// start by creating an array the same size as the map (or a field in the map udt) . I'm assuming here the map is 32x32.

h = 24
w = 24
int pathing[h,w];

// create a doneflag to record when a search pass didn't do anthing. initialise to zero to make a first pass.
int doneflag = 0;

// set all elements to a large value, like 256.
for(xx=0; xx<w; xx++) {
  for(yy=0; yy<h; yy++) {
    pathing[xx,yy] = 256;
  }
}

// set the element where the player is to 0.
pathing[player.x/8, player.y/8] = 0;

// loop while there are still passes to do.
while (doneflag == 0) {

// set a doneflag to 1 to say we are done.
doneflag = 1;

// start a double loop through x and y.
for(xx=0; xx<w; xx++) {
  for(yy=0; yy<h; yy++) {


// if you find an element with value < 256 then look at four neighbours. if any of those is a floor tile, AND has value 256 then set it equal to value+1.

     if(pathing[xx,yy] < 256) {
       if(pathing[xx-1,yy] == 256 && ds_grid_get(global.mainGrid,xx,yy) = 0)  {pathing[xx-1,yy]=pathing[xx,yy]+1; doneflag=0;}
       if(pathing[xx+1,yy] == 256 && ds_grid_get(global.mainGrid,xx+1,yy) = 0) {pathing[xx+1,yy]=pathing[xx,yy]+1; doneflag=0;}
       if(pathing[xx,yy-1] == 256 && ds_grid_get(global.mainGrid,xx,yy-1) = 0) {pathing[xx,yy-1]=pathing[xx,yy]+1; doneflag=0;}
       if(pathing[xx,yy+1] == 256 && ds_grid_get(global.mainGrid,xx,yy+1) = 0) {pathing[xx,yy+1]=pathing[xx,yy]+1; doneflag=0;}
        }
// close the double loop
    }
}

//close while
}