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Although TGS is written using C++ and uses an object oriented architecture, it is not necessary for the application program to be written in C++. All API functions are duplicated using standard function calls compatible with languages such as C, Pascal, and Fortran.

TGS Session and System Objects:

TGCL_Session - the session object. This stores all the operational parameters for the current session.

Generally one session object is used per application.

TGCL_System - the complete TGS system object. Multiple objects allow multiple windows within an application.

The session and system objects provide the overall organization and control of TGS.

The session object has the job of managing a complete operating environment.

Generally there is one session object per TGS application running on the system. This approach allows dynamic link libraries to handle each separate application program individually. In addition it allows complex TGS environments to exist with multiple configurations running simultaneously, even in embedded equipment.

The system object has the job of managing a single drawing or display window.

Resources:

TGCL_Resource - generic TGS resource (drawing tool). (abstract class)

• TGCL_Pen

• TGCL_Brush

• TGCL_Font

The resources used in a drawing are owned and managed by an individual system object. A resource table within the system object stores pointers to the resource objects.

2D Primitives:

TGCL_Primitive - Generic TGS primitive. (abstract class)

• TGCL_CtrlPrimitive
  Control (non-drawing) primitive. (abstract class)
  • TGCL_PlaceHolder
    used to mark a deleted table entry

  • TGCL_SetRealUnits

  • TGCL_SetRealWindow

  • TGCL_SetScale

  • TGCL_SetPagePosition

  • TGCL_SetRotationAngle

  • TGCL_SetGrid

  • TGCL_SetTabRuler
    • Scaling and positional parameters may be changed multiple times on a single drawing sheet.

• TGCL_GrPrimitive

  Graphic (drawing) primitive. (abstract class)

  • TGCL_Point

  • TGCL_Line

  • TGCL_Polyline

  • TGCL_Arc

  • TGCL_Rectangle

  • TGCL_RoundRect

  • TGCL_Ellipse

  • TGCL_Pie

  • TGCL_Chord

  • TGCL_Polygon

  • TGCL_Path

  • TGCL_Text

  • TGCL_Bitmap

A primitive table within the system object stores pointers to the primitive objects. Each time the drawing or display image is processed, the table is scanned from start to finish. Hence primitives later in the table can overdraw those earlier in the table.

Control primitives are not displayed, but pass commands to the system object. These are generally used for changes to the scaling system. Complex drawings can have multiple groups of control primitives and graphic primitives. This allows different parts of a drawing to be scaled and positioned separately.

Graphic primitives are used to produce the images. All standard geometric elements are provided as well as paths and bitmaps.

A path is a compound curve, generated from series of line segments, arcs, and bezier curves. Paths may be closed, and filled with a brush as required. Multiple sub-paths can exist per path.

A bitmap is a scanned image containing pixel data. The bitmap primitive stores the pixel data, a color lookup table for 1, 2, 4, and 8 bit per pixel formats (not required for the 32 bit full color format), and floating point coordinates storing the corners of the bitmap for scaling and positioning.

Groups and Symbols:

TGCL_Group (concrete class)

• TGCL_Symbol (abstract class)
  • inherited by all symbols

A group is a collection of primitives that can be operated on collectively for editing purposes.

Symbols are a special class of group. They are individually written objects that control the operation of one or more primitives, generally for animation purposes.

One example of a symbol is a special form of text that remains upright, regardless of display rotation. When the display is updated this symbol reads the rotation angle of the display and sends a command to the text primitive it owns to rotate it in the opposite direction.

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