1526097 - Consider removing nsIFrame::eBlockFrame flag for "IsFrameOfType", in favor of QueryFrame-backed "IsBlockFrameOrSubclass()" method

Status: RESOLVED FIXED

(Core :: Layout, enhancement, P3)

Description

[Daniel Holbert [:dholbert]]

For now, IsFrameOfType() is a virtual function call (unless/until we act on bug 1364813). So, calls to IsFrameOfType(nsIFrame::eBlockFrame) are kind of expensive.

In bug 1525628, I'm adding a non-virtual function, nsIFrame::IsBlockFrameOrSubclass(), which should serve the same purpose and which is implemented using do_QueryFrame (which is non-virtual as of bug 1364815).

In theory we should be able to remove nsIFrame::eBlockFrame and migrate its IsFrameOfType() callsites to use IsBlockFrameOrSubclass() instead.

One prerequisite: in its initial version, IsBlockFrameOrSubclass() is a non-const method. To make it correctly "const", we should probably also make the QueryFrame machinery become const-friendly. That might be the first part of this bug, and it'll be necessary to make this IsBlockFrameOrSubclass() function callable at some of our IsFrameOfType() callsites, e.g. this one:

https://searchfox.org/mozilla-central/rev/490ab7f9b84570573a49d7fa018673ce0d5ddf22/layout/generic/ReflowInput.cpp#127-128

(We could also just make IsBlockFrameOrSubclass do a hacky const_cast internally, but it seems like we should attempt to fix QueryFrame first before resorting to that.)

Comment 1

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

do_QueryFrame becomes more const-friendly in bug 1527519. I think this bug is now doable.

Comment 2

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

Attachment: Bug 1526097 - Remove nsIFrame::eBlockFrame flag. r?dholbert

Only nsBlockFrame recognizes the eBlockFrame flag, so we can replace the
usage of IsFrameOfType(nsIFrame::eBlockFrame) with either
nsIFrame::IsBlockFrameOrSubclass() or a do_QueryFrame() call for
nsBlockFrame*.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/f3471544869b
Remove nsIFrame::eBlockFrame flag. r=dholbert

Comment 4

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/f3471544869b