Simple Text Rotation

Introduction

I am working on a kind of CAD-Software and needed a function that was able to rotate text around its center inside a rectangle. Because Windows only provides text rotation around the left-bottom corner of the specified text, I had a problem. I was searching through websites for this piece of code, but I didn't find anything. So I tried it on my own, and this is the code I am using in my program.

First, create a CFont with the angle of rotation specified in nEscapement. Let your DC select this font and call the following function:

#include <cmath>
 
// pDC : pointer to your device-context
// str : the text
// rect: the rectangle
// nOptions: can be a combination of ETO_CLIPPED and ETO_OPAQUE
// (see documentation of ExtTextOut for more details)
void DrawRotatedText(CDC* pDC, const CString str, CRect rect, 
                     double angle, UINT nOptions = 0)
{
   // convert angle to radian
   double pi = 3.141592654;
   double radian = pi * 2 / 360 * angle;
 
   // get the center of a not-rotated text
   CSize TextSize = pDC->GetTextExtent(str);
   CPoint center;
   center.x = TextSize.cx / 2;
   center.y = TextSize.cy / 2;
 
   // now calculate the center of the rotated text
   CPoint rcenter;
   rcenter.x = long(cos(radian) * center.x - sin(radian) * center.y);
   rcenter.y = long(sin(radian) * center.x + cos(radian) * center.y);
 
   // finally draw the text and move it to the center of the rectangle
   pDC->SetTextAlign(TA_BASELINE);
   pDC->SetBkMode(TRANSPARENT);
   pDC->ExtTextOut(rect.left + rect.Width() / 2 - rcenter.x, 
                   rect.top + rect.Height() / 2 + rcenter.y,
                   nOptions, rect, str, NULL);
}

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