[Classic] function with parameter

Development

6 years ago

Hi,

Beginner question: I've made a small function that slides in an image from the top of the screen. When I call it, I want to send the bitmap name as a parameter, but it doesn't work and displays nothing. I suspect it's because the string in the parameter is in the wrong format so it gets ignored in the function, but cannot find a way to get it to work. Can anyone see what's wrong?

function:

void slideIn(char myimg[])
{
   gb.display.drawBitmap(0,y,myimg);
   if (i <21)
   {
      i = ++i; 
      y = y + (easing[i]);
   }  
}

and then I call it this way:

slideIn("img1");

Sutchig

NEW 6 years ago

Hi,

drawBitmap needs a pointer to the bitmap array - not the name of that array (after compilation the name isnt there anymore) see https://gamebuino.com/academy/reference/graphics-drawbitmap for usage (works basically with legacy gamebuino too - except the meta stuff like yellow color ;))

exocet

NEW 6 years ago

Thanks for your answer. Concretely how do I send a pointer to the bitmap array to the function, not just the name of the array? I can't see anything different from what I'm doing on the reference page.

Sorunome

NEW 6 years ago

Try this:

void slideIn(uint8_t* myimg)
{
   gb.display.drawBitmap(0,y,myimg);
   if (i <21)
   {
      i = ++i; 
      y = y + (easing[i]);
   }  
}

and then

slideIn(img1);

The difference here is, that you don't pass a string "img1" to the function, but the pointer to the actual buffer itself. A string of a name of a variable is something totally different than a variable

1 reply

exocet

6 years ago

Thanks! I got it now. It works with the uint8_t* data type and it also works with byte, which I was using initially:

void slideIn(byte myimg[])
{
   gb.display.drawBitmap(0,y,myimg);
   if (i <21)
   {
      i = ++i; 
      y = y + (easing[i]);
   }  
}

and then:

slideIn(img1);

exocet

NEW 6 years ago

Sorunome

Thanks! I got it now. It works with the uint8_t* data type and it also works with byte, which I was using initially:

void slideIn(byte myimg[])
{
   gb.display.drawBitmap(0,y,myimg);
   if (i <21)
   {
      i = ++i; 
      y = y + (easing[i]);
   }  
}

and then:

slideIn(img1);