Enlarge Touch area of an asset/sprite

Dikkesnoek · July 2012

Hello,

Regarding my previous question (Sprites with random text), is it possible like in Xcode/Cocoa
to enlarge the touch area of a sprite? I have a sprite, for example 80x80 px and want a touch
area of 100x100 px (10 pixels extra around the sprite).

Also can you always use onMouse events instead of onTouches? They both work on the simulator.

Thanks,

Marc

Mells · July 2012

Hi Marc,

I'm not sure if what you ask is available.
But an alternative way would be to add a bigger child (touch area) to your sprite (text container), that would be responsible of event listeners (like a "bounding" or "collision" box).
When this touch area detects an event, an action is triggered on its parent (getParent()).

techdojo · July 2012

Sorry @Mells - actually it's easy

.

When you add a touch listener to a sprite, ALL sprites with touch listeners receive all the events (unless one calls the event.stopPropagation() function), so all you have to do is instead of calling Sprite:testHitPoint() just call Sprite:getBounds() which returns the screen position and then adjust the size of the bounds and do the in box comparison yourself. It's exactly what I do when I press a button - I have an "extended" area around the sprite so you can slightly move off without loosing a potential press.

eg.

function Object:touchListener(event)
    local x,y,w,h = self:getBounds(stage)
    x = x - extend
    y = y - extend
    w = w + extend + extend
    h = h + extend + extend
 
    if event.x < x or event.x > (x+w) then return end
    if event.y < y or event.y > (y+h) then return end
 
    -- hit this object...
 
    event.stopPropagation()
end

Mells · July 2012

@techdojo ha, at least I've tried

Dikkesnoek · July 2012

Thanks again. First I tried to enlarge the sprite with some extra transparent space.
But this will also reduce the available space in my sprite sheet.

Regards,

Marc

ar2rsawseen · July 2012

Hmm, how about

function Object:touchListener(event)
    --scale object
    self:setScale(2) --or whatever scale you want
    if self:hitTestPoint(event.x, event.y) then
        --you've got a touch event
    end
    --scale back
    self:setScale(1)
    event.stopPropagation()
end

Scouser · July 2012

@ar2rsawseen: That would only work if the object's anchor point was centred. As you currently can't set the anchor point for shapes or text areas then this method wouldn't work.

ar2rsawseen · July 2012

@Scouser, yes you're right. It was just a spontaneous idea

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