17:00:37 RRSAgent has joined #css
17:00:37 logging to https://www.w3.org/2019/02/26-css-irc
17:00:39 RRSAgent, make logs public
17:00:39 Zakim has joined #css
17:00:41 Meeting: Cascading Style Sheets (CSS) Working Group Teleconference
17:00:41 Date: 26 February 2019
17:01:45 present+
17:01:54 futhark has joined #css
17:02:38 TabAtkins: Hi I’m here on 7th floor. Can you or someone let me in?
17:03:20 futhark has joined #css
17:09:01 AmeliaBR has joined #css
17:09:06 bgirard has joined #css
17:10:23 presenter has joined #css
17:12:06 skk has joined #css
17:14:42 myles_ has joined #css
17:15:03 scribenick: gregwhitworth
17:15:22 bdc has joined #css
17:15:48 rachelandrew has joined #css
17:15:49 https://g.co/hangout/google.com/csswg
17:16:38 xfq has joined #css
17:16:40 Topic: ResizeObserver device-pixel-border-box
17:16:46 Github: https://github.com/w3c/csswg-drafts/issues/3554
17:17:44 atotic: I've been working on the spec
17:18:10 atotic: the graphics team came to me - the problem they have is a way to determine the device pixel size of canvas
17:18:27 atotic: why do they need to do this - the reason why they need to do this - is there is no way to do this
17:19:14 atotic: the way the devs do hidpi in canvas it has CSS Pixels and what they do is they create the bitmap size they create the canvas in physical pixels it gets shrunk to CSS pixels so they can draw really fine hairlines
17:19:30 atotic: device pixels are never rounded - there is no doubles or floating point, etc
17:19:41 jensimmons has joined #css
17:19:46 atotic: how we do this is by pixel snapping, there is no way for webdevs to determine this
17:20:14 atotic: pixel snapping depends on not only pixels but also position
17:20:34 atotic: I asked to add it to canvas, and they said sure but they also need to be notified when its resize
17:20:57 atotic: currently the proposal will be that you will get device pixel inline and border size if its a canvas
17:21:10 fantasai: are you proposing to add it somewhere else
17:21:17 atotic: no
17:21:31 fantasai: so the only way to get this is to add the resizeObserver
17:21:36 atotic: yes
17:22:09 dholbert: does devicePixelRatio?
17:22:28 atotic: they get a bad pattern from hacking this because it can't do pixel snapping correctly
17:22:48 dbaron: under what conditions does Chrome change the device pixel backing size when it's repositioned?
17:23:43 dbaron: atotic is saying that, if you make a subpixel change in the top coordinate of a canvas, if it's 100.25 px tall
17:24:10 present+
17:24:20 dbaron: and it's top is positioned at a pixel aligned position it would round to 100, if it's further down it will be 101
17:24:29 dbaron: do you actually change the backing store
17:24:39 dbaron: the number of image pixels in the canvas
17:24:48 dbaron: I guess thats the height and width
17:25:22 dbaron: they want to change those the attrs based on the device pixel sizes
17:26:03 atotic: the developer determines the size of the backing store, what Chrome does it will copy that bitmap to the CSS size of the canvas, if the ratio is a nice even number then we don't get moar patterns - if we don't
17:26:24 how is that different from a url background image?
17:26:27 atotic: there is a CSS size which can be fractional - but there is also the real bitmap to paint the canvas and that bitmap is in physical pixels
17:26:43 " if the ratio is a nice even number then we don't get moar patterns - if we don't"
17:26:45 that bit
17:27:09 s/moar/moire/g
17:27:26 dbaron: bkardell_ is asking why don't you get moire pattern in background images
17:27:44 atotic: it will scale, but background image is fundamentally different
17:28:00 I can unmute and talk, I just dont want to interupt and don't knwo if this is enough to warrant a q
17:28:12 atotic: we probably do get them but you usually aren't doing hidpi background image or you can't tell
17:28:31 atotic: where they primarily have this issue is in the 3d context and they'll have patterns that look different
17:28:56 q+
17:29:06 bkardell_: the act of painting a thing on a canvas - the bitmap comes from an image and we rescale the image - it shoudln't matter who creates this image?
17:29:38 atotic: you will see artifacts - but they'll create 3 different images
17:29:43 So I understand the use case -- but I'm a little suspicious of making it