12747 - [perf] height/width: inherit cause massive performance hit

Status: VERIFIED FIXED

(Core :: Layout, defect, P2)

Description

[Sam Allen]

The rules height: inherit and width: inherit cause massive performance hits. See
attached testcase

Comment 1

[Sam Allen]

Attachment: testcase

Comment 2

[troy]

The problem seems to be an infinite loop in HaveAutoWidth in nsBlockFrame.cpp

In particular this code:

    const nsHTMLReflowState* prs = (const nsHTMLReflowState*)
      aReflowState.parentReflowState;
    if (!prs) {
      return PR_TRUE;
    }
    pos = prs->mStylePosition;

If we're unlucky and the parent reflow state also has 'inherit' (as is the case
with this example), then we'll never exit.

It looks like:
    const nsHTMLReflowState* prs = (const nsHTMLReflowState*)
      aReflowState.parentReflowState;

should be doing something like this instead:
    prs = (const nsHTMLReflowState*)prs->parentReflowState;

Do we really need this code? The HTML reflow state takes 'inherit' into account
when calculating the computed width.

Comment 3

[kipp]

A simple infinite loop...fixed

Comment 4

[Sam Allen]

verified fixed in 9/10/99 build.

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/a16e0e6223ac
[fenix] Create ToolbarPosition enum (https://github.com/mozilla-mobile/fenix/pull/12747)