How can a component at designtime determine the project directory

Question

I write a component which should store some information relative to the project directory. Every time a property of my component is changed it should write a file. So how can a component determine the current project directory at design time.

Thanks in advance

EDIT:
I want to generate a delphi source file every time a property of my component is changed, so that I always get the latest version when I compile my code. Think of it as a kind of code generator.

At the moment I set whole path and filename where the source should be stored but I prefer a relative path to the project (or the form/datamodule which contains my component) to make it easier to copy the project on different developer machines.

Answer 1

Thanks for the hints. Open Tools API is the way to go and using the Open Tools API from a component on a form at designtime is possible.

So here is my solution:

I need two units, one for the component and one for registering the component and the code which use the Open Tools API.

Here comes the component unit:

unit TestLabels;

interface

uses
  SysUtils, Classes, Windows, Controls, StdCtrls;

type
  TTestLabel = class(TLabel)
  private
    FTestProperty: Boolean;
    procedure SetTestProperty(const Value: Boolean);
    procedure Changed;
  published
    property TestProperty: Boolean read FTestProperty write SetTestProperty;
  end;

var
  OnGetUnitPath: TFunc;

implementation

{ TTestLabel }

procedure TTestLabel.Changed;
begin
  if not (csDesigning in ComponentState) then
     Exit; // I only need the path at designtime

  if csLoading in ComponentState then
     Exit; // at this moment you retrieve the unit path which was current before

  if not Assigned(OnGetUnitPath) then
    Exit;

  // only for demonstration
  Caption := OnGetUnitPath;
  MessageBox(0, PChar(ExtractFilePath(OnGetUnitPath)), 'Path of current unit', 0);
end;

procedure TTestLabel.SetTestProperty(const Value: Boolean);
begin
  if FTestProperty  Value then
  begin
    FTestProperty := Value;
    Changed;
  end;
end;

end.

Here is the unit for registering the component and the call to the Open Tools API:

unit TestLabelsReg;

interface

uses
  SysUtils, Classes, Controls, StdCtrls, TestLabels;

procedure register;

implementation

uses
  ToolsAPI;

function GetCurrentUnitPath: String;
var
  ModuleServices: IOTAModuleServices;
  Module: IOTAModule;
  SourceEditor: IOTASourceEditor;
  idx: integer;

begin
  Result := '';
  SourceEditor := nil;

  if SysUtils.Supports(BorlandIDEServices, IOTAModuleServices,
    ModuleServices) then
  begin
    Module := ModuleServices.CurrentModule;

    if System.Assigned(Module) then
    begin
      idx := Module.GetModuleFileCount - 1;

      // Iterate over modules till we find a source editor or list exhausted
      while (idx >= 0) and not SysUtils.Supports(Module.GetModuleFileEditor(idx), IOTASourceEditor, SourceEditor) do
        System.Dec(idx);

      // Success if list wasn't ehausted.
      if idx >= 0 then
        Result := ExtractFilePath(SourceEditor.FileName);
    end;

  end;

end;

procedure register;
begin
  RegisterComponents('Samples', [TTestLabel]);
  TestLabels.OnGetUnitPath := GetCurrentUnitPath;
end;

end.