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179 lines
6.2 KiB
Plaintext
179 lines
6.2 KiB
Plaintext
unit VTAccessibilityFactory;
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// The contents of this file are subject to the Mozilla Public License
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// Version 1.1 (the "License"); you may not use this file except in compliance
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// with the License. You may obtain a copy of the License at http://www.mozilla.org/MPL/
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//
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// Alternatively, you may redistribute this library, use and/or modify it under the terms of the
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// GNU Lesser General Public License as published by the Free Software Foundation;
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// either version 2.1 of the License, or (at your option) any later version.
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// You may obtain a copy of the LGPL at http://www.gnu.org/copyleft/.
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//
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// Software distributed under the License is distributed on an "AS IS" basis,
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// WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for the
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// specific language governing rights and limitations under the License.
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//
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// The original code is VirtualTrees.pas, released September 30, 2000.
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//
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// The initial developer of the original code is digital publishing AG (Munich, Germany, www.digitalpublishing.de),
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// written by Mike Lischke (public@soft-gems.net, www.soft-gems.net).
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//
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// Portions created by digital publishing AG are Copyright
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// (C) 1999-2001 digital publishing AG. All Rights Reserved.
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//----------------------------------------------------------------------------------------------------------------------
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// class to create IAccessibles for the tree passed into it.
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// If not already assigned, creates IAccessibles for the tree itself
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// and the focused item
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// the tree accessible is returned when the tree receives an WM_GETOBJECT message
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// the AccessibleItem is returned when the Accessible is being asked for the first child
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// To create your own IAccessibles, use the VTStandardAccessible unit as a reference,
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// and assign your Accessibles to the variables in the unit's initialization.
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// You only need to add the unit to your project, and voilá, you have an accessible string tree!
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//
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// Written by Marco Zehe. (c) 2007
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interface
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uses
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System.Classes, Winapi.oleacc, VirtualTrees;
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type
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IVTAccessibleProvider = interface
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function CreateIAccessible(ATree: TBaseVirtualTree): IAccessible;
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end;
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TVTAccessibilityFactory = class(TObject)
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strict private class var
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FAccessibilityAvailable: Boolean;
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FVTAccessibleFactory: TVTAccessibilityFactory;
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strict private
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FAccessibleProviders: TInterfaceList;
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private
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class procedure FreeFactory;
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public
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constructor Create;
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destructor Destroy; override;
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function CreateIAccessible(ATree: TBaseVirtualTree): IAccessible;
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class function GetAccessibilityFactory: TVTAccessibilityFactory; static;
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procedure RegisterAccessibleProvider(const AProvider: IVTAccessibleProvider);
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procedure UnRegisterAccessibleProvider(const AProvider: IVTAccessibleProvider);
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end;
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implementation
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{ TVTAccessibilityFactory }
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constructor TVTAccessibilityFactory.Create;
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begin
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inherited Create;
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FAccessibleProviders := TInterfaceList.Create;
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FAccessibleProviders.Clear;
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end;
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function TVTAccessibilityFactory.CreateIAccessible(
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ATree: TBaseVirtualTree): IAccessible;
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var
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I: Integer;
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TmpIAccessible: IAccessible;
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// returns an IAccessible.
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// 1. If the Accessible property of the passed-in tree is nil,
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// the first registered element will be returned.
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// Usually, this is the IAccessible that provides information about the tree itself.
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// If it is not nil, we'll check whether the AccessibleItem is nil.
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// If it is, we'll look in the registered IAccessibles for the appropriate one.
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// Each IAccessibleProvider will check the tree for properties to determine whether it is responsible.
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// We'll work top to bottom, from the most complicated to the most simple.
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// The index for these should all be greater than 0, e g the IAccessible for the tree itself should always be registered first, then any IAccessible items.
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begin
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Result := nil;
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if ATree <> nil then
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begin
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if ATree.Accessible = nil then
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begin
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if FAccessibleProviders.Count > 0 then
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begin
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Result := IVTAccessibleProvider(FAccessibleProviders.Items[0]).CreateIAccessible(ATree);
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Exit;
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end;
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end;
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if ATree.AccessibleItem = nil then
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begin
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if FAccessibleProviders.Count > 0 then
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begin
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for I := FAccessibleProviders.Count - 1 downto 1 do
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begin
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TmpIAccessible := IVTAccessibleProvider(FAccessibleProviders.Items[I]).CreateIAccessible(ATree);
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if TmpIAccessible <> nil then
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begin
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Result := TmpIAccessible;
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Break;
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end;
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end;
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if TmpIAccessible = nil then
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begin
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Result := IVTAccessibleProvider(FAccessibleProviders.Items[0]).CreateIAccessible(ATree);
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end;
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end;
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end
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else
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Result := ATree.AccessibleItem;
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end;
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end;
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destructor TVTAccessibilityFactory.Destroy;
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begin
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FAccessibleProviders.Free;
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FAccessibleProviders := nil;
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inherited Destroy;
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end;
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class procedure TVTAccessibilityFactory.FreeFactory;
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begin
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FVTAccessibleFactory.Free;
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end;
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procedure TVTAccessibilityFactory.RegisterAccessibleProvider(const AProvider: IVTAccessibleProvider);
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// Ads a provider if it is not already registered
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begin
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if FAccessibleProviders.IndexOf(AProvider) < 0 then
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FAccessibleProviders.Add(AProvider)
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end;
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procedure TVTAccessibilityFactory.UnRegisterAccessibleProvider(const AProvider: IVTAccessibleProvider);
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// Unregisters/removes an IAccessible provider if it is present
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begin
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if FAccessibleProviders.IndexOf(AProvider) >= 0 then
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FAccessibleProviders.Remove(AProvider);
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end;
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class function TVTAccessibilityFactory.GetAccessibilityFactory: TVTAccessibilityFactory;
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// Accessibility helper function to create a singleton class that will create or return
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// the IAccessible interface for the tree and the focused node.
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begin
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// first, check if we've loaded the library already
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if not FAccessibilityAvailable then
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FAccessibilityAvailable := True;
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if FAccessibilityAvailable then
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begin
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// Check to see if the class has already been created.
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if FVTAccessibleFactory = nil then
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FVTAccessibleFactory := TVTAccessibilityFactory.Create;
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Result := FVTAccessibleFactory;
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end
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else
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Result := nil;
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end;
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initialization
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finalization
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TVTAccessibilityFactory.FreeFactory;
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end.
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