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DeviceLoop

Draw across multiple screen devices

#include <Quickdraw.h> Graphics Devices

void DeviceLoop( drawingRgn, drawingProc, userData, flags );

RgnHandle drawingRgn ; Region in which you want to draw

ProcPtr drawingProc ; Pointer to your drawing procedure (see below)

long userData ; Data forwarded to your drawing procedure

DeviceLoopFlags flags ; Flags described below

returns none

The DeviceLoop procedure searches all active screen devices, calling your

drawing procedure whenever it en counters a screen that intersects your

drawing region. You supply a handle to the region in which you wish to draw

and a pointer to your drawing procedure. The drawing region is in local

coordinates, and is the same as a window port's visRgn value, for example,

after a BeginUpdate call. In the userData parameter, you pass a long integer

of data that is forwarded to your drawing procedure.

If the DeviceLoop procedure en counters similar devices - having the same

pixel depth, black-and-white/color setting, and matching color table seeds - it

makes only one call to your drawing procedure, pointing to the first such device

en countered. You can modify this behavior by supplying a flags parameter with

one of the following values.

Flag Meaning

singleDevices If you set the singleDevices flag, then similar devices

are not grouped together when the drawing procedure is

called. If this flag is not set, DeviceLoop only calls

your drawing procedure once for each set of similar

devices, and the first one found is passed as the target

device. It is assumed to be representative of all of the

other similar devices.

dontMatchSeeds If you set the dontMatchSeeds flag, then DeviceLoop

doesn't consider color table seeds when comparing

devices for similarity. DeviceLoop ignores this flag if

the singleDevices flag is set.

allDevices If you set the allDevices flag, the drawingRgn

parameter is ignored and DeviceLoop calls your

drawing procedure for all active screens. The current

port's visRgn value is not affected when this flag is set.

Each time your drawing procedure is called, the current port's visRgn will

have been set to the intersection of the original port's visRgn and the

intersecting portion of the target device.

Your drawing procedure should be declared as follows:

typedef pascal void (*DeviceLoopDrawingProcPtr)(short depth, short

deviceFlags, GDHandle targetDevice, long userData);

The depth parameter contains the pixel size of the target device, the

deviceFlags parameter contains the gdFlags values from the target device's

graphics device record, and the targetDevice parameter is a handle to the

target device.

The long integer of user data passed to DeviceLoop is passed on to your

drawing procedure.

When called from a computer without Color QuickDraw, the targetDevice

parameter is set to NULL.

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