How do we cheat Windows Help System from Delphi Form to execute our own form?

Question

In the TForm we have the HelpFile, HelpType and HelpKeyword properties. We set the file and keyword. when we press F1 the magic comes. Everybody knows it.

But what if we want to use a data base with keyword and help fields and create a new custom form to show the help, using the HelpKeyword from the visual components to know which db record to show in the custom form, disabling the standard windows help system. Can we do that? How?

Answer 1

You can either:

1. Assign a handler to the OnHelp event of TApplication/Events.

2. Write a class that implements the ICustomHelpViewer and IExtendedHelpViewer interfaces, and then register that class for use via RegisterViewer().

Answer 2

Yes. See the TApplication.OnHelp event. You can easily connect it using a TApplicationEvents component (on the Additional component palette) in recent Delphi versions, or declare it yourself in older versions that don't have that component.

function TForm1.ApplicationEvents1Help(Command: Word; Data: NativeInt;
  var CallHelp: Boolean): Boolean;
begin
  // Stop normal help processing from being called
  CallHelp := False;

  // Command is the help command being sent.
  // Data is the context information; it varies based on Command
  // Use them to decide what your help window should do, and what
  // it should display
end;