main.m

/* Cocoa accessibility framework for intercepting Spotlight user input. */
#import <Cocoa/Cocoa.h>
#import <AppKit/NSAccessibility.h>

static void searchFieldCallback(AXObserverRef observer,
                               AXUIElementRef element,
                               CFStringRef notification,
                               void *data) {
  CFTypeRef subrole, value;
  
  /**
   * Check that the component in question is the search field.
   * If so, print the current value.
   */
  if (AXUIElementCopyAttributeValue(element, kAXSubroleAttribute, &subrole) == kAXErrorSuccess && 
    CFGetTypeID(subrole) == CFStringGetTypeID() &&
    CFStringCompare(kAXSearchFieldSubrole, (CFStringRef)subrole, 0) == kCFCompareEqualTo &&
    AXUIElementCopyAttributeValue(element, kAXValueAttribute, &value) == kAXErrorSuccess &&
    CFGetTypeID(value) == CFStringGetTypeID()) {
  
    NSLog(@"> %@", (NSString *) value);
  }
  
  if (subrole) {
    CFRelease(subrole);
  }
    
  if (value) {
    CFRelease(value);
  }
}

// Figure out the PID for a bundle identifier
static OSStatus FindProcessIDForBundleIdentifier(CFStringRef identifier, pid_t *pid) {

  ProcessSerialNumber psn = {0, kNoProcess};
  OSStatus status;
  
  while ((status = GetNextProcess(&psn)) == noErr) {
    CFDictionaryRef info = ProcessInformationCopyDictionary(
        &psn, kProcessDictionaryIncludeAllInformationMask);
    CFStringRef bundle;
      
    if (CFDictionaryGetValueIfPresent(info, kCFBundleIdentifierKey, (const void **) &bundle) && 
          CFStringCompare(bundle, identifier, 0) == kCFCompareEqualTo) {
      return GetProcessPID(&psn, pid);
    }
  }
  
  return status;
}


int main(int argc, char *argv[])
{
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
  
  if (!AXAPIEnabled()) {
    NSLog(@"The accessibility API isn't enabled!");
    return 1;
  }
  
  if (argc != 2) {
    NSLog(@"Usage: %s BUNDLE_IDENTIFIER\n", argv[0]);
    return EXIT_FAILURE;
  }
  
  CFStringRef bundle_identifier = (CFStringRef)[NSString stringWithUTF8String:argv[1]];
  pid_t process_pid;
  OSStatus status = FindProcessIDForBundleIdentifier(bundle_identifier, &process_pid);
  
  if (status != noErr) {
    NSLog(@"Could not find PID for bundle identifier \"%@\"", (NSString *)bundle_identifier);
    return status;
  }
  
  AXObserverRef observer;
  AXError err = AXObserverCreate(process_pid, searchFieldCallback, &observer);
  
  if (err != kAXErrorSuccess) {
    NSLog(@"Failed to create observer");
    return err;
  }
  
  // Sign up for notifications on the process ID for the specified bundle
  AXUIElementRef element = AXUIElementCreateApplication(process_pid);
  
  if (!element) {
    NSLog(@"Couldn't register for element changes");
    return EXIT_FAILURE;
  }
  
  err = AXObserverAddNotification(observer, element, kAXValueChangedNotification, NULL);
  CFRelease(element);
  
  if (err != kAXErrorSuccess) {
    NSLog(@"Failed adding observer");
    return err;
  }
  
  CFRunLoopAddSource(CFRunLoopGetMain(),
                     AXObserverGetRunLoopSource(observer),
                     kCFRunLoopCommonModes);
  
  [NSApplication sharedApplication];
  [NSApp run];
  [pool drain];
}

spotlight-ax.m

/* Cocoa accessibility framework for intercepting Spotlight user input. */
#import <Cocoa/Cocoa.h>
#import <AppKit/NSAccessibility.h>

static void searchFieldCallback(AXObserverRef observer,
                               AXUIElementRef element,
                               CFStringRef notification,
                               void *data) {
  CFTypeRef query1, query2;
  
  /**
   * Check that the component in question is the search field.
   * If so, print the current value.
   */
  if (AXUIElementCopyAttributeValue(element, kAXSubroleAttribute, &query1) == kAXErrorSuccess && 
    CFGetTypeID(query1) == CFStringGetTypeID() &&
    CFStringCompare(kAXSearchFieldSubrole, (CFStringRef) query1, 0) == kCFCompareEqualTo &&
    AXUIElementCopyAttributeValue(element, kAXValueAttribute, &query2) == kAXErrorSuccess &&
    CFGetTypeID(query2) == CFStringGetTypeID()) {
  
    NSLog(@"> %@", (NSString *)query2);
  }
  
  if (query1)
    CFRelease(query1);
    
  if (query2)
    CFRelease(query2);
}

// Figure out the PID for a bundle identifier
static OSStatus FindProcessIDForBundleIdentifier(CFStringRef identifier, pid_t *pid) {

  ProcessSerialNumber psn = {0, kNoProcess};
  OSStatus status;
  
  while ((status = GetNextProcess(&psn)) == noErr) {
    CFDictionaryRef info = ProcessInformationCopyDictionary(
        &psn, kProcessDictionaryIncludeAllInformationMask);
    CFStringRef bundle;
      
    if (CFDictionaryGetValueIfPresent(info, kCFBundleIdentifierKey, (const void **) &bundle) && 
          CFStringCompare(bundle, identifier, 0) == kCFCompareEqualTo) {
      return GetProcessPID(&psn, pid);
    }
  }
  
  return status;
}


int main(int argc, char *argv[])
{
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
  
  if (!AXAPIEnabled()) {
    NSLog(@"The accessibility API isn't enabled!");
    return 1;
  }
  
  if (argc != 2) {
    NSLog(@"Usage: %s BUNDLE_IDENTIFIER\n", argv[0]);
    return EXIT_FAILURE;
  }
  
  CFStringRef bundle_identifier = (CFStringRef)[NSString stringWithUTF8String:argv[1]];
  
  pid_t process_pid;
  OSStatus status = FindProcessIDForBundleIdentifier(bundle_identifier, &process_pid);
  
  if (status != noErr) {
    NSLog(@"Could not find PID for bundle identifier \"%@\"", (NSString *)bundle_identifier);
    return status;
  }
  
  AXObserverRef observer;
  AXError err = AXObserverCreate(process_pid, searchFieldCallback, &observer);
  
  if (err != kAXErrorSuccess) {
    NSLog(@"Failed to create observer");
    return err;
  }
  
  // Sign up for notifications on the process ID for the specified bundle
  AXUIElementRef element = AXUIElementCreateApplication(process_pid);
  
  if (!element) {
    NSLog(@"Couldn't register for element changes");
    return EXIT_FAILURE;
  }
  
  err = AXObserverAddNotification(observer, element, kAXValueChangedNotification, NULL);
  CFRelease(element);
  
  if (err != kAXErrorSuccess) {
    NSLog(@"Failed adding observer");
    return err;
  }
  
  CFRunLoopAddSource(CFRunLoopGetMain(),
                     AXObserverGetRunLoopSource(observer),
                     kCFRunLoopCommonModes);
  
  [NSApplication sharedApplication];
  [NSApp run];
  
  [pool drain];
}