71992 - Getting references to the getter and setter functions

Status: VERIFIED FIXED

(Core :: JavaScript Engine, enhancement, P1)

Description

[Jeff Yates]

First of all...

Great JOB guys.  I love what you have done to JavaScript in this version.  You 
all have made it into a powerhouse.

The suggestion...

I have been playing with the __defineGetter__ and __defineSetter__ functions 
and I would like to make a suggestion.  It would be benificial if you made a 
method of getting a reference the getter and setter functions for a property, 
and the ability to over-ride them.

I will give you an example:  You have a style set on a div element (say the 
width property) that you want to change in responce to an expression.  If you 
use element.style.__defineGetter__("width", functionRef ) then the value of the 
element.style.width will return the value of the function referenced, but it 
will not be reflected in the layout.

I would suggest a method such as __getGetter__("propertyName") and __getSetter__
("propertyName") that would return a reference to this function.  Or you may 
need some other method like __replaceGetter__/__replaceSetter__.

The whole point of this is to be able to emulate the setExpression method from 
IE.  This is a very powerful method for dynamic layout.

Jeff Yates

Comment 1

[Phil Schwartau]

cc'ing Brendan, shaver, jst -

Comment 2

[Brendan Eich [:brendan]]

I'll take this and supply a patch that adds __lookupGetter__ and __lookupSetter__.

/be

Comment 3

[Jeff Yates]

Brendan, 

Would __lookupGetter__ and __lookupSetter__ allow you to override them?  Or 
would this be 2 more functions that would have to be added?

Don't get me wrong, these two are important even if you did over-ride them so 
that the method used to over-ride the property may need to call the origional 
getter/setter functions.

Jeff.

Comment 4

[Brendan Eich [:brendan]]

I see no need to provide more than the minimum: o.__lookupGetter__('p') returns
the getter function for o.p, or undefined if o.p has no getter.  Users can wrap
and layer.  Patch next.

/be

Comment 5

[Brendan Eich [:brendan]]

Attachment: proposed fix

Comment 6

[Brendan Eich [:brendan]]

Testing and review welcome.  rogerl, shaver, how about r= and sr=?

/be

Comment 7

[Mike Shaver (:shaver emeritus)]

I like it. r/sr=shaver.

(Man, we should so just expose the whole MOP here.)

Comment 8

[rogerl (gone)]

r=rogerl

Comment 9

[Brendan Eich [:brendan]]

We all flunk the "don't forget to OBJ_DROP_PROPERY after LOOKUP" test ('cept I
remembered just now, will the prof give me credit?).

/be

Comment 10

[Brendan Eich [:brendan]]

Attachment: fixed fix

Comment 11

[Brendan Eich [:brendan]]

I think silence is golden here, so returning undefined if there is no such
property, or the property has no getter, beats throwing an exception. Comments?

/be

Comment 12

[Mike Shaver (:shaver emeritus)]

I am shamed, and consent to your silence.  r=shaver again.

Comment 13

[Brendan Eich [:brendan]]

Fix in, but give me a reason (future compatibility?) for throwing instead of
returning void?

/be

Comment 14

[Phil Schwartau]

Added testcase to JS testsuite:

                 js/tests/js1_5/GetSet/getset-006.js


JS Engine passing testcase on WinNT, Linux.
Marking Verified -