Diagram tool suggestions

Suggestions for future development of the EiffelStudio Diagram Tool

Add a "Diagram" top-level menu to the main menu. It would contain items for all of the options currently available on the Diagram toolbar, plus "Customize Toolbar". The menu might have additional options, like "Show Diagram Tool". (PR#5427)

Allow scrolling of the diagram without the mouse. One way to do this would be with the arrow keys, Page Up/Down, Home and End. These keys currently do nothing when the diagram has focus, so they should work fine. (PR#4287)

The Diagram tool's keyboard shortcuts sometimes don't work. Various buttons on the Diagram toolbar have keyboard shortcuts, but these shortcuts do nothing if the zoom combo box has focus. To get them to work, I first have to click on the diagram surface. (PR#4282)

If the zoom is a large number on a large diagram, then the "Export diagram to PNG" button sometimes displays a "Warning" dialog with the message, "Could not save diagram to C:\ANY.png". The file is created, but is only a few bytes in size. (PR#4281)