/test_html5.c
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Original file line number Diff line number Diff line change
Expand Up @@ -264,8 +264,8 @@ void mainloop()
for(int i = 0; i < numGamepads && i < 32; ++i)
{
EmscriptenGamepadEvent ge;
int failed = emscripten_get_gamepad_status(i, &ge);
if (!failed)
int ret = emscripten_get_gamepad_status(i, &ge);
if (ret == EMSCRIPTEN_RESULT_SUCCESS)
{
int g = ge.index;
for(int j = 0; j < ge.numAxes; ++j)
Expand Down