Why Jpeg is accepted in the uses clause in some projects and in others vcl.imaging.jpeg is required?

Question

I am updating some projects to XE2 and I don't understand why on some projects

uses jpeg;

is accepted

and in other i need to write

uses vcl.imaging.jpeg;

Could you explain me please?

Answer 1

The difference is down to the the unit scope names setting in the project options for your various projects.

If you have Vcl.Imaging included in that setting then you don't need to fully specify the unit scope. Typically, old projects that are upgraded from previous Delphi versions will have Vcl.Imaging included in the unit scope names setting. New projects do not.

This is described in the documentation for Unit Scope Names.