DIRECTORY
Devices, DeviceClassTypes, DeviceTypes, RefTab;

DevicesImpl: CEDAR PROGRAM
IMPORTS RefTab
EXPORTS Devices, DeviceTypes =
BEGIN

Device: TYPE = DeviceTypes.Device;
DeviceClass: TYPE = DeviceClassTypes.DeviceClass;
DeviceClassObj: PUBLIC TYPE = DeviceClassTypes.DeviceClassObj;
DeviceState: TYPE = DeviceTypes.DeviceState;

globalDevices: RefTab.Ref ¬ RefTab.Create[];

QuaClass: PUBLIC PROC [ref: REF] RETURNS [class: DeviceClass] = {
WITH ref SELECT FROM
dc: DeviceClass => class ¬ dc;
ENDCASE => class ¬ NIL;
};
NameOfClass: PUBLIC PROC [class: DeviceClass] RETURNS [name: ATOM] = {
name ¬ class.name;
};
ClassOfDevice: PUBLIC PROC [device: Device] RETURNS [class: DeviceClass] = {
class ¬ device.class;
};

RegisterClass: PUBLIC PROC [class: DeviceClass, name: ATOM] = {
[] ¬ RefTab.Store[globalDevices, name, class];
};

ClassFromName: PUBLIC PROC [name: ATOM] RETURNS [class: DeviceClass ¬ NIL] = {
found: BOOL;
val: REF;
[found, val] ¬ RefTab.Fetch[globalDevices, name];
IF found THEN class ¬ NARROW[val];
};

InitialDeviceState: PUBLIC PROC [device: Device] RETURNS [DeviceState] = {
RETURN[device.class.getDeviceState[device]];
};
END.

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DevicesImpl.mesa
Copyright Ó 1991, 1992 by Xerox Corporation.  All rights reserved.
Bier, November 6, 1991 10:21 am PST
Contents:  Routines on devices and device classes (e.g., keyboards, mice, pens, etc.).

Narrows ref to DeviceClass.  Clients can't do this themselves because DeviceTypes.DeviceClass is an Opaque type.  Returns NIL if ref is the wrong type.

For keyboards and mice, this returns the state with all keys up.  For pointing devices, the device begins at position [0,0] in 2D, [0,0,0] in 3D, etc.

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