18766 - [CODE CLEANUP] Add method to clear struct nsHTMLReflowMetrics

Status: VERIFIED WONTFIX

(Core :: Layout, defect, P3)

Description

[rbs]

In a number of places in the layout frame constrution code, one can
see snippets like:

    aMetrics.width = 0;
    aMetrics.height = 0;
    aMetrics.ascent = 0;
    aMetrics.descent = 0;
    if (nsnull != aMetrics.maxElementSize) {
      aMetrics.maxElementSize->width = 0;
      aMetrics.maxElementSize->height = 0;
    }
}

Since this is done in a number of places, it would look nice to
use a simple method, say aMetrics.Clear(), to do job. I have seen
a XXX comment somewhere suggesting to do just that, and I am filing
this bug to give prominence to the suggestion and to ensure that
it doesn't falled into oblivion.

I could go ahead and add the method as indicated below, but frame
owners know best where they have zeroed their metrics.

struct nsHTMLReflowMetrics { // defined in nsIFrame.h
...

void Clear {
  width = height = 0;
  ascent = descent = 0;
  if (nsnull != maxElementSize) {
    maxElementSize->width = 0;
    maxElementSize->height = 0;
  }
}
...
}

Comment 1

[troy]

I forgot to add that the reason I'm marking this WONTFIX is that it seems
undesirable that we have a number of places that are clearing (reseting to the
default values) the nsHTMLReflowMetrics struct.

I question whether people should be doing that, and maybe that problem should be
fixed rather than making it easier for people

Comment 2

[Pulsebot]

Pushed by ffxbld-merge:
https://hg.mozilla.org/releases/mozilla-beta/rev/4f75f56d0c2e
[fenix] [SDK-246] Change Nimbus `channel` input to use the same method as Glean (https://github.com/mozilla-mobile/fenix/pull/18766)