| A page environment variable is a read only
variable that is associated with a given page, template, library
object or genie. Because it is read only it can only be set from
within Graphics Builder by using the page environment dialog box.
The value of the environment variables associated with a given page
can be read using the DspGetEnv() cicode function. Page environment
variables were introduced into Citect to give added flexibility in
making version 3 backward compatible with version 2. In version two
pages, page cicode was used to put standard buttons onto pages
(page next, page last etc.). In version 3 templates these buttons
are already defined so this cicode should not be used. This is
controlled by the PageCicodeOn environment variable.
Typically you might use a page environment variable to specify
some form of behaviour which is unique to a page. This way you can
write a generic piece of cicode which then gets the value of the
page environment variable and then uses that data to modify its
behaviour. This way you don't have to write a unique piece of
cicode for each page. A common example of this would be when
creating a menu system. So from a main menu you can press buttons
to goto sub pages, then from the sub pages you can press a button
which goes back to the higher level menu. You could create unique
buttons commands on each page to do this for example:
| Page
|
Button
|
Command
|
| Menu1
|
Sub1
|
PageDisplay("Sub1");
|
| Menu1
|
Sub2
|
PageDisplay("Sub2");
|
| Sub1
|
Menu
|
PageDisplay("Menu1");
|
| Sub2
|
Menu
|
PageDisplay("Menu1");
|
This will be fine for simple menus however when you have many
menus this can become complex. It is far better to put a command on
the Sub pages which gets the value of a page environment variable
and uses that variable to goto the required menu. As this code will
be the same for all pages you can then put this code in a template
and so you don't have to modify it for any of your pages. For
example:
| Page
|
Button
|
Command
|
| anypage
|
Menu
|
PageDisplay(DspGetEnv("Menu"));
|
Then when you create the Sub1 page you put the page environment
variable "Menu=Menu1". This is a much cleaner way to configure
menus.
This is a very handy feature and you should try to put as much
data which is local to that page in the page environment variables.
This will make you project much easier to configure and
maintain.
|
