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From Alex Harui <aha...@adobe.com>
Subject Re: [FlexJS]Layout redux
Date Wed, 22 Feb 2017 07:46:44 GMT
It is probably time for our annual "revisiting of the layout code".  I
think if you look at source code history, Peter or I do this every so
often as we get more examples to work with.

From memory, there are issues like whether we have to set
position:relative or not that came out of the MDL swc.  And when/if we
need to set the width on a parent for percentage width to work in the
children/grandchildren.

It is great to finally have some people actually paying attention that
know how this stuff is actually normally done in JS.  Peter and I were
mostly guessing since, if you think about it, we were basically doing Flex
until we got into FlexJS and are not experienced in HTML/JS.

So, fundamentally, if you have to stack things vertically, should you use
display:block?  If you have to line up a bunch of divs horizontally,
should you use display:inline-block?

Is there a better way to do BasicLayout?  We ended up using a completely
handwritten set of code to essentially make everything use absolute
positioning.

Is border-box working as expected?  Do you set the height/width to include
the padding or not?

I think some layouts can use CSS but others have to be written in code to
override default browser behavior.  But I'd love to be wrong about that
(at least, without relying on latest browsers or polyfills).

And finally, are there ways we can call the layout fewer times than we
currently do?

For sure, we need to the the JS side right and then worry about the SWF
side.  I think there are way fewer behavior issues on the SWF side to deal
with.

My 2 cents,
-Alex

On 2/21/17, 12:35 PM, "Peter Ent" <pent@adobe.com> wrote:

>I think this is generally a good approach.
>
>I've been thinking that we have some refactoring to do which might help.
>For instance, Core should probably be edited to include interfaces,
>events, and whatever else works across all packages. HTML should probably
>be just the HTML classes (Div, H1, TextNode, etc) so anyone that wants
>HTML+ActionScript can use that and then use CSS to do all their layouts;
>HTML would not have a SWF version.
>
>Then Basic could be SWF & JS with layouts that are light on the JS side
>using CSS and AS code to mimic them on the SWF side. Express would do what
>it is doing now and compose components by extending the Basic set and
>adding common beads.
>
>I've been hung up with the JS side having stuck on the display and
>position values and deferring them might be the best solution.
>
>—peter
>
>On 2/21/17, 2:25 PM, "carlos.rovira@gmail.com on behalf of Carlos Rovira"
><carlos.rovira@gmail.com on behalf of carlos.rovira@codeoscopic.com>
>wrote:
>
>>Hi Peter,
>>
>>it seems HTML rely for this task heavily on CSS to the point that almost
>>nothing is done in html or js code.
>>So maybe we are not in the right way for HTML platform and we should make
>>our code be mainly CSS.
>>An example is here:
>>
>>https://css-tricks.com/snippets/sass/placing-items-circle/
>>
>>Another point is SWF. I'm not focusing in that output and even I didn't
>>compile to SWF for long time, so don't know how
>>is looking, but for what I saw in other discussions seems that Flash
>>needs
>>to implement the old Flex architecture of
>>updateDisplayList to manage refresh to avoid continuous redrawing of the
>>screen.
>>
>>So my bet is that our AS3 layout components should do:
>>
>>1.- In JS -> add className to "some-class-layout" (for example for
>>circle,
>>if we have circle-layout, we should have a "circleLayout" css class
>>selector, that we could assign to out flexjs "list component"
>>
>>2.- in SWF -> we should stick with the way this was done in Flex4 but
>>implementing as a bead and with the "updateDisplayList" performance
>>
>>What do you think?
>>
>>
>>
>>
>>2017-02-21 20:10 GMT+01:00 Peter Ent <pent@adobe.com>:
>>
>>> A lot of this work is mine and it seems to need to be thought through
>>>once
>>> again. The dichotomy of SWF & JS has presented problems for me in the
>>>past.
>>>
>>> Maybe the layouts, for JS platform, should do as little as possible,
>>> replying on CSS as much as possible. Then make the SWF platform mimic
>>>that.
>>>
>>> One issue that comes up for me is that we automatically set display and
>>> position for every element soon after its created. If you were to
>>> hand-write the HTML you probably would not do that.
>>>
>>> So perhaps FlexJS should not set these styles at all and instead let
>>>the
>>> layout set them if the layout even needs to do that.
>>>
>>> Thoughts?
>>> ‹peter
>>>
>>> On 2/21/17, 1:42 PM, "Harbs" <harbs.lists@gmail.com> wrote:
>>>
>>> >We¹re really struggling with layout.
>>> >
>>> >Yishay just mentioned the fact that padding is not working, but the
>>> >problems seem to go much deeper than that.
>>> >
>>> >1. VerticalLayout has the following code:
>>> >                               for (i = 0; i < n; i++)
>>> >                               {
>>> >                                       var child:WrappedHTMLElement =
>>> children[i];
>>> >                                       child.flexjs_wrapper.
>>> setDisplayStyleForLayout('block');
>>> >                                       if (child.style.display ===
>>>'none')
>>> >                                       {
>>> >                                               child.flexjs_wrapper.
>>> setDisplayStyleForLayout('block');
>>> >                                       }
>>> >                                       else
>>> >                                       {
>>> >                                               // block elements don't
>>> measure width correctly so set to inline
>>> >for a second
>>> >                                               child.style.display =
>>> 'inline-block';
>>> >                                               maxWidth =
>>> Math.max(maxWidth, child.offsetLeft + child.offsetWidth);
>>> >                                               child.style.display =
>>> 'block';
>>> >                                       }
>>> >                                       child.flexjs_wrapper.
>>> dispatchEvent('sizeChanged');
>>> >                               }
>>> >
>>> >There is a number of problems that I can see with this. Firstly, it¹s
>>> >horribly inefficient:
>>> >                                               child.style.display =
>>> 'inline-block';
>>> >                                               maxWidth =
>>> Math.max(maxWidth, child.offsetLeft + child.offsetWidth);
>>> >The above will force a browser redraw at every step of the loop. If
>>>you
>>> >have hundreds of children, there will be hundreds of redraws just to
>>> >figure out the children width. If anything, there should probably be
>>> >three loops: One to set the inline-blocks, The second to measure all
>>>the
>>> >children (the first measure would trigger a redraw, but subsequent
>>>ones
>>> >not) The third to set inline-block back.
>>> >
>>> >Secondly, there¹s only a need to measure the children if the container
>>>is
>>> >sized to content. If the container has a fixed width or a percentage
>>> >width, I don¹t see why the children should be measured at all. The
>>>only
>>> >exception I can see is if there is overflow:auto.
>>> >
>>> >Thirdly, I don¹t understand how setting the child to inline-block
>>>helps.
>>> >What about the grandchildren? Don¹t those need to be measured too?
>>> >Fourthly, Both Horizontal and VerticalLayout have code which
>>>temporarily
>>> >sets inline-block. BasicLayout does not, and I don¹t understand why
>>> >there¹s a difference. (BasicLayout has the same re-rendering problem
>>> >though.)
>>> >2.
>>> >                               if (!hasWidth && n > 0 &&
>>> !isNaN(maxWidth)) {
>>> >                                       var pl:String =
>>> scv['padding-left'];
>>> >                                       var pr:String =
>>> scv['padding-right'];
>>> >                                       var npl:int =
>>> parseInt(pl.substring(0, pl.length - 2), 10);
>>> >                                       var npr:int =
>>> parseInt(pr.substring(0, pr.length - 2), 10);
>>> >                                       maxWidth += npl + npr;
>>> >                                       contentView.width = maxWidth;
>>> >                               }
>>> >
>>> >This seems totally wrong. Why is the padding being added when we¹re
>>>using
>>> >box-sizing: border-box?
>>> >
>>> >3. Percentage size seems to be set based on the children rather than
>>>the
>>> >parents.
>>> >
>>> >4. I¹m not sure I understand the layout lifecycle very well. We have
>>>had
>>> >cases where children did not seem to be layout, and forcing a layout
>>> >seemed to be very difficult to do.
>>> >
>>> >Harbs
>>>
>>>
>>
>>
>>-- 
>>
>>Carlos Rovira
>>Director General
>>M: +34 607 22 60 05
>>http://www.codeoscopic.com
>>http://www.avant2.es
>>
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>

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