372084 - Redundant calls to nsFrame::IntrinsicWidthOffsets

Status: NEW

(Core :: Layout: Tables, defect)

Description

[Boris Zbarsky [:bzbarsky]]

Looking at the profile for bug 352367, we call nsFrame::IntrinsicWidthOffsets from GetWidthInfo(nsIRenderingContext*, nsTableCellFrame*, nsStylePosition const*) three times -- once via GetMinWidth, once via GetPrefWidth, and once directly.  Is there any way we could combine these so we only have to do this once?  About 5% of the pageload there is spent under nsFrame::IntrinsicWidthOffsets...

Comment 1

[Boris Zbarsky [:bzbarsky]]

I guess the GetMinWidth and GetPrefWidth calls call nsFrame::IntrinsicWidthOffsets on the block inside the table cell, while the direct call is for the table cell itself...

Comment 2

[Boris Zbarsky [:bzbarsky]]

One option would be to have a one-slot cache:  Basically have a static nsIFrame* that callers who plan to call both GetMinWidth and GetPrefWidth can assign to, and a boolean indicating whether for that nsIFrame* the offsets have already been computed.  If the boolean is set, just use the cached offsets, otherwise compute into the cached offset struct...  Seems like a lot of work for effectively a 2% win on this rather abnormal testcase.