Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!ucbvax!dewey.soe.berkeley.edu!oster
From: oster@dewey.soe.berkeley.edu (David Phillip Oster)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Finding the size of the screen under Multifinder/Color QD
Message-ID: <33404@ucbvax.BERKELEY.EDU>
Date: 30 Dec 89 03:41:55 GMT
References: <10139@saturn.ucsc.edu>
Sender: usenet@ucbvax.BERKELEY.EDU
Reply-To: oster@dewey.soe.berkeley.edu.UUCP (David Phillip Oster)
Organization: School of Education, UC-Berkeley
Lines: 67

In article <10139@saturn.ucsc.edu> sirkm@ssyx.ucsc.edu (Greg Anderson) writes:
>TN #117 says to look at the QuickDraw variable screenbits.bounds to
>find the size of the screen, but on my Mac IIx, this rectangle is
>always (0,0,0,0) when MultiFinder is installed (color or b&w).

Tim Maroney is right, it should return the bounding rectangle of the CRT
that has the menu bar. It always has for me.

>First question:  what _is_ a gDevice?  Is there one & only one gDevice
>per monitor (/other display device) hooked up to the Mac, or might there
>be multiple devices referencing a single monitor?  If the later, why?

There should only be one at a time. Some video boards change the number of
pixels they display depending on what mode they are in: i.e, they might be
640x480 in 8-bit per pixel mode, by 1024x1204 withe one bit per pixel. In
addition, since graphic devices hold the inverse color table data
structures (used for color matching when you do a CopyBits of a pixmap
with one color table to a pixmap with a different table) there may be
graphic devices that aren't connected to screens.

>The reason I wish to know the size of the screen is simply to center my
>dialogs on the screen.  Given this purpose, should I just look at one
>gDevice (namely, the one returned by GetGDevice)?  Once I have this handle,
>how should I determine the screen bounds?  Get the PixMap from
>(*gDev)->gdPMap and then look at pixMap.bounds?

use screenBits.bounds.

Here _is_ a use for gDevices:
I redefine the zoom box, so that windows zoom to the full size of the CRT
they are on, rather than Apple's default. There is nothing more annoying
than working with a two-monitor system, clicking on the zoom box of a
window, and have it leap to the other, smaller montior.
Here is a code fragment:

/* GetBiggestZoom - set r to the dimensions of the largest
    extern SysEnvRec world;

    biggdh = NIL;
    if(world.hasColorQD){
        for(gdh = GetDeviceList(); gdh != NIL; gdh = GetNextDevice(gdh)){
            if(TestDeviceAttribute(gdh, screenDevice) &&
                TestDeviceAttribute(gdh, scrnActive)){
                if(biggdh == NIL || (**gdh).gdRect.bottom - (**gdh).gdRect.top >
                            (**biggdh).gdRect.bottom - (**biggdh).gdRect.top){
                    biggdh = gdh;
                }
            }
        }
    }
    if(biggdh == NIL){
        *r = screenBits.bounds;
        r->top += GetMBarHeight();
    }else{
        *r = (**biggdh).gdRect;
        if(TestDeviceAttribute(biggdh, mainScrn)){
            r->top += GetMBarHeight();
        }
    }
}


> The mac is a detour in the inevitable march of mediocre computers.
> drs@bnlux0.bnl.gov (David R. Stampf)
--- David Phillip Oster          -master of the ad hoc odd hack. 
Arpa: oster@dewey.soe.berkeley.edu 
Uucp: {uwvax,decvax}!ucbvax!oster%dewey.soe.berkeley.edu