VTHeaderPopup.pas

unit VTHeaderPopup;

//----------------------------------------------------------------------------------------------------------------------
//
// Version 4.7.0
//
// The contents of this file are subject to the Mozilla Public License
// Version 1.1 (the "License"); you may not use this file except in
// compliance with the License. You may obtain a copy of the License at
// http://www.mozilla.org/MPL/
//
// Alternatively, you may redistribute this library, use and/or modify it under the terms of the
// GNU Lesser General Public License as published by the Free Software Foundation;
// either version 2.1 of the License, or (at your option) any later version.
// You may obtain a copy of the LGPL at http://www.gnu.org/copyleft/.
//
// Software distributed under the License is distributed on an "AS IS"
// basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
// License for the specific language governing rights and limitations
// under the License.
//
// The Original Code is VTHeaderPopup.pas.
//
// The Initial Developer of the Original Code is Ralf Junker <delphi@zeitungsjunge.de>. All Rights Reserved.
//
// September 2004:
//  - Bug fix: TVTHeaderPopupMenu.OnMenuItemClick used the wrong Tag member for the event.
// 
// Modified 12 Dec 2003 by Ralf Junker <delphi@zeitungsjunge.de>.
//   - Added missing default storage specifier for Options property.
//   - To avoid mixing up image lists of different trees sharing the same header 
//     popup, set the popup's image list to nil if hoShowImages is not in the 
//     tree's header options.
//   - Added an additional check for the PopupComponent property before casting 
//     it hardly to a Virtual Treeview in OnMenuItemClick. See entry 31 Mar 2003.
//
// Modified 14 Sep 2003 by Mike Lischke <public@delphi-gems.com>.
//   - Renamed event type name to be consistent with other event types (e.g. used in VT).
//   - Added event for hiding/showing columns.
//   - DoXXX method are now virtual.
//   - Conditional code rearrangement to get back Ctrl+Shift+Up/Down navigation.
//
// Modified 31 Mar 2003 by Mike Lischke <public@soft-gems.net>.
//   - Added a check for the PopupComponent property before casting it hardly to 
//     a Virtual Treeview. People might (accidentally) misuse the header popup.
//
// Modified 20 Oct 2002 by Borut Maricic <borut.maricic@pobox.com>.
//   - Added the possibility to use Troy Wolbrink's Unicode aware popup menu. 
//     Define the compiler symbol TNT to enable it. You can get Troy's Unicode 
//     controls collection from http://home.ccci.org/wolbrink/tnt/delphi_unicode_controls.htm.
//
// Modified 24 Feb 2002 by Ralf Junker <delphi@zeitungsjunge.de>.
//   - Fixed a bug where the OnAddHeaderPopupItem would interfere with 
//     poAllowHideAll options.
//   - All column indexes now consistently use TColumnIndex (instead of Integer).
//
// Modified 23 Feb 2002 by Ralf Junker <delphi@zeitungsjunge.de>.
//   - Added option to show menu items in the same order as the columns or in 
//     original order.
//   - Added option to prevent the user to hide all columns.
//
// Modified 17 Feb 2002 by Jim Kueneman <jimdk@mindspring.com>.
//   - Added the event to filter the items as they are added to the menu.
//----------------------------------------------------------------------------------------------------------------------

interface

uses
  {$ifdef TNT}
    TntMenus,
  {$else}
    Menus,
  {$endif TNT}
  VirtualTrees;

type
  TVTHeaderPopupOption = (
    poOriginalOrder, // Show menu items in original column order as they were added to the tree.
    poAllowHideAll   // Allows to hide all columns, including the last one.
  );
  TVTHeaderPopupOptions = set of TVTHeaderPopupOption;

  TAddPopupItemType = (
    apNormal,
    apDisabled,
    apHidden
  );

  TAddHeaderPopupItemEvent = procedure(const Sender: TBaseVirtualTree; const Column: TColumnIndex;
    var Cmd: TAddPopupItemType) of object;
  TColumnChangeEvent = procedure(const Sender: TBaseVirtualTree; const Column: TColumnIndex; Visible: Boolean) of object;

  {$ifdef TNT}
    TVTMenuItem = TTntMenuItem;
  {$else}
    TVTMenuItem = TMenuItem;
  {$endif}

  {$ifdef TNT}
    TVTHeaderPopupMenu = class(TTntPopupMenu)
  {$else}
    TVTHeaderPopupMenu = class(TPopupMenu)
  {$endif}
  private
    FOptions: TVTHeaderPopupOptions;

    FOnAddHeaderPopupItem: TAddHeaderPopupItemEvent;
    FOnColumnChange: TColumnChangeEvent;
  protected
    procedure DoAddHeaderPopupItem(const Column: TColumnIndex; out Cmd: TAddPopupItemType); virtual;
    procedure DoColumnChange(Column: TColumnIndex; Visible: Boolean); virtual;
    procedure OnMenuItemClick(Sender: TObject);
  public
    procedure Popup(x, y: Integer); override;
  published
    property Options: TVTHeaderPopupOptions read FOptions write FOptions default [];

    property OnAddHeaderPopupItem: TAddHeaderPopupItemEvent read FOnAddHeaderPopupItem write FOnAddHeaderPopupItem;
    property OnColumnChange: TColumnChangeEvent read FOnColumnChange write FOnColumnChange;
  end;

//----------------------------------------------------------------------------------------------------------------------

implementation

uses
  {$ifdef TNT}
    TnTClasses
  {$else}
    Classes
  {$endif TNT};

type
  TVirtualTreeCast = class(TBaseVirtualTree); // Necessary to make the header accessible.

//----------------- TVTHeaderPopupMenu ---------------------------------------------------------------------------------

procedure TVTHeaderPopupMenu.DoAddHeaderPopupItem(const Column: TColumnIndex; out Cmd: TAddPopupItemType);

begin
  Cmd := apNormal;
  if Assigned(FOnAddHeaderPopupItem) then
    FOnAddHeaderPopupItem(TVirtualTreeCast(PopupComponent), Column, Cmd);
end;

//----------------------------------------------------------------------------------------------------------------------

procedure TVTHeaderPopupMenu.DoColumnChange(Column: TColumnIndex; Visible: Boolean);

begin
  if Assigned(FOnColumnChange) then
    FOnColumnChange(TVirtualTreeCast(PopupComponent), Column, Visible);
end;

//----------------------------------------------------------------------------------------------------------------------

procedure TVTHeaderPopupMenu.OnMenuItemClick(Sender: TObject);

begin
  if Assigned(PopupComponent) and (PopupComponent is TBaseVirtualTree) then
    with TVTMenuItem(Sender),
      TVirtualTreeCast(PopupComponent).Header.Columns.Items[Tag] do
    begin
      if Checked then
        Options := Options - [coVisible]
      else
        Options := Options + [coVisible];

       DoColumnChange(TVTMenuItem(Sender).Tag, not Checked);
    end;
end;

//----------------------------------------------------------------------------------------------------------------------

procedure TVTHeaderPopupMenu.Popup(x, y: Integer);

var
  I: Integer;
  ColPos: TColumnPosition;
  ColIdx: TColumnIndex;

  NewMenuItem: TVTMenuItem;
  Cmd: TAddPopupItemType;

  VisibleCounter: Cardinal;
  VisibleItem: TVTMenuItem;

begin
  if Assigned(PopupComponent) and (PopupComponent is TBaseVirtualTree) then
  begin
    // Delete existing menu items.
    I := Items.Count;
    while I > 0 do
    begin
      Dec(I);
      Items[I].Free;
    end;

    // Add column menu items.
    with TVirtualTreeCast(PopupComponent).Header do
    begin
      if hoShowImages in Options then
        Self.Images := Images
      else
        // Remove a possible reference to image list of another tree previously assigned.
        Self.Images := nil;
      VisibleItem := nil;
      VisibleCounter := 0;
      for ColPos := 0 to Columns.Count - 1 do
      begin
        if poOriginalOrder in FOptions then
          ColIdx := ColPos
        else
          ColIdx := Columns.ColumnFromPosition(ColPos);

        with Columns[ColIdx] do
        begin
          if coVisible in Options then
            Inc(VisibleCounter);
          DoAddHeaderPopupItem(ColIdx, Cmd);
          if Cmd <> apHidden then
          begin
            NewMenuItem := TVTMenuItem.Create(Self);
            NewMenuItem.Tag := ColIdx;
            NewMenuItem.Caption := Text;
            NewMenuItem.Hint := Hint;
            NewMenuItem.ImageIndex := ImageIndex;
            NewMenuItem.Checked := coVisible in Options;
            NewMenuItem.OnClick := OnMenuItemClick;
            if Cmd = apDisabled then
              NewMenuItem.Enabled := False
            else
              if coVisible in Options then
                VisibleItem := NewMenuItem;
            Items.Add(NewMenuItem);
          end;
        end;
      end;

      // Conditionally disable menu item of last enabled column.
      if (VisibleCounter = 1) and (VisibleItem <> nil) and not (poAllowHideAll in FOptions) then
        VisibleItem.Enabled := False;
    end;
  end;
  
  inherited;
end;

//----------------------------------------------------------------------------------------------------------------------

end.