Add more widgets

[lewark]

If possible, I'd like to add the following widgets:

• BoxContainer
• GridContainer
• ScrollContainer
• TabContainer
• CheckBox
• ComboBox
• Image
• MenuBar
• ProgressBar
• Slider
• TextArea (unfinished)

[lewark]

BoxContainer

Would provide TOP, BOTTOM, LEFT, RIGHT, CENTER alignments for contents.

GridContainer

Would allow arrangement of child widgets in a grid. Widgets could span multiple rows/columns and be given alignment/fill settings per axis. Might make BoxContainer and/or LinearContainer redundant.

ScrollContainer

A scrollable container would be useful for a broader variety of GUIs, but implementing this could be challenging for a few reasons:

Coordinates

Currently, all widget coordinates are absolute. For situations like this coordinates might be generated with respect to the parent instead, and then translated to absolute before widgets are drawn to the screen. This would require changes to multiple systems.

Rendering

Rendering within a scrollable container must be clipped to its boundaries. It also could be handled in multiple ways. For performance it might be good to store a buffer of the container's contents for faster scrolling, but this could be premature optimization.

ComboBox, MenuBar

Both require widgets to be drawn on top of one another, with proper blocking of event handling from widgets underneath. This would require changes to the event system and the rendering of Root.

Image

This widget would display images in ComputerCraft-compatible formats. It would support CC's builtin format through the paintutils API, and possibly the Nitrogen Fingers Text (NPaintPro) format through the API added by CC:Tweaked. (I should also test if the latter format supports the Teletext characters from later CC versions.)

ProgressBar

Would be useful for displaying progress of running tasks, amounts of stored resources, etc. Another good name for this widget might be Meter.

TextArea

• Add scrolling
• Fix wrapping behavior

The current implementation of TextArea is buggy, and I may need to rewrite it. The newer version might use virtual lines for text wrapping and allow wrapping to be disabled.