The DDK VGA driver source provides support for a Pen-Capable VGA display. To build a Pen-Capable VGA driver, you must set the PENWIN environment variable to 1.
Display drivers that support Windows for Pen Computing provide a set of functions and resources that permit the display drivers to carry out inking. Windows for Pen Computing is a version of Windows in which character-recognition software (the RC Manager) allows a pen device to be used in place of a keyboard. Inking is drawing done by a display driver in response to input from the RC Manager.
Display drivers that support inking must be prepared to process inking requests whenever pen input generates an interrupt. The drivers must export the following functions:
If the RC Manager requires inking, it calls the GetLPDevice function to retrieve a pointer to the display driver's physical device structure (PDEVICE). The RC Manager uses this pointer in subsequent calls to the display driver's Output function to complete the inking. The color and width of the ink is set by the RC Manager.
Before calling Output, the RC Manager calls the InkReady function to notify the display driver that it is ready to ink. The display driver must determine whether any other drawing operation is under way. If so, the display driver must wait until the current operation is complete before starting the inking. In any case, the display driver calls a callback function supplied with the call to InkReady to start the inking.
Display drivers that support inking must provide the following cursor resources.
| Value | Use |
| IDC_NEPEN (32630) | Pen points to northeast. |
| IDC_NWPEN (32631) | Pen points to northwest. |
| IDC_SEPEN (32632) | Pen points to southeast. |
| IDC_SWPEN (32633) | Pen points to southwest. |
| IDC_PEN (32633) | Default pen is same as IDC_SWPEN. |
The pen cursors must be added to the driver in the same way as standard Windows cursors.