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Chapter 12: Migrating to Different Platforms

This version of Dialog System is primarily for Windows 95 and Windows NT.

This chapter explains the major differences between these environments and gives you guidelines for handling screensets that are used in more than one environment.

You can run a screenset on other operating systems if you have the appropriate earlier version of Dialog System, because the system uses the appropriate run-time software (it is not the responsibility of the calling program). Some object definitions are not portable across environments. Dialog System provides optional portability warnings. If enabled, Portability warnings on the Options, Include menu causes Dialog System to display a warning message whenever you are about to create an object that is not portable.

When dealing with portability issues, we recommend that you test your application thoroughly, as Dialog System cannot guarantee to detect all portability violations because of the way the environment is constantly changing.

12.1 Differences Across Environments

Superficially, many of the objects and controls look the same on any of the supported environments. Objects such as radio buttons and check boxes provide the most obvious differences between Presentation Manager and Windows.

The objects that Dialog System creates follow the appearance of similar objects in the current environment. Therefore, in applications created under Presentation Manager, radio buttons appear as outlined ovals that are filled with a color when selected. As you move the screenset from one environment to another, the appearance of the objects changes.

The behavior of the mouse varies between the environments but can be fixed by the design of the application.

There are some objects and menu choices that are available on only some environments. For example, the OLE2 object is available only under Windows.

If you want an application to be portable, you must use the functions and facilities that are common among the environments you want to run on, so that the application has a common look and feel on all environments, rather than taking advantage of any one environment's functions. If you don't need a portable application, you can design just for the one environment and take full advantage of anything specific to that environment.

For example, if you want to exploit the 32-bit Windows interface, you can use the class library of your COBOL system to extend your Dialog System interface. However the interface will not be portable to any earlier versions of Dialog System.

12.1.1 Desktop Mode

One major difference among the environments is how Dialog System starts up.

Presentation Manager:
Under Presentation Manager, Dialog System starts up with the Dialog System window. Every window you create is created as a clipped window within the Dialog System window, unless you switch to Desktop mode. In Desktop mode, you create objects directly on the desktop.

Under Windows, Dialog System starts up in Desktop mode. This is because Windows does not permit the creation of clipped windows with menus. Obviously, this causes a problem because the first window you need to create would be clipped if it was within the Dialog System window. Creating windows directly on the desktop avoids this problem.

Under Windows you must be in Desktop mode to see a menu bar on a window. However, you can edit a menu bar even if you are not in Desktop mode.

12.2 Developing for Graphical and GUI Emulation Environments

GUI emulation is supported in 16-bit versions of Dialog System. For information on creating screensets that are portable for GUI emulation, see your 16-bit product documentation.

12.3 General Portability Guidelines

These guidelines are primarily for portability between graphical interfaces. If your screenset is to be portable to a GUI emulation environment, consider the guidelines given in the section Developing for Graphical and GUI Emulation Environments in your 16-bit product documentation.

12.4 Other Cross Environment Issues

If you are creating a screenset for use on all three graphical environments, you should select Portability Warnings on the Options, Include menu, so that you are aware of the implications when you create particular types of objects.

When a warning is displayed, you can continue to create the object that caused it (and ignore the warning), but if you intend to run the screenset on the environment mentioned in the warning, the results will not be as you intend. In most cases, you will be able to redesign that part of the screenset to use objects that are supported on all the target environments.

In particular, note the following:

12.5 Backward Compatibility Issues

There are two issues here:

12.5.1 Notebooks

The tab control object replaces the notebook control object that was available in previous versions of Dialog System. The functionality of the tab control is similar to that of the notebook, but the following features that were available with the notebook control are no longer available with the tab control:

In addition, the base release of Windows 95 does not support tab orientation. However, an upgrade to the operating system is included in Microsoft Internet Explorer 3.0 and later which provides this support. Also, note that unlike with notebooks, display corruption may result if the tab text or bitmap does not fit completely within the tab.

Dialog System will preserve the properties of notebook objects created using previous versions of Dialog System. However, those properties that are no longer supported cannot be edited from within the definition software.

12.5.2 Containers

The container implementation in Dialog System uses a Windows control called a List View. This control provides a subset of the functionality that was available with the container object.

The main limitation of the List View control is that the first column in the list view must contain only icons, and the remaining columns must contain only text.

In addition, the following features of the container are no longer supported:

If you intend to implement any new container objects in your application, consider using the List View object in the GUI class library, as it provides more control over the list view object.

12.6 Compatibility Chart

Presentation Manager Windows GUI Emulation Windows NT and 95 (16-bit) Windows NT and 95 (32-bit)
3-D objects x y x y y
Bitmaps y y y y y
Check box y y y y y
Color y(9) y(9) x y(9) y(9)
Container y y x y x(11)
Dialog box y y y y y
Entry field y y y y y
Group box y y y y y
Fonts y(8) y(8) x y(8) y(8)
Icon/Bitmapped buttons y y x y y
List box y y y y y
List view x x x x y
Menu bar y y y y y
Message box y y (4) y y (4) y (4)
Multiple line entry field y y (5) y y y
Primary window y (1) y (1) y (1) y (1) y (1)
Push button y y (6) y y (6) y (6)
Radio button y y y y y
Scroll bars y y y y y
Secondary window (clipped) y y (3) y y (3) y (3)
Secondary window (not clipped) y y(2) y y (2) y (2)
Selection box y y y y y
Tab Control y y x y x(10)
Tab Control Page x x x x y(10)
Text y y y(7) y y
User control x x x x y


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