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Introducing the ABL GUI Designer : Concepts : Paging in SmartObjects
 

Paging in SmartObjects

Every SmartContainer (SmartWindow, SmartFrame, and SmartDialog) gives you the ability to organize sets of SmartObjects into logical pages. The primary purpose of the paging mechanism is to give you control over when these sets of objects are initialized and displayed.
This allows you to make the best use of limited screen space, and to keep the attention focused my limiting the amount of information displayed at one time.
The SmartFolder provides a convenient way to reserve screen space and control the display of logical pages. The GUI Designer also allows you to manage pages in other ways. For example, you can use the paging mechanism to create multiple-window applications.

Special pages

There are three page designations that have special meaning in the paging system:
Page 0
Page 0 is the default page in every SmartContainer. If you create a SmartContainer and add objects to it without changing any of the paging settings, then all the objects are on Page 0. Also, any basic objects (widgets) you add directly to a SmartContainer are placed on Page 0 regardless of the Design Page setting.
Objects placed on Page 0 are always displayed in addition to any objects on any other pages that have been selected for display.
Startup page
You have the option of designating one page, in addition to Page 0, to be displayed at the time the SmartContainer is run. This is called the Startup Page.
Page 0 is the default Startup Page. Unless you explicitly specify a non-zero page number as the Startup Page, only the objects placed on Page 0 will display when you run the SmartContainer.
For example, if you are using a SmartFolder to organize the viewing and hiding of pages, you would typically designate Page 1 (which always corresponds to the leftmost folder tab) as the Startup Page. If you leave the Startup page set to Page 0 when you are using a SmartFolder, then the area within the folder object will be blank when the application starts up.
You set the Startup Page in the Pages dialog box, which you invoke from the Procedure Settings dialog.
Design page
This is the page you are working in at any given time while you are building the application. As the name suggests, the Design Page setting is relevant only in design mode. It is ignored when the SmartContainer is running.
The Design Page setting is indicated in the status bar of the GUI Designer window. You can set the Design Page by double-clicking the Page Number field in the GUI Designer main window, or by choosing the Design button in the Pages dialog box.

Paging system limited to SmartObjects

It is important to note that only SmartObjects can be placed on pages other than Page 0.
Only SmartObjects are capable of responding to SmartLinks, and a SmartContainer controls the paging system by means of a set of special SmartLinks. When you assign a SmartObject to Page n, the GUI Designer automatically creates a SmartLink of type Pagen from the SmartContainer to the SmartObject. For more information see, About SmartObjects