Nov 98 Tips & Tidbits

by Jeff Clites

Strings and Numbers - The Twain Shall Meet

String and numbers are different animals, but programmers are constantly faced with the need to translate back and forth between the two. For integers, it is easy: StringToNum() and NumToString() to the job nicely. But for floating-point numbers, things get a little more tricky, because there are a myriad of choices about how to format them. Apple has provided StringToExtended() and ExtendedToString() to give you complete control over the process - too much control, you might say. Sometimes, you don't want the hassle of the page of code needed, and a simple solution would be appreciated. The classic solution in C is to use sprintf(), but this can wastefully increase the size of your executable if this is the only Standard Library function you need, and it doesn't respect localization settings. The following clever solution convinces the Apple Event Manager to do the work for you:

#include "AppleEvents.h"

OSErr ConvertDoubleToString( double inValue, AEDesc *outResult )
{
   OSErr theErr = noErr;
 
   theErr = AECoercePtr( typeFloat,            // input data type--'doub'
                  (const void *) &inValue, // pointer to input data.
                  (Size) (sizeof(double)),     // size of input data
                  typeChar,       // desired 'want' type is character
                  outResult );    // pointer to AEDesc for output data

   return theErr;                 // the error returned by the coercion.
}

The returned AEDescriptor will contain a descriptor type of typeChar ('TEXT') and a Handle to a block of text (use GetHandleSize() to determine the resulting string length). Of course, don't forget to AEDispose() the AEDescriptor returned by this call.

Stephen L. Reid
sreid@ti.com

Loading a Graphics File with QuickTime

QuickTime makes it easy to load a graphics file into an offscreen GWorld, but as simple as the process is, it can be hard to track down sample code to show you how it is done. The following simple snippet illustrates the process nicely, and has two of my favorite characteristics in a snippet: it doesn't omit error checking, and once you have looked it over it is so intuitive that you will be able to recreate it when you need it, without digging up the actual example:

FSSpec                   fsp;
ComponentInstance        gi;
Rect                     r;
ImageDescriptionHandle   idH;
GWorldPtr                outGWp;
OSErr                    errCode = noErr;

// fill in the FSSpec

if(noErr == errCode){ errCode = GetGraphicsImporterForFile(fsp, &gi); }
if(noErr == errCode){ errCode = GraphicsImportGetImageDescription(gi, &idH); }
if(noErr == errCode){
   r.left = 0;
   r.top = 0;
   r.right = (**idH).width;
   r.bottom = (**idH).height;
   errCode = NewGWorld(&outGWp,(**idH).depth, &r, nil, nil,0);
   if(noErr != errCode){
      errCode = NewGWorld(&outGWp, (**idH).depth, &r, nil, nil,
                          useTempMem);
   }
}
if(noErr == errCode){
   CGrafPtr   savePort;
   GDHandle   saveGD;

   GetGWorld(&savePort, &saveGD);
   SetGWorld(outGWp, nil);
   EraseRect(&r);                   // in case PICT has transparent areas
   GraphicsImportSetBoundsRect(gi, &r);
   GraphicsImportSetGWorld(gi, outGWp, nil);
   errCode = GraphicsImportDraw(gi);
   SetGWorld(savePort, saveGD);
}

if(noErr != errCode && nil != outGWp){  // error occurred
   DisposeGWorld(outGWp);
   outGWp = nil;
}
if(nil != idH){
   DisposeHandle(reinterpret_cast<Handle>(idH));
}
if(nil != gi){
   CloseComponent(gi);
}

If outGWp is not nil, it is a GWorld of the file.

David Phillip Oster
oster@netcom.com