Apple PowerBook 520 Technical Information download pdf (Page 95)

CHAPTER 5

Software

Adding Control Strip Modules 81

Contents of Module Files 5

The only required resource in a module ﬁle is a resource containing the code necessary

for the module to interact with the control strip. A module ﬁle may contain more than

one code resource if it is to provide multifunctional support. In that case, each module in

the ﬁle is loaded and initialized separately and treated as an independent entity.

If a ﬁle contains only a single code resource, the resource may be unnamed, and the

module will be referenced by its ﬁlename. If more than one module is contained within a

module ﬁle, each module is required to have a unique name describing its functionality.

All other resources in a module ﬁle are optional, but there are several that are

recommended in order to support a custom icon and version information. The

recommended resources are

■ 'BNDL'

■ 'FREF'

■ 'ICN#', 'icl4', 'icl8', 'ics#', 'ics4', 'ics8'

■ signature resource (same type as ﬁle’s creator)

■ 'vers', ID=1

Developers should conﬁne their resources to the range 256–32767.

Module Interface 5

The module’s interface to the control strip consists of a code resource of type 'sdev'.

This code is responsible for performing all of the functions required by the control strip

(see below) as well as any functions that are custom to the module itself. The module’s

entry point is at the beginning of the resource and is deﬁned as

pascal long ControlStripModule(long message,

long params,

Rect *statusRect,

GrafPtr statusPort);

Interactions between a module and the control strip are managed by passing messages to

the module to tell it what to do or to obtain information about the module and its

capabilities. Each module is required to observe Pascal register saving conventions. A

module may trash registers D0, D1, D2, A0, and A1, but must preserve all other registers

across its call.

Field descriptions

message A message number, from the list in the section “Control Strip

Module Messages”, that tells the module what action to perform.

params This is the result returned by the initialize call to the module. This

would typically be the handle to the module’s private variables

since modules can’t have global variables. It will be passed to the

module on all subsequent calls.

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Apple PowerBook 520 Technical Information Page 95