Rich Text Support

[Pedro Duque Vieira]

I'm not sure, but I think Robert might have only replied to me (probably by
mistake) and not the whole openjfx list as well. It has happened to me
before :)
He makes some points that are probably of interest to this discussion. If
his email didn't get to the openjfx mailing list, it is below.

I'd like to make some comments to the points he raised:

When I mentioned TextFlow I was mentioning it for the rich text display
part only. As I mentioned, for the editing, I think it would be good to
have more API in the JavaFX SDK to facilitate developing a Rich text
editor. Like I said, FontMetrics would be a nice addition, not just for
rich text editing but for anything that involves laying out text and other
things. So this would be very good to have. Right now you have to resort to
hacks when laying out text, and for some things you simply don't have the
API.
Other good additions to the API, which are also relevant to this
discussion, would be to be able to know which character has been clicked on
in a text node, either via mouse or touch. FontMetrics could also help with
this.

When creating a Rich Text editor with a scene graph approach and retained
mode (vs using an approach like using Canvas), we'd have to use a technic
that doesn't use a Node for every character or word. Otherwise we will
eventually have thousands of nodes in the scene which will kill performance
and memory. One of those techniques is to use virtualization, via the use
of a ListView for example. Each cell can be a TextFlow representing a line
that would automatically be re-used by the ListView. So I don't think we
must resort to using Canvas. Personally I prefer using a scene graph based
approach.

Like I said, I've never actually implemented or tried to implement a rich
text editor, so there might be people with better knowledge and experience
in this list to talk about this.
My 2 cents.








On Mon, Oct 8, 2018 at 3:05 PM Robert Lichtenberger <
r.lichtenberger at gmail.com> wrote:

> Am 03.10.2018 um 14:21 schrieb Pedro Duque Vieira:
> > Hi,
> >
> > Have you guys tried JavaFX TextFlow class and such for just the display
> > part of rich text?
>
> I have some (albeit very old now) background in writing an editor for an
> IDE.
>
> The the best of my knowledge, TextFlow is not even usable to display
> large amounts of (colored/highlighted) text let alone make it editable.
>
> I've tried and rigged together a little piece of code that would display
> an XML file in a colorful way (i.e. three to five Texts per line plus an
> additional Text-Object per line).
>
> Displaying a file with 5 MB will consume a whopping 800 MB of
> Text-objects in that way. The application has never been able to render
> anything beyond tiny files.
>
> Displaying text files in a graph of nodes is just plain wrong. You have
> to invert the situation so that only the part of the file that is
> currently visible gets rendered.
> That is where things get complicated (in my opinion), because JavaFX
> dictates (AFAIK) that rendering has to be the other way round. While
> painting callbacks may seem like an artifact of the past they are
> superior when it comes to rendering texts. (Model-View-Controller ...
> anyone still remembering ?)
>
> Maybe something can be done with a Canvas in a ScrollPane (will have to
> try that), but TextFlow seems to rather mislead people into the wrong
> direction.
>
> BTW, TextArea is also very bad performance-wise: Loading the 5 MB file
> into a textarea makes the application unresponsive (on both Linux and
> Windows)
>
> Robert Lichtenberger
>
>

-- 
Pedro Duque Vieira - https://www.pixelduke.com