Question

Salve! When I try Mozilla’s Validator on my addon, it get the following error related to my treatment of clipboard usage:

nsITransferable has been changed in Gecko 16.

Warning: The nsITransferable interface has changed to better support
Private Browsing Mode. After instantiating the object, you should call
the init function on it before any other functions are called.
See https://developer.mozilla.org/en-US/docs/Using_the_Clipboard for more
information.

var trans = Components.classes["@mozilla.org/widget/transferable;1"].createInstance(Components.interfaces.nsITransferable);
if ('init' in trans){ trans.init(null);};

I can’t understand this.

Here is my code – I am clearly calling trans.init:

var clip = Components.classes["@mozilla.org/widget/clipboard;1"].getService(Components.interfaces.nsIClipboard);
if (!clip) return "";

var trans = Components.classes["@mozilla.org/widget/transferable;1"].createInstance(Components.interfaces.nsITransferable);
if ('init' in trans){ trans.init(null);};  //<--IT DOESN'T LIKE THIS
if (!trans) return false;
trans.addDataFlavor("text/unicode");

I’ve also tried the Transferable function from Mozilla’s example here, but get the same non-validation report.

One of the Mozilla AMO editors told me to write exactly this, and it still doesn’t validate.

I’ve also tried, simply:

var trans = Components.classes["@mozilla.org/widget/transferable;1"].createInstance(Components.interfaces.nsITransferable);
trans.init(null);   //<---LOOK HERE
if (!trans) return false;
trans.addDataFlavor("text/unicode");

The Validator does not report any errors – just this warning. Everything works properly. Mozilla updated their Gecko engine, and they want devlopers to match up to the new standard.

In my usage, we want to be able to use the contents of the clipboard that was probably gotten from outside the application, too, so we do want to call the init function with null instead of window.

Any advice would be wonderful!

Answer 1

trans.init(null) is valid in some circumstances, such as yours. It can also cause privacy leaks if used in the wrong circumstances, so the validator flags all uses of it as potentially requiring changing. Therefore, it is a warning that you can ignore in this case.