TextFieldBuffer

Class

Common

class TextFieldBuffer
internal constructor(
    initialValue: TextFieldCharSequence,
    initialChanges: ChangeTracker? = null,
    internal val originalValue: TextFieldCharSequence = initialValue,
    private val offsetMappingCalculator: OffsetMappingCalculator? = null,
) : Appendable

A text buffer that can be edited, similar to StringBuilder.

This class provides methods for changing the text, such as:

replace
append
insert
delete

This class also stores and tracks the cursor position or selection range. The cursor position is just a selection range with zero length. The cursor and selection can be changed using methods such as:

placeCursorAfterCharAt
placeCursorBeforeCharAt
placeCursorAtEnd
selectAll

To get one of these, and for usage samples, see TextFieldState.edit. Every change to the buffer is tracked in a ChangeList which you can access via the changes property.

Properties

Common

val length: Int

The number of characters in the text field.

Common

val originalText: CharSequence

Original text content of the buffer before any changes were applied. Calling revertAllChanges will set the contents of this buffer to this value.

Common

val originalSelection: TextRange

Original selection before the changes. Calling revertAllChanges will set the selection to this value.

Common

@ExperimentalFoundationApi
val changes: ChangeList

The ChangeList represents the changes made to this value and is inherently mutable. This means that the returned ChangeList always reflects the complete list of changes made to this value at any given time, even those made after reading this property.

Common

val hasSelection: Boolean

True if the selection range has non-zero length. If this is false, then the selection represents the cursor.

Common

var selection: TextRange

The selected range of characters.

Places the selection around the given range in characters.

If the start or end of TextRange fall inside surrogate pairs or other invalid runs, the values will be adjusted to the nearest earlier and later characters, respectively.

To place the start of the selection at the beginning of the field, set this value to TextRange.Zero. To place the end of the selection at the end of the field, after the last character, pass TextFieldBuffer.length. Passing a zero-length range is the same as calling placeCursorBeforeCharAt.

Functions

fun replace(start: Int, end: Int, text: CharSequence)

Replaces the text between start (inclusive) and end (exclusive) in this value with text, and records the change in changes.

Parameters


start	The character offset of the first character to replace.
end	The character offset of the first character after the text to replace.
text	The text to replace the range ``start, end)` with.

fun charAt(index: Int): Char

Returns the Char at index in this buffer.

fun asCharSequence(): CharSequence

Returns a CharSequence backed by this buffer. Any subsequent changes to this buffer will be visible in the returned sequence as well.

fun revertAllChanges()

Revert all changes made to this value since it was created.

After calling this method, this object will be in the same state it was when it was initially created, and changes will be empty.

fun placeCursorBeforeCharAt(index: Int)

Places the cursor before the character at the given index.

If index is inside a surrogate pair or other invalid run, the cursor will be placed at the nearest earlier index.

To place the cursor at the beginning of the field, pass index 0. To place the cursor at the end of the field, after the last character, pass index TextFieldBuffer.length or call placeCursorAtEnd.

Parameters


index	Character index to place cursor before, should be in range 0 to `TextFieldBuffer.length`, inclusive.

fun placeCursorAfterCharAt(index: Int)

Places the cursor after the character at the given index.

If index is inside a surrogate pair or other invalid run, the cursor will be placed at the nearest later index.

To place the cursor at the end of the field, after the last character, pass index TextFieldBuffer.length or call placeCursorAtEnd.

Parameters


index	Character index to place cursor after, should be in range 0 (inclusive) to `TextFieldBuffer.length` (exclusive).

fun addStyle(spanStyle: SpanStyle, start: Int, end: Int)

Adds the given spanStyle to the text between start and end on this buffer.

Caution: You should only use this function from an OutputTransformation. Styling is not yet supported by InputTransformation or TextFieldState. Any added styling by OutputTransformation will be presented to the user without being part of the state.

Also, the added styling is not tracked by this TextFieldBuffer if further edits are made. Please call this function after text content is finalized.

fun addStyle(paragraphStyle: ParagraphStyle, start: Int, end: Int)

Adds the given paragraphStyle to the text between start and end on this buffer.

Also, the added styling is not tracked by this TextFieldBuffer if further edits are made. Please call this function after text content is finalized.