1234409 - "Assertion failure: mUnit == eCSSUnit_Percent (not a percent value)" with webkit gradient syntax

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, defect)

Description

[Jesse Ruderman]

Attachment: testcase

With:
  user_pref("layout.css.prefixes.webkit", true);

Assertion failure: mUnit == eCSSUnit_Percent (not a percent value), at nsCSSValue.h:532

Comment 1

[Jesse Ruderman]

Attachment: stack

Comment 2

[Daniel Holbert [:dholbert]]

So this is a case where:
 (1) the author provided no color stops, so we pad the color-stop list with 2 transparent stops.
 (2) the radiuses are in the opposite order that we expect them to be -- the first one is larger -- so we reverse the positions of their color-stops.

And the problem is that our auto-generated "padding" color stops from (1) have no position specified, so when we try to inspect their positions in (2), we trip this assertion.

The fix is easy -- we should just have dummy 0.0/1.0 (start/end) positions for these transparent padding color stops. All color stops that come from authors will have positions, so our internal auto-generated ones should too.

Comment 3

[Daniel Holbert [:dholbert]]

Attachment: fix v1

Comment 4

[Daniel Holbert [:dholbert]]

I verified that the added property_database.js line is an effective test for this bug. (With that line, test_value_computation.html trips this bug's fatal assertion, until I apply the fix.)

Comment 5

[Daniel Holbert [:dholbert]]

If you like, for a refresher on why we're messing with these color-stops (beyond comment 2), see these multi-line comments within CSSParserImpl::FinalizeRadialWebkitGradient:
http://mxr.mozilla.org/mozilla-central/source/layout/style/nsCSSParser.cpp?rev=1f2dd0904614&mark=10392-10399,10413-10416#10392

The assertion-failure is happening during the call to "colorStop.mLocation.GetPercentValue()" just below the comments there, for a dummy color-stop that we generated in the area of code touched by the patch.

Comment 6

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/6cdded7c7414

Comment 7

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/6cdded7c7414