39748 - [feature] Fix nsITransferable to allow promises

Status: RESOLVED FIXED

(Core :: XUL, defect, P3)

Description

[Mike Pinkerton (not reading bugmail)]

We have a situation now where any time text is copied to the clipboard, the 
transferable must have all of the data, in every available format, up front, 
regardless of whether or not that flavor is asked for. This generally involves 
lots of xif->text or xif->html conversions, which are not cheap, and are probably 
wasted.

The transferable api's need to be redesigned to understand the notion of a 
promise, where the client can be called back when the data is actually needed. 

This won't really help us for macOS clipboard since all the data needs to be 
handed to the clipboard up front, but everything else, as well as macDND, 
supports the notion of promises.

Comment 1

[Mike Pinkerton (not reading bugmail)]

accepting, M18. not sure if we'll get to this or not...

breakdown:
- figure out how to change APIs (2 days)
- implement changes in transferable (2 days)
- fix native clipboard, d&d (3 days, 1 x 3platforms)
- update all clients of transferable (1 day)

Comment 2

[Peter Trudelle]

This was on my list of remaining features sent to PDT on 5/22, but was
apparently overlooked, perhaps because it had no nsbeta2 nomination.  Adding it
now, along with nsbeta3, since this is really performance work that we are just
treating as a new feature because it will take signficant time.

Comment 3

[Peter Trudelle]

[nsbeta2-]

Comment 4

[Peter Trudelle]

Moving to future (pink sighs...)

Comment 5

[Mike Pinkerton (not reading bugmail)]

for my own reference:

all that's needed to implement an interface on a JS object is to declare methods
on the object with the names of the methods being called. The XPConnect wrapper
handles the QI/etc. This makes it very easy to have an API that is implemented
in either JS or c++ that is called when the data finally arrives, or is needed.

Comment 6

[Mike Pinkerton (not reading bugmail)]

fffffffuture

Comment 7

[Simon Fraser [no longer active]]

Taking

Comment 8

[Simon Fraser [no longer active]]

Clients of nsITransferable can now use an nsIFlavorDataProvider to implement
data promises.