TextInputDelegate

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ceramic.TextInputDelegate (Interface) → EditText

Interface for text layout information providers used by text input systems.

TextInputDelegate defines methods that provide essential text layout information required for cursor navigation, text selection, and input handling in multi-line text fields. Implementers of this interface (typically Text-based classes) provide the layout metrics needed for proper cursor movement and text manipulation.

This interface enables:

  • Vertical cursor navigation (up/down arrow keys)
  • Mapping between visual positions and text indices
  • Line-based text operations
  • Proper cursor positioning in wrapped or formatted text
class MyTextEditor extends Visual implements TextInputDelegate {
    var text:Text;
    function textInputNumberOfLines():Int {
        return text.numLines;
    }
    function textInputIndexForPosInLine(lineNumber:Int, lineOffset:Int):Int {
        // Convert line position to absolute text index
        return text.getIndexAtLinePosition(lineNumber, lineOffset);
    }
    // ... implement other methods
}
See: TextInput The text input handler that uses this delegate, EditText An editable text field that implements this interface

Instance Members

textInputClosestPositionInLine(fromPosition: Int, fromLine: Int, toLine: Int): Int

Finds the closest character position when moving cursor between lines.

When navigating vertically (e.g., arrow up/down), this method determines which character position in the destination line best corresponds to the cursor's current visual position. This maintains horizontal cursor position when possible during vertical navigation.

The method should account for:

  • Variable character widths in proportional fonts
  • Different line lengths
  • Visual alignment preferences
Name Type Description
fromPosition Int The character position within the source line (0-based)
fromLine Int The source line number (0-based)
toLine Int The destination line number (0-based)
Returns Description
Int The best matching character position in the destination line * haxe // Moving cursor from line 2, position 10 to line 3 var newPos = delegate.textInputClosestPositionInLine(10, 2, 3); // Returns position in line 3 that's visually closest to position 10 in line 2
textInputNumberOfLines(): Int

Returns the total number of lines in the text.

This includes all visible lines, whether they result from explicit line breaks (\n) or automatic word wrapping. Empty lines are counted.

Returns Description
Int The total number of lines (always ≥ 1) * haxe var lineCount = delegate.textInputNumberOfLines(); // Use for boundary checking in cursor navigation if (cursorLine < lineCount - 1) { // Can move down }
textInputIndexForPosInLine(lineNumber: Int, lineOffset: Int): Int

Converts a line-relative position to an absolute text index.

Given a line number and a position within that line, returns the corresponding index in the complete text string. This is essential for mapping visual cursor positions to text buffer positions.

Name Type Description
lineNumber Int The line number (0-based)
lineOffset Int The character position within the line (0-based)
Returns Description
Int The absolute character index in the text string * haxe // Get text index for character 5 on line 2 var textIndex = delegate.textInputIndexForPosInLine(2, 5); // Can now use textIndex to insert/delete at that position text = text.substring(0, textIndex) + "new" + text.substring(textIndex);
textInputLineForIndex(index: Int): Int

Determines which line contains the character at the given text index.

Maps an absolute position in the text string to the line number where that character appears. Useful for determining cursor line after text modifications.

Name Type Description
index Int The absolute character index in the text (0-based)
Returns Description
Int The line number containing this character (0-based) * haxe // Find which line the cursor is on after inserting text var cursorLine = delegate.textInputLineForIndex(cursorIndex);
textInputPosInLineForIndex(index: Int): Int

Gets the position within a line for a character at the given text index.

Returns how far into its line a character appears. This is the complement to textInputLineForIndex, providing the column position within the line.

Name Type Description
index Int The absolute character index in the text (0-based)
Returns Description
Int The character's position within its line (0-based) * haxe // Get full cursor position from text index var line = delegate.textInputLineForIndex(cursorIndex); var column = delegate.textInputPosInLineForIndex(cursorIndex); trace('Cursor at line $line, column $column');