Introduction to dGE
dGe is an add-on package for Xbase languages. It allows programmers to incorporate
graphical features into their otherwise completely text-based applications. dGE’s features are diverse, and range from a simple data representation in the form of a line
or bar chart to a more complex event-driven mouse interface. Over 100 graphical
functions now exist in dGE which has been available since 1984 and is widely regarded
as the de-facto standard for PC database graphics.
The dGE library interacts with your applications through a series of function calls (Clipper 5.0 users can use the supplied Graphics Language if they wish). dGE works
With Xbase programs that are cpmpiled or interpreted. Programs that are compiled
Have the necessary dGE instructions embedded in an executable .EXE image, or into
An overlay file at link time. Your product(s) can then be distributed and can run freely
Under DOS as stand-alone applications.
dGE comes with a run-time licence, so you can give away your creations completely
free of any royalty payments. Interpreted program (raw ASCII .PRG files) such as those
running directly under dBASE III/III+ (from the aow ancient dot prompt mode)
execute the various dGE function through the use of a screen escape codes,
and a small Terminate and Stay Resident program (TSR). Your program
communicates with the TSR program directly, and this enables various graphical functions to be invoked.
1.1 Why design Graphical Systems and lnterfaces?
Even though dGE has many facilities for the creation of WIMP-style graphical user
Interfaces, it was not interded solely for this purpose. Stated quite simply, dGE can be
Used in the design of many different types of systems, and is best suited to those applications that need to present a combination of textual and graphical information,
Especially statistical information in the form of graphs, charts and so on. dGE does not
Have to be used solely in the design of database of database applications; you may want to implement a system with graphical connotations bus without the normal database functionality, for example a textual/pictorial demonstration disk for a new company
Service or product.
Futhermore, it is quite possible for an application to have a type of GUI and not be based around the WIMP philosophy at all. We could do without many WIMP-style
Features and still have a type of GUI and many facilities for the construction of user interfaces. The type of system that you eventually design must therefore be based upon
Strict user reqirements and more importantly, must be easy to use. You can spend hours designing an intricate mouse-driven interface when your users will be just as happy pressing a series of function keys!
There is obviously a time and a place for each particular type of user interface.Moving to a graphically based environment will not be panacea to all your programming problems; dGE came about to give Xbase programmers access to graphical tools and perhapas to leave behind their older interfaces and text-based interfaces.Abandoning any previous style of programming is not the best of ideas in my opinion,since most of the best results that can be achieves with dGE are gained when integrating its facilities with your existing Xbase applications.
1.2 dGE 4 and 5 –The Differences
In dGE version 4.1,the main facilities available to the developer could be briefly summarized as:
An event system and mouse interface
Numberous drawing and graphing functions
The Clipper 5 Graphics Language
Limited screen saving and clipping windows
Font and icon support
The dGX graphics design centre
TSR and linkable driver interface
.PCX image support (read/write)
In dGE version 5,the developer has yet more facilities which can be utilised.These, in addition, include:
Super VGA support (up to 1024x768
Unlimited memory for screen saving
A less memory-hungry system overall
New grahs: 3D pie charts,and bubble charts
.BMP and .PCX image file support
Colour (Windows) icon support
Proportional fonts and a selection of sample fonts to utilize in your programs
Screen tiling feature (as in Windows), and scrolling screen regions
Aurograph functions – these are to replace the Clipper 5 Graphics Language.
Low – level graphics programming (dGE 5 API system)
1.3 dGE 5 – for clipper/Foxpro Programmers Only
it should be mentioned that dGE 5 does not support languages which use the older TSR system, a prime example being dBASE III, It is, therefore, important not to rule out older versions of dGE, and the older version 4 will continue to support such languages.
dGE version 5 is primarily for use with xbase dialcets such as Clipper and Foxpro. Support for languages such as C and assembler are also provided through a low-level API system interface (Styled rather like the Windows GDI). The API will lead to even greater performance for graphics drawing, even allowing the developer to bypass the common higer-level interface supplied with dGE. The API can be interfaced through Clipper’s Extern system with a language such as C, although not through Clipper directly.