/*

     File: PreferencesExample.c

 Abstract: Simple CFPreferences example program; reads/writes a preference.

  Version: 1.1

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 */

#include <CoreFoundation/CoreFoundation.h>

#include <stdio.h>

#include <stdlib.h>

// This function will print the provided arguments (printf style varargs) out to the console.

// Note that the CFString formatting function accepts "%@" as a way to display CF types.

// For types other than CFString and CFNumber, the result of %@ is mostly for debugging

// and can differ between releases and different platforms.

void show(CFStringRef formatString, ...) {

    CFStringRef resultString;

    CFDataRef data;

    va_list argList;

    va_start(argList, formatString);

    resultString = CFStringCreateWithFormatAndArguments(NULL, NULL, formatString, argList);

    va_end(argList);

    data = CFStringCreateExternalRepresentation(NULL, resultString, CFStringGetSystemEncoding(), '?');

    if (data != NULL) {

        printf ("%.*s\n\n", (int)CFDataGetLength(data), CFDataGetBytePtr(data));

        CFRelease(data);

    }

    CFRelease(resultString);

}

/* Read old high score, which is saved as a CFNumber under the key "High Score"; bump it up and save it.

*/

void simplePreferencesExample(void) {

    CFStringRef appName = CFSTR("A Game");

    CFStringRef highScoreKey = CFSTR("High Score");

    CFNumberRef value;

    int highScore;

    // First retrieve the previous value...

    // CFPreferencesCopyAppValue() and CFPreferencesSetAppValue() are the most straightforward way

    // for an app to read/write preferences that are per user and per app; they will apply on all 

    // machines (on which this user can log in, of course --- for users who are local to a machine,

    // the preferences will end up being restricted to that host). These functions also do a search 

    // through the various cases; if a preference has been set in a less-specific domain (for 

    // instance, "all apps"), its value will be retrieved with this call. This allows globally 

    // setting some preference values (which makes more sense for some preferences than others).

    // Note that you can read/write any "property list" type in preferences; these are

    // CFArray, CFDictionary, CFNumber, CFBoolean, CFData, and CFString.

    // This example just shows CFNumber.

    value = CFPreferencesCopyAppValue(highScoreKey, appName);   

    if (value) {

    // Numbers come out of preferences as CFNumbers.

    if (!CFNumberGetValue(value, kCFNumberIntType, &highScore)) highScore = 0;

    CFRelease(value);

    show(CFSTR("The old high score was %d."), highScore);

    } else {

    // No previous value

    show(CFSTR("There is no old high score."));

    highScore = 0;

    }

    highScore += 5;

    show(CFSTR("Recording new high score, %d"), highScore);

    value = CFNumberCreate(NULL, kCFNumberIntType, &highScore); 

    CFPreferencesSetAppValue(highScoreKey, value, appName);

    CFRelease(value);

    // Without an explicit synchronize, the saved values actually do not get written out.

    // If you are writing multiple preferences, you might want to sync only after the last one.

    // A preference panel might want to synchronize when the user hits "OK".

    // In some cases you might not want to sync at all until the app quits.

    // The AppKit automatically synchronizes on app termination, so Cocoa apps don't need to do this.

    (void)CFPreferencesAppSynchronize(appName);

}

int main (int argc, const char *argv[]) {

    simplePreferencesExample();

    return 0;

}