TFileItemCompareEvent procedure type

Declaration

TFileItemCompareEvent = function(Item1: TFileItem; Item2: TFileItem)
: Integer of object

Arguments

Function result

Integer with the relative sort order for the compared file items.

Description

TFileItemCompareEvent is the type used to implement the OnSortCompare event handler in TCustomShellTreeView. TFileItemCompareEvent compares the file items specified in the Item1 and Item2 arguments to determine which value occurs first in the sort order.

The return value is an Integer with the relative sort order for the compared values:

A negative value (<0)

Indicates that Item1 occurs before Item2 in the sort order.

A positive value (>0)

Indicates that Item1 occurs after Item2 in the sort order.

0 (zero)

Indicates that Item1 and Item2 have the same value in the sort order.

An application can implement and assign a routine using the signature to the OnSortCompare event handler in TCustomShellTreeView. Set its FileSortType property to fstCustom to enable the handler routine.

The following is an item compare function, as implemented by forum member d7_2_laz, used to order items with leading Underscore characters:

function TForm1.SortCompareUnderscore(Item1, Item2: TFileItem): integer;
begin
  // Make sure that folders are moved to the top
  Result := ord(Item2.isFolder) - ord(Item1.isFolder);
  if Result = 0 then
    if (pos('_', Item1.FileInfo.Name) = 1) or 
      (pos('_', Item2.FileInfo.Name) = 1) then
      Result := AnsiCompareText(Item1.FileInfo.Name, Item2.FileInfo.Name)
    else
      Result := CompareText(Item1.FileInfo.Name, Item2.FileInfo.Name);
end;

Sort File Items by Date

function TForm1.SortCompareByDate(Item1, Item2: TFileItem): integer;
begin
  // Folders first ...
  Result := ord(Item2.isFolder) - ord(Item1.isFolder);
  if Result = 0 then
  begin
    // then file date ...
    Result := CompareValue(Item1.FileInfo.TimeStamp, Item2.FileInfo.TimeStamp);
    if Result = 0 then
      // then file name
      Result := CompareText(Item1.FileInfo.Name, Item2.FileInfo.Name);
  end;
end;

Sort File Items by Size

function TForm1.SortCompareBySize(Item1, Item2: TFileItem): integer;
begin
  // Folders first
  Result := ord(Item2.isFolder) - ord(Item1.isFolder);
  if Result = 0 then
  begin
    // then file size ...
    Result := Item1.FileInfo.Size - Item2.FileInfo.Size;
    if Result = 0 then
      // then file name
      Result := CompareText(Item1.FileInfo.Name, Item2.FileInfo.Name);
  end;
end;

See also

• OnSortCompare
• FileSortType
• TFileItem