RFR: 8237469: CssStyleHelper reuse check fixed

[David Grieve]

On Fri, 17 Jan 2020 14:09:54 GMT, Dean Wookey <dwookey at openjdk.org> wrote:

> Everything passes with the fix and 5 of the new tests fail without the fix.
> 
> removingThenAddingNodeToDifferentBranchGetsNewFontStyleTest
> movingBranchToDifferentBranchGetsNewCssVariableTest
> removingThenAddingNodeToDifferentBranchGetsCorrectInheritedValue
> removingThenAddingNodeToDifferentBranchGetsIneritableStyle
> movingNodeToDifferentBranchGetsNewFontStyleTest
> 
> I doubt this will cause a significant performance decrease. I think it's worth it for correctness. The only other thing is that I kept the fix to the minimum, but technically canReuseHelper now has a side effect. I could try rewrite some things if necessary, or maybe rename the method? Else leave it as is?
> 
> Originally introduced here: https://bugs.openjdk.java.net/browse/JDK-8090462/ https://github.com/openjdk/jfx/commit/834b0d05e7a2a8351403ec4a121eab312d80fd24#diff-9ec098280fa1aeed53c70243347e76ab

Changes requested by dgrieve (Reviewer).

modules/javafx.graphics/src/main/java/javafx/scene/CssStyleHelper.java line 134:

> 133:             node.styleHelper.triggerStates.addAll(triggerStates[0]);
> 134: 
> 135:             updateParentTriggerStates(node, depth, triggerStates);

In canReuseStyleHelper, there is this check
       // If the style maps are the same instance, we can re-use the current styleHelper if the cacheContainer is null.
        // Under this condition, there are no styles for this node _and_ no styles inherit.
        if (node.styleHelper.cacheContainer == null) {
            return true;
        }
And later in the same function is a check for (parent == null) that returns true. In both cases, firstStyleableAncestor will still point to the old first-styleable ancestor.

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PR: https://git.openjdk.java.net/jfx/pull/87