A Graphical Petri Nets Simulator - Rochester Institute of Technology

4.6. The Graphical Driver
The core of the graphical driver uses the concepts found in the Simple
Graphical Package(SGP)[6]. It allows the user to display
pictures of two-
dimensional objects and transmits input actions from the user to the
application program in order to establish user-computer interaction.
The SGP is divided into six distinct classes :
1. Graphic output primitives the functions that result in CPU to display
on the view surface.
2. Attribute-setting the functions that determine the line style of
subsequent lines and the color ofall subsequent output primitives.
3. Segment control the functions that group logically
related output
primitives into segments (the units of selective modification of the
display program). Functions are available to delete, rename, or change
the visibility of segments, and to translate the image on the screen
which was produced by a segment.
4. Viewing operation -
the
two functions that together specify to the
package what part of the world coordinate system to display on what
portion ofthe screen.
- 5. Input the
program.
- 6. Control the
functions that control user interaction with the application
INITIALIZE function helps the package initialize its own
tables and the graphics status and mode flags / registers; it also
initializes the default values for the window (the unit square) and the
viewport (the entire screen). The TERMINATE function clears the
screen and closes out the graphics device to provide and orderly exit.
The details of the SGP can be found in Fundamentals ofInteractive Computer
Graphics[6], This project only developed a one screen net editor, so the fourth
class is omitted.
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