Beginners Question

tguclu

Hi
I've started Sparrow couple of days ago. I have a very simple question - probably fundamentals -
Here is the thing.
I'm want to implement a basic game like PingPong just to get used to platform. As you know there are two rackets moving vertically back and forth in the pingpong game. When placing leftSide and rightSide racket I would like them to have a little gap from the borders.Lets say width to a racket (rectangular box) is 10 , so rackets will be 10px away from the edges. But I'm having trouble with placing rightSide racket.
Please see my code snippet below;

mBackground = [[SPImage alloc] initWithContentsOfFile:@"background.jpg"];
[_contents addChild:mBackground];

NSString *text = @"CLICK TO START";

CGRect screenRect = [[UIScreen mainScreen] bounds];
CGFloat screenWidth = screenRect.size.width;
CGFloat screenHeight = screenRect.size.height;

//loads the basket, positions in the middle of the ground,
//adds a touch listener and adds it as a child
leftSide = [[SPImage alloc] initWithContentsOfFile:@"left-hand.png"];
leftSide.pivotX = leftSide.width/2;
leftSide.pivotY = leftSide.height/2;
leftSide.x = leftSide.width;
leftSide.y = mBackground.height/2;
[leftSide addEventListener:@selector(onHandTouched:) atObject:self forType:SP_EVENT_TYPE_TOUCH];
[self addChild:leftSide];

//loads the basket, positions in the middle of the ground,
//adds a touch listener and adds it as a child
rightSide = [[SPImage alloc] initWithContentsOfFile:@"right-hand.png"];
rightSide.pivotX = rightSide.width/2;
rightSide.pivotY = rightSide.height/2;
rightSide.x = screenWidth - rightSide.width;
rightSide.y = mBackground.height/2;
[rightSide addEventListener:@selector(onHandTouched:) atObject:self forType:SP_EVENT_TYPE_TOUCH];
[self addChild:rightSide];

If I use

rightSide.x = mBackground.height - rightSide.width;

then racket is not displayed probably goes beyond border.
But screenWidth is working good. On the other hand if I change to other simulator device I get similar problems.

Do you have any idea how to overcome this problem ?

Daniel

The problem is that you set the pivot point to the center of the paddle! The pivot point is what you move around when you set the "x" and "y" properties.

So you move the pivot point (→ the center of the paddle) to the right side of the screen. This means that half of the paddle will be outside.

What you need to do is take the pivot point into account and move it to e.g.:

rightSide.x = screenWidth - rightSide.width / 2;

Does that help?

BTW, sorry for the late reply! 🙈

straydogstrut

I could be completely wrong - seriously out of touch - but I think there may be more to it than that (but your point about Pivots is also useful)

Tguclu said that the right paddle is completely offscreen so i'd be interested to know what the position values are returned by NSLog()

I think the screenWidth value is likely the culprit. From what i've read [[UIScreen mainScreen] bounds] will always report the size of the screen in portrait mode (for now). From his description it sounds like his game is landscape.

For example, here's the output for the Scaffold project in both orientations:

2014-08-25 16:04:17.577 Scaffold[3998:60b] new size: 320x568 (portrait)
2014-08-25 16:04:17.579 Scaffold[3998:60b] ScreenWidth: 320.000000
2014-08-25 16:04:17.579 Scaffold[3998:60b] ScreenHeight: 568.000000
2014-08-25 16:04:24.706 Scaffold[3998:60b] new size: 568x320 (landscape)
2014-08-25 16:04:24.708 Scaffold[3998:60b] ScreenWidth: 320.000000
2014-08-25 16:04:24.709 Scaffold[3998:60b] ScreenHeight: 568.000000

This is because [[UIScreen mainScreen] bounds] is not orientation-dependant. It always reports the original portrait mode even if an app starts in landscape. The work around is to get the bounds of the parent object. (Note that in iOS8 [[UIScreen mainScreen] bounds] is now orientation-dependent and returns the correct size depending on the orientation: View Controller Advancements in iOS8: UIScreen)

In our case, I think the Scaffold project already handles this really well:

int gameWidth = Sparrow.stage.width;
int gameHeight = Sparrow.stage.height;

There is even a call in the Resize event to handle an app that supports changes in orientation.

The output using the above is as follows:

2014-08-25 16:04:17.577 Scaffold[3998:60b] new size: 320x568 (portrait)
2014-08-25 16:04:17.577 Scaffold[3998:60b] gameWidth: 320
2014-08-25 16:04:17.577 Scaffold[3998:60b] gameHeight: 568
2014-08-25 16:04:24.706 Scaffold[3998:60b] new size: 568x320 (landscape)
2014-08-25 16:04:24.707 Scaffold[3998:60b] gameWidth: 568
2014-08-25 16:04:24.707 Scaffold[3998:60b] gameHeight: 320

Of course, I could be completely off track; in that case i'll crawl back under my rock.. 😕

Daniel

Ah, that's a good point! Indeed, that could be the other part of the puzzle. 🙂
Please let us know it that helps, tguclu!

Shilo

Right on straydogstrut, that was my first guess. You don't sound out of touch at all. Of course Daniel had useful info also!

I didn't even know iOS 8 finally made improvements to UIScreen bounds! I can only imagine how many apps it will break, I bet I will have to make some changes to lots of my apps also, thank you Apple.