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In GUI applications, the code to get user input is much more
complex than the code for a command line program.
Much user input is via the mouse, button press or motion.
Some user input is from the keyboard.
Mouse button press input in examples:
w2.c X Windows
w2gl.c OpenGL
W2frame.java Java
Getting input data, text, into a graphical user interface program
is much more difficult. The input of numbers is accomplished by
inputting a character string and converting the character string
to a number inside the program.
The X Windows Motif program w5a has one pull-down menu on the menu bar,
"Set Values". On the pull-down there are five menu items:
"Number"
"View Angle"
"Name"
"Apply"
"Quit"
The selecting one of the first three causes a popup dialog box to
appear. The dialog box is where the user enters the data.
The source code is:
w5a.c X Windows
w5.h
In OpenGL and GLUT I wrote my own data entry in fixed windows.
These could be made into separate windows and could be
selected by a menu.
test_text_in.c OpenGL
demo_text_in.c
text_in.h
text_in.c
Now, add a popup dialog window for user data entry.
w5gl.c
The Java implementation is the shortest.
Similar "toolkit" classes should be available for
Microsoft C++ and C#.
W5frame.java Java
Another simple screen input/output Java program is Fahrenheit.java
When you can input text, a character string, then you can
use your programming language to open and read and write files.
You can get numeric data when needed but do not use this as
a substitute for mouse input for numeric data,
with possible use a grid for accuracy.
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