[web-animations-1] Specify how to compute property values #5255
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When it comes to the term "computed value", the spec is currently very confused. It appears to be making several references to "the" computed value (as in [1]), when in reality the intention is (I believe) to apply the *process* that calculates the computed value ([1]) to the value specified (locally) in the keyframe. This process is not described in a reusable way anywhere (I think), so I've added the algorithm "compute a property value" for this. I'm using the term "property value", since it's already extensively used in this spec. Possibly it would be more suited for css-cascade, but I'm proposing it for this spec until we need it somewhere else. In general I want to maintain a clear distinction between when we mean the actual computed value [1], and when we mean some value that has undergone the "compute a property value" process. Hence, I think we should avoid referring to a value that has undergone the "compute a property value" process as "a" computed value, as it's too easily confused with *the* computed value. I've included some text and an examples that hopefully clarify the expected interpolation behavior a little bit. It seemed somewhat natural to place this in the "Computing property values" section, since resolving dependencies is part of the process when computing values. [1] https://drafts.csswg.org/css-cascade/#computed
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@birtles : Please review. I will try to tackle css-animations/getKeyframes as well, but since web-animations is responsible for the core animation behavior, we have to start here. (Also cc @kevers-google, @flackr) |
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This looks good to me. I'm not sure if @tabatkins or @fantasai have any thoughts about if there is a better place for such a definition.
Also, as a very minor nit, we should probably aim to use more semantic line-breaking going forward (specifically, at least, starting new sentences on a new line).
| console.log(getComputedStyle(elem).fontSize); // Should be 15px | ||
| console.log(getComputedStyle(elem).width); // Should be 225px | ||
| </pre> | ||
| In this example, in order to <a>compute a property value</a> for |
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Nit: this link doesn't work for me. I think it needs to be [=compute a property value|computing a property value=].
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Ah, thanks. Fixed.
(Although the broken link didn't appear on the source line you highlighted).
OK, I made that change in the most obvious places, at least. |
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@birtles FYI, I don't have write access, so I can't merge this. (In case you're waiting for me). |
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Sorry, I didn't realize you don't have write access! |
When it comes to the term "computed value", the spec is currently
very confused. It appears to be making several references to
"the" computed value (as in [1]), when in reality the intention is
(I believe) to apply the process that calculates the computed
value ([1]) to the value specified (locally) in the keyframe. This
process is not described in a reusable way anywhere (I think), so I've
added the algorithm "compute a property value" for this. I'm using
the term "property value", since it's already extensively used in this
spec. Possibly it would be more suited for css-cascade, but I'm
proposing it for this spec until we need it somewhere else.
In general I want to maintain a clear distinction between when we
mean the actual computed value [1], and when we mean some value that
has undergone the "compute a property value" process. Hence, I think
we should avoid referring to a value that has undergone the
"compute a property value" process as "a" computed value, as it's
too easily confused with the computed value.
I've included some text and an examples that hopefully clarify
the expected interpolation behavior a little bit. It seemed somewhat
natural to place this in the "Computing property values" section,
since resolving dependencies is part of the process when computing
values.
Fixes #5125.
[1] https://drafts.csswg.org/css-cascade/#computed