func (e *Element) AttachHandler(handler *EventHandler) {
attachedHandlers, hasAttachments := eventHandlers[e.handle]
if hasAttachments {
if _, exists := attachedHandlers[handler]; exists {
// This exact event handler is already attached to this exact element.
return
}
}
// Don't let the caller disable ATTACH/DETACH events, otherwise we
// won't know when to throw out our event handler object
subscription := handler.Subscription()
subscription &= ^uint32(DISABLE_INITIALIZATION & 0xffffffff)
tag := uintptr(unsafe.Pointer(handler))
if subscription == HANDLE_ALL {
if ret := C.HTMLayoutAttachEventHandler(e.handle, (*[0]byte)(unsafe.Pointer(goElementProc)), C.LPVOID(tag)); ret != HLDOM_OK {
domPanic(ret, "Failed to attach event handler to element")
}
} else {
if ret := C.HTMLayoutAttachEventHandlerEx(e.handle, (*[0]byte)(unsafe.Pointer(goElementProc)), C.LPVOID(tag), C.UINT(subscription)); ret != HLDOM_OK {
domPanic(ret, "Failed to attach event handler to element")
}
}
if !hasAttachments {
eventHandlers[e.handle] = make(map[*EventHandler]bool, 8)
}
eventHandlers[e.handle][handler] = true
}
// This is the same as AttachHandler, except that behaviors are singleton instances stored
// in a master map. They may be shared among many elements since they have no state.
// The only reason we keep a separate set of the behaviors is so that the event handler
// dispatch method can tell if an event handler is a behavior or a regular handler.
func (e *Element) attachBehavior(handler *EventHandler) {
tag := uintptr(unsafe.Pointer(handler))
if subscription := handler.Subscription(); subscription == HANDLE_ALL {
if ret := C.HTMLayoutAttachEventHandler(e.handle, (*[0]byte)(unsafe.Pointer(goElementProc)), C.LPVOID(tag)); ret != HLDOM_OK {
domPanic(ret, "Failed to attach event handler to element")
}
} else {
if ret := C.HTMLayoutAttachEventHandlerEx(e.handle, (*[0]byte)(unsafe.Pointer(goElementProc)), C.LPVOID(tag), C.UINT(subscription)); ret != HLDOM_OK {
domPanic(ret, "Failed to attach event handler to element")
}
}
}