Support radial-gradients with relative offsets

Support radial-gradients with relative offsets

The center of a radial-gradient can be determined four
different ways. It can be defined with lengths, percentages,
keywords or by combining keywords with lengths or percentages.
This patch makes the usage of the latter combinations
possible.

R=fmalita@chromium.org
BUG=389205
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=177082

[f(malita), 2014-06-26 20:33:43]

Nice patch! Looks good, but maybe we can simplify it a bit and reuse the same
logic for right/bottom pairs.

https://codereview.chromium.org/356683005/diff/1/Source/core/css/CSSGradientV...
File Source/core/css/CSSGradientValue.cpp (right):

https://codereview.chromium.org/356683005/diff/1/Source/core/css/CSSGradientV...
Source/core/css/CSSGradientValue.cpp:391: static float
positionFromPairValue(CSSPrimitiveValue* value, int edgeDistance, const
CSSToLengthConversionData& conversionData)
I think we can fold this into the original method, see below.

https://codereview.chromium.org/356683005/diff/1/Source/core/css/CSSGradientV...
Source/core/css/CSSGradientValue.cpp:402: static float
positionFromValue(CSSPrimitiveValue* value, const CSSToLengthConversionData&
conversionData, const IntSize& size, bool isHorizontal)
How about something like this instead:

static float positionFromValue(CSSPrimitiveValue* value, const
CSSToLengthConversionData& conversionData, const IntSize& size, bool
isHorizontal)
{
    int origin = 0;
    int sign = 1;
    int edgeDistance = isHorizontal ? size.width() : size.height();

    if (Pair* pair = value->getPairValue()) {
        CSSValueID originID = pair->first()->getValueID();
        value = pair->second();

        if (originID == CSSValueRight || originID == CSSValueBottom) {
            // For right/bottom, the offset is relative to the far edge.
            origin = edgeDistance;
            sign = -1;
        }
    }

    if (value->isNumber())
        return origin + sign * value->getFloatValue() * conversionData.zoom();

    if (value->isPercentage())
        return origin + sign * value->getFloatValue() / 100.f * edgeDistance;

    if (value->isCalculatedPercentageWithLength())
        return origin + sign *
value->cssCalcValue()->toCalcValue(conversionData)->evaluate(edgeDistance);

    switch (value->getValueID()) {
        ... // same as before
    }

    return origin + sign * value->computeLength<float>(conversionData);
}

https://codereview.chromium.org/356683005/diff/1/Source/core/css/CSSGradientV...
Source/core/css/CSSGradientValue.cpp:405: if (Pair* pair =
value->getPairValue()) {
We should probably add an inline comment describing the type of CSS gradient
syntax covered by this branch.

[reni, 2014-06-27 00:13:48]

@Florin: Thanks for the review! The patch is updated according to your review.

[f(malita), 2014-06-27 01:08:14]

On 2014/06/27 00:13:48, renata.hodovan wrote:
> @Florin: Thanks for the review! The patch is updated according to your review.

Thanks Reni, LGTM.

[reni, 2014-06-27 07:30:26]

The CQ bit was checked by rhodovan.u-szeged@partner.samsung.com

[commit-bot: I haz the power, 2014-06-27 07:31:09]

CQ is trying da patch. Follow status at

https://chromium-status.appspot.com/cq/rhodovan.u-szeged@partner.samsung.com/...

[commit-bot: I haz the power, 2014-06-27 08:38:09]

Change committed as 177082