Windows 3.1 Application Compatibility (part 2 of 7)

The information in this article applies to:

• Microsoft Windows Software Development Kit (SDK) for Windows version 3.1

SUMMARY

Application Compatibility Document for Windows 3.1

Due to the amount of information in this document, it has been broken into seven pieces. To find all seven pieces of this document and the Windows 3.1 Compatibility Test checklist, query this knowledge base on the words:

   prod(winsdk) and 31compattest


                         Multimedia and Sound
                         ====================

MS-DOS SOUND APPLICATIONS

Potential Problem

Some MS-DOS-based applications that use audio cards, such as SoundBlaster, may not run correctly in virtual machines or may run incorrectly after Windows terminates.

Test

Carry out each of the following steps. Be sure your application runs correctly as you complete each step:

1. Run the MS-DOS-based application in a virtual machine.

2. Exit Windows and run your application under MS-DOS.

WINDOWS SOUND APPLICATIONS

Potential Problem

Although Windows sound functions are 100 percent backward compatible, some Windows-based applications may not function properly with the new functions.

Test

Run your application and try all the sound capabilities.

UNUSUAL DRIVERS

Potential Problem

Applications requiring unusual drivers, such as WinFax, may not be compatible with Multimedia extensions.

Test

Run your application and try the functions of your application that the driver supplies.

                          Window Management
                          =================

In some cases, Windows version 3.1 will ensure compatibility with existing Windows version 3.0 applications by supporting both the Windows versions 3.0 and 3.1 implementations. If an application's Windows version as set by Resource Compiler (RC) is 3.0, Windows version 3.1 carries out the Windows 3.0 implementation; that is, the Windows version 3.1 enhancement has no impact on an existing Windows version 3.0 application. However, if a Windows version 3.0 application's Windows version is changed to 3.1 without corresponding changes to the application code, the application may encounter problems wherever Windows version 3.1 carries out the 3.1 implementation.

MOVING AND SIZING

For Windows 3.0 applications, the SetWindowPos function assumes that SWP_NOMOVE and SWP_NOSIZE are set if SWP_HIDEWINDOW or SWP_SHOWWINDOW was set. Thus, hiding and showing a window and changing its size and position are not possible in an atomic operation. Windows version 3.1 applications are not so limited.

Potential Problem

Any Windows version 3.0 application whose version number is changed to 3.1 may make unnecessary calls to SetWindowPos.

In a Windows version 3.0 application, if you call SetWindowPos with SWP_SHOWWINDOW when the window is already visible, SetWindowPos always causes the entire window to be redrawn. This also affects the operation of ShowWindow. In a Windows version 3.1 application, a call to SetWindowPos with SWP_SHOWWINDOW on a window that is already visible will not redraw (unless other areas must be updated as a result of a size, move, or z-order operation specified in addition to SWP_SHOWWINDOW).

Potential Problem

Any Windows version 3.0 application whose version number is changed to 3.1 may encounter problems if it depends on redrawing on each call to SetWindowPos with SWP_SHOWWINDOW set.

MoveWindow is shorthand for a call to SetWindowPos with the SWP_NOZORDER and SWP_NOACTIVATE flags set. If the MoveWindow fRedraw parameter is FALSE, then SWP_NOREDRAW is also set. In a Windows 3.0 application, when MoveWindow is called on a top-level window with fRedraw set to FALSE, Windows calls SetWindowPos without setting the SWP_NOREDRAW flag and then calls ValidateRect to prevent the client area from repainting. However, WM_NCPAINT and WM_ERASEBKGND messages will have been sent, even though fRedraw was FALSE. In a Windows version 3.1 application, MoveWindow no longer makes this special case.

Potential Problem

Any Windows version 3.0 application whose version number is changed to 3.1 may encounter problems if it depends on receiving WM_NCPAINT and WM_ERASEBKGND messages after a call to MoveWindow.

In a Windows version 3.0 application, Windows always redraws a window's frame completely when the window is moved or sized. In a Windows version 3.1 application, Windows no longer redraws a window's frame completely in all cases. For example, the following code sequence will not redraw the window border:

   MoveWindow(hwnd, ..., FALSE);
       .
       .
       .
   InvalidateRect(hwnd, NULL, TRUE);

Potential Problem

Any Windows version 3.0 application whose version number is changed to 3.1 may have an incomplete window frame if it depends on Windows redrawing the frame completely after moving and sizing.

Tests

1. Start your application in its default state. Maximize and minimize it; be sure it paints correctly after each operation.

2. Move your application as far right and left as you can in small increments, watching for repaint problems each time you stop moving.

3. Resize your application using the mouse to drag the border.