FOXTOOLS.FLL Calls to GetDC, GetDeviceCaps and ReleaseDC

• Microsoft Visual FoxPro for Windows, version 3.0
• Microsoft FoxPro for Windows, versions 2.5x, 2.6, 2.6a

SUMMARY

The code below demonstrates how to use the FOXTOOLS.FLL library commands to call the following Microsoft Windows application programming interface (API) functions:

   GetDC()
   GetDeviceCaps()
   ReleaseDC()

MORE INFORMATION

The program first loads the FOXTOOLS.FLL library that is supplied with FoxPro for Windows and creates some variables. It then retrieves the handle to the display device and calls the GetDeviceCaps() function. Next, it displays the width and height of the physical display in millimeters in two consecutive windows that can be seen by clicking the left mouse button. Finally, it releases the handle to the device context and the library.

   set library to sys(2004)+"foxtools.fll" additive

   * create variables to pass index to GetDeviceCaps()
   * these values are found in the WINDOWS.H file

   HORZSIZE = 4
   VERTSIZE = 6

   * get the handle to the device context

   gethdc = RegFN("GetDC","I","I")
   hdc = CallFN(gethdc,0)

   * get the screen size in millimeters

   getsize = RegFN("GetDeviceCaps","II","I")
   Hsize = CallFN(getsize,hdc,HORZSIZE)
   Vsize = CallFN(getsize,hdc,VERTSIZE)

   * display the results in two windows

   wait window "Width is: " + alltrim(str(Hsize)) + " mm"
   wait window "Height is: " + alltrim(str(Vsize)) + " mm"

   * release the handle to the device context

   releasehdc = RegFN("ReleaseDC","II","I")
   = CallFN(releasehdc,0,hdc)

   release library sys(2004)+"foxtools.fll"

REFERENCES

Microsoft Windows Software Development Kit, "Programmer's Reference, Volume 2: Functions," pages 350-354, 785

FOXTOOLS.WRI located in the C:\FOXPROW\GOODIES\FOXTOOLS subdirectory

WINDOWS.H located in the C:\C700\INCLUDE subdirectory