One text widget to rule them all

[Luro02]

What the text widget should be able to do?

• Display text
• Wrap text if parent is too small: word wrapping and if that is not possible character based wrapping
• Stylized text like bold, italic, colored, underlined
• Have clickable links in the text
• Align the text horizontally
• Allow for vertical alignment, if the text uses more height than necessary like is the case with JTextPane
• Changing the font/text size
• Selectable text to copy it

These are basic requirements that modern UI frameworks satisfy through a text widget. For swing, this is not the case at all, there are many different widgets, none satisfying everything

• JLabel (or JBLabel): Does not support wrapping
• JTextPane: Occupies more height than necessary -> Needs vertical centering/other hacks that I have yet to figure out
• DslLabel: IntelliJ subclass of JTextPane, doesn't really work with wrapping
• JTextArea

The best candidate for an universal widget at the moment is a decently modified JTextPane with an underlying HtmlEditorTextKit, but it suffers from some issues like using too much vertical space (-> text must be aligned or the bug must be fixed) or styles not always applying.

For reference, this might work.

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This issue is in parts related to #162.

[Luro02]

The recently committed TextWidget (which is based on JTextPane) might be the one widget for everything.

There are some improvements to be made

• Keep track of text attributes that were added through the builder with a dedicated AttributeSet field, and reapply all of them after setText was called
• Styling is limited at the moment
• unify with the DslLabel API
• Check whether Links work?

It would be nice to transfer the adjustments made in DslLabel to TextWidget, making our code independent of that internal API.

The main changes seem to be

• Rewriting the Hyperlink parts with an icon and underline
• Patching some code related to carets
• Implementing baseline calculations, note: This, in combination with overriding the minimum size might solve the alignment issues?

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Using HTMLEditorKit

I want to use this space to document some of the work that I did, and had to later discard:

In a previous (uncomitted version), I was using the HTMLEditorKit instead of the StylizedEditorKit. A major problem was that I could not get the text aligned correctly.

The text has a bounded box in which it resides, the minimum size. When you resize it to fit multiple lines, the minimum size will change as well, because it now requires more lines.

The problem is that on resize (shrinking back to a single line), the minimum height would not adjust. As a workaround one could override the minimum size to return the preferred height (which would be correct in this case), but that sadly didn't solve the issues. The text would still be in the same wrong position, just with a smaller bounded box. I think this has to do with the baseline not adjusting.

I then spent the next two days trying to figure out what of the underlying code is causing the minimum size to be wrong...

What is might be causing this visual bug?

The kit implements the displaying based on Views. These Views are shared between the different kits, like the BoxedView. The HTMLEditorKit uses a ParagraphView that inherits from a BoxedView with one or more child InlineView. The InlineView inherit from GlyphView which is responsible for text breaking and actually painting the text.

From my observations, I noticed that the InlineView was duplicate, but I am unsure about it. Debugging it is difficult. Another thing I observed is that it has extra new lines in front and at the end of the text to be displayed, that might be an issue as well.

Horizontal alignment could be accomplished by overriding the layout major axis method of the containers. They seem to have the Y axis as major and X as minor. I spent some time trying to get the alignment to work correctly, but was unable to do it. It seems similar to the currently committed CenteredBoxView, but I likely overrode the wrong element.

Another problem that I should document here:
Some of the interesting parts like the Row class (which extends the InlineView) are not accessible, so you have to copy-paste them. Sometimes it is not enough to override the parent class and use the setParent which is supposed to delegate to a specific instance. Same solution here, copy-paste all the code from the source or manually override every method/implement all of the interfaces to delegate to the variable.

Did nobody else solve this?

From what I can tell, no. I spent a good amount of time searching through stackoverflow, GitHub and the intellij-community repo. In stackoverflow I found people having the same problem, only to be told that they should use a different text component. Well, the alternatives have their own problems like no support for wrapping, which is why I moved away from them.

Another useful API that I found was the HTMLEditorKitBuilder in the IntelliJ repository, makes it much easier to extend the factory.

What ended up happening to it?

The whole investigation took up 3 days, with no end in sight, I still don't know why it doesn't work correctly.

The committed code uses the less powerful StyledEditorKit. It still draws a too large bounded box, but because of the text being vertically centered, it is difficult to notice. For now, I refuse to spend any more time going through this convoluted mess. The current solution works good enough, only links seem to be missing, but that seems doable.