ufws canvas transition

My last flash version of UFWS (Episode #12) went up on Monday morning. The rest of Monday was spent transitioning all the actionscript code to javascript (and writing some notes down). Tuesday was spent finishing up and recoding some parts which basically meant cleaning up the original code a bit. The rest of the day was spent making the background and updating the three widget graphics used. I was a bit crunched for time to get some decent gameplay in unfortunately. Overall, though the transition was much smoother than I imagined; there are some things I still don't have figured out. Today Episode #13 is released and is now using the Canvas tag.

The rest of my notes:

• There are some anti-aliasing differences between the Safari on OS X and Firefox on windows - The "game-over Congrats!" image has rendered text in a PNG displays on major blurrage in firefox for some reason, on OS X this text is crisp


• no text rendering is a problem, will need to get creative when I want to display any signage (like popup menus I had in the previous flash episodes)


• No native IE 7 canvas (or SVG) support continues to sadden me.

JavaScript Core in Leopard (The Basics)

I just discovered the JavaScriptCore.framework which is new to Leopard. Creating a hello world or a similar very basic app is always the first step I take when try to learn some new programming API and the javascript framework was no exception for me. Here is an example of something entirely useless with no practical use: Defining a function using javascript which returns the sum of two numbers, then calling that javascript function from C through the JavaScriptCore.framework. Maybe I should've had it read the two numbers from stdin?

The getObjectProperty function was borrowed from another Apple sample. Remember you'll need to add the JavaScriptCore.framework to your application.

What happens in this example:

• A javascript context is created and then the global object is obtained


• The target javascript is converted from a NSString/CFStringRef to a JSStringRef


• The javascript is evaluated which in this case defines the sum function.


• The sum function is located in the global object and called with two arguments


• The result of calling the function is converted to a number and then printed to stdout


• javascript context is released

#import <JavaScriptCore/JavaScriptCore.h>

/* Convenience function for getting a property that is an object. */
static JSObjectRef getObjectProperty(JSContextRef ctx, JSObjectRef object, CFStringRef name)
{
    JSStringRef nameJS = JSStringCreateWithCFString(name);
    JSValueRef function = JSObjectGetProperty(ctx, object, nameJS, NULL);
    JSStringRelease(nameJS);

    if (!function || !JSValueIsObject(ctx, function))
        return NULL;
    return (JSObjectRef)function;
}
int main (int argc, const char * argv[])
{
 JSGlobalContextRef g_context = JSGlobalContextCreate(NULL);
 JSObjectRef jsGlobalObject = JSContextGetGlobalObject(g_context);
 NSString *script = @"\
 function sum(a,b) { return a+b; } \n\
 ";


 JSStringRef scriptJS = JSStringCreateWithCFString((CFStringRef)script);
 JSEvaluateScript(g_context, scriptJS, NULL, NULL, 0, NULL);
 JSStringRelease(scriptJS);

 JSObjectRef function = getObjectProperty(g_context, jsGlobalObject, CFSTR("sum"));
 if(!function)
 {
  printf("no function called sum!\n");
 }
 else
 {
  JSValueRef arguments[] = { JSValueMakeNumber(g_context, 123.456 ), JSValueMakeNumber(g_context, 543.21 ) };
  JSValueRef result = JSObjectCallAsFunction(g_context, function, NULL, 2, arguments, NULL);

  printf("resulting number: %f", JSValueToNumber(g_context, result, NULL) );

 }

 JSGlobalContextRelease( g_context );
 return 0;
}

Other resources:
2 JavaScriptCore samples from Apple (that I've found):
JSPong
JSInterpreter