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Re: Proposal: getStyleAs(property, primitiveValue)

From: Garrett Smith <dhtmlkitchen@gmail.com>
Date: Tue, 5 Jan 2010 14:47:00 -0800
Message-ID: <c9e12661001051447t5b19b665hd3959f76c66c4ca5@mail.gmail.com>
To: Giovanni Campagna <scampa.giovanni@gmail.com>
Cc: Patrick Garies <pgaries@fastmail.us>, Travis Leithead <travil@microsoft.com>, www-style <www-style@w3.org>, info@gtalbot.org
The strategies used to read styles for cross-browser applications are absurd.

It is a shame on Microsoft for ignoring this thread. Last post was
from Leithead, and that was over three months ago. Travis' reply did
not answer the initial problem in my initial message explaining that
there is no good API for reading a style value and that currentStyle
is different.

DOM2 Style is an API to read styles. If Microsoft intends on
implementing that, they should say so.

Microsoft has repeatedly made the decision to not support DOM 2 Style
in release after release of MSIE.

What does Microsoft propose authors use to read computed style values in IE?

Not all of DOM 2Style is necessary for web compatibility, but the
parts that are need careful consideration and testing before releasing
a next versoin of IE that is running in one mode (with no
compatibility mode buttons or weird meta tags).

If Microsoft decides to implements DOM2 style, it should do so in a
way that is web-compatible.

Mozilla may be removing the underspecified, clunker
"getPropertyCSSValue" and friends, so that would be one thing that
could be omitted.

// Do not use this error-prone clunker for production.
var view = document.defaultView;
var styleObj = view.getComputedStyle(document.body,"");
var cssValue = styleObj.getPropertyCSSValue("color");
var rgbColor = .getRGBColorValue();
var redValue = .red.cssText;

If Microsoft is planning to implement defaultView.getComputedStyle, it
would at least provide some way to read computed styles in IE.

If Microsoft is not going to implement defaultView.getComputedStyle
(and the record in the past 10 years indicates that possibility to be
very likely), then there should be an alternate functionality for
reading styles.

If there is new functionality for reading style, it should address
reading absolute style values in a chosen unit and consider reading
cascaded style values.

API Considerations:
 1) Read absolute style values
 2) Read absolute style values in desired unit
 3) Read cascade style value

Based on program needs and existing code, reading absolute style
values is the #1 important case.

Reading absolute style values in desired unit can't be done reliably,
cross browser, with today's browsers and APIs, and not without a lot
of code to do that. However, just because it is not possible does not
mean it is not going to be useful. There shoul be an API to get things
like sizes in em, so a script can read and set an element's style in
em units, for example.

What does Microsoft propose to address the problem of reaing absolute
styles in IE?

Garrett
[1]https://bugzilla.mozilla.org/show_bug.cgi?id=474655#c4


On Sat, Jan 2, 2010 at 10:50 PM, Garrett Smith <dhtmlkitchen@gmail.com> wrote:
> Was this unclear or confusing?
>
> Does Microsoft intend to provide an API to read styles for IE9?
>
>
> On Tue, Dec 22, 2009 at 12:57 PM, Garrett Smith <dhtmlkitchen@gmail.com> wrote:
>> On Tue, Dec 22, 2009 at 4:53 AM, Giovanni Campagna
>> <scampa.giovanni@gmail.com> wrote:
>>> On Tue, Dec 22, 2009 at 10:30 AM, Patrick Garies <pgaries@fastmail.us> wrote:
>>>> On 9/22/2009 8:08 PM, Garrett Smith wrote:
>>>>>>
>>>>>> I also assume that getStyleAs can return a plethora of possible values
>>>>>> from strings to other interfaces...
>>>>>>
>>>>>
>>>>> I was thinking it would return a string although |asNumber| param
>>>>> might a possibility:-
>>>>>
>>>>> x.getStyleAs("length", "px", "number");
>>>>>
>>>>> Returns a number representing the length, in css pixels.
>>>>
>>
>> Ah, no, there is no "length" /property/.
>>
>> How about "width" for an element.
>>
>> // Read el's computed width, in px, but as a number.
>>  el.getStyleAs("width", "px", "number");
>>
>> On second glance, the method returning either string or number is
>> complex and inconsistent. The extra - valueType - argument is
>> responsible for this problem. It should be omitted and the method
>> should return a string. And so that leaves:
>>
>>  el.getStyleAs("width", "px")
>>
>> - which is already complicated enough.
>>
>> This fulfills the goal of reading a computed style.
>>
>> This does not allow for reading/parsing of numbers, nor does it allow
>> for value object.
>>
>>>> For some reason, I'm thinking Travis was wondering what all the types of
>>>> returnable values are. So far, pixels, integers, and RGBA seem to be covered
>>>> based upon your examples. |rgb| is also mentioned, but it's not clear if
>>>> that's a reference to the hexadecimal or functional notation.
>>>>
>>
>> The string "rgb" would get an RGB functional notation string
>>
>> el.getStyleAs("color", "rgb");
>> => "rgb(0, 0, 0)";
>>
>> el.getStyleAs("color", "rgba");
>> => "rgba(0,0,0,1)"
>>
>> el.getStyleAs("color", "#");
>> => "#000000"
>>
>> Other situations will want an Object or number: getStyleObject, getStyleNumber.
>>
>> var c = el.getStyleObject("color", "rgb");
>> [c.r, c.g, c.b] + "";
>> => "0, 0, 0"
>>
>> And for the number case, something like:
>>
>> var c = el.getStyleNumber("color", "rgb");
>> => 0
>>
>> The idea of style.width.px++ wont be compatible with the web today and
>> 2++ would be an error. However, parts of the idea could be used for a
>> different object.
>>
>> Another proposal to read computedStyle on an HTMLElement that is not
>> disconnected, call it "ElementComputedStyle". Example:
>>
>> el.computedStyle.color+ ""
>> => "inherit";
>>
>> el.computedStyle.color.rgb.r
>> => 0
>>
>> el.computedStyle.width.r
>> => undefined
>>
>> As you can see, the object returned from the css property name varies.
>> If it is a css length type of property, the object will have a - px -
>> property. If it is a CSS Color object, it will have an - r- property.
>>
>> A setter for the computedStyle object would not make sense because it
>> is a *computed* style.
>>
>> For setting values on an element, the element's style object could be
>> used. Example:
>>
>> el.style.width  = el.computedStyle.width.percent + "%";
>>
>> Finally, a third idea is "LiveStyle".
>>
>> LiveStyle mixes computedStyle (for getting), overrideStyle (for
>> setting), and cascaded style, for default value in toString, into one
>> object. The object would have a toString function that returns the
>> *cascaded* style. The LiveStyle interface implements CSS2Properties,
>> but each CSS2Property of a LiveStyle has a new DynamicStyle properties
>> that implements CSS2Properties
>>
>> interface LiveStyle : CSS2Properties {
>>  string toString()
>> }
>>
>> Interface DynamicStyle : CSSStyleDeclaration {
>>  string toString()
>>  long valueOf()
>> }
>>
>> The properties for a DynamicStyle depend on the property in question.
>> For RGBColor, an - r - property would be present, but for width, no r
>> property would be present. For property values that read a
>> computedStyle and set an overrideStyle. The liveStyle value itself
>> serializes the cascaded style.
>>
>> el.liveStyle + "";
>> => "color: red; width: auto"
>>
>> el.liveStyle.width + ""; // cascaded style, as declared.
>> "auto";
>>
>> el.liveStyle.width.px; // computed style, in px
>> => 10
>>
>> el.liveStyle.width.px++; // Read computedStyle in px, add 1, and set
>> override Style, in px
>> => 11
>>
>> el.liveStyle.color;
>> => "inherit"
>>
>> el.liveStyle.color.r += 10;
>> => 255
>>
>> Shorthand properties such as margin, pading, borderWidth, etc add
>> complexity with multiple CSS value types for both proposals. The
>> complexity of shorthand properties have to be considered to either
>> ignore, or consider handling iff is the property takes a length and
>> all values are equal.
>>
>> // Shorthand, but risky.
>> el.style.margin = el.computedStyle.margin + "px";
>>
>> There are the three proposals.
>> 1) getStyleAs - reads a computed style, returns a string
>> 2) ElementComputedStyle - reads computed style from non-disconnected element.
>> 3) LiveStyle reads cascade style, computed style, sets override style.
>>
>> Aside from it would be useful to have a standard specify conversion of
>> ToString for the setter of style property. So that setting a style
>> property to an object would result in calling the internal ToString
>> for the assigned value.
>>
>> // Assign a string value.
>> el.style.width = "10px"; Standard.
>>
>> // Proposed:
>> // Leverage ECMAScript internal [[ToString]]
>> anotherEl.style.width = { toString: function(){ return "10px"; }};
>>
>> Garrett
>>
>
Received on Tuesday, 5 January 2010 22:47:33 GMT

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