MFC's Coordinate System?

[clow]

Hello,

I am drawing in a simple (square) MFC window. I realize that (0,0) starts in the upper left hand corner. I wanted to see how MFC handled drawing of angles, so I use this code:

double CompassDegreesToRadians(double compassDegrees)
{
	return((PI / 2.0f) - (compassDegrees * PI / 180.0f));
}

// Make pen
CPen penRed;
penRed.CreatePen(PS_SOLID | PS_COSMETIC, 1, RGB(255, 0, 0));

// Test Angles
CRect rectClient;
GetClientRect(rectClient);
float angle1 = 0;
int radius = rectClient.CenterPoint().x;
int x1 = radius * cos(CompassDegreesToRadians(angle1));
int y1 = radius * sin(CompassDegreesToRadians(angle1));
dc.MoveTo(rectClient.CenterPoint());
dc.LineTo(x1, y1);

Using this code, and changing the value of angle1 to these values (0, 90, 180, 270) I think MFC uses the coordinate system:

             180 -y
              |
              |
  -x 270---------------- 90 +x
              |
              |
              0 +y

This seems like a strange coordinate system to use. Am I doing something wrong? If this is correct, how can I convert my calculations to this coordinate system? (compass degrees):

               0 +y
               |
               |
  -x 270---------------- 90 +x
               |
               |
              180 -y

[VladimirF]

If you do not like this coordinate system, change your mapping mode from MM_TEXT to something like MM_HIMETRIC (or MM_HIENGLISH).

[clow]

Hello,

Yeah I saw those functions, and tried MM_LOENGLISH, but when I did that, nothing appeared on the screen. How would I calculate the coordinate system transform by normal C++ code between the two systems I listed above?

Thanks!

[Igor Vartanov]

Or just have resultant y1 coordinate multiplied by -1.

[VladimirF]

...tried MM_LOENGLISH, but when I did that, nothing appeared on the screen.

With those mapping modes, your (0,0) point is in the LOWER-LEFT corner of the window, X grows to the right and Y - up.