[csswg-drafts] [css-images-4] Defining coordinate systems for various types of images.

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== [css-images-4] Defining coordinate systems for various types of 
images. ==
In the [css-ui-3 spec's definition of the cursor 
property](https://drafts.csswg.org/css-ui-3/#cursor), we find this :
> <x><y>
>The x-coordinate and y-coordinate of the position in the cursor’s 
coordinate system (left/top relative) which represents the precise 
position that is being pointed to.
>>Note: This specification does not define how the coordinate systems 
of the various types of <image> are established, and defers these 
definitions to [CSS4-IMAGES].

This is when discussing the x and y values of the property, that 
position the cursor hotspot in the cursor image.

As far as I can tell, css-images (regardless of level), doesn't do 
that. Did I miss it?

That the origin is at the top left is clear. This also probably means 
* that for a bitmap image the unit is in image pixels
* that for an svg image, the unit is the unitless length integer

However, it isn't clear what this means for a gradient or
an image-set, which has images at multiple resolutions.

The full list of possible <image> values is:

`<image> = 
<url> | <image()> | <image-set()> | <element()> | <cross-fade()> | 

We need to define this (and css-image seems does seem like the right 
place, so that things just work when new `<image>` values are added).

As for the actual definitions, I propose:
 -> the unit is the image pixel for bitmap images

 -> the svg unit

 -> the coordinate system of the image you end up loading
    ISSUE: what to do if we fallback to a color?

 -> the coordinate system of the first image in the list

 -> CSS pixels?

 -> the coordinate system of the `<cf-mixing-image>`

 -> each axis goes from 0 to 100

Please view or discuss this issue at 
https://github.com/w3c/csswg-drafts/issues/652 using your GitHub 

Received on Wednesday, 26 October 2016 16:36:00 UTC