Add an optimization to make line height and box placement calculations faster

[Dave Hyatt]

Add an optimization to make line height and box placement calculations faster.  Basically try to avoid spending as much time in computeLogicalBoxHeights and placeBoxesInBlockDirection.

[Dave Hyatt]

Created attachment 87219 [details]
Patch

[Dave Hyatt]

Created attachment 87353 [details]
Patch

[Darin Adler]

Comment on attachment 87353 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=87353&action=review

> Source/WebCore/rendering/InlineFlowBox.cpp:105
> +        InlineFlowBox* childFlowBox = static_cast<InlineFlowBox*>(child);
> +        if (childFlowBox->hasTextDescendants())
> +            m_hasTextDescendants = true;

I don’t think the local variable here is helpful.

> Source/WebCore/rendering/InlineFlowBox.cpp:110
> +        RenderStyle* parentStyle = renderer()->style(m_firstLine);
> +        RenderStyle* childStyle = child->renderer()->style(m_firstLine);

Seems a shame to always compute these, since they are not always used.

> Source/WebCore/rendering/InlineFlowBox.cpp:111
> +        bool changeResult = false;

Not sure what “change result” means in this name. Can you come up with a better name.

> Source/WebCore/rendering/InlineFlowBox.cpp:521
> -        if (curr->isInlineFlowBox())
> -            static_cast<InlineFlowBox*>(curr)->computeLogicalBoxHeights(rootBox, maxPositionTop, maxPositionBottom, maxAscent, maxDescent,
> -                                                                        setMaxAscent, setMaxDescent, strictMode, textBoxDataMap,
> -                                                                        baselineType, verticalPositionCache);
> +        if (inlineFlowBox)
> +            inlineFlowBox->computeLogicalBoxHeights(rootBox, maxPositionTop, maxPositionBottom, maxAscent, maxDescent,
> +                                                    setMaxAscent, setMaxDescent, strictMode, textBoxDataMap,
> +                                                    baselineType, verticalPositionCache);

It’s better to not line up the subsequent lines so you don’t have to move them when making a change like this one. Also, there should be braces in this if statement.