Display drivers can improve mouse cursor visibility (especially on liquid crystal displays) by supporting mouse trails. A mouse trail is a sequence of two or more cursor images that mark current and previous mouse cursor positions. A display driver creates a mouse trail by drawing a cursor at each new mouse position and leaving additional cursors at previous positions. The driver delays erasing the previous cursors until a specified number of cursors are visible.
A display driver provides support for mouse trails by processing the MOUSETRAILS escape in its Control function. The MOUSETRAILS escape enables or disables mouse trails. It also sets the maximum number of cursors to be displayed in the trail. The display driver must also process the QUERYESCSUPPORT escape, returning the status of the mouse trails if the requested escape is MOUSETRAILS.
The display driver draws the mouse trail when it processes the MoveCursor function. Any trailing cursors must have the same shape as the current cursor. The display driver should provide mouse trails for system cursors, such as the pointer and hourglass, and for application-specific cursors as well. Currently, support is not provided for mouse trails for XOR-only cursors, such as the I-beam and the cross-hair cursor used by PaintBrush.
The display driver is responsible for recording the mouse trail status by maintaining the MouseTrails value in the registry. The driver switches this setting to a positive value to indicate that mouse trails capability is enabled. The value also specifies the number of cursors to display. The driver switches this setting to a zero or a negative value when mouse trails capability is disabled. The absolute value specifies the number of cursors to display prior to being disabled.
Users can turn mouse trails on or off by using Control Panel. The mouse settings dialog box displays a Mouse Trails option.
Applications should not enable or disable mouse trails. However, third-party mouse configuration programs could.