Also fix a bug related to coordinate that preventing margin color to be correctly drawn:
opengl uses a coordinate system with the origin at lower-left corner and positive y-axis up, while other parts uses a coordinate system with the origin at upper-left corner and positive y-axis down.
Also fix a bug related to coordinate that preventing margin color to be correctly drawn:
opengl uses a coordinate system with the origin at lower-left corner and positive y-axis up, while other parts uses a coordinate system with the origin at upper-left corner and positive y-axis down.