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Complexity of a Text Input Widget

Both of the v1.6 patches so far have addressed regressions in Lagrange's text input widget. This is because I did a major rewrite of its internals to better support multiline long-form content. Since the widget is quite complex, several details and edge cases broke in its behavior.

This got me thinking, exactly how complex is the `InputWidget` class? It has the following functionality in addition to the normal behavior of any `Widget`:

full Unicode support (internally UTF-8), including bidirectional text
variable or monospace font
hard-wrapped lines (\n)
word-wrapping to fit widget width
user preference for Return key modifier for line break/accept
moving the cursor via arrow keys
moving up/down by a word-wrapped line segment
jumping to next/previous word
jumping to start/end of the line
jumping to start/end of the word-wrapped line segment
jumping to start/end of content
page up/down
some keys depend on the operating system (e.g., select all)
copy to and paste from system clipboard
undo
option to revert all edits when pressing Escape
insert/overwrite cursor mode
backspace and forward delete a character or an entire marked range
marking text for selecting while holding Shift
positioning cursor with the mouse pointer
marking text for selection by dragging the pointer
selecting whole words with the pointer (after double click)
select all with a triple click
scrolling with mouse wheel or trackpad
drawing only the currently visible lines, some of which are word-wrapped
drawing the selection mark
drawing a blinking cursor that stops blinking when typing
drawing a hint text if the field is empty
periodic content backup (for the upload editor)
expanding/shrinking widget height depending on amount of content, but only to some maximum height
if only a single visible line is allowed: scroll horizontally or vertically? (earlier it was horizontally, then expanding, now vertically)
URL mode that disables word wrapping
sensitive input mode that renders all characters as •
sensitive input mode disallows line breaks
fixed-length mode that also disallows line breaks (e.g., UI scale factor)
option to select all when widget is focused
configurable paddings (e.g., room for lock icon in URL field)
buffer all visible content for faster drawing when unfocused
validator callback to see if content can be accepted
traditional editor mode that ignores user's preference on line break keyboard modifier
highlight domain name in URLs (still broken in v1.6.2)
omit "gemini:" from URLs if short on space (since it's the default, broken in v1.6.2)

😬

With a feature list like this, one can understand why text editors are apps in their own right. (The class stands at 2000 lines of code at the moment.)

Even if I was using a ready-made text editor from some GUI framework, there's plenty of custom functionality here that would complicate things. Some of these could be quite difficult to do depending on the framework.

I'll be making more tweaks and fixes for v1.6.3. Fortunately, severity of the remaining bugs is trending down.

skyjake

📅 2021-08-04

🏷 Lagrange

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