FireMonkey Accessibility Package

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FireMonkey desktop accessibility support is available for Delphi Berlin for Win32, Win64, and OS X applications. The FireMonkey accessibility package is available as a download on the Registered Users site: http://cc.embarcadero.com/item/29850

The FireMonkey accessibility package supports:

• The JAWS screen reader from Freedom Scientific on Windows
• The VoiceOver screen reader from Apple on OS X

Technology

FireMonkey accessibility support is based on the Microsoft MSAA interface on Windows (Microsoft Active Accessibility architecture) and for OS X, it is based on the OS X accessibility protocol.

Information on the APIs can be found at:

• MSAA:
  • http://msdn.microsoft.com/en-us/library/ms971310.aspx
• OS X Accessibility:
  • https://developer.apple.com/library/mac/documentation/AppKit/Reference/NSAccessibility_Protocol_Reference/index.html

The Windows MSAA implementation has been tested with Freedom Scientific JAWS and Microsoft Windows Narrator. On OS X, it has been tested against the Apple VoiceOver applications.

Architecture

To implement the operating system accessibility interfaces, a new form class is derived from the default FireMonkey TForm. This form class TAccForm has a separate implementation for the Windows platform target that implements the Windows MSAA interface and deals with all interaction of MSAA and FireMonkey controls on the form, and it also has its counterpart implementation for OS X.

This TAccForm class has built-in handling for the most common and standard FireMonkey controls. This means that other than descending forms from TAccForm instead of TForm, you have no extra steps to take to enable accessibility in FireMonkey applications.

 

Getting Started

To enable a multi-device form for accessibility, first add the required units that implement this. Accessibility comes in three units:

• FMX.ScreenReader
• FMX.ScreenReader.Mac
• FMX.ScreenReader.Win.

The uses list as such becomes:

uses
  System.SysUtils, System.Types, System.UITypes, System.Rtti,
  System.Classes, System.Variants, FMX.Types, FMX.Controls, FMX.Forms,
  FMX.Dialogs, FMX.StdCtrls, FMX.ScreenReader
  {$IFDEF MACOS}
  , FMX.ScreenReader.Mac
  {$ELSE}
  , FMX.ScreenReader.Win
  {$ENDIF}
  ;

Next, descend the form from TAccForm, instead of TForm:

type
  TForm1 = class(TAccForm)
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

Supported Controls

The FireMonkey accessibility implementation has built-in support for following FireMonkey standard controls:

FireMonkey Control	Accessibility Class
TButton	PUSHBUTTON
TSpeedButton	PUSHBUTTON
TTracker	SLIDER
TEdit	TEXT
TListBox	LIST
TComboBox	COMBOBOX
TComboEdit	COMBOBOX
TSpinBox	SPINBUTTON
TLabel	STATICTEXT
TCheckBox	CHECKBUTTON
TRadioButton	RADIOBUTTON
TMainMenu	MENU
TMemo	TEXT
TTreeView	OUTLINE ITEM
TCustomGrid	CELL

When you use any of these controls in your FireMonkey application, there are no extra steps to take. The TAccForm properly allows the used screenreader software to read the control's text or state. Note also that all controls descending from these standard FireMonkey controls also automatically inherit the accessibility support.

Adding Accessibility Support to FireMonkey Custom Controls

To add support for a custom control for accessibility, add the interface IFMXAccessibility to your control and implement it.

IFMXAccessibility is defined as:

 // Interface for custom controls to add accessibility support
 IFMXAccessibility = interface
 ['{49AF90E5-341A-4869-9D3E-F659670FB4D8}']
   // Return the text to read by the accessibility interface
   function GetControlText: string;
   // Returns the accesibility role of the custom control
   function GetRole: TFMXRole;
 end;

This interface consists of two simple methods:

• GetRole: returns the role of the custom control
• GetControlText: returns the text the screenreader should voice when the control has focus

The TFMXRole type is defined as:

 TFMXRole = (rStaticText, rCell, rText, rButton, rCheckBox, rRadioButton, rGrid, rList, rSlider, rComboBox, rTabGroup);

For a custom edit control (that does not descend from a standard FireMonkey edit control that already has accessibility support), this can be implemented as:

type

  TMyOwnFireMonkeyEdit = class(TControl, IFMXAccessibility)
  protected
    function GetControlText: string;
    function GetRole: TFMXRole;
  end;



implementation

{ TMyOwnFireMonkeyEdit }

function TMyOwnFireMonkeyEdit.GetControlText: string;
begin
  Result := GetMyControlText,
end;

function TMyOwnFireMonkeyEdit.GetRole: TFMXRole;
begin
  Result := rText;
end;

See Also

• Registered Users Download Page for FireMonkey Accessibility