CDC::Arc

Статья
10/16/2008

Draws an elliptical arc.

BOOL Arc(
   int x1,
   int y1,
   int x2,
   int y2,
   int x3,
   int y3,
   int x4,
   int y4 
);
BOOL Arc(
   LPCRECT lpRect,
   POINT ptStart,
   POINT ptEnd 
);

Параметры

x1
Specifies the x-coordinate of the upper-left corner of the bounding rectangle (in logical units).
y1
Specifies the y-coordinate of the upper-left corner of the bounding rectangle (in logical units).
x2
Specifies the x-coordinate of the lower-right corner of the bounding rectangle (in logical units).
y2
Specifies the y-coordinate of the lower-right corner of the bounding rectangle (in logical units).
x3
Specifies the x-coordinate of the point that defines the arc's starting point (in logical units). This point does not have to lie exactly on the arc.
y3
Specifies the y-coordinate of the point that defines the arc's starting point (in logical units). This point does not have to lie exactly on the arc.
x4
Specifies the x-coordinate of the point that defines the arc's endpoint (in logical units). This point does not have to lie exactly on the arc.
y4
Specifies the y-coordinate of the point that defines the arc's endpoint (in logical units). This point does not have to lie exactly on the arc.
lpRect
Specifies the bounding rectangle (in logical units). You can pass either an LPRECT or a CRect object for this parameter.
ptStart
Specifies the x- and y-coordinates of the point that defines the arc's starting point (in logical units). This point does not have to lie exactly on the arc. You can pass either a POINT structure or a CPoint object for this parameter.
ptEnd
Specifies the x- and y-coordinates of the point that defines the arc's ending point (in logical units). This point does not have to lie exactly on the arc. You can pass either a POINT structure or a CPoint object for this parameter.

Возвращаемое значение

Nonzero if the function is successful; otherwise 0.

Заметки

The arc drawn by using the function is a segment of the ellipse defined by the specified bounding rectangle.

The actual starting point of the arc is the point at which a ray drawn from the center of the bounding rectangle through the specified starting point intersects the ellipse. The actual ending point of the arc is the point at which a ray drawn from the center of the bounding rectangle through the specified ending point intersects the ellipse. The arc is drawn in a counterclockwise direction. Since an arc is not a closed figure, it is not filled. Both the width and height of the rectangle must be greater than 2 units and less than 32,767 units.

Пример

void CDCView::DrawArc(CDC* pDC)
{
   // Fill the client area with a thin circle. The circle's
   // interior is not filled. The circle's perimeter is
   // blue from 6 o'clock to 3 o'clock and red from 3
   // o'clock to 6 o'clock.

   // Get the client area.
   CRect rectClient;
   GetClientRect(rectClient);

   // Make a couple of pens.
   CPen penBlue;
   CPen penRed;
   CPen* pOldPen;

   penBlue.CreatePen(PS_SOLID | PS_COSMETIC, 1, RGB(0, 0, 255));
   penRed.CreatePen(PS_SOLID | PS_COSMETIC, 1, RGB(255, 0, 0));

   // Draw from 3 o'clock to 6 o'clock, counterclockwise,
   // in a blue pen.

   pOldPen = pDC->SelectObject(&penBlue);

   pDC->Arc(rectClient,
      CPoint(rectClient.right, rectClient.CenterPoint().y),
      CPoint(rectClient.CenterPoint().x, rectClient.right));

   // Draw from 6 o'clock to 3 o'clock, counterclockwise,
   // in a red pen.
   pDC->SelectObject(&penRed);

   // Keep the same parameters, but reverse start
   // and end points.
   pDC->Arc(rectClient,
      CPoint(rectClient.CenterPoint().x, rectClient.right),
      CPoint(rectClient.right, rectClient.CenterPoint().y));

   // Restore the previous pen.
   pDC->SelectObject(pOldPen);
}