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Windoid XCMD
Volume Number:6
Issue Number:12
Column Tag:XCMD Corner

Related Info: Event Manager Window Manager

Windoids and HyperCard 2.0

By Donald Koscheka, MacTutor Contributing Editor

If you’ve been writing XCMDs for some time now, you might be a little concerned over how much work is involved in porting your xcmds to Hypercard 2.0. For the most part, this is a trivial process and you need not modify any of your code to support Hypercard 2.0. You will need to recompile with the new xcmd libraries though as the callback engine has been completely re-written to allow for a larger number of callbacks (some 75 as opposed to the 30 or so in HC1.0; the number is a little vague because I found a few callbacks in the library that are not documented anywhere).

For those of you using Think “C”, you will need to convert the XCMD library, “HyperXLib.o” to a Think “C” library. I got this file in MPW format and ran the “oConv” utility on it to convert it to something that Think can use. I then built a library from this. There is one small catch, the Library entry points are all uppercase. You will need to modify your calls to uppercase. For example, PasToZero becomes PASTOZERO. Of course, you might just wait until someone comes along with a more convenient library than the one that is currently distributed.

As I said, your xcmd should work “for the most part”. Certain xcmds will not work very well under Hypercard 2.0 or they will work but their behaviour will be such that you won’t recognize them (kind of like my 2 year old when she skips her nap).

The reason for this is that Hypercard 2.0 implements a completely new external window schema which offers a tremendous benefit to the xcmd writer but which also requires that you rethink your windowing strategy. The benefit of making your xcmds HC2.0 “windoid” friendly is tremendous -- windoids that function in the HC windoid layer will be able to communicate directly with Hypercard and use the Hypercard callbacks. In effect, you get a multiple-window Hypercard stack.

Windoids don’t come for free in Hypercard 2.0 and that’s good. In effect, Apple is leaving it up to each developer to decide what to do with external windows. The only rules that you must obey are those that will allow your windows to function within the external windows layer. This way, your windows will work correctly with other xcmds that also create external windows. Hypercard keeps track of which windows are owned by which xcmds, and it passes window events to each external windoid appropriately.


Listing 1, “Windoids.c” is an external window xcmd skeleton. It incorporates two new functions of HC 2.0 xcmds: (1) it handles the “?” and “!” queries from the user and (2) it responds to windoid events. The former was covered last month is quite straightforward. We will look at the windoid events in greater detail in this and future columns.

Take a look at the entry point in Listing 1. Note that the first thing we do is check the number of parameters being passed to us by Hypercard. If the parameter count is less than zero (specifically, -1), then we are being passed an external windoid event for a window that we created earlier. If there is only one parameter and it’s “?” or “!” then return the appropriate information about the xcmd back to the caller. In the case of the “?”, you should return usage information. In the case of the “!” you should return a note about who created the xcmd and what it does. This is also a good place to put your copyright notice.

If the parameter count is greater than or equal to zero, then you treat the parameters as ordinary xcmd parameters. However, if the parameter count is less than zero, then you decode the parameter block in an entirely different manner. In this case, the first parameter, params[0] (“C”) or params[1] (Pascal), contains a POINTER to an xcmd event record. This record contains the following fields:

/* 1 */
struct XWEventInfo {
 long   eventParams[9];
 Handle eventResult;
 }XWEventInfo, *XWEventInfoPtr;

The eventrecord is identical to the event manager event record. The windowPtr is a pointer to the windoid that should get this event. The event parameters and event result have other meanings that we will no doubt explore in the future but which are not required for the code in Listing 1.

In the listing, we call HandleHCEvent with the xcmd parameter block if paramcount is less than zero, otherwise we move to HandleHCmessage which should treat the parameter block like an ordinary xcmd activation. After a little thought this mechanism begs a question -- if we are responding to events in HandleHCEvent, why do we pass the entire parameter block rather than just the xwindow event record? This question gives rise to yet another question -- if that’s the case, why isn’t the parameter block just declared thusly:

/* 2 */

 typedef union{
 XCmdPBlock xcmdParams;

These questions did seem troubling to me at first -- I like to pass only those parameters that will be needed by a routine to that routine. An event handler should not need access to the parameter block, should it? The answer is absolutely and herein lies the answer -- by passing the entire parameter block to HandleHCevent, we are able to access Hypercard globals and make callbacks from inside our event loop. The answer to the second question should now be obvious -- we need to keep the parameter block intact so that xcmds can get to the callbacks. Thus the mechanism developed for handling events is correct. We can put our minds at ease and get back to the business of writing the code which is always easier once you develop this sort of intuitive feel for the data that you’re working with; a concept which is axiomatic in object oriented programming, by the way.

If your code needs to dispathc to HandleHCMessage, then you can treat the activation as a routine xcmd call and do whatever you like in HandleHCMessage. You might create a new external window here or close an existing window. Keep in mind that you should not directly call the toolbox calls to open and close windows. Rather, you must use the calls, NewXWindow and CloseXwindow which will create the windows for you and “register” them in the xwindow layer. Aside from that, window management is almost identical in Hypercard as in a stand-alone application.

/* 3 */

extern pascal WindowPtr NEWXWINDOW( XCmdPtr paramPtr,
 Rect *boundsRect,
 StringPtr title, 
        Boolean visible,
 short procID,
 Boolean color,
 Boolean floating); 

extern pascal WindowPtr GETNEWXWINDOW(XCmdPtr paramPtr,
 ResType  templateType,
 short  templateID,
 Boolean  color,
extern pascal void CLOSEXWINDOW(XCmdPtr paramPtr, WindowPtr window);

When you create an external window, you use either the call to NewXWindow or the call to GetNewXWindow. Don’t draw in the window or do anything more yet. Hypercard will tell you when the window is ready for use by sending your event loop an Xwindow event called “xOpenEvt”. Not until your xcmd gets this event are you guaranteed to have a window that is ready for use.

At openEvt, you might want to invalidate the window to force an update or append some private data to the refcon. What you do is up to you, just don’t do anything to the window until you get the xOpenEvt.

Similarly, if you have a call to xwindoids of the form: Xwindoids “Close”, windowID then you should do nothing more than issue a call to CloseXWindow and go away. Later on, your xcmd will get the “xCloseEvt” event. At this time you can deallocate any private memory that the window uses and set the passFlag to true advising Hypercard that it’s okay to close the window.

Between xOpenEvt and xCloseEvt, your window will receive more or less normal events and should respond to them in a more or less normal fashion. Things start getting a little fuzzy here as I have noticed that this event loop can have different behaviors depending on what you do with the passflag. The code in Listing 1 does work, and you might want to play with the event loop to learn a little more about the behaviour of xwindows (or xwindoids as I prefer to call them to avoid confusion with that other windowing environment).

Pay particular attention to the goaway and drag code in listing 1. The goaway method does nothing more than advise Hypercard that the user wants to close the window. Later on, HC will pass back to use the xCloseEvt event. In the meantime, the window should just be in limbo.

The drag code works fine here. I discovered that setting the passflag to true will cause Hypercard to handle dragging the window. I hope to learn more about these undocumented parts of the window code as we go along. The content, activate and update methods are pure vanilla. On activate, we just check to see if we’re going active. I take the liberty of invalidating the window to force an update, but this should not be necessary. The invalRgn should be accumulated correctly for the window.

One last thing I would like to recommend is how you respond to suspend/resume events. I like the idea of hiding all my windows on suspend so that they aren’t in the way of the next application. On resume, you should show those windows that were visible at the last suspend. You will need to keep a separate flag for this, the window’s visible won’t be much use here.

In subsequent articles, we’ll hang more decorations on this skeleton and explore Hypercard xWindoids in greater detail. In the meanwhile, take a little time to master listing 1 and get comfortable with this “call and wait” mechanism for opening and closing windows. Overall I think the structure is quite workable and should lead to some very exciting extensions to Hypercard 2.0 in the future. If you discover anything about HC2.0 that you would like to share with your fellow developers, please drop me a line. My new AppleLink is D6845. See you next month.

Listing:  Windoids.c

/* File: Donald Koscheka.c*/
/* --------------------------------*/
/* ©1990 Donald Koscheka  */
/* All Rights Reserved    */

#ifndef MouseMovedEvt
#define MouseMovedEvt0xFA 
 /* Mouse moved event code*/
#ifndef SuspendResumeEvt
#define SuspendResumeEvt  0x01
 /* Suspend/Resume event code */
#define ResumeEvtMask0x1  
 /* Supend or Resume selector */
#define ConvertScrapMask  0x2 
 /* Scrap conversion flag */

pascal void HandleHCEvent( XCmdPtr pp);
pascal void HandleHCMessage( XCmdPtr pp);
pascal void UpdateWindow( WindowPtr wind );
pascal void DoContent(  WindowPtr wind, XWEventInfoPtr ip);

pascal void main( pp )
 pp->returnValue = NIL;
 if( pp->paramCount < 0 )
 HandleHCEvent( pp );
 if( pp->paramCount == 1 )
 if( **(pp->params[0]) == '!'  || **(pp->params[0]) == '?' ){
 switch(  **(pp->params[0]) ){
 case '!': 
 pp->returnValue = PASTOZERO( pp, "\pWindoids ©1990, 1991 Donald Koscheka, 
 case '?':
 pp->returnValue = PASTOZERO( pp, "\pWindoids [command] <parameters>" 
 HandleHCMessage( pp ); 
 UnloadA4Seg( 0L );

pascal void HandleHCEvent( pp )
* Handle events in our xWindows  
* returns true if the event was handled ok
 short  windoPart;
 Rect   r;
 XWEventInfoPtr  ip= pp->params[0];
 pp->passFlag = FALSE;

 switch( ip->event.what ){
 case mouseDown:
 whichWindow = ip->eventWindow;
 windoPart = FindWindow( ip->event.where, &whichWindow );
 if( whichWindow )
 switch ( windoPart ){
 case inGoAway:
 if (TrackGoAway(whichWindow, ip->event.where)) {
 CLOSEXWINDOW( pp,whichWindow );
 pp->passFlag = FALSE;
 case inDrag: /* handled by hypercard */
 pp->passFlag = TRUE;
 case inGrow:
 case inContent:
 if (whichWindow != FrontWindow() )
 SelectWindow( whichWindow );
 DoContent( whichWindow, ip );
 pp->passFlag = TRUE;
 }/* window part */
 case mouseUp:
 case keyDown:
 case autoKey:
 case activateEvt: /* [DK] ON ACTIVATE, DRAW THE MENUS,
 if ( ip->event.modifiers & activeFlag ){
 r= (ip->eventWindow)->portRect;
 InvalRect( &r );
 pp->passFlag = TRUE;
 case updateEvt: 
 UpdateWindow(  ip->eventWindow );
 pp->passFlag = TRUE;
 case app4Evt:
 unsigned char *evtType = &(ip->event.message);
 switch( *evtType ){
 case MouseMovedEvt:
 case SuspendResumeEvt:
 if( ip->event.message & ResumeEvtMask )
 pp->passFlag = TRUE;
 case xOpenEvt:
 ShowWindow( ip->eventWindow );
 pp->passFlag = TRUE;
 case xCloseEvt:
 pp->passFlag = TRUE;
 } /* switch theEvent->what */

pascal void DoContent( wind, ip )
 XWEventInfoPtr  ip;
* Handle the content region in a mouse down in an xwindow. ip is  a pointer 
to the HyperXevent record, needed to see where the mouse is and what 
the modifiers are.
{ SetPort( wind ); }

pascal void HandleHCMessage( pp )
* Hypercard has sent us a message which we need to respond to. The command 
is passed in parameter 1 and the arguments are passed in parameter 2..N
* Perhaps you'll add a little parser here to accept valid commands and 
dispatch to the correct command handler. You may pass a command here 
called "openwindow" and another called "closewindow" to allow users to 
create & destroy external windows. 
{ }

pascal void UpdateWindow( xwind )
* Draw the contents of the window.
* You need to develop some mechanism for storing window specific data. 
 You might try storing the info in the window's refcon.  The choice is 
up to you.  
 BeginUpdate( wind );
 SetPort( wind );
 ClipRect( &wind->portRect );
 EndUpdate( wind );


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