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Cursors
VCL Components
The Cursor property controls the cursor that is displayed when the user moves the mouse
cursor over the component. Windows automatically changes cursors for some components.
For example, Windows changes the cursor to an I-beam when the cursor is moved over an
Edit, a Memo, or a RichEdit component, to name just a few. To let Windows manage the
cursor, leave the Cursor property set to crDefault. If you have specialized windows
(components), you can specify one of the other cursors. When the mouse is moved over that
component, Windows will change the cursor to the one you have specified.
Frequently you will need to change cursors at runtime. A long process, for instance, should
be indicated to the user by displaying the hourglass cursor. When you reset the cursor you
need to be sure to set the cursor back to whatever it was originally. The following code snippet
illustrates:
TCursor oldCursor = Cursor;
Cursor = TCursor(crHourGlass);
// do some stuff which takes a long time
Cursor = oldCursor;
This ensures that the cursor that was originally set for the application is properly restored.
Another cursor property, DragCursor, is used to set the cursor that is used when the mouse
cursor is being dragged from the component and the target can accept the drag. As with
colors, you should be prudent in your use of cursors. Use custom cursors when needed, but
don’t overdo it.
Enabled
NOTE
Components can be enabled or disabled through the Enabled property. When a component
is disabled, it cannot accept focus (clicking on it has no effect), and usually it gives some visual
cue to indicate that it is disabled. In the case of buttons, for instance, the button text is grayed
out as is any bitmap on the button. Enabled is a boolean property—set it to true to enable
the component, or set it to false to disable the component. Enabling and disabling windows
(remember that windowed components are windows, too) is a feature of Windows itself.
Some components show their disabled state at design time, but most do
not. The BitBtn component is one that does show its disabled state at
design time.
The Enabled property applies mostly to windowed components, but can apply to nonwindowed
components as well. The SpeedButton component is an example of a non-windowed
component that can be disabled.
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