Software » Campo » libocelli

As long as the touch is pressed, the coordinates are read out periodically and an event is emited.

There is no need to send move-events to widgets when the coordinates did not change.
There can be an threshold implemented to filter out jittering between two pixels.

An more rocket-science would be to calculate the actual distance. An overkill whenn we just want to filter 1 pixel distance.
But function can be prepared in "OPoint".

int findSqrtInt(int x)
{
    // for 0 and 1, the square roots are themselves
    if (x < 2)
        return x;

    // considering the equation values
    int y = x;
    int z = (y + (x / y)) / 2;

    // as we want to get upto 5 decimal digits, the absolute
    // difference should not exceed 0.00001
    while (abs(y - z) >= 1) {
        y = z;
        z = (y + (x / y)) / 2;
    }
    return z;
}

int main(int argc, char *argv[])
{
    printf("Distance: %d\n", (int)findSqrtInt( 4*4 + 4*4 ));
    printf("Distance: %d\n", (int)findSqrtInt( 4*4 + 0 ));
}