Title: Most recently used files
Question: Many programs provide a list of the most recently used (MRU) files. How can this be done?
Answer:
Administration of the most recently files of an application is a quite easy task, however, a bit annoying if this is repeated from project to project. Therefore, I wrote a little component (TMRUManager) which simplifies this task:
(*******************************************************************************
MRU Manager
--------------------------------------------------------------------------------
a component to get access to the most recently used (MRU) files.
Usage:
- Drop the component on the form which opens files, usually this is the main
form of an application.
- If the form has a toolbar with a "file open" tool button: drop a popup menu
and change the button style to "tbsDrowpDown". Set the property "DropdownMenu"
of the toolbutton to point to the popup menu.
- In the procedure that opens the file add a call to the "Add" method of the
MRU Manager and pass the filename as a parameter. This adds the filename to
the MRU list. The MRU list will be appended to the file menu of the form and
will appear also in to popup menu.
- Write an event handler for the MRU manager event "OnSelected". This event is
fired when the user has selected a most recently used file either from the
file or the popup menu. The event handler gets the name of the requested
file as a parameter. It should open this file. Also, the event handler should
call the Add method of the MRU Manager again, if the file should be
re-positioned at the top of the MRU list.
- If you want to save the MRU items in an ini file, call "SaveToIni" in the
OnDestroy event and "LoadFromIni" in the OnCreateEvent of the main form.
- That's all.
Properties:
- MaxCount : integer
Maximum number of most recently used items. Default: 10. If the MRU list gets
longer, the oldest item will be deleted.
- ItemCount : integer
Current count of MRU items in the list.
- ReverseOrder: boolean
if false (default) the oldest items are at the bottom of the menus,
if true, they are at the top.
- FileMenu : TMenuItem
points to the menu of the form's main menu to which the MRU items will be
appended. Normally this is the "file" menu.
- PopupMenu: TPopupMenu
points to a TPopupMenu component that will be expanded with the MRU items.
As shown above, this popup menu can be connected to a DropDown toolbutton in
the form's toolbar.
- AddNumbersToFileMenu, AddNumbersToPopupMenu : boolean
each MRU item in the file or popup menu is preceded by a sequential number.
- IniKey : string;
A string to label the sections in the ini file where the MRU items are written
to (see: SaveToIni, LoadFromIni).
- FileMustExist : boolean
if true, files that do not exist are not added to the MRU list.
- OnSelected: Event handler for processing of the user selecting an MRU item in
the file or the dropdown menu. Usually the event handler should load the
file whose name is passed as a parameter.
Methods:
- function Add(item:string) : boolean;
adds a filename to the MRU list. To be called from the main form whenever a
file is to be opened.
The result is false when the filename could not be appended, e.g. when the
file does not exist (and FileMustExist is true).
- SaveToIni(ini:TIniFile)
writes the MRU items to an ini file. To be called from the form's OnCloseQuery
or OnDestroy event handler.
- LoadFromIni(ini:TIniFile)
load the MRU items saved in a previous session from the ini file. To be called
from the form's OnCreate event handler.
- Create, Destroy
constructor and destructor, as usual.
(c) W.Pamler, June 2001
*******************************************************************************)
unit MRUManager;
interface
uses
Classes, Menus, IniFiles;
type
TMRUEvent = procedure(Sender:TObject; const MRUItem:string) of object;
TMRUManager = class(TComponent)
private
FItems : TStringList;
FAddNumbersToFileMenu : boolean;
FAddNumbersToPopupMenu : boolean;
FMaxCount : integer;
FReverseOrder : boolean;
FFileMenu : TMenuItem;
FPopupMenu : TPopupMenu;
FFilesMustExist : boolean;
FIniKey : string;
FOnSelected : TMRUEvent;
procedure AddToMenu(menu:TMenuItem; AddNumbers:boolean);
procedure ClearMenu(menu:TMenuItem);
function GetItemCount : integer;
procedure MenuClicked(Sender:TObject);
procedure SetAddNumbersToFileMenu(value:boolean);
procedure SetAddNumbersToPopupMenu(value:boolean);
procedure SetFileMenu(value:TMenuItem);
procedure SetIniKey(value:string);
procedure SetMaxCount(value:integer);
procedure SetPopupMenu(value:TPopupMenu);
procedure SetReverseOrder(value:boolean);
procedure UpdateMenus;
public
constructor Create(AOwner:TComponent); override;
destructor Destroy; override;
function Add(const AItem:string) : boolean;
procedure LoadFromIni(ini:TIniFile);
procedure SaveToIni(ini:TIniFile);
published
property AddNumbersToFileMenu : boolean read FAddNumbersToFileMenu
write SetAddNumbersToFileMenu default true;
property AddNumbersToPopupMenu : boolean read FAddNumbersToPopupMenu
write SetAddNumbersToPopupMenu default true;
property MaxCount : integer read FMaxCount write SetMaxCount default 10;
property Itemcount : integer read GetItemCount;
property ReverseOrder : boolean read FReverseOrder write SetReverseOrder;
property FileMenu : TMenuItem read FFileMenu write SetFileMenu;
property PopupMenu : TPopupMenu read FPopupMenu write SetPopupMenu;
property IniKey : string read FIniKey write SetIniKey;
property FilesMustExist : boolean
read FFilesMustExist write FFilesMustExist default true;
property OnSelected : TMRUEvent read FOnSelected write FOnSelected;
end;
procedure Register;
//==============================================================================
implementation
//==============================================================================
uses
SysUtils;
const
MRU_Tag = 20010607;
// Note: the menu items that the MRU manger has appended to the menus will
// be marked by tags ranging between MRU_Tag and MRU_Tag+n+1, where n is the
// value of the MRU Mangager MaxCount property
resourcestring
SNoIniKey = 'Property "IniKey" cannot be empty.';
SNoIni = 'TMRUManger''s ini file is not initialized.';
//==============================================================================
constructor TMRUManager.Create(AOwner:TComponent);
begin
inherited Create(AOwner);
FItems := TStringList.Create;
FMaxCount := 10;
FIniKey := 'MRU';
FFilesMustExist := true;
FAddNumbersToFileMenu := true;
FAddNumbersToPopupMenu := true;
end;
//------------------------------------------------------------------------------
destructor TMRUManager.Destroy;
begin
FItems.Free;
inherited Destroy;
end;
//------------------------------------------------------------------------------
function TMRUManager.Add(const AItem:string) : boolean;
var
i : integer;
begin
result := false;
if (FilesMustExist and FileExists(AItem)) or (not FilesMustExist) then begin
// if new item is already in list put it at the last position.
for i:=0 to FItems.Count-1 do begin
if UpperCase(FItems[i])=Uppercase(AItem) then begin
FItems.Exchange(i, FItems.Count-1);
UpdateMenus;
exit;
end;
end;
if FItems.Count=FMaxCount then FItems.Delete(0);
FItems.Add(AItem);
UpdateMenus;
result := true;
end;
end;
//------------------------------------------------------------------------------
procedure TMRUManager.AddToMenu(menu:TMenuItem; AddNumbers:boolean);
var
newItem: TMenuItem;
i,j : integer;
begin
if FItems.Count0 then begin
// Remove old MRU menu items
ClearMenu(menu);
// Add separator
if menu.Count0 then begin
newItem := TMenuItem.Create(self);
with NewItem do begin
caption := '-';
tag := MRU_Tag;
end;
Menu.Add(NewItem);
end;
// Append MRU list to the menu
if FReverseOrder then begin
for i:=0 to FItems.Count-1 do begin
newItem := TMenuItem.Create(self);
with newItem do begin
if AddNumbers
then Caption := Format('&%d - %s ', [i+1, FItems[i]])
else Caption := FItems[i];
Tag := MRU_Tag+i+1;
OnClick := MenuClicked;
end;
Menu.Add(NewItem);
end;
end else begin
for i:=FItems.Count-1 downto 0 do begin
j := FItems.Count-i;
newItem := TMenuItem.Create(self);
with NewItem do begin
if AddNumbers
then Caption := Format('&%d - %s ', [j, FItems[i]])
else Caption := FItems[i];
Tag := MRU_Tag+i+1;
OnClick := MenuClicked;
end;
Menu.Add(NewItem);
end;
end;
end;
end;
//------------------------------------------------------------------------------
procedure TMRUManager.ClearMenu(menu:TMenuItem);
var
i : integer;
begin
with menu do begin
for i:=count-1 downto 0 do begin
if (Items[i].Tag=MRU_Tag) and (Items[i].Tag then Delete(i);
end;
end;
end;
//------------------------------------------------------------------------------
function TMRUManager.GetItemCount : integer;
begin
result := FItems.Count;
end;
//------------------------------------------------------------------------------
procedure TMRUManager.LoadFromIni(ini:TIniFile);
var
n, i : integer;
begin
if FIniKey='' then
raise Exception.Create(SNoIniKey);
if Assigned(ini) then begin
n := ini.ReadInteger(FIniKey, 'Count', 0);
if n0 then begin
for i:=1 to n do
Add(ini.ReadString(FIniKey, Format('Item%d', [i]), ''));
UpdateMenus;
end;
end else
raise Exception.Create(SNoIni);
end;
//------------------------------------------------------------------------------
procedure TMRUManager.MenuClicked(Sender:TObject);
var
i : integer;
begin
if (Sender is TMenuItem) then begin
i := (Sender as TMenuItem).Tag - MRU_Tag - 1;
if (i=0) and ( i then FOnSelected(Sender, FItems[i]);
end;
end;
//------------------------------------------------------------------------------
procedure TMRUManager.SaveToIni(ini:TIniFile);
var
i : integer;
begin
if FIniKey='' then
raise Exception.Create(SNoIniKey);
if Assigned(ini) then begin
ini.WriteInteger(FIniKey, 'Count', FItems.Count);
for i:=0 to FItems.Count-1 do
ini.WriteString(FIniKey, Format('Item%d', [i+1]), FItems[i]);
end else
raise Exception.Create(SNoIni);
end;
//------------------------------------------------------------------------------
procedure TMRUManager.SetAddNumbersToFileMenu(value:boolean);
begin
FAddNumbersToFileMenu := value;
if Assigned(FFileMenu) then AddToMenu(FFileMenu, value);
end;
//------------------------------------------------------------------------------
procedure TMRUManager.SetAddNumbersToPopupMenu(value:boolean);
begin
FAddNumbersToPopupMenu := value;
if Assigned(FPopupMenu) then AddToMenu(FPopupMenu.Items, value);
end;
//------------------------------------------------------------------------------
procedure TMRUManager.SetFileMenu(value:TMenuItem);
begin
if Assigned(FFileMenu) and (valueFFileMenu) then ClearMenu(FFileMenu);
FFileMenu := value;
if Assigned(FFileMenu) then AddToMenu(FFileMenu, FAddNumbersToFileMenu);
end;
//------------------------------------------------------------------------------
procedure TMRUManager.SetIniKey(value:string);
begin
if value='' then
raise Exception.Create(SNoIniKey);
FIniKey := value;
end;
//------------------------------------------------------------------------------
procedure TMRUManager.SetMaxCount(value:integer);
// Set maximum number of MRU items.
var
i : integer;
begin
if value if FReverseOrder
then for i:=FItems.Count-value-1 downto 0 do FItems.Delete(i)
else for i:=FItems.Count-1 downto value do FItems.Delete(i);
end;
FMaxCount := value;
end;
//------------------------------------------------------------------------------
procedure TMRUManager.SetPopupMenu(value:TPopupMenu);
begin
if Assigned(FPopupMenu) and (value FPopupMenu)
then ClearMenu(FPopupMenu.Items);
FPopupMenu := value;
if Assigned(FPopupMenu)
then AddToMenu(FPopupMenu.Items, FAddNumbersToPopupMenu);
end;
//------------------------------------------------------------------------------
procedure TMRUManager.SetReverseOrder(value:boolean);
// Change the order of the items (oldest items at the bottom or at the top).
var
i : integer;
begin
if (valueFReverseOrder) and (FItems.Count0) then begin
for i:=0 to (FItems.Count-1) div 2 do FItems.Exchange(i, FItems.Count-i-1);
UpdateMenus;
end;
FReverseOrder := value;
end;
//------------------------------------------------------------------------------
procedure TMRUManager.UpdateMenus;
begin
if Assigned(FFileMenu)
then AddToMenu(FFileMenu, FAddNumbersToFileMenu);
if Assigned(FPopupMenu)
then AddToMenu(FPopupMenu.Items, FAddNumbersToPopupMenu);
end;
//==============================================================================
procedure Register;
begin
RegisterComponents('Your Components', [TMRUManager]);
end;
//==============================================================================
end.