Layout FAQ

Is there a way to do profiling of what is going on in Mozilla? Is there a framework for this?

If you're on Linux, then you can try using jprof. Instructions are available at Jprof Readme On more recent linux versions sysprof can also be used. also lists some profiles.

How do you find out if there are any reflows that are pending and wait to show the view until afterwards, but if none are pending, show the view immediately? What is the best way to determine whether there are any pending changes?

On the reflow branch you could check the DIRTY and DIRTY_CHILDREN framestate flags. That won't help with pending style changes, but it'll work to detect cases when the popup or something in it needs to be reflown.

What are the lowercase items called "line"?

Block(body)(1)@035FF490 {120,120,8820,600} [state=00000010]
sc=035FF264(i=2,b=0)<
   line 035FFC18: count=1
state=inline,clean,prevmarginclean,not impacted,not
wrapped,before:nobr,after:linebr[0x5100] {0,0,330,300} <
    Inline(span)(0)@035FFA04 next=035FFC48
next-continuation=035FFC48 {0,7,330,285} [content=0359ED50]
[sc=035FF990]<
      Text(0)@035FFA8C[0,4,T]  next=035FFB1C {0,0,330,285}
[state=41600020] sc=035FFA3C pst=:-moz-non-element<
        "\nabc"
      >
      Frame(br)(1)@035FFB1C {330,225,0,0} [state=00000020]
[content=035AEBF0]
    >
  > 

The linebox is used to contain everything on a single line: Example

How do you fix inconsistent float behavior in firefox involving a two column layout using display:table and floating div elements?

This is a bug in Firefox. You can work around it by removing display:table in the style rule with the "#main" selector or adding clear:both to it.

Why does move movement disappear when I use mouse events to click and drag?

Since the dragging action is involved, you might need to disable it. Try using event.preventDefault()

What is the purpose of the NS_LossyConvertUCS2toASCII() function?

This function converts an nsAString to an nsACString by assuming that all the 16-bit units are ASCII and just dropping the high byte on them all.