Quote:Original post by DevFred
Could you test if the following, simpler code also works?

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Quote:Original post by Zahlman
First, note the repetitiveness of the original code. The repetition comes from treating one iteration of each outer loop as somehow "special". Also, we can fix the bounds of the loops. All we want is for each value to range from 0 to 255, inclusive. That means we logically should start counting from 0, while < 256 (notice, one more than the last value, because of the strict inequality). Then, the colour values will be 255 - whatever: 255 - 0 = 255, and 255 - 255 = 0, so this will produce the whole valid range of values - from 255 to 0, inclusive.

private void button1_Click(object sender, EventArgs e){    while (Visible)    {        for (int c = 0; c < 255 && Visible; c++)        {            for (int a = 0; a < 255 && Visible; a++)            {                for (int b = 0; b < 255 && Visible; b++)                {                    Application.DoEvents();                    System.Threading.Thread.Sleep(3);                    this.BackColor = Color.FromArgb(255 - c, 255 - a, 255 - b);                }            }        }    }}

Next, we note that a simple 'return' can eliminate the repeated checks for 'Visible'ity:

private void button1_Click(object sender, EventArgs e){    while (true)    {        for (int c = 0; c < 255; c++)        {            for (int a = 0; a < 255; a++)            {                for (int b = 0; b < 255; b++)                {                    Application.DoEvents();                    System.Threading.Thread.Sleep(3);                    this.BackColor = Color.FromArgb(255 - c, 255 - a, 255 - b);                    if (!Visible) return;                }            }        }    }}

Now, we note that Color.FromArgb() is also overloaded to take one int argument, a single "packed" colour value. We are in effect "counting down" through all the possible colours: in the ARGB representation, the blue byte is least significant. The largest colour value we want to use is the one corresponding to a = 0, r = 255, g = 255, b = 255. If you look at that as a base -256 number, you can see what it equals: the same as FFFFFF in hex (since two hex digits correspond exactly to one base-256 digit). The smallest is zero, of course.

private void button1_Click(object sender, EventArgs e){    while (true)    {        for (int colour = 0xffffff; colour >= 0; --colour)        {            Application.DoEvents();            System.Threading.Thread.Sleep(3);            this.BackColor = Color.FromArgb(colour);            if (!Visible) return;        }    }}

Finally, we can set up the colour to loop around indefinitely, thus making the while loop redundant. We can do that by not having a loop-exit condition in the for loop, and using some modulus arithmetic in the per-loop change. However, now we can simply move our explicit loop exit (the Visible check) back into the for-initializer, since there is only one place we want to check. That's awkward, though: the loop exit has nothing to do with our "counter" variable, so it's a highly nonstandard way to use the for loop construct. Instead, we just use a while loop, initializing the "counter" outside.

private void button1_Click(object sender, EventArgs e){    int colour = 0xffffff;    while (Visible)    {        Application.DoEvents();        System.Threading.Thread.Sleep(3);        this.BackColor = Color.FromArgb(colour);        colour = (colour + 0xffffff) % 0x1000000); // or & 0xffffff, if you prefer    }}