Re: [changeset] Missing ScreenSize & ScreenPixelsPerInch properties

[John W. Eaton]

On 22-Jan-2009, Michael Goffioul wrote:

| On Thu, Jan 22, 2009 at 2:13 PM, John W. Eaton <address@hidden> wrote:
| > On 22-Jan-2009, Shai Ayal wrote:
| >
| > | OK. But I don't know how hard it will be to make this cross platform.
| > | We might try to "steal" some code from fltk to discover the
| > | platform.
| >
| > Why?  This seems to be a compile-time thing.  We can discover if the
| > build system has X11, or is Windows, or is OS X, and then we just need
| > to know how to get the screen characteristics on those systems.  I
| > provided the example code for X11.  Now someone else needs to do the
| > same for Windows and OS X.
| 
| Under Windows, it would be done using GetSystemMetrics and
| GetDeviceCaps functions.

Does the following program do the right thing?

Thanks,

jwe

#include <iostream>

#include <Windows.h>

int
main (void)
{
  HDC hdc = GetDC (0);

  if (hdc)
    {
      int ht = GetDeviceCaps (hdc, VERTRES);
      int wd = GetDeviceCaps (hdc, HORZRES);

      std::cerr << wd << "x" << ht << " pixels" << std::endl;

      double ht_mm = GetDeviceCaps (hdc, VERTSIZE);
      double wd_mm = GetDeviceCaps (hdc, HORZSIZE);

      std::cerr << wd_mm << "x" << ht_mm << " mm" << std::endl;

      double resy = wd * 25.4 / wd_mm;
      double resx = ht * 25.4 / ht_mm;

      std::cerr << resx << " resx" << std::endl;
      std::cerr << resy << " resx" << std::endl;

      std::cerr << (resx + resy) / 2 << " avg dpi" << std::endl;

      int depth = GetDeviceCaps (hdc, BITSPIXEL)

      std::cerr << depth << " bit depth" << std::endl;
    }
  else
    std::cerr << "failed to get device context" << std::endl;

  return 0;
}