The Extra! host graphics emulation provided by Extra! allows you to emulate a host graphics terminal and to work with vector graphics applications on the mainframe. Extra!'s host graphics emulation gives you true graphics terminal emulation. This means that the mainframe computer treats your computer as if it were a mainframe graphics terminal. Extra! supports four mainframe graphics applications: AS, SAS. GDDM, and GRAFPAK. You have three graphics models to choose from for your emulation: 3179G or 3192G, 3472G, and 3270PCG.
NOTE:Many GDDM applications may not support display models 4 and 5.
The terms you will encounter frequently while using Extra! host graphics emulation are explained below. A graphics session is a terminal session that supports host graphics. It has options that work specifically with host graphics applications.The graphics cursor is the pointer that affects the host graphic image. It is different from and operates differently from the Windows pointer and can be displayed as crosshair or boxed.
Graphics Terminal Characteristics
A standard terminal displays text characters in rows and columns. A model 2 terminal screen displays 1920 cells of 24 rows with 80 characters in each row. Each cell can display a character defined in the character set for the terminal.
These characters cells, however, are not the smallest display unit on the screen. Each cell is composed of rows and columns of pixels, tiny areas of light that can be turned off or on individually. To form a character in a cell, the terminal lights up only those pixels that form a representation of the character.
A graphics terminal uses pixels to draw characters or graphic images. It does this by processing instructions from the mainframe application that tell it to construct images using basic graphics elements. These elements, called primitives, consist of objects such as lines, ellipses, arcs, curves, and patterns. When these elements are received by the graphics terminal, the terminal then searches its character definition set and constructs the elements on the screen by lighting up the appropriate pixels.
This type of graphics construction, where the terminal can process the primitives directly, is called vector graphics. It is also called All Points Addressable (APA) graphics.
Host graphics applications have two layers: a text layer and a graphics layer.
The text layer contains the application interface text, such as menus, list of commands, and display characters. The graphics layer contains an image and the space surrounding it.
The text layer is superimposed over the graphics layer to form the image you see in the display space. The text layer can contain both transparent text (which allows the graphical image to show through) and non transparent text (which overlays the graphical image). These layers are the same size. On a standard IBM 3179G terminal, the size would be 720x384 pixels.
Loadable Symbols
Loadable symbols, also called graphic symbol sets, are sets of symbols up to 32x32 pixels in size that are treated as small, individual bitmaps.
There are different uses of loadable symbols. They can appear in the graphics layer or the text layer. In the graphics layer, they are commonly referred to as Graphics Symbol Sets and can be used as markers, fill patterns, or custom text. In the text layer, they are referred to as Program Symbols and are used as custom text. In either case, the symbol sets are created on a mainframe host graphics application and then downloaded to the graphics terminal. The application then selects a symbol or group of symbols to display on the text or graphics layer.
True Graphics Terminal Emulation
Graphics Terminal Emulation has the capability of displaying all the primitives as an IBM graphics terminal, such as the 3179G or the 3472G, would. Primitives such as lines, ellipses, arcs, patterns, and loadable symbols are all rendered correctly and scaled to fit within the terminal window on your display screen. This is important since certain mainframe graphics applications will perform properly only on terminals having certain display characteristics. Using this program your display can appear as an IBM 3179G, a 3192G, a 3472G, or a 3270PCG.
The window dimensions for the terminal emulation session might not be the same as configured for the display (3179G or 3472G). If the dimensions deviate significantly from the proportions of the configured display resolution, the image may appear stretched or compressed as it is sized to fit the terminal window. The Extra! display fonts allows you to display graphics correctly.
To display your graphics correctly, in your graphics session, choose from ATM Graphics from Fonts in the Settings dialog box.
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