I have developed an extension for Safari which uses a context menu.
In the code, I am listening to the command event of the context menu item using:
safari.application.addEventListener("command", commandHandler, false);
In the commandHandler() function, I have added an alert statement for debugging purposes. By doing so, I found that the function commandHandler() is firing twice whenever I click on the context menu item.
Also I added a tool bar item, which also fires the command() event on clicking. The function attached to the command() event is also firing twice after clicking on the item.
Does anybody know of this issue and how to resolve it?
Without more information, this sounds like a problem of insufficient filtering. That is, you’re receiving all command messages without determining which they are or why they’re flowing across your callback layer, and your callback layer receives two messages per click of, as given, unknown disposition.
The event notification callback structure for Safari extensions allows you to register multiple events against the same event type, and multiple distinct events may be generated in many cases. To this end, your attempt to add an event listener to the “command” scope means you’re literally receiving all commands passed to the callback layer. These may be multi-firing in cases where you have, for example, a complex nesting relationship (A contains B, where A and B both notify) or a complex behavior pattern (for example, a mousedown followed by a mouseup).
Apple provides guidance on how to handle this scenario, by binding the command to a specific target or specific command, which is what you should do here. And just in case that’s insufficient, here’s additional documentation on how the callback system works to help you define your events properly.
Following the guidance should allow you to work through this issue by properly binding your events to your object and only operating on the events you need. Everything else should simply be ignored by your event handler.