How to override loading a TImage from the object inspector (at run-time)?
- by Mawg
Further to my previous question, which did not get a useful answer despite a bounty, I will try rephrasing the question.
Basically, when the user clicks the ellipsis in the object inspector, Delphi opens a file/open dialog. I want to replace this handling with my own, so that I can save the image's path.
I would have expected that all I need to do is to derive a class from TImage and override the Assign() function, as in the following code. However, when I do the assign function is never called. So, it looks like I need to override something else, but what?
unit my_Image;
interface
uses
Classes, ExtCtrls, Jpeg, Graphics;
type
Tmy_Image = class(Timage)
private
FPicture : TPicture;
protected
procedure OnChange(Sender: TObject);
public { Public declarations }
Constructor Create(AOwner: TComponent); override;
procedure SetPicture(picture : TPicture);
procedure Assign(Source: TPersistent); override;
published { Published declarations - available in the Object Inspector at design-time }
property Picture : TPicture read FPicture write SetPicture;
end; // of class Tmy_Image()
procedure Register;
implementation
uses Controls, Dialogs;
procedure Register;
begin
RegisterComponents('Standard', [Tmy_Image]);
end;
Constructor Tmy_Image.Create(AOwner: TComponent);
begin
inherited; // Call the parent Create method
Hint := 'Add an image from a file|Add an image from a file'; // Tooltip | status bar text
AutoSize := True; // Control resizes when contents change (new image is loaded)
Height := 104;
Width := 104;
FPicture := TPicture.Create();
self.Picture.Bitmap.LoadFromResourceName(hInstance, 'picture_poperty_bmp');
end;
procedure Tmy_Image.OnChange(Sender: TObject);
begin
Constraints.MaxHeight := Picture.Height;
Constraints.MaxWidth := Picture.Width;
Self.Height := Picture.Height;
Self.Width := Picture.Width;
end;
procedure Tmy_Image.SetPicture(picture : TPicture);
begin
MessageDlg('Tmy_Image.SetPicture', mtWarning, [mbOK], 0); // never called
end;
procedure Tmy_Image.Assign(Source: TPersistent);
begin
MessageDlg('Tmy_Image.Assign', mtWarning, [mbOK], 0); // never called
end;
end.
