| Summary: | 碩士 === 中原大學 === 資訊工程研究所 === 84 === When we use a traditional method to develop a graphical user
interface, we do it in two steps. The first step is to lay out
the interface. The second step is to write down the code for
handling input events. There are basically two ways for a
component to handle input events. One isto use both callbacks
and event handlers. The other is to use just callbacks. CY2 is
a user interface development system. It separates a program
into four parts: the system component layer, the lexical layer,
the syntactic layer, and the application part of the program.
The system component is responsible for maintaining the so-
called retained mode graphics. The lexical layer is responsible
for doing feedbacks. The syntactic layer is responsible for
doing dialog control. The application part is the part of the
program that has nothing to do with the interface. Underlying
the CY2 programming environment is a library called Dt (for
Drawing Toolkit). Dt supports the use of interactors at the
lexical level. When an interactor reaches its final state in a
normal way, the interaction enters the syntactical level.
Formally, the syntactic layer is composed of final functions of
all interactors. While the interactors themselves are
responsible for doing feedbacks, their final functions (the
syntactical layer) are responsible for processing user
commands. The programming methodology that CY2 supports
emphasizes the separation of interface and application. It
also supports further modularization of the interface into the
fore-mentioned three layers.
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