230249 - [FIX]Assertion: Negative Width Input - very bad: 'mComputedWidth >= 0'

Status: VERIFIED FIXED

(Core :: Layout, defect, P1)

Description

[Philip K. Warren]

In a debug build from today, I am getting the following assertion several
hundred times while running the editor. It seems to be triggered just from
moving the mouse around the user interface - i.e. move the mouse from the text
input area over all of the buttons on the toolbar and all of the menus.

###!!! ASSERTION: Negative Width Input - very bad: 'mComputedWidth >= 0', file
/home/pkw/sb/mozilla/trunk/mozilla/layout/html/base/src/nsHTMLReflowState.cpp,
line 2532
Break: at file
/home/pkw/sb/mozilla/trunk/mozilla/layout/html/base/src/nsHTMLReflowState.cpp,
line 2532

I have only tested this on AIX (GTK2 build) for now so I'm not sure if this
affects all platforms or not.

The assertion (not necessarily the code which triggers the assertion) is a
result of the checkin for Bug 227819.

Comment 1

[Philip K. Warren]

This assertion is not limited to the Editor - I am also getting it in the Browser.

Comment 2

[Boris Zbarsky [:bzbarsky]]

What are the steps to reproduce for browser?

Comment 3

[Philip K. Warren]

Same as for the Editor - it is triggered just by moving the mouse around the 
interface (not clicking anything).

Comment 4

[Boris Zbarsky [:bzbarsky]]

The problem here is that
athttp://lxr.mozilla.org/seamonkey/source/layout/xul/base/src/nsBoxToBlockAdaptor.cpp#802
on the first layout of the adaptor size.width is 0, so availableWidth for the
reflow state is 0.  But the style for the area frame involved has nonzero
margins, so when nsHTMLReflowState::ComputeBlockBoxData does:

          mComputedWidth = availableWidth - mComputedMargin.left -
            mComputedMargin.right - mComputedBorderPadding.left -
            mComputedBorderPadding.right;

we end up with a negative computed width.

I would think that we should use a PR_MAX with 0 here...

Comment 5

[Boris Zbarsky [:bzbarsky]]

Attachment: Patch

Comment 6

[Boris Zbarsky [:bzbarsky]]

Comment on attachment 138536 [details] [diff] [review]
Patch

David, would you review?

Comment 7

[Boris Zbarsky [:bzbarsky]]

Checked in.

Comment 8

[Philip K. Warren]

I am no longer seeing this warning in today's build.