Just using our programming skills to produce static "drawings" is not satisfying. Luckily we have a couple small functions which allow for user interaction - in other words, we'll be able to write mini-games soon!
Our two new friends are:
These two should be used together, wrapped in the endless while loop (you may allow it to exit after some
condition though) - so that program repeatedly checks for new click coordinates from user (and may do some
action if click happened).
Their definitions are like this:
graph.click() -- returns two (!) values, for X and Y
graph.delay(millis)
The first function should be used in assignment with two variables on the left (otherwise we only give single
X value). The second takes integer parameter - milliseconds to wait (i.e. 1000 is for 1 second).
Let's try the small example which draws circles whenever user clicks on the canvas.
graph.init()
c = 0 -- circles counter
while c < 10 do -- let's stop after 10 circles
x, y = graph.click()
if x >= 0 then -- negative value means there was no new click yet
graph.circle(x, y, 20 + c * 5)
c = c + 1
end
graph.delay(30)
end
As you may note from the comment or by experiment, graph.click() returns -1, -1 if there was no click since the
previous call to this function. This prevents program from crazily drawing zounds of circles at the same point.