Bug 190675 – BackForwardClient needs to be able to support UIProcess-only back/forward lists

• Status: RESOLVED
• Resolution: FIXED
• Component: New Bugs

[Alex Christensen]

BackForwardClient needs to be able to support UIProcess-only back/forward lists

[Alex Christensen]

Created attachment 352606 [details]
Patch

[Alex Christensen]

Created attachment 352607 [details]
Patch

[Alex Christensen]

Created attachment 352616 [details]
Patch

[Alex Christensen]

Created attachment 352621 [details]
Patch

[Alex Christensen]

http://trac.webkit.org/r237233

[Radar WebKit Bug Importer]

<rdar://problem/45349080>

[Daniel Bates]

Comment on attachment 352621 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=352621&action=review

> Source/WebCore/ChangeLog:10
> +        Also use unsigned for the back and forward list counts because they can never be negative.

This may be true. I do not think this fact is best conveyed using unsigned. Data types should be chosen based on the range of representable values needed for the problem being solved. It seems a key design decision for this class was to expose a getter than takes a delta and every other decision falls out from this. Maybe this isn’t the right design, but it seems intuitive and it comes with a nice property as shown in the implementation of count(): “back count” + 1 “forward count” represents the entire range of an int. And this has another nice property that iterating over all items is a for-loop from -“back count” to “forward count” (seen in the webPage.cpp code). I find it hard to imagine a client would have anything close to 2^31 - 1 history items backwards and/or forwards, but I find it inconceivable that a client would have 2^32 - 1 items backwards and/or forwards.

[Alex Christensen]

Well counts that are never less than zero certainly don't need to be signed.