Add a way to remove a single event listener (#20983)

ChangeLog.md

@@ -20,6 +20,8 @@ See docs/process.md for more on how version tagging works.
 
 4.0.20 (in development)
 -----------------------
+- Added `emscripten_html5_remove_event_listener` function in `html5.h` in order to be
+  able to remove a single callback. (#25535)
 - The standalone `file_packager.py` script no longer supports `--embed` with JS
   output (use `--obj-output` is now required for embedding data).  This usage
   has been producing a warning since #16050 which is now an error.  (#25049)

site/source/docs/api_reference/html5.h.rst

@@ -90,6 +90,54 @@ The ``useCapture`` parameter  maps to ``useCapture`` in `EventTarget.addEventLis
 
 Most functions return the result using the type :c:data:`EMSCRIPTEN_RESULT`. Zero and positive values denote success. Negative values signal failure. None of the functions fail or abort by throwing a JavaScript or C++ exception. If a particular browser does not support the given feature, the value :c:data:`EMSCRIPTEN_RESULT_NOT_SUPPORTED` will be returned at the time the callback is registered.
 
+Unregister function
+-------------------
+
+In order to unregister a single event handler callback, call the following function:
+
+  .. code-block:: cpp
+
+    EMSCRIPTEN_RESULT emscripten_html5_remove_event_listener(
+      const char *target,   // ID of the target HTML element.
+      void *userData,       // User-defined data (passed to the callback).
+      int eventTypeId,      // The event type ID (EMSCRIPTEN_EVENT_XXX).
+      void *callback        // Callback function.
+    );
+
+
+The ``target``, ``userData`` and ``callback`` parameters are the same parameters provided in ``emscripten_set_some_callback`` with the only difference being that, since this function applies to all types of callbacks, the type of ``callback`` is ``void *``.
+
+Note in particular that the value of ``userData`` will need to match with the call that was used to register the callback. If you are having trouble, double check the value of ``userData``.
+
+The ``eventTypeId`` represents the event type, the same Id received in the callback functions.
+
+The function returns ``EMSCRIPTEN_RESULT_SUCCESS`` when the event handler callback is removed and ``EMSCRIPTEN_RESULT_INVALID_PARAM`` otherwise.
+
+  .. code-block:: cpp
+
+    // Example
+
+    bool my_mouse_callback_1(int eventType, const EmscriptenMouseEvent *mouseEvent, void *userData) {
+      // ...
+    }
+
+    bool my_mouse_callback_2(int eventType, const EmscriptenMouseEvent *mouseEvent, void *userData) {
+      // ...
+    }
+
+    void main() {
+
+      // 1. set callbacks for mouse down and mouse move
+      emscripten_set_mousedown_callback("#mydiv", 0, my_mouse_callback_1);
+      emscripten_set_mousedown_callback("#mydiv", (void *) 34, my_mouse_callback_2);
+      emscripten_set_mousemove_callback("#mydiv", 0, my_mouse_callback_1);
+
+      // 2. remove these callbacks
+      emscripten_html5_remove_event_listener("#mydiv", 0, EMSCRIPTEN_EVENT_MOUSEDOWN, my_mouse_callback_1);
+      emscripten_html5_remove_event_listener("#mydiv", (void *) 34, EMSCRIPTEN_EVENT_MOUSEDOWN, my_mouse_callback_2);
+      emscripten_html5_remove_event_listener("#mydiv", 0, EMSCRIPTEN_EVENT_MOUSEMOVE, my_mouse_callback_1);
+    }
+
 
 Callback functions
 ------------------

src/lib/libhtml5.js

@@ -201,6 +201,19 @@ var LibraryHTML5 = {
       return {{{ cDefs.EMSCRIPTEN_RESULT_SUCCESS }}};
     },
 
+    removeSingleHandler(eventHandler) {
+      for (var [i, handler] of JSEvents.eventHandlers.entries()) {
+        if (handler.target === eventHandler.target
+          && handler.eventTypeId === eventHandler.eventTypeId
+          && handler.callbackfunc === eventHandler.callbackfunc
+          && handler.userData === eventHandler.userData) {
+          JSEvents._removeHandler(i);
+          return {{{ cDefs.EMSCRIPTEN_RESULT_SUCCESS }}};
+        }
+      }
+      return {{{ cDefs.EMSCRIPTEN_RESULT_INVALID_PARAM }}};
+    },
+
 #if PTHREADS
     getTargetThreadForEventCallback(targetThread) {
       switch (targetThread) {
@@ -291,6 +304,8 @@ var LibraryHTML5 = {
     var eventHandler = {
       target: findEventTarget(target),
       eventTypeString,
+      eventTypeId,
+      userData,
       callbackfunc,
       handlerFunc: keyEventHandlerFunc,
       useCapture
@@ -405,6 +420,18 @@ var LibraryHTML5 = {
   },
 #endif
 
+  emscripten_html5_remove_event_listener__proxy: 'sync',
+  emscripten_html5_remove_event_listener__deps: ['$JSEvents', '$findEventTarget'],
+  emscripten_html5_remove_event_listener: (target, userData, eventTypeId, callback) => {
+    var eventHandler = {
+      target: findEventTarget(target),
+      userData,
+      eventTypeId,
+      callbackfunc: callback,
+    };
+    return JSEvents.removeSingleHandler(eventHandler);
+  },
+
   emscripten_set_keypress_callback_on_thread__proxy: 'sync',
   emscripten_set_keypress_callback_on_thread__deps: ['$registerKeyEventCallback'],
   emscripten_set_keypress_callback_on_thread: (target, userData, useCapture, callbackfunc, targetThread) =>
@@ -495,6 +522,8 @@ var LibraryHTML5 = {
       allowsDeferredCalls: eventTypeString != 'mousemove' && eventTypeString != 'mouseenter' && eventTypeString != 'mouseleave', // Mouse move events do not allow fullscreen/pointer lock requests to be handled in them!
 #endif
       eventTypeString,
+      eventTypeId,
+      userData,
       callbackfunc,
       handlerFunc: mouseEventHandlerFunc,
       useCapture
@@ -586,6 +615,8 @@ var LibraryHTML5 = {
       allowsDeferredCalls: true,
 #endif
       eventTypeString,
+      eventTypeId,
+      userData,
       callbackfunc,
       handlerFunc: wheelHandlerFunc,
       useCapture
@@ -658,6 +689,8 @@ var LibraryHTML5 = {
     var eventHandler = {
       target,
       eventTypeString,
+      eventTypeId,
+      userData,
       callbackfunc,
       handlerFunc: uiEventHandlerFunc,
       useCapture
@@ -702,6 +735,8 @@ var LibraryHTML5 = {
     var eventHandler = {
       target: findEventTarget(target),
       eventTypeString,
+      eventTypeId,
+      userData,
       callbackfunc,
       handlerFunc: focusEventHandlerFunc,
       useCapture
@@ -759,6 +794,8 @@ var LibraryHTML5 = {
     var eventHandler = {
       target: findEventTarget(target),
       eventTypeString,
+      eventTypeId,
+      userData,
       callbackfunc,
       handlerFunc: deviceOrientationEventHandlerFunc,
       useCapture
@@ -827,6 +864,8 @@ var LibraryHTML5 = {
     var eventHandler = {
       target: findEventTarget(target),
       eventTypeString,
+      eventTypeId,
+      userData,
       callbackfunc,
       handlerFunc: deviceMotionEventHandlerFunc,
       useCapture
@@ -907,6 +946,8 @@ var LibraryHTML5 = {
     var eventHandler = {
       target,
       eventTypeString,
+      eventTypeId,
+      userData,
       callbackfunc,
       handlerFunc: orientationChangeEventHandlerFunc,
       useCapture
@@ -1014,6 +1055,8 @@ var LibraryHTML5 = {
     var eventHandler = {
       target,
       eventTypeString,
+      eventTypeId,
+      userData,
       callbackfunc,
       handlerFunc: fullscreenChangeEventhandlerFunc,
       useCapture
@@ -1512,6 +1555,8 @@ var LibraryHTML5 = {
     var eventHandler = {
       target,
       eventTypeString,
+      eventTypeId,
+      userData,
       callbackfunc,
       handlerFunc: pointerlockChangeEventHandlerFunc,
       useCapture
@@ -1556,6 +1601,8 @@ var LibraryHTML5 = {
     var eventHandler = {
       target,
       eventTypeString,
+      eventTypeId,
+      userData,
       callbackfunc,
       handlerFunc: pointerlockErrorEventHandlerFunc,
       useCapture
@@ -1706,6 +1753,8 @@ var LibraryHTML5 = {
     var eventHandler = {
       target,
       eventTypeString,
+      eventTypeId,
+      userData,
       callbackfunc,
       handlerFunc: visibilityChangeEventHandlerFunc,
       useCapture
@@ -1821,6 +1870,8 @@ var LibraryHTML5 = {
       allowsDeferredCalls: eventTypeString == 'touchstart' || eventTypeString == 'touchend',
 #endif
       eventTypeString,
+      eventTypeId,
+      userData,
       callbackfunc,
       handlerFunc: touchEventHandlerFunc,
       useCapture
@@ -1904,6 +1955,8 @@ var LibraryHTML5 = {
       allowsDeferredCalls: true,
 #endif
       eventTypeString,
+      eventTypeId,
+      userData,
       callbackfunc,
       handlerFunc: gamepadEventHandlerFunc,
       useCapture
@@ -1990,6 +2043,8 @@ var LibraryHTML5 = {
     var eventHandler = {
       target: findEventTarget(target),
       eventTypeString,
+      eventTypeId,
+      userData,
       callbackfunc,
       handlerFunc: beforeUnloadEventHandlerFunc,
       useCapture
@@ -2040,6 +2095,8 @@ var LibraryHTML5 = {
     var eventHandler = {
       target: battery,
       eventTypeString,
+      eventTypeId,
+      userData,
       callbackfunc,
       handlerFunc: batteryEventHandlerFunc,
       useCapture

src/lib/libhtml5_webgl.js

@@ -440,6 +440,8 @@ var LibraryHtml5WebGL = {
     var eventHandler = {
       target: findEventTarget(target),
       eventTypeString,
+      eventTypeId,
+      userData,
       callbackfunc,
       handlerFunc: webGlEventHandlerFunc,
       useCapture

src/lib/libsigs.js

@@ -666,6 +666,7 @@ sigs = {
   emscripten_has_threading_support__sig: 'i',
   emscripten_hide_mouse__sig: 'v',
   emscripten_html5_remove_all_event_listeners__sig: 'v',
+  emscripten_html5_remove_event_listener__sig: 'ippip',
   emscripten_idb_async_clear__sig: 'vpppp',
   emscripten_idb_async_delete__sig: 'vppppp',
   emscripten_idb_async_exists__sig: 'vppppp',

system/include/emscripten/html5.h

@@ -420,6 +420,8 @@ EMSCRIPTEN_RESULT emscripten_get_element_css_size(const char *target __attribute
 
 void emscripten_html5_remove_all_event_listeners(void);
 
+EMSCRIPTEN_RESULT emscripten_html5_remove_event_listener(const char *target __attribute__((nonnull)), void *userData, int eventTypeId, void *callback __attribute__((nonnull)));
+
 #define EM_CALLBACK_THREAD_CONTEXT_MAIN_RUNTIME_THREAD ((pthread_t)0x1)
 #define EM_CALLBACK_THREAD_CONTEXT_CALLING_THREAD ((pthread_t)0x2)
 

test/codesize/test_codesize_hello_dylink_all.json

@@ -1,7 +1,7 @@
 {
-  "a.out.js": 245421,
+  "a.out.js": 245799,
   "a.out.nodebug.wasm": 574167,
-  "total": 819588,
+  "total": 819966,
   "sent": [
     "IMG_Init",
     "IMG_Load",
@@ -681,6 +681,7 @@
     "emscripten_has_asyncify",
     "emscripten_hide_mouse",
     "emscripten_html5_remove_all_event_listeners",
+    "emscripten_html5_remove_event_listener",
     "emscripten_idb_async_clear",
     "emscripten_idb_async_delete",
     "emscripten_idb_async_exists",

test/test_browser.py

@@ -2675,6 +2675,9 @@ def test_html5_core(self, opts):
       self.cflags.append('--pre-js=pre.js')
     self.btest_exit('test_html5_core.c', cflags=opts)
 
+  def test_html5_remove_event_listener(self):
+    self.btest_exit('test_html5_remove_event_listener.c')
+
   @parameterized({
     '': ([],),
     'closure': (['-O2', '-g1', '--closure=1'],),