Rainbowduino drawLine issue with 8x8 matrix

Hello. I have a new Rainbowduino connected to an 8x8 RGB LED matrix. I’ve been experimenting with the sample code for drawing shapes, letters, and numbers on the matrix. Generally I have been able to make minor adjustments to the code and be successful with what I want to do, such as spelling out my name.

However, I’m having an issue with the drawLine function. One line of sample code is this:

Rb.drawLine(0, 0, 7, 7, 0x00FF00);

This does behave as expected. It displays a green line diagonally from the top left of the matrix to the bottom right. So, I wanted simply to blank that out and display a line diagonally from the top right to the bottom left (i.e., the other diagonal direction). However, when I try "Rb.drawLine(7, 0, 0, 7, 0x00FF00); ", it displays a horizontal line in the bottom row. When I try “Rb.drawLine(0, 7, 7, 0, 0x00FF00);”, it displays a vertical line at the far right.

It seems to me that one or both of these should work. Any suggestions?

Seems to me the opposite diagonal would be:

Rb.drawLine(7, 7, 0, 0, 0x00FF00);

At least worth a try…

I am seeing the same results you did…

7,0,0,7 paints a horizontal line
0,7,7,0 paints a vertical line

and what I suggested: 7,7,0,0
paints a single dot at 7,7 and locks up - will not continue from that point forward in the code.

Seems to be a bug in the function somewhere… maybe it affects all diagonals in that direction.