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                        Knob VBX Control  

              Copyright 1994 Northeast Data Corp.

                     All Rights Reserved

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   Release 1.0

   March 1994


This document describes the Knob Custom VBX Control. 


               CONTENTS

1. Product Description
2. Legal Information
3. Installation
4. Usage
5. Ordering Information

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1. Product Description

The Knob VBX Control is a Microsoft Windows DLL designed and 
implemented in compliance with Microsoft standards for
interfacing with Visual Basic.

The control appears to the end user as a knob similar to those 
used on audio/video equipment such as stereos, tuners, and amplifiers.

To the application programmer, the interface to the knob is similar
to the one for the MS Windows standard scroll bar. The programmer can
set a range of values that will be fed back to the application as the
end user adjusts the position of the knob.

Being a VBX control, the programmer can add the Knob Control to the 
tool palette in Visual Basic. This allows use of the control in Visual
Basic forms. Since Visual C++ supports use of VBX controls, the knob
control can also be used in the Visual C++ environment.

Use of the Knob Control in a finished application requires the
Knob Control DLL (knob.vbx) to be installed with the application.
This is true of all custom controls written for MS Windows.

There are properties available that allow the programmer to control
the behavior and appearance of the knob Control. The knob can use
a dot or a line as a pointer.  The knob can increment it's values
in either a clockwise or counter clockwise direction.  The knob can 
also specify the range of degrees used for rotation.  This feature
allows the knob to rotate several times before reaching it's stop.

The range of the knob can be set to any range with low and high values
varying from 0 to 32767.

All communication between the Knob Control and the application is 
performed using the standard Windows message mechanism for controls. 
Design of the knob Control message mechanism allows the application to
continuously monitor the setting of the control.


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2. Legal Information

The purchaser of the Knob Control is allowed to use it and
distribute it in applications without paying any royalty, and without
printing or displaying a copyright notice for the control. This only
includes distribution of the Knob Control DLL (KNOB.VBX). It does 
not include distribution of documentation that comes with the Knob 
Control. 

The purchaser of the Knob Control may distribute the control DLL with
applications that are networked (multiple users accessing the DLL from
a file server) without paying any license fees to Northeast Data Corp.


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3. Installation

Create a "knob" directory on your hard disk and copy all files from
the distribution disk to the directory. These files include:


   KNOB.VBX       
   FORM1.FRM       
   PROJECT1.MAK       
   README.TXT       
   VBTEST.EXE 

If you have downloaded the knob1.zip file from Compuserve, use
PKUNZIP to extract the files into the directory.

Start Visual Basic or the Visual C++ App Studio applications and use
the custom control installation function to install the knob.vbx
control.


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4. Usage


PROPERTIES
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   BackColor - Sets the background color.

   DegreeMax - The maximum degree value used during rotation (long).

   DegreeMin - The minimum degree value used during rotation (long).

   Delay     - The number of milliseconds used for the delay while
               holding the left mouse button down.

   Direction - The direction used to increment the value of the knob.
               0 - Normal (clockwise) 1 - Reversed (counter clockwise).

   FaceColor - Sets the color of the knob face.

   Height    - Height of control.
   
   HighlightColor - Sets the outer bevel color.

   KnobType  - 0 - Point, 1 - Line
 
   Left      - Left position.
   
   Max       - Maximum knob value. This must be greater than the
               minimum knob value.

   Min       - Minimum knob value. This must be less than the maximum
               knob value.

   PointColor - Sets the color of the point or line.

   Pos       - Current knob position. This must be a value between
               or including the current minimum and maximum values of
               the knob.

   ShadowColor - Sets the color of the focus bevel.

   TabStop   - If this is turned on (1 instead of 0), the knob can
               be activated by tabbing to it with the TAB key.

   Tag       - Control tag.

   Top       - Top of control window.

   Visible   - Visible/Invisible attribute.

   Width     - Width of control.

   
EVENTS
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These events work the same way as for other VBX controls.

   DblClick 
   DragDrop  
   DragOver
   GotFocus
   KeyDown
   KeyUp
   LostFocus
   LMouseDown  - Occurs when the left mouse button is pressed down
   LMouseUp    - Occurs when the left mouse button is released
   ValueChanged - Occurs when the value of the knob has changed

In order to update values in your application based on the current
position of the knob control, you should handle the ValueChanged
event.


Ordering Information
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To order the commercial version of the Knob Control, send a check to:

   Northeast Data Corp.
   2117 Buffalo Rd., Suite 290
   Rochester, NY  14624

The prices are:

   Knob VBX Control (for Visual Basic and Visual C++)    - $55
   
   Knob DLL Custom Control (for C)                       - $50

   Both controls                                         - $75

   Source code (includes both controls)                  - $235


Include your phone number and Compuserve ID if applicable. In return for
your check, you will get the software, a telephone number for support, and
a Compuserve ID for support.
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