GraphApp allows programs to have a graphical user interface. This interface is designed to look very similar to many common graphical user interfaces, such as the Microsoft Windows interface and the various X-Windows interfaces, such as Motif and Gnome.
GraphApp does not use other GUI toolkits or native widget sets to implement its graphical user interface. Instead, it uses its own code. This means that GraphApp can provide its own features, such as support for Unicode fonts and text, which other toolkits may be lacking. Conversely, GraphApp widgets may not work in precisely the same manner as the native widgets on a given platform.
Because GraphApp emulates the widgets found on other platforms, it is a cross-platform programming tool. That is, it is possible to create a GraphApp program and compile it for two different operating systems (for example, Windows and Linux) and it will look and function the same way on both platforms. This is a different approach to portability than is advocated by those who assert that a graphical program's appearance on each platform should blend in with the appearance of the other applications on that platform. Both approaches to portability are valid and have their uses. GraphApp is designed with inter-platform portability in mind, rather than the more common "local look and feel" approach.
GraphApp provides support for Unicode fonts and text encodings for internationalised text. Internally, GraphApp code assumes the use of the UTF-8 text encoding. A bitmapped Unicode font is also provided with GraphApp to allow display and editing of UTF-8 encoded Unicode strings.
Text can be cut, copied and pasted using Control-X, Control-C and Control-V respectively. GraphApp checks to see if the text can be represented in one-byte-per-character format, and if so, pastes text in that format. This gives interoperability with many existing applications, which assume text on the clipboard is in that format. GraphApp will accept from the clipboard such text or else UTF-8 text. It converts all text into UTF-8 for use internally.
There is a way to input Unicode characters into any GraphApp program. The ALT key can be used to compose some characters. For example, ALT ' e produces é and ALT / O produces Ø. This composition technique allows the input of many glyphs from European languages.
The Alt key is held down to produce the accent, then released, followed by the letter. The Shift key may also be needed to type the appropriate accent or the following character.
Alt ~ n produces the Spanish small letter n with tilde: ñ
Alt / o produces the Danish/Norwegian small letter o with a slash: ø
Alt ` E produces capital E with a grave accent: È
Alt A E produces capital AE ligature: Æ
The general rules are:
Alt ' produces an acute (rising line) above a letter.
Alt ` produces a grave (falling line) above a letter.
Alt ~ produces a tilde above a letter: ñ
Alt ^ produces a circumflex above a letter: â
Alt " produces a diaeresis (double dots) above a letter: ö
Alt . produces a dot above a letter.
Alt - produces a macron (line) above a letter, or a stroke through it: Ð
Alt _ produces a horizontal line joined to the bottom of a letter.
Alt | produces a vertical line joined to the left of a letter.
Alt / produces an angled stroke through a letter: Ø
Alt , produces a cedilla for consonants or an ogonek for vowels: ç
Alt u produces a breve (u shape) above a letter.
Alt n produces an inverted breve above a letter.
Alt v produces a caron (v shape) above a letter.
Alt o produces a ring above a letter: Å
Alt O produces a ring around a letter, e.g. copyright or registered symbol.
Ligatures are produced by typing the two letters, so
Alt o e produces lowercase oe ligature (not e with a ring above!)
Alt D z produces Dz ligature.
Alt 1 2 produces the fraction one half: ½. Some other fractions work similarly.
If the second letter typed is a space, it can modify the first.
Alt ! (space) produces upside-down exclamation mark: ¡
Alt ? (space) produces upside-down question mark: ¿
Alt x (space) produces a multiplication symbol.
Alt ' (space) produces an acute accent (similar for other accents listed).
Greek letters are produced phonetically by preceding with Alt \
Alt \ a produces lowercase alpha
Alt \ p produces lowercase pi
Alt \ f produces lowercase phi
Alt \ u produces lowercase upsilon
Alt \ U produces uppercase upsilon
In some cases there is no obvious equivalent in English:
Alt \ Y produces uppercase psi
Alt \ H produces uppercase eta
Alt \ C produces uppercase xi
Alt \ X produces uppercase chi
Alt \ v produces lowercase non-final sigma
Cyrillic letters are produced phonetically by preceding with Alt ]
Some letters require Alt [ as the prefix instead.
Alt ] A produces uppercase Cyrillic A.
Alt ] T produces uppercase Cyrillic TE.
Alt [ T produces uppercase Cyrillic TSE.
Any GraphApp program which has a text entry field can thus be used to compose European characters, for pasting into other applications.
GraphApp implements a core set of routines which behave the same way on each platform. This core set include drawing routines, font selection, and navigation of folders (directories).
Folder names are assumed to be separated by forward slashes, following the Web and Unix convention. So, a program would open a file using open_file("/My Documents/stuff.txt", "r") rather than fopen("\My Documents\stuff.txt, "r") on a Windows platform (or any platform, for that matter). Internally, GraphApp converts forward slashes to whatever the native directory separator is. This allows GraphApp programs a great degree of portability. Folder and file names can be represented in one format in source code and in data files, and the library handles the conversion to whatever the operating system requires.
Text can be written to and read from files in either the UTF-8 or ISO-Latin-1 encodings. All text is converted to the UTF-8 format internally, so it is not valid to assume one character is stored in one byte if you use the GraphApp file input routines. This is convenient for manipulating Unicode text, such as a document which contains a mixture of English, Greek and Chinese text.
If you read data into a GraphApp program as ISO-Latin-1 text (one byte per character) it will probably be displayed and edited correctly, but there is no guarantee that this will always work. For example, the ligature Æ followed immediately by the English pound sign £ is actually a UTF-8 encoding for a completely different letter (Latin small letter OI). To avoid this problem, use the GraphApp input routines to correctly convert the data based on its original encoding.
Because GraphApp implements drawing routines portably, the appearance of a program will generally be exactly the same on another computer or operating system. This means you can rely on the pixel placement of buttons, lines, and fonts (if using the portable fonts included in the GraphApp package).
One problem with this pixel-level approach to portability is that screen resolutions may differ, and so the bitmapped font supplied with GraphApp may not be of a good resolution for all platforms. In practice, this seems to not be too much of a problem, because the font is quite large (it has to be, to allow correct rendering of complex Asian glyphs). Also, GraphApp programs can be configured to use native fonts, such as Helvetica and Times, although this usually precludes the correct display of Unicode glyphs.
Application resources can be added into a GraphApp application. A resource is a font or other file or directory structure containing files. These can be added on to the end of a compiled program, and used at run-time by that program. The tools directory within the GraphApp package contains some tools for manipulating resources, as well as documentation.
One benefit of resources is that the portable Unicode font can be added onto a compiled application, and that program can then be distributed to friends or clients, and there is no installation required for them to use the program. The font will automatically be found and used by the GraphApp program because it is visible to GraphApp within the program's resources.
This means it is possible to completely guarantee a program's look-and-feel using GraphApp, down to the availability of a Unicode font and its pixel representation. This level of portability is not even available within Java.
Resources are simply files tacked on the end of a program's executable file, separated by a single NUL byte and indexed by a "resource directory" data structure which is the last thing added to the application. It's quite a simple but powerful idea, because it's trivial to implement, but saves a lot of tedious mucking about with installation programs.