Changing Focus from QuickWin Using the Windows API

• Microsoft FORTRAN Compiler for MS-DOS, version 5.1

SUMMARY

This article shows by example how to use Windows API calls to switch focus between windows.

There are 2 concerns with adding functionality to a QuickWin application with the Windows API.

• A large portion of the functionality in a Windows-based application is provided outside the API (by message handling, and so forth). For this reason, much of this functionality can't be provided under QuickWin. To get a full GUI interface, you'll need to use Visual C++ or Visual Basic.
• Many APIs will not behave as expected. In this example, GetFocus() works well at first, but if the user changes focus to a different window while the command setvideomode() is executing, the call to GetFocus() gets the handle of the wrong window. In a Windows-based application, the program would keep track of each window's handle as the window is created, rather than trying to determine the handle of a window by assuming that it currently has the focus.

MORE INFORMATION

The following QuickWin program creates a text window and a graphics window, sets focus to the text window, waits for the user response, and then returns focus to the graphics window.

This example assumes that the QuickWin Graphics Library update has been made.

To install the graphics update, follow the instructions in the README.TXT file on the installation disk labelled "Microsoft FORTRAN, QuickWin Graphics Library" (NOTE: The "QuickWin Graphics Library" is in fine print.)

Sample Code

C Compile options needed: /MW C Link with modified library LLIBFEW.LIB

      interface to integer*2 function getfocus
     +  [PASCAL,alias:'GetFocus']()
      end
      interface to integer*2 function setfocus
     +  [PASCAL,alias:'SetFocus'](i)
      integer*2 i
      end

      include'fgraph.fi'
      include'fgraph.fd'

      integer*2 i, texthandle, graphicshandle, getfocus, setfocus

      texthandle = getfocus()

      i=setvideomode($sres256color)

      graphicshandle=getfocus()

      i = setfocus(texthandle)
      write(*,*) "Hit <Enter> to continue"
      read(*,*)

      i=setfocus(graphicshandle)
      end