THotPDF Loaded Form Field Editing Methods

Updates field constraints and widget appearance dictionaries in an existing AcroForm while preserving incremental-save and render-cache correctness

Field-level methods

procedure SetLoadedFormFieldFlags(FieldIndex, AFlags: Integer);
procedure SetLoadedFormFieldMaxLength(FieldIndex, AMaxLength: Integer);
procedure SetLoadedFormFieldJustification(FieldIndex: Integer;
  AJustification: THPDFFormFieldJustification);
procedure SetLoadedFormFieldTooltip(FieldIndex: Integer; const ATooltip: AnsiString);

• SetLoadedFormFieldFlags replaces the complete PDF /Ff bit mask
• SetLoadedFormFieldMaxLength writes /MaxLen; zero or a negative value removes the limit
• THPDFFormFieldJustification contains ffjLeft, ffjCenter, and ffjRight for PDF /Q values 0 through 2

Widget geometry

function GetLoadedFormFieldWidgetCount(FieldIndex: Integer): Integer;
function GetLoadedFormFieldWidgetRect(FieldIndex, WidgetIndex: Integer;
  out ARect: THPDFRect): boolean;
procedure SetLoadedFormFieldWidgetRect(FieldIndex, WidgetIndex: Integer;
  X1, Y1, X2, Y2: Single);

• Field and widget indexes are zero based
• Widget enumeration exposes every /Kids entry of radio groups and other multi-widget fields
• Rectangle endpoints use raw PDF user-space points and are normalized before writing

Widget appearance and visibility

procedure SetLoadedFormFieldRotation(FieldIndex, ADegrees: Integer);
procedure SetLoadedFormFieldBorderColor(FieldIndex: Integer;
  ARed, AGreen, ABlue: Single);
procedure SetLoadedFormFieldVisibility(FieldIndex: Integer;
  AVisible, APrintable: boolean);
procedure SetLoadedFormFieldBorderWidth(FieldIndex: Integer; AWidth: Single);
procedure SetLoadedFormFieldBackgroundColor(FieldIndex: Integer;
  ARed, AGreen, ABlue: Single);

• Rotation accepts positive or negative multiples of 90 degrees and stores the normalized /MK /R value
• Border and background RGB components are clamped to the PDF DeviceRGB range from 0 through 1
• Appearance and visibility setters update every widget belonging to the selected field
• Visibility preserves unrelated annotation flags while controlling Hidden, NoView, and Print

Incremental update behavior

• Field, widget, /MK, and /BS dictionaries are marked dirty at the level where each value is stored
• Visual changes invalidate only the affected page's cached DPI variants
• Invalid field or widget indexes leave the document unchanged

Example

PDF.BeginIncrementalUpdate('input.pdf');
PDF.SetLoadedFormFieldMaxLength(0, 40);
PDF.SetLoadedFormFieldJustification(0, ffjCenter);
PDF.SetLoadedFormFieldRotation(0, 90);
PDF.SetLoadedFormFieldBorderColor(0, 0.1, 0.4, 0.8);
PDF.SetLoadedFormFieldWidgetRect(1, 1, 80, 150, 100, 170);
PDF.SaveIncrementalUpdate('updated.pdf');

Related APIs

Loaded form field methods · Loaded document toolkit · THotPDF