JDK-8130738 TextFlow's tab width is static

Kevin Rushforth kevin.rushforth at oracle.com
Mon Sep 30 23:21:50 UTC 2019

Hi Scott,

Thanks for the update. I haven't had much time lately between the Skara 
switch and trying to keep up with jpackage changes...

The next step is, as you note, to continue discussion any issues around 
the API, including whether and how it might interact with a rich text 
editor that wanted to have a list of variable tab stops (like many word 
processors use). On this point, I wouldn't imagine wanting to implement 
variable tab stops in TextFlow, but I would want to think through how a 
feature layered on top of TextFlow would override the fixed tab width 
that TextFlow has; since we have this problem today, I don't think this 
is making it worse, but some discussion on that point would be good.

Once there is general buy-in on adding this feature, and on the 
approach, it would be good to review the API, although that's quite simple.

Finally, I would want Phil's input before approving the API.

-- Kevin

On 9/30/2019 9:48 AM, Scott Palmer wrote:
> Okay, current work relocated to a clone of the new official Git repo.
> My initial implementation is here:
> https://github.com/swpalmer/jfx/commit/cc6193451bf8a693093f3ded5dcbe47af2fcbe8f 
> I would submit it as a pull request but that seems premature since 
> there hasn’t been any real discussion of challenges I’ve overlooked. 
>  All I have are the famous last words, “It works for me.”
> I saw in the archives a concern about tab width vs tab stops. For some 
> reason I didn’t get the email.  Anyway, I don’t think arbitrary tab 
> stop positions, at different intervals that is, are what was asked 
> for.  That certainly would require a significantly different 
> implementation.
> Would love to keep some momentum going on this before I become busy 
> with other things and won’t have time for it.
> Scott
>> On Sep 23, 2019, at 3:57 PM, Scott Palmer <swpalmer at gmail.com 
>> <mailto:swpalmer at gmail.com>> wrote:
>> My current work is here 
>> https://github.com/javafxports/openjdk-jfx/compare/develop...swpalmer:jdk-8130738?expand=1 
>> While writing a unit test I realized that the StubToolkit isn’t 
>> really running the Prism layout code, so I’m not sure how that gets 
>> tested.  I made it work with StubTextLayout for now.
>> Regards,
>> Scott
>>> On Sep 20, 2019, at 12:57 PM, Scott Palmer <swpalmer at gmail.com 
>>> <mailto:swpalmer at gmail.com>> wrote:
>>> Thanks Kevin.
>>> My current implementation appears to be working for TextFlow and 
>>> Text, with the TextFlow overriding the tabWidth of the child Text 
>>> nodes.  This seems to work out naturally from the way TextFlow 
>>> overrides the TextLayout instance used by the Text node.
>>> If there are tricky corner-cases that I’m missing, I guess figuring 
>>> out all the cases it will need to handle is part of this discussion. 
>>>  It didn’t seem to be that challenging so far, so perhaps I am 
>>> missing something (hopefully not).  I wrote a small test app to 
>>> visually see that things were working as I expected.  I have not yet 
>>> written the unit tests.
>>> Cheers,
>>> Scott
>>>> On Sep 20, 2019, at 10:58 AM, Kevin Rushforth 
>>>> <kevin.rushforth at oracle.com <mailto:kevin.rushforth at oracle.com>> wrote:
>>>> Hi Scott,
>>>> I'm sure Phil will have more comments on this. While the API seems 
>>>> simple enough on the surface, I suspect that this will be a 
>>>> challenging feature to implement correctly for all of the cases it 
>>>> will need to handle. It would need careful review and testing as 
>>>> well. My only comment on the API itself is that if we do accept 
>>>> this feature, it should probably go on both Text and TextFlow, and 
>>>> be one of the attributes of Text that is ignored / overridden when 
>>>> a Text node is in a TextFlow.
>>>> -- Kevin
>>>> On 9/18/2019 6:14 PM, Scott Palmer wrote:
>>>>> I would like to implement this feature, being able to adjust the 
>>>>> tab size in a TextFlow or Text node (JDK-8130738 
>>>>> <https://bugs.openjdk.java.net/browse/JDK-8130738>).  It involves 
>>>>> new public API, so I want to start a discussion about it here. 
>>>>>  (My motivation is that RichTextFX suggests an entirely 
>>>>> unacceptable workaround of substituting actual spaces when the tab 
>>>>> character is typed and cites the lack of this API.)
>>>>> I’ve already jumped the gun and taken a crack at an 
>>>>> implementation.  It is currently incomplete as I was just poking 
>>>>> around to see if it was going to be easy enough to not take up too 
>>>>> much of my time.  It boils down to:
>>>>> TextFlow and Text get a new property for tab width, an integer 
>>>>> representing the number of spaces taken by a tab. (The value is 
>>>>> only used to initialize the tab width for the TextLayout when needed.)
>>>>> TextLayout interface gets a new method:  boolean setTabWidth(int 
>>>>> spaces)
>>>>> TextLayout gets a new constant: DEFAULT_TAB_WIDTH = 8;
>>>>> PrismTextLayout implements the new setTabWidth API.
>>>>> I’m not sure that the Text node needs this new property.  I 
>>>>> figured it would be rarely used on that class, so I had 
>>>>> implemented it via an added property in the private TextAttributes 
>>>>> class.  Maybe it isn’t needed at all.
>>>>> What’s the next step?
>>>>> Regards,
>>>>> Scott

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