1048582 - Should be consistent about whether nsHTMLReflowMetrics wants frame's writing mode or parent's writing mode

Status: NEW

(Core :: Layout: Block and Inline, defect)

Description

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

I was looking at nsHTMLReflowMetrics, whose constructor takes either a writing mode, or a reflow state from which it can get the writing mode.

It should be documented whether this is supposed to be the frame's writing mode or its parent's writing mode (and same for reflow state).

Then we should be consistent about whether we pass the frame's or the parent's.  Some callers pass the frame's, such as:
  nsBulletFrame::Get{Min,Pref}ISize
  nsColumnSetFrame::ReflowChildren
  nsFlexContainerFrame::MeasureFlexItemContentHeight
  nsFlexContainerFrame::SizeItemInCrossAxis
  nsFlexContainerFrame::DoFlexLayout
while some callers pass the parent's, such as:
  nsAbsoluteContainingBlock::ReflowAbsoluteFrame
  nsBlockFrame::ReflowBullet (and its 3 callers)
  nsBlockReflowContext::nsBlockReflowContext
  nsCanvasFrame::Reflow
  nsContainerFrame::ReflowOverflowContainerChildren
  nsHTMLFramesetFrame::ReflowPlaceChild
  nsHTMLCanvasFrame::Reflow
while some (for inlines) use the line writing mode:
  nsLineLayout::ReflowFrame
while some callers pick yet other options, such as:
  nsFrame::RefreshSizeCache
  nsFrame::DoLayout
  nsHTMLScrollFrame::ReflowContents

(this list compiled from the first half of the alphabet in
  layout/generic/ns[A-M]*
)

This API was introduced in https://hg.mozilla.org/mozilla-central/rev/72591e9d49a8 and https://hg.mozilla.org/mozilla-central/rev/63a4ad62401a

Comment 1

[Jonathan Kew [:jfkthame]]

Yes indeed, we should clarify this and make things consistent. Offhand, I'm inclined to say we should be using the parent's writing mode, but I'd like to know what Simon thinks.

Comment 2

[Simon Montagu :smontagu]

In general, I agree the parent's writing mode, but perhaps we can't be 100% consistent? Using the line writing mode for inlines seems to me a legitimate exception to the rule.