231892 - gPrintPreviewObs.QueryInterface should not throw NS_NOINTERFACE for nsISupports

Status: RESOLVED FIXED

(SeaMonkey :: UI Design, defect)

Description

[timeless]

Exception ``2147500034'' thrown from function anonymous(iid=XPComponent:{7}) in
<chrome://navigator/content/browser.js> line 189.
Stopped for thrown exception.

#0: function anonymous(iid=XPComponent:{7}) in
<chrome://navigator/content/browser.js> line 189

     QueryInterface : function(iid)
    185     {
 -  186      if (iid.equals(Components.interfaces.nsIObserver) ||
iid.equals(Components.interfaces.nsISupportsWeakReference))
 -  187       return this;
    188      
 -  189      throw Components.results.NS_NOINTERFACE;
    190     }

0001: iid.number
$[1] = [string] "{00000000-0000-0000-c000-000000000046}"

Comment 1

[Stefan Borggraefe]

I don't really know what needs to be done here (/me feels embarrassed by [good
first bug] in the status whiteboard ;-) ).

Timeless suggested to reassign this bug to you, Silver. I hope you don't mind.

Comment 2

[James Ross]

Since this is a [good first bug], I'll explain what it's about for future reference.

XPCOM objects support interfaces to describe what they do, and at the base of
this is nsISupports (very like IUnknown in MS COM). Every interface decends from it.

This means you should be able to QI any XPCOM object to the nsISupports
interface, and that includes JavaScript-implemented objects. So the change
needed here is simply adding an extra case that returns |this|, for nsISupports.

Comment 3

[James Ross]

Attachment: Allow QI to nsISupports

Comment 4

[[e-mail]]

Comment on attachment 153395 [details] [diff] [review]
Allow QI to nsISupports

Nit: That doesn't appear to be the prevailing brace style.

Is there a bug for fixing printPreviewProgress.js?

Comment 5

[Boris Zbarsky [:bzbarsky]]

Silver, does this need to be checked in?  If not, then what's left in this bug?

Comment 6

[James Ross]

It needs to be checked in.

Comment 7

[Boris Zbarsky [:bzbarsky]]

Want me to do it?  Or is it under control?

Comment 8

[James Ross]

Checked in --> FIXED.

Sorry for taking so long, sort of got lost. :)