972703 - Massive 3d transforms aren't displayed

Status: RESOLVED FIXED

(Core :: Layout, defect, P4)

Description

[Matt Woodrow (:mattwoodrow)]

Attachment: Archive.zip

+++ This bug was initially created as a clone of Bug #952011 +++

Testcase attached.

When we 3d transform an element to be 'massive', such that it overflows the max nscoord value in both directions, it is no longer displayed.

The issue is when converting the transformed size from float pixels into app units (done for both the display item bounds, and frame overflow computation).

We clamp the values to nscoord_MIN/MAX giving us:

(nsRect) $65 = {
  mozilla::gfx::BaseRect<int, nsRect, nsPoint, nsSize, nsMargin> = {
    x = -1073741824
    y = -1073741824
    width = 1073741824
    height = 1073741824
  }
}

This rect doesn't intersect the viewport, so the item fails visibility computation and is hidden.

Comment 1

[Matt Woodrow (:mattwoodrow)]

Attachment: transforms-fix

Comment 2

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Comment on attachment 8376018 [details] [diff] [review]
transforms-fix

Review of attachment 8376018 [details] [diff] [review]:
-----------------------------------------------------------------

::: layout/base/nsLayoutUtils.cpp
@@ +1647,5 @@
> +  }
> +
> +  if (aStart <= nscoord_MIN) {
> +    if (aSize == nscoord_MAX) {
> +      aStart = nscoord_MIN/2;

This discontinuity seems a bit dodgy... what if aSize == nscoord_MAX - 1?

How about we explicitly compute x/xmost, clamp those to nscoord_MIN/2 and nscoord_MAX/2, and then convert back to start/length.

Comment 3

[Matt Woodrow (:mattwoodrow)]

Attachment: transforms-fix v2

Yeah, you're right. I think this one makes more sense :)

Comment 4

[Matt Woodrow (:mattwoodrow)]

https://hg.mozilla.org/integration/mozilla-inbound/rev/ef3d90780478

Comment 5

[Phil Ringnalda (:philor)]

Backed out along with bug 972703 in https://hg.mozilla.org/integration/mozilla-inbound/rev/89b9078be02a - between the two there's a b2g build failure, https://tbpl.mozilla.org/php/getParsedLog.php?id=34764895&tree=Mozilla-Inbound, and an assertion, https://tbpl.mozilla.org/php/getParsedLog.php?id=34765199&tree=Mozilla-Inbound / https://tbpl.mozilla.org/php/getParsedLog.php?id=34764908&tree=Mozilla-Inbound, to deal with.

Comment 6

[Phil Ringnalda (:philor)]

* along with bug 889959

Comment 7

[Matt Woodrow (:mattwoodrow)]

https://hg.mozilla.org/integration/mozilla-inbound/rev/c2e9792b72d4

Comment 8

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/c2e9792b72d4