LineDisplay Class (POS for .NET v1.12 SDK Documentation)

  • Article

2/27/2008

Defines the programmatic interface for a UPOS Line Display device.

Namespace: Microsoft.PointOfService
Assembly: Microsoft.PointOfService (in microsoft.pointofservice.dll)

Syntax

'Declaration
Public MustInherit Class LineDisplay
    Inherits PosCommon

public abstract class LineDisplay : PosCommon

public ref class LineDisplay abstract : public PosCommon

public abstract class LineDisplay extends PosCommon

public abstract class LineDisplay extends PosCommon

Remarks

All Line Display devices in POS for .NET support text character display as their default capability.

In addition, a Line Display device can support the following operations:

  • Marquee-like scrolling of the window, either vertical or horizontal, or both;

  • Waiting periods between displaying characters, for a teletype effect;

  • Character-level or device-level blinking;

  • One or more descriptors. Descriptors are small indicators with a fixed label, and they are typically used to indicate transaction states such as "Item," "Total," and "Change"; and

  • Control of device brightness, with one or more levels of device dimming, in addition to the default, software-based support of brightness levels of "normal" and "blank."

The general programming model of a Line Display:

  • Consists of one or more rows that contains one or more columns of characters. The characters in the default character set will include at least one of the following, with a capability defining the character set:

    • The digits '0' through '9' plus space, minus ('-'), and period ('.').

    • The previous set plus uppercase 'A' through 'Z.'

    • All ASCII characters from 0x20 through 0x7F. This includes space, digits, uppercase, lowercase, and some special characters.

  • The rows and columns are numbered that begins with (0, 0) at the upper-left corner of the window.

  • Window 0 is always defined as follows:

    • Its "viewport," the part of the display that is updated by the window, covers the display.

    • The size of the window matches the display.

    Therefore, window 0 that is also known as the "device window," maps directly onto the display.

  • Additional windows can be created. A created window has the following characteristics:

    • Its viewport covers part or all the display.

    • The window can either match the size of the viewport, or it can be larger than the viewport in either the horizontal or vertical direction. In the second case, marquee scrolling of the window can be set.

    • The window maintains its own values for rows and columns, current cursor row and column, cursor update flag, scroll type and format, and timers.

    • All viewports behave transparently. If two viewports overlap, then the last character displayed at a position by either of the windows will be visible.

Display Modes

  • Immediate mode

    In effect when MarqueeType is none and InterCharacterWait is 0.

    If the window is bigger than the viewport, only those characters that map into the viewport will be seen.

  • Teletype mode

    In effect when MarqueeType is None and InterCharacterWait is not 0.

    DisplayText and DisplayTextAt requests are queued and processed in the order they are received. The InterCharacterWait timer specifies the time to wait between outputting each character. InterCharacterWait applies only to those characters within the viewport.

  • Marquee mode

    In effect when MarqueeType is a value other than None.

    The window must be bigger than the viewport.

    A marquee is typically initialized after entering Marquee Init mode by setting MarqueeType to Init, then calling ClearText, DisplayText, and DisplayTextAt methods. Then, when MarqueeType is changed to an "on" value, Marquee On mode is entered, and the marquee begins to be displayed in the viewport beginning at the start of the window (or end if the type is right or down).

    When the mode is changed from Marquee On mode to off, the marquee stops in place. A later change back to Marquee On mode continues from the current position.

    When the mode is switched from Marquee On mode to Marquee Init mode, the marquee stops. Changes can be made to the window, then the window can be returned to Marquee On mode to restart the marquee with the new data.

    It is illegal to use DisplayText, DisplayTextAt, ClearText, RefreshWindow, and ScrollText unless in Marquee Init mode or marquees are off.

Device Sharing

The Line Display device is an exclusive-use device. Its device-sharing rules are as follows:

  • The application must claim the device before it enables it.

  • The application must claim and enable the device before accessing some properties or calling methods that update the device.

Inheritance Hierarchy

System.Object
   Microsoft.PointOfService.PosDevice
     Microsoft.PointOfService.PosCommon
      Microsoft.PointOfService.LineDisplay
         Microsoft.PointOfService.BasicServiceObjects.LineDisplayBasic

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread-safe. Any instance members are not guaranteed to be thread-safe.

See Also

Reference

LineDisplay Members
Microsoft.PointOfService Namespace