Hacker’s Guide to Visual FoxPro
An irreverent look at how Visual FoxPro really works. Tells you the inside scoop on every command, function, property, event and method of Visual FoxPro.
Enabled
This property determines whether a control or form can get focus. It’s Visual FoxPro’s equivalent to FoxPro 2.x’s SHOW GET ENABLE | DISABLE.
Usage
oObject.Enabled = lValue
lValue = oObject.Enabled
When Enabled is .F., the object is dimmed. In addition, you can’t click on the object. Okay, you can click on it, but nothing happens. You can’t tab to it, either.
Grids behave a little differently than other controls in this regard. If you disable the control in a column of a grid, then click on that control, the grid cell itself receives “focus” of some sort. You can’t use the control, but the cell is highlighted. You still can’t tab into that control.
Disable controls when they don’t make sense. By selectively enabling and disabling controls based on the responses of the user, you can both encourage and shepherd the users along the path of “normal” choices and prevent them from choosing inappropriate or nonsensical choices.
There’s one potential gotcha with Enabled. When you disable a container (like a form), the objects in that container (like controls) are inaccessible, but they don’t get dimmed, so there’s no visual cue to the user. We like the fact that disabling the container keeps users away from the contents—it would be a pain to have to cycle through the contents and disable them individually. We just wish there were an easy way to get a visual cue. Our best suggestion is to create a custom method for the container, EnableIt, which accepts .T. or .F., then issues SetAll(Enabled, <the passed value>), followed by This.Enabled = <the passed value>. Use the custom method instead of simply setting Enabled for the container. Starting in VFP 6, you can use an Assign method of the Enabled property of a container to do this.
Example
* You may want to enable the Save button of a dialog
* as soon as the user makes a change to a particular field.
* You could put something like this in the InteractiveChange
* method of that field:
ThisForm.btnSave.Enabled=.T.