Function CHARAT_EXTENSION

packages/blockly/blocks/text.ts:1008–1035

(this: CharAtBlock)

 * Does the initial mutator update of text_charAt and adds the tooltip
 */
const CHARAT_EXTENSION = function (this: CharAtBlock) {
  const dropdown = this.getField('WHERE') as FieldDropdown;
  dropdown.setValidator(function (this: FieldDropdown, value: any) {
    const newAt = value === 'FROM_START' || value === 'FROM_END';
    const block = this.getSourceBlock() as CharAtBlock;
    if (newAt !== block.isAt_) {
      block.updateAt_(newAt);
    }
    return undefined; // FieldValidators can't be void.  Use option as-is.
  });
  this.updateAt_(true);
  this.setTooltip(() => {
    const where = this.getFieldValue('WHERE');
    let tooltip = Msg['TEXT_CHARAT_TOOLTIP'];
    if (where === 'FROM_START' || where === 'FROM_END') {
      const msg =
        where === 'FROM_START'
          ? Msg['LISTS_INDEX_FROM_START_TOOLTIP']
          : Msg['LISTS_INDEX_FROM_END_TOOLTIP'];
      if (msg) {
        tooltip +=
          '  ' +
          msg.replace('%1', this.workspace.options.oneBasedIndex ? '#1' : '#0');
      }
    }
    return tooltip;
  });
};

Extensions.register('text_indexOf_tooltip', INDEXOF_TOOLTIP_EXTENSION);