import { _PdfDictionary, _PdfName, _PdfReference } from './../pdf-primitives';
import { _PdfCrossReference } from './../pdf-cross-reference';
import { PdfField, PdfCheckBoxField } from './field';
import { PdfFormFieldsTabOrder, _SignatureFlag } from './../enumerator';
import { PdfPage } from './../pdf-page';
import { PdfFont } from './../fonts/pdf-standard-font';
/**
 * Represents a PDF form.
 * ```typescript
 * // Load an existing PDF document
 * let document: PdfDocument = new PdfDocument(data, password);
 * // Access the form of the PDF document
 * let form: PdfForm = document.form;
 * // Save the document
 * document.save('output.pdf');
 * // Destroy the document
 * document.destroy();
 * ```
 */
export declare class PdfForm {
    /**
     * Cross-reference of the owning PDF document.
     *
     * @private
     */
    _crossReference: _PdfCrossReference;
    /**
     * AcroForm dictionary containing form-wide entries.
     *
     * @private
     */
    _dictionary: _PdfDictionary;
    /**
     * References to top-level fields in the form.
     *
     * @private
     */
    _fields: Array<_PdfReference>;
    /**
     * References to widget annotations associated with form fields.
     *
     * @private
     */
    _widgetReferences: Array<_PdfReference>;
    /**
     * Cache of parsed fields keyed by index.
     *
     * @private
     */
    _parsedFields: Map<number, PdfField>;
    /**
     * Indicates whether the viewer should generate appearances.
     *
     * @private
     */
    _needAppearances: boolean;
    /**
     * Indicates use of a default appearance for widgets.
     *
     * @private
     */
    _isDefaultAppearance: boolean;
    /**
     * Indicates whether the form contains fields with kids.
     *
     * @private
     */
    _hasKids: boolean;
    /**
     * Indicates whether to generate appearance streams for fields.
     *
     * @private
     */
    _setAppearance: boolean;
    /**
     * Exports fields even if they are empty.
     *
     * @private
     */
    _exportEmptyFields: boolean;
    /**
     * Field names in the order they were parsed.
     *
     * @private
     */
    _fieldNames: Array<string>;
    /**
     * Indexed field names.
     *
     * @private
     */
    _indexedFieldNames: Array<string>;
    /**
     * Actual field names without indices or suffixes.
     *
     * @private
     */
    _actualFieldNames: Array<string>;
    /**
     * Indexed actual field names list.
     *
     * @private
     */
    _indexedActualFieldNames: Array<string>;
    /**
     * Global tab order setting for form fields.
     *
     * @private
     */
    _tabOrder: PdfFormFieldsTabOrder;
    /**
     * Collection of parsed field instances.
     *
     * @private
     */
    _fieldCollection: PdfField[];
    /**
     * Terminal field dictionaries discovered during form field parsing.
     *
     * @private
     */
    _terminalFields: _PdfDictionary[];
    /**
     * Map from terminal field dictionary to its indirect reference.
     *
     * @private
     */
    _fieldsMap: Map<_PdfDictionary, _PdfReference>;
    /**
     * Grouped widget dictionaries organized by field name.
     * Stores multiple widget dictionaries that share the same field name,
     * primarily used for radio button groups.
     *
     * @private
     */
    _widgetDictionary: Map<string, _PdfDictionary[]>;
    /**
     * Set of field names that have been added during form field creation.
     * Used to track and avoid duplicate field names when processing widgets.
     *
     * @private
     */
    _addedFieldNames: Set<string>;
    /**
     * Per page tab order map.
     *
     * @private
     */
    _tabCollection: Map<number, PdfFormFieldsTabOrder>;
    /**
     * Signature flag indicating required usage or certification.
     *
     * @private
     */
    _signFlag: _SignatureFlag;
    /**
     * Cached indicator for NeedAppearances usage.
     *
     * @private
     */
    _isNeedAppearances: boolean;
    /**
     * List of form names in document order.
     *
     * @private
     */
    _formNames: Array<string>;
    /**
     * Enables automatic naming for newly added fields.
     *
     * @private
     */
    _fieldAutoNaming: boolean;
    /**
     * Generated or user-specified field names.
     *
     * @private
     */
    _fieldName: Array<string>;
    /**
     * Cache of fonts used across fields keyed by font name.
     *
     * @private
     */
    _fontCache: Map<string, PdfFont>;
    /**
     * Cache of fonts used across fields keyed by font name.
     *
     * @private
     */
    _fontResources: _PdfDictionary;
    /**
     * Indicates whether additional post-processing is required.
     *
     * @private
     */
    _requiresPostProcessing: boolean;
    /**
     * Indicates whether the kids are valid or not.
     *
     * @private
     */
    _isValidKids: boolean;
    /**
     * Indicates page widget references.
     *
     * @private
     */
    _pageWidgetReference: Map<_PdfReference, _PdfDictionary>;
    /**
     * Represents a loaded from the PDF document.
     *
     * @private
     * @param {_PdfDictionary} dictionary Form dictionary.
     * @param {_PdfCrossReference} crossReference Cross reference object.
     */
    constructor(dictionary: _PdfDictionary, crossReference: _PdfCrossReference);
    /**
     * Gets the fields count (Read only).
     *
     * @returns {number} Fields count.
     *
     * ```typescript
     * // Load an existing PDF document
     * let document: PdfDocument = new PdfDocument(data, password);
     * // Access loaded form
     * let form: PdfForm = document.form;
     * // Gets the fields count
     * let count: number = form.count;
     * // Destroy the document
     * document.destroy();
     * ```
     */
    readonly count: number;
    /**
     * Gets a value indicating whether need appearances (Read only).
     *
     * @returns {boolean} Need appearances.
     *
     * ```typescript
     * // Load an existing PDF document
     * let document: PdfDocument = new PdfDocument(data, password);
     * // Access loaded form
     * let form: PdfForm = document.form;
     * // Gets the boolean flag indicating need appearances
     * let needAppearances: number = form.needAppearances;
     * // Destroy the document
     * document.destroy();
     * ```
     */
    readonly needAppearances: boolean;
    /**
     * Gets a value indicating whether allow to export empty fields or not.
     *
     * @returns {boolean} Export empty fields.
     * ```typescript
     * // Load an existing PDF document
     * let document: PdfDocument = new PdfDocument(data, password);
     * // Access loaded form
     * let form: PdfForm = document.form;
     * // Gets a value indicating whether allow to export empty fields or not.
     * let exportEmptyFields: boolean = form.exportEmptyFields;
     * // Save the document
     * document.save('output.pdf');
     * // Destroy the document
     * document.destroy();
     * ```
     */
    /**
    * Sets a value indicating whether allow to export empty fields or not.
    *
    * @param {boolean} value Export empty fields.
    * ```typescript
    * // Load an existing PDF document
    * let document: PdfDocument = new PdfDocument(data, password);
    * // Access loaded form
    * let form: PdfForm = document.form;
    * // Sets a value indicating whether allow to export empty fields or not.
    * form.exportEmptyFields = false;
    * // Save the document
    * document.save('output.pdf');
    * // Destroy the document
    * document.destroy();
    * ```
    */
    exportEmptyFields: boolean;
    /**
     * Gets the current signature flags of the form (`SigFlags`).
     *
     * @private
     * @returns {_SignatureFlag} The active signature flags bitmask.
     */
    /**
    * Sets the form's signature flags and updates the `SigFlags` entry in the AcroForm dictionary.
    *
    * @private
    * @param {_SignatureFlag} value The signature flags bitmask to set.
    * @returns {void}
    */
    _signatureFlag: _SignatureFlag;
    /**
     * Gets a value indicating whether the automatic field naming is enabled for form fields.
     *
     * @returns {boolean} Indicates if field auto naming is enabled.
     *
     * ```typescript
     * // Create new document.
     * let document: PdfDocument = new PdfDocument();
     * // Access loaded form
     * let form: PdfForm = document.form;
     * // Gets the value indicating if automatic field naming is enabled
     * let fieldAutoNaming: boolean = form.fieldAutoNaming;
     * // Destroy the document
     * document.destroy();
     * ```
     */
    /**
    * Sets a value indicating whether field auto-naming is enabled for form fields.
    *
    * @param {boolean} value Enable or disable field auto naming. The default value is false.
    * ```typescript
    * // Create a new document
    * let document: PdfDocument = new PdfDocument();
    * // Access loaded form
    * let form: PdfForm = document.form;
    * // Enable automatic field naming for new form fields.
    * form.fieldAutoNaming = true;
    * // Save the document
    * document.save('output.pdf');
    * // Destroy the document
    * document.destroy();
    * ```
    */
    fieldAutoNaming: boolean;
    /**
     * Gets the `PdfField` at the specified index.
     *
     * ```typescript
     * // Load an existing PDF document
     * let document: PdfDocument = new PdfDocument(data, password);
     * // Access the loaded form field
     * let field: PdfField = document.form.fieldAt(0);
     * // Save the document
     * document.save('output.pdf');
     * // Destroy the document
     * document.destroy();
     * ```
     *
     * @param {number} index Field index.
     * @returns {PdfField} Loaded PDF form field at the specified index.
     */
    fieldAt(index: number): PdfField;
    /**
     * Builds a map of widget annotation references from all pages in the document.
     * This collection is used to associate terminal fields with their corresponding
     * page-level widget annotations, enabling proper field-to-page linkage.
     *
     * @private
     * @returns {void}
     */
    _getPageWidgetCollection(): void;
    /**
     * Retrieves a form field by its index within the terminal fields collection.
     * Resolves the field dictionary with its associated page widget reference when available.
     *
     * @private
     * @param {number} index The index of the field in the terminal fields array.
     * @returns {PdfField} The parsed PDF form field, or `null` if not found or out of range.
     */
    _getField(index: number): PdfField;
    /**
     * Parses a form field from a given field dictionary, resolving page widget associations
     * and constructing the appropriate PDF field type via `_parseFields`.
     *
     * @private
     * @param {_PdfDictionary} fieldDictionary The field dictionary to parse.
     * @returns {PdfField} The constructed PDF form field, or `null` if parsing fails.
     */
    _getFieldFromDictionary(fieldDictionary: _PdfDictionary): PdfField;
    /**
     * Parses a terminal form field from its dictionary and reference, instantiating the appropriate
     * field type based on `FT` and `Ff` (e.g., text, button, choice, signature).
     *
     * @private
     * @param {_PdfDictionary} dictionary The field dictionary to parse.
     * @param {_PdfReference} reference The indirect reference of the field.
     * @returns {PdfField} The constructed field instance.
     */
    _parseFields(dictionary: _PdfDictionary, reference: _PdfReference): PdfField;
    /**
     * Add a new `PdfField`.
     *
     * ```typescript
     * // Load an existing PDF document
     * let document: PdfDocument = new PdfDocument(data, password);
     * // Add a new form field
     * let index: number = document.form.add(field);
     * // Save the document
     * document.save('output.pdf');
     * // Destroy the document
     * document.destroy();
     * ```
     *
     * @param {PdfField} field Field object to add.
     * @returns {number} Field index.
     */
    add(field: PdfField): number;
    /**
     * Adds a field to the form, updates the AcroForm `Fields` array, caches the parsed field,
     * and sets appearance/signature flags when applicable.
     *
     * @private
     * @param {PdfField} field The field to add to the form.
     * @returns {number} The index of the added field in the form.
     */
    _doAdd(field: PdfField): number;
    /**
     * Groups a new field with an existing field having the same name by wiring widget parents,
     * merging kids, syncing flags/appearance, and handling radio options/selection where needed.
     *
     * @private
     * @param {PdfField} field The new field to group.
     * @param {PdfField} oldField The existing field with the same name.
     * @returns {number} The index of the grouped field (existing field’s index).
     */
    _groupingFormFields(field: PdfField, oldField: PdfField): number;
    /**
     * Finds the first item index within a checkbox field that has an `exportValue`
     * matching the provided `value`.
     *
     * @private
     * @param {PdfCheckBoxField} field The checkbox field to search.
     * @param {string} value The export value to match.
     * @returns {number} The index of the first matching item, or `-1` when not found.
     */
    _findFirstByExportValue(field: PdfCheckBoxField, value: string): number;
    /**
     * Returns the export value of the currently selected item in a checkbox field.
     * If the field dictionary contains a `/V` entry it is returned first; otherwise
     * the checked state of individual `PdfStateItem`s is consulted.
     *
     * @private
     * @param {PdfCheckBoxField} field The checkbox field to query.
     * @returns {string} The selected export value, or `undefined` if none.
     */
    _getSelectedExportValue(field: PdfCheckBoxField): string;
    /**
     * Converts a standalone field into a parent with `Kids` by creating a new parent dictionary,
     * moving relevant entries, and attaching both the old and new field widgets under it.
     *
     * @private
     * @param {PdfField} oldField The existing field that will become the parent.
     * @param {PdfField} newField The new field whose first widget is added as a kid.
     * @returns {void}
     */
    _updateFieldsKids(oldField: PdfField, newField: PdfField): void;
    /**
     * Populates the `Opt` array for a radio button group when duplicate export values are present,
     * ensuring unique option entries for appearance resolution.
     *
     * @private
     * @param {PdfField} baseField The radio button field used to derive option values.
     * @returns {void}
     */
    _addItemsToOptionsArray(baseField: PdfField): void;
    /**
     * Computes a unique field name by appending a generated identifier when the base name already exists.
     *
     * @private
     * @param {string} name The proposed field name.
     * @returns {string} A unique field name derived from the input.
     */
    _getCorrectName(name: string): string;
    /**
     * Generates a simple pseudo-random identifier string for field auto-naming.
     *
     * @private
     * @returns {string} The generated identifier.
     */
    _generateUniqueIdentifier(): string;
    /**
     * Remove the specified PDF form field.
     *
     * ```typescript
     * // Load an existing PDF document
     * let document: PdfDocument = new PdfDocument(data, password);
     * // Access the loaded form field
     * let field: PdfField = document.form.fieldAt(3);
     * // Remove the form field
     * document.form.removeField(field);
     * // Save the document
     * document.save('output.pdf');
     * // Destroy the document
     * document.destroy();
     * ```
     *
     * @param {PdfField} field Field object to remove.
     * @returns {void} Nothing.
     */
    removeField(field: PdfField): void;
    /**
     * Remove the PDF form field from specified index.
     *
     * ```typescript
     * // Load an existing PDF document
     * let document: PdfDocument = new PdfDocument(data, password);
     * // Remove the form field from the specified index
     * document.form.removeFieldAt(3);
     * // Save the document
     * document.save('output.pdf');
     * // Destroy the document
     * document.destroy();
     * ```
     *
     * @param {number} index Field index to remove.
     * @returns {void} Nothing.
     */
    removeFieldAt(index: number): void;
    /**
     * Rebuilds the parsed fields cache after a removal, compacting indices above the removed position.
     *
     * @private
     * @param {number} index The removed field index.
     * @returns {void}
     */
    _reorderParsedAnnotations(index: number): void;
    /**
     * Sets the flag to indicate the new appearance creation
     * If true, appearance will not be created. Default appearance has been considered.
     * If false, new appearance stream has been created from field values and updated as normal appearance.
     *
     * ```typescript
     * // Load an existing PDF document
     * let document: PdfDocument = new PdfDocument(data, password);
     * // Set boolean flag to create a new appearance stream for form fields.
     * document.form.setDefaultAppearance(false);
     * // Save the document
     * document.save('output.pdf');
     * // Destroy the document
     * document.destroy();
     * ```
     *
     * @param {boolean} value Set default appearance.
     * @returns {void} Nothing.
     */
    setDefaultAppearance(value: boolean): void;
    /**
     * Order the form fields.
     *
     * ```typescript
     * // Load an existing PDF document
     * let document: PdfDocument = new PdfDocument(data, password);
     * // Order the form fields.
     * document.form.orderFormFields();
     * // Save the document
     * document.save('output.pdf');
     * // Destroy the document
     * document.destroy();
     * ```
     *
     * @returns {void}
     */
    orderFormFields(): void;
    /**
     * Order the form fields based on page tab order.
     *
     * ```typescript
     * // Load an existing PDF document
     * let document: PdfDocument = new PdfDocument(data, password);
     * // Order the form fields based on page tab order.
     * document.form.orderFormFields(PdfFormFieldsTabOrder.row);
     * // Save the document
     * document.save('output.pdf');
     * // Destroy the document
     * document.destroy();
     * ```
     *
     * @param {PdfFormFieldsTabOrder} tabOrder tab order types for form fields.
     * @returns {void}
     */
    orderFormFields(tabOrder: PdfFormFieldsTabOrder): void;
    /**
     * Order the form fields based on tab collection.
     *
     * ```typescript
     * // Load an existing PDF document
     * let document: PdfDocument = new PdfDocument(data, password);
     * //Set the tab collection to order the form fields.
     * let values: Map<number, PdfFormFieldsTabOrder> = new Map<number, PdfFormFieldsTabOrder>();
     * // Set the tab order for the page index 1.
     * values.set(1, PdfFormFieldsTabOrder.column);
     * // Set the tab order for the page index 2.
     * values.set(2, PdfFormFieldsTabOrder.row);
     * // Order the form fields based on tab collection.
     * document.form.orderFormFields(values);
     * // Save the document
     * document.save('output.pdf');
     * // Destroy the document
     * document.destroy();
     * ```
     *
     * @param {Map<number, PdfFormFieldsTabOrder>} tabCollection collection of tab order with page index.
     * @returns {void}
     */
    orderFormFields(tabCollection: Map<number, PdfFormFieldsTabOrder>): void;
    /**
     * Traverses the AcroForm field tree, collects terminal fields, repairs missing `Parent` links,
     * and initializes the form's field list and known form names.
     *
     * @private
     * @returns {void}
     */
    _createFields(): void;
    private _createFieldCollection;
    private _processRemainingWidgets;
    /**
     * Checks whether a field dictionary contains a non-empty `Kids` array.
     *
     * @private
     * @param {_PdfDictionary} dictionary The field dictionary to inspect.
     * @returns {boolean} Returns `true` if `Kids` exists and is non-empty; otherwise, `false`.
     */
    _hasValidKids(dictionary: _PdfDictionary): boolean;
    /**
     * Validates a field (and its descendants) against the page widget lists, removing any invalid
     * kid references and determining whether the field has at least one valid descendant.
     *
     * @private
     * @param {_PdfDictionary} dictionary The field or node dictionary.
     * @param {Map<number, _PdfDictionary[]>} pageWidgets A mapping of page index to widget dictionaries.
     * @param {_PdfReference} ref The reference of the current field/widget.
     * @param {_PdfReference[]} widgetCollection Flat list of widget references found in pages.
     * @returns {boolean} Returns `true` if the field or any child remains valid; otherwise, `false`.
     */
    _removeInvalidFields(dictionary: _PdfDictionary, pageWidgets: Map<number, _PdfDictionary[]>, ref: _PdfReference, widgetCollection: _PdfReference[]): boolean;
    /**
     * Determines whether a terminal field dictionary represents a valid widget by checking for
     * page and rectangle entries or by matching against known page widgets.
     *
     * @private
     * @param {_PdfDictionary} fieldDictionary The terminal field dictionary to validate.
     * @param {Map<number, _PdfDictionary[]>} pageWidgets A mapping of page index to widget dictionaries.
     * @param {_PdfReference} ref The reference of the field/widget under validation.
     * @param {_PdfReference[]} widgetCollection Flat list of widget references found in pages.
     * @returns {boolean} Returns `true` if the field is valid; otherwise, `false`.
     */
    _validateField(fieldDictionary: _PdfDictionary, pageWidgets: Map<number, _PdfDictionary[]>, ref: _PdfReference, widgetCollection: _PdfReference[]): boolean;
    _compareWidgets(widget: _PdfDictionary, annotDictionary: _PdfDictionary): boolean;
    /**
     * Create form fields from previously discovered terminal widgets starting at index.
     * Mirrors the C# CreateFormFieldsFromWidgets logic: add terminal fields not yet added
     * and merge radio-group items when multiple widgets share the same name.
     *
     * @private
     * @param {number} startIndex The starting index into terminal fields.
     * @returns {void}
     */
    _createFormFieldsFromWidgets(startIndex: number): void;
    /**
     * Process terminal fields starting from the specified index.
     * Adds fields to the form, tracking added field names to avoid duplicates.
     *
     * @private
     * @param {number} startIndex The starting index into terminal fields.
     * @returns {void}
     */
    private _processTerminalFields;
    /**
     * Process widget dictionary to handle radio button groups and single widgets.
     * Merges radio button items when multiple widgets share the same name.
     *
     * @private
     * @returns {void}
     */
    private _processWidgetDictionary;
    /**
     * Process multiple widgets with the same name, merging radio button items.
     *
     * @private
     * @param {_PdfDictionary[]} list The list of widget dictionaries with the same name.
     * @returns {void}
     */
    private _processMultipleWidgets;
    /**
     * Merge radio button items from one field into another.
     *
     * @private
     * @param {PdfRadioButtonListField} targetField The target radio button field to merge into.
     * @param {PdfRadioButtonListField} sourceField The source radio button field to merge from.
     * @returns {void}
     */
    private _mergeRadioButtonItems;
    /**
     * Handle field naming by either correcting duplicate names or adding to the field name list.
     *
     * @private
     * @param {PdfField} field The field to process for naming.
     * @returns {void}
     */
    private _handleFieldNaming;
    /**
     * Process a single widget dictionary entry.
     *
     * @private
     * @param {_PdfDictionary} dict The widget dictionary to process.
     * @returns {void}
     */
    private _processSingleWidget;
    /**
     * Validates whether a field name is unique within the form.
     *
     * @private
     * @param {PdfField} field The field to validate.
     * @returns {boolean} Returns `true` if the field name is valid (unique); otherwise, `false`.
     */
    _validFieldName(field: PdfField): boolean;
    /**
     * Determines whether the provided `Kids` collection represents a non widget node
     * (i.e., its first child is not a `Widget` subtype).
     *
     * @private
     * @param {any[]} kids The array of kid dictionaries or references.
     * @returns {boolean} Returns `true` if the entry is a non terminal node; otherwise, `false`.
     */
    _isNode(kids: Array<any>): boolean;
    /**
     * Enumerates and collects all widget annotation references for the form's fields,
     * traversing each field’s `Kids` or the field itself when no children are present.
     *
     * @private
     * @returns {Array<_PdfReference>} The array of widget references.
     */
    _parseWidgetReferences(): Array<_PdfReference>;
    /**
     * Performs post-processing for all fields: applies tab order re arrangement (when manual),
     * generates appearances or flattens as required, and removes fields flattened for the specified page.
     *
     * @private
     * @param {boolean} isFlatten When `true`, flatten field appearances into the page content.
     * @param {PdfPage} [pageToImport] Optional page context to restrict processing/removal.
     * @returns {void}
     */
    _doPostProcess(isFlatten: boolean, pageToImport?: PdfPage): void;
    /**
     * Resolves a field's index by matching against stored names, indexed names, actual names,
     * and indexed actual names.
     *
     * @private
     * @param {string} name The field name to locate.
     * @returns {number} The matching field index, or `-1` if not found.
     */
    _getFieldIndex(name: string): number;
    /**
     * Materializes and returns all parsed `PdfField` instances for the current form.
     *
     * @private
     * @returns {PdfField[]} The array of loaded fields.
     */
    _getFields(): PdfField[];
    /**
     * Maps a tab order enumeration to its corresponding name object (`'R'`, `'C'`, `'S'`), or `null` for `none`.
     *
     * @private
     * @param {PdfFormFieldsTabOrder} tabOrder The tab order mode.
     * @returns {_PdfName} The corresponding name entry, or `null` if none.
     */
    _getOrder(tabOrder: PdfFormFieldsTabOrder): _PdfName;
    /**
     * Compares two fields for ordering based on page index and the current tab order mode
     * (`row`, `column`, `manual`, `none`, `structure`, `widget`).
     *
     * @private
     * @param {any} field1 The first field to compare.
     * @param {any} field2 The second field to compare.
     * @returns {number} A negative value if `field1` precedes `field2`, positive if after, or `0` if equal.
     */
    _compareFields(field1: any, field2: any): number;
    /**
     * Retrieves the `Rect` array from the specified dictionary.
     *
     * @private
     * @param {_PdfDictionary} dictionary The dictionary containing a `Rect` entry.
     * @returns {number[]} The rectangle `[x1, y1, x2, y2]`, or `undefined` if absent.
     */
    _getRectangle(dictionary: _PdfDictionary): number[];
    /**
     * Gets a representative widget rectangle for a field with kids, preferring the parent field's
     * rectangle first.
     *
     * @private
     * @param {PdfField} field The field whose widget rectangle is requested.
     * @returns {number[]} The widget rectangle `[x1, y1, x2, y2]`, or `undefined` if unavailable.
     */
    _getItemRectangle(field: PdfField): number[];
    /**
     * Compares two numeric values.
     *
     * @private
     * @param {number} x The first number.
     * @param {number} y The second number.
     * @returns {number} Returns `1` if `x > y`, `-1` if `x < y`, otherwise `0`.
     */
    _compare(x: number, y: number): number;
    /**
     * Compares two widget references by their rectangles according to the current tab order.
     *
     * @private
     * @param {_PdfReference} x The first widget reference.
     * @param {_PdfReference} y The second widget reference.
     * @returns {number} A negative, positive, or zero value indicating relative order.
     */
    _compareKidsElement(x: _PdfReference, y: _PdfReference): number;
    /**
     * Sorts a field's items by page/tab order and returns the effective page used for ordering.
     *
     * @private
     * @param {PdfField} field The field whose items should be sorted.
     * @param {boolean} hasPageTabOrder When `true`, uses the page's tab order for sorting.
     * @returns {PdfPage} The page used to determine ordering.
     */
    _sortItemByPageIndex(field: PdfField, hasPageTabOrder: boolean): PdfPage;
    /**
     * Sorts the parsed items of supported fields (text, list box, checkbox, radio) using
     * the current tab order comparator.
     *
     * @private
     * @param {PdfField} field The field whose items are to be sorted.
     * @returns {void}
     */
    _sortFieldItems(field: PdfField): void;
    /**
     * Compares two field items by page index and rectangle, honoring the current tab order
     * `row` or `column`.
     *
     * @private
     * @param {any} item1 The first item to compare.
     * @param {any} item2 The second item to compare.
     * @returns {number} A negative, positive, or zero value indicating relative order.
     */
    _compareFieldItem(item1: any, item2: any): number;
    /**
     * Clears the form’s field reference list and the parsed field cache.
     *
     * @private
     * @returns {void}
     */
    _clear(): void;
    /**
     * Checks whether two fields are of the same field class (e.g., both text, both radio).
     *
     * @private
     * @param {PdfField} field1 The first field.
     * @param {PdfField} field2 The second field.
     * @returns {boolean} Returns `true` if the field types are compatible; otherwise, `false`.
     */
    _checkType(field1: PdfField, field2: PdfField): boolean;
}