exp/textinput: byte slice APIs to handle big texts

[hajimehoshi]

Operating System

• Windows
• macOS
• Linux
• FreeBSD
• OpenBSD
• Android
• iOS
• Nintendo Switch
• PlayStation 5
• Xbox
• Web Browsers

What feature would you like to be added?

The current APIs treat string objects:

func (f *Field) SetTextAndSelection(text string, selectionStartInBytes, selectionEndInBytes int)
func (f *Field) Text() string
func (f *Field) TextForRendering() string

This is inefficient especially when this handles pretty big text.

We might need APIs to handle byte slices (e.g. AppendText(bytes []byte) []byte). Also, the implementation can be a more efficient one, like a piece table.

Why is this needed?

In order to handle big texts.

[hajimehoshi]

First, I thought treating big text should be an API user's responsibility, not exp/textinput's responsibility. However, this is pretty tricky, expecially for tricky text replacements on macOS by holding to press a key.