Think C Shell for XCMDs
Incorporating XCMDs into your application without alteration
By Gerry H. Kenner, Magna, Utah
Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.
About the author
Gerry Kenner is a professional electrical and computer engineering consultant, university researcher and sometimes writer who specializes in image analysis systems for investigative scientists.
Recently, I submitted an article to MacTech Magazine entitled Three Subclasses for Screen Input/Output in which I described the creation of three THINK C classes which I use as general utilities when developing applications. These classes were named BGetTCLInfo, BDisplayDoc and BBitMapDoc whose functions were to ask for data input, output data and output bitmap dumps respectively. In this article, I am going to show how BGetTCLInfo and BDisplayDoc can be used for development of XCMDs. The use of two other classes, BEditDoc and BEditPane will also be demonstrated.
The idea is to write XCMDs in such a way that they can be incorporated in either THINK C application or code resource projects without alteration. The XCMD can be written in standard C or it can be object oriented. Once incorporated into a THINK C object oriented application shell, standard debugging techniques can be used to follow the execution of the code.
The code resource project consists of the standard main function for interfacing with HyperCard. This function then calls the code for the XCMD which is in a separate file.
The application project is somewhat more complicated in that it initially creates an object of class BGetTCLInfo for getting whatever information is needed by the XCMD, puts it in HyperCard usable form, executes the XCMD code and then uses a BDisplayDoc object to pass the results back to the programmer.
If the programmer wants to use HyperTalk utility functions, he must create a code file named something like HyperUtil.c (or HyperXcmd.c for that matter) and provide alternate source code for any functions called. I have not done this because I feel that HyperTalk utilities should be avoided in favor of THINK C library functions or SANE toolbox calls.
I havent had occasion to try it but programming windoids may be a problem.
Descriptions of the classes BGetTCLInfo, BDisplayDoc, BEditDoc and BEditPane are not included in this article. The reader will need to obtain the February, 1993 issue (page 18) of MacTech Magazine in which they are described and/or purchase a copy of the MacTech Magazine disk for this issue to get the source code. [Or you can download it from one of the online services. - Ed.]
As in my previous article, I am only including the code necessary to understand the project. This code is enough for an intermediate programmer to fill in what is missing. Typically, I do not declare variables or state which header files must be included. A copy of the complete project is available on the MacTech Magazine disk.
CODE RESOURCE PROJECT
This is a regular code resource with the difference that code resource specific code is included in the main function while a call is made to the XCMD code which is in a separate file. In this example the code necessary for setting up A4 addressing will not execute properly in a standalone application so it executed in the main function of the XCMD.
Create a new project named Flash.Π and two empty code files named FlashXCMD.c and Flash.c. Incorporate these files as well as the libraries ANSI-A4 and MacTraps into the project. Flash.c will contain the XCMD code that is common to both the code resource project and the application project. FlashXCMD.c will contain the main function of the Flash code resource.
Set up the project to build a code resource named FlashXCMD of type XCMD with a resource number such as 30.
The code of the main function is as follows:
/* 1 */
pascal void main(XCmdPtr pp)
RememberA0(); //Setup and save register A4
RememberA0 and SetUpA4 set up A4 addressing while RestoreA4 removes it. FlashMain is a call to the XCMD code. For the above code to compile, it is necessary to #include the files SetUpA4.h and Flash.h.
FlashMain is part of a file named Flash.c. It contains code for flashing the screen and beeping the number of times the user specifies in the HyperCard stack where the XCMD is called. It then returns this number to HyperCard. Its code is as follows. This method is based on a HyperCard XCMD demonstration program originally written by Apple Computer.
/* 2 */
pascal void FlashMain(XCmdPtr paramPtr)
Str255 str, tempStr;
// First param is flash count.
// Convert it to a pascal string
returnHdl = NewHandle(256L);
(char*)*(unsigned char **)paramPtr->params);
// Convert the string to a number
// Invert the screen and sound the beep.
for (again = 0; again < flashCount; again++)
// Build the return string.
strcpy((char*)tempStr, The number of flashes was );
paramPtr->returnValue = returnHdl;
Short, brief and simple as an example should be. The only other thing you need to know is that Flash.h contains the prototype declaration of the function FlashMain and #includes HyperXCmd.h.
Create a HyperCard stack named Flash Stack with one button which contains the following script.
/* 3 */
put FlashXCMD(5) into msg
Compile the code resource and merge it with the above stack. Run the XCMD to confirm that it is functional.
The purpose of this object oriented code is to provide a dialog box asking for input, convert it to a HyperCard usable format, call the XCMD code and then display return information.
The easiest way to get the necessary project is to make a copy of THINK Cs Starter Project, compile it and then make the appropriate name changes, i.e., Starter.Π to FlashObject.Π, Starter.c to FlashObject.c, StarterApp.c to flApp.c, etc. Remove the StarterDoc and StarterPane classes from the project and eliminate any references to them as they are not necessary. In the StarterApp files change all instances of the prefix Starter with fl. Add all the dialog box classes. Add CButton, CCheckBox, CIconPane, CRadioControl and CRadioGroupPane of the control classes. The ANSI and SANE libraries will be required before the project is finished. Finally, add Flash.c from above to the project.
In this case, the main function will look something like this when the changes have been made.
/* 4 */
theApp = new flApp;
The flApp object is entered via the XcmdRun method to avoid complications which would result from overriding the Run method of the CApplication class.
In the flApp class, the methods CreateDocument and OpenDocument must be overridden to become donothing methods or else removed entirely. This is to prevent the creation of unwanted windows.
Four new methods need to be added to the flApp class. These are named XcmdRun, GetParams, FillParamPtr and DumpData. They have the following functions.
XcmdRun Access method. Launch XCMD.
GetParams Get input parameters.
FillParamPtr Convert input parameters to HyperCard readable form.
DumpData Dump results to a window.
XcmdRun gets the input, sends it out for conversion, calls the XCMD and then outputs the result. Its code is as follows.
/* 5 */
paramPtr = (XCmdPtr)NewPtr(136L); // Size of XCmdBlock.
// A real program would dispose of paramPtr and its handles
// at this point.
The parameter data is input by creating an object of class BGetTCLInfo which displays a dialog box containing an edit text box into which information can be entered. The format used for entering the information is First set of data,Second set of data, etc just as is done in HyperCard scripts. In the case of our example, we would enter something like 3. By enclosing it between quotes just about anything including 32k text files can be read in this way.
/* 6 */
void flApp::GetParams(char *paramStr)
#define DLOGinfo601 // Resource ID for DLOG template
BGetTCLInfo*theDocument = NULL;
SetRect(&boxDescription, 20, 20, 260, 60);
theDocument = new(BGetTCLInfo);
theDocument->GetInfo(Number of flashs, paramStr);
The FillParamPtr method is a conversion routine which takes data input in the format given above and creates handles pointing to the text between each pair of quotation marks.
/* 7 */
void flApp::FillParamPtr(XCmdPtr paramPtr, char *paramStr)
short count = 0;
char *tempPtr, *tokenPtr;
tempPtr = paramStr;
while (*tempPtr != 0x00)
tokenPtr = (char*)&tokenStr;
if (*tempPtr == 0x22)
while (*tempPtr != 0x22)
*tokenPtr = *tempPtr;
if (*tempPtr == 0x2C)
while (*tempPtr != 0x2C)
*tokenPtr = *tempPtr;
*tokenPtr = 0x00;
theLength = strlen(tokenStr);
paramPtr->params[count] = NewHandle(theLength + 1);
paramPtr->paramCount = count;
FlashMain was listed above as part of the code resource project. It is found in the Flash.c file.
Once the program has returned from the FlashMain call, the DumpData method is called to create an output window displaying the data returned by the XCMD code. This is done by creating an object of class BDumpData. The code is as follows.
/* 8 */
void flApp::DumpData(Handle theData)
theOutput = new BDisplayOutput;
Use the above listings to add the methods to the flApp.c file. Add the following #include statements.
/* 9 */
Make the appropriate changes in the flApp.h file and add #include HyperXCmd.h. Add BGetTCLInfo.c, BDisplayOutput.c, BEditDoc.c and BEditPane.c to the project. Add the DLOG and DITL resources listed below to the resource file. Compile and do whatever additional tweaking is necessary. One of the tweaks will be to increase the project memory to about 500k if it hasnt already been done.
DLOG and DITL resources numbered 601 must be added to provide a template for the prompt dialog box. This consists of an OK button centered at the bottom, one line of static text at the top with a large edit text box in between. The exact size and layout of the resource are determined by programmer tastes and requirements.
When the project is run, a dialog box will appear soliciting user input. Type in a number in quotation marks such as 5 just as it would appear in the parameter list for a Hypercard call. The computer will then beep for the listed number of times but will not flash. Finally, a window will appear with the message The number of flashes was 5. Although interesting, I did not consider it worth the effort for this paper to determine why the screen did not flash on a Power Book 100.
I have been using this system for over a year. The principle advantages over using compiler statements to alternate between creating XCMDs and applications is that readability is not sacrificed and the input/output capabilities make it easy to keep track of what is going on.
I can be reached on internet at firstname.lastname@example.org and AppleLink at UUTL.