InfoTip extension allow you to supply a short text that will be shown when user hovers the document. Use it to display an advanced document information.

    The InfoTip handler is an ActiveX library like all other Shell Extensions. The first step to do is to create a new ActiveX Library. Create it with the following sequence of operations: open the Repository dialog using File | New | Other... menu, then select the ActiveX tab and click the ActiveX Library icon.

Fig. 1. New ActiveX Library creation.

    Save the created project.

    The next step is to add the instance of TSxDataModule to the project. Every Shell+ component should be placed on SxDataModule ¹. This special descendant of TDataModule supplies several internal methods that allow Shell+ components to safely operates in multiple Shell threads and automates their registration and initialization. Note that you can place several Shell+ components onto the same SxDataModule as well as you can add multiple TSxDataModule instances to your project. It is easy to add new SxDataModule to the project - just click corresponding icon in the Repository:

Fig. 2. How to create new SxDataModule instance.

    You can save the project now.

Now add the TSxInfoTip component from the Shell+ palette page. This component wraps interfaces required be shell and allows you to handle shell requests in a simple manner.

    The properties of TSxInfoTip component are as follows:

Table 1. TSxInfoTip properties.

    Use Object Inspector to set TSxInfoTip properties as shown below:

Fig 3. TSxInfoTip properties

    Every time Shell needs the InfoTup text it calls corresponding shell extension interface. As a result the OnGetInfoTip event is fired in the example. The info text should be prepared and returned as a result of this event.
    Select the Events tab of Object Inspector and doubleclick the OnGetInfoTip event. Add the following code to the event handler:

procedure TSxModule1.SxInfoTip1GetInfoTip(Sender: TSxInfoTip;
  var InfoTip: String);
var
  TempStr:TStrings;
begin
  TempStr:=TStringList.Create;
  try
    TempStr.LoadFromFile((Sender as TSxInfoTip).Filename);
    InfoTip:='Words: '+IntToStr(WordCount(TempStr.Text,[' ']))+#13+#10+
             'Lines: '+IntToStr(TempStr.Count)+#13+#10+
             'Pages: '+InttoStr(TempStr.Count div 60);
  finally
    TempStr.Free;
  end;
end;

    Add and auxilliary procedure to count words in the text document:

function WordCount(const S: string; const WordDelims: TCharSet): Integer;
var
  SLen, I: Cardinal;
begin
  Result := 0;
  I := 1;
  SLen := Length(S);
  while I <= SLen do begin
    while (I <= SLen) and (S[I] in WordDelims) do Inc(I);
    if I <= SLen then Inc(Result);
    while (I <= SLen) and not(S[I] in WordDelims) do Inc(I);
  end;
end;

    Save the project and compile it - it is ready now! As well as any other ActiveX library the Shell+ project requires registration. You can register it in several ways:

• from command prompt using MS regsvr32 utility: regsvr32.exe Project1.dll
• from command prompt using Borland's tregsvr utility: tregsvr Project1.dll

To know more about shell extension installation please follow the link.

        Test the example now. To do it create and empty text document on the desktop or in any other folder. Move mouse pointer over this file and wait a couple of seconds. The InfoTip will pop-up, it will look like shown below:

    Enter a couple of text lines into the document now then look on info tip again:

    Don't forget to uninstall the example when all tests are finished. Note that it is an example only and it will show its confirmation window until you will not unregister it. As well as installation the uninstallation can be done in many ways:

• from command prompt using MS regsvr32 utility: regsvr32.exe /u Project1.dll
• from command prompt using Borland's tregsvr utility: tregsvr -u Project1.dll

The detailed information about extension uninstallation is available here.