Q: My application crashes in HIThemexxx on Mac OS X 10.2 (Jaguar). Why?A: Because most of the HITheme APIs (see list below), introduced and publicly available in Mac OS X 10.3, were private on Mac OS X 10.2 and their argument list were different. Since the HITheme APIs are not available on all versions of Mac OS X, developers should weak-link with and, at runtime, test for their availability prior to calling and there lies the problem: the test mechanism most commonly used is to simply check a particular API name against NULL (see Listing 1): Listing 1: Weak-linked API common runtime check.
if ( HIThemeGetTextDimensions != NULL )
HIThemeGetTextDimensions( ... );
else
GetThemeTextDimensions( ... );
But, on Mac OS X 10.2, since most of the HITheme APIs were present, although private, the test above will execute the HITheme API. Unfortunately, the list of arguments that those APIs were expecting on Mac OS X 10.2 is different than the list of arguments that was eventually published when they were introduced in Mac OS X 10.3. Any attempt to call a HITheme API on Mac OS X 10.2 with an argument list such as expected by Mac OS X 10.3 (and later) will provoke a crash on Mac OS X 10.2. The exhaustive list of private HITheme APIs present on Mac OS X 10.2: HIThemeApplyBackground HIThemeDrawButton HIThemeDrawChasingArrows HIThemeDrawFocusRect HIThemeDrawGenericWell HIThemeDrawGrabber HIThemeDrawMenuBackground HIThemeDrawMenuBarBackground HIThemeDrawMenuItem HIThemeDrawMenuSeparator HIThemeDrawMenuTitle HIThemeDrawPaneSplitter HIThemeDrawPlacard HIThemeDrawPopupArrow HIThemeDrawScrollBarDelimiters HIThemeDrawSeparator HIThemeDrawTab HIThemeDrawTabPane HIThemeDrawTextBox HIThemeDrawTickMark HIThemeDrawTitleBarWidget HIThemeDrawTrack HIThemeDrawTrackTickMarks HIThemeDrawWindowFrame HIThemeGetButtonBackgroundBounds HIThemeGetButtonContentBounds HIThemeGetScrollBarTrackRect HIThemeGetTextDimensions HIThemeGetTrackBounds HIThemeGetTrackDragRect HIThemeGetTrackLiveValue HIThemeGetTrackPartBounds HIThemeGetTrackParts HIThemeGetTrackThumbPositionFromOffset HIThemeGetWindowRegionHit HIThemeHitTestScrollBarArrows HIThemeHitTestTrack
Thus, in this situation, the correct solution is to check against a particular version of the HIToolbox before calling a HITheme API (see Listing 2) using the GetHIToolboxVersion function given in Listing 3: Listing 2: HIToolbox version check.
if ( GetHIToolboxVersion() >= 0x130)
HIThemeGetTextDimensions( ... );
else
GetThemeTextDimensions( ... );
Listing 3: GetHIToolboxVersion.
UInt32 GetHIToolboxVersion()
{
CFBundleRef bundle;
CFStringRef versStr = NULL;
static UInt32 version = 0;
// let's do the heavy following code only once...
if (version != 0) return version;
bundle = CFBundleGetBundleWithIdentifier(CFSTR("com.apple.HIToolbox"));
if ( bundle != NULL )
versStr = (CFStringRef)CFBundleGetValueForInfoDictionaryKey(bundle,
CFSTR("CFBundleShortVersionString"));
if ( versStr != NULL &&
CFGetTypeID(versStr) == CFStringGetTypeID())
{
int major = 0, minor = 0, bugfix = 0;
char sz[20];
CFStringGetCString(versStr, sz, sizeof(sz), kCFStringEncodingUTF8);
sscanf(sz, "%d.%d.%d", &major, &minor, &bugfix);
version = ( major << 8 ) + ( minor << 4 ) + bugfix;
}
return version;
}
Document Revision History| Date | Notes |
|---|
| 2004-10-27 | Explains why weak-linked API common runtime check is not good enough for the HITheme APIs. |
Posted: 2004-10-27
| 