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delphidelphi-7

icon on the taskbar does not move to second monitor

I recently got a new development computer with again 2 monitors, but unfortunate it has windows 10.
Now I also have some tools still developed in Delphi 7 and they work but with one annoying problem.

When I start an Delphi 7 application the icon on the taskbar does not move to the second monitor.
The taskbar is setup to show icons on the taskbar of the monitor they are open. This works for all applications, except for the Delphi 7 applications.
The icon always stays on the primary monitor.

I have the source available, so I wonder is there something I have to put into the source code, or setup some property, to get this working ?

Googling this bring up lots of cases where the form does not moves to the second monitor, but I did not find anything about the icon on the taskbar.

Solution

  • This is because the window handle associated with the taskbar button is the window handle owned by the Application object rather than the window handle of your main form.

    In later versions of Delphi you would write Application.MainFormOnTaskBar := True in your .dpr file and that would change behaviour so that the taskbar button was associated with your main form instead. I believe that MainFormOnTaskBar was introduced in Delphi 2007.

    Migrating to a modern version of Delphi is the ideal way to solve the problem. If you cannot do that then you'll need to hack your way around the VCL code to ensure that the main form's window handle is the one associated with the taskbar button. That's not likely to be an easy job. Fundamentally, you are paying the price for continuing to develop with tools that are long out of date.

    As Remy points out there isn't much hacking required to do the bare minimum. Change the window style of the Application window to remove the WS_EX_APPWINDOW style, and have the main form override the CreateParams method to set its owner window to NULL, i.e. Params.WndParent := 0.

    I suspect that the behaviour will not be quite as smooth as you'd get with a modern VCL app. For instance, the VCL has been modified to reduce the amount of window recreation it does which is more important now that the main window is associated with the taskbar button.