Q125693: HOWTO: AngleArc in Windows 3.1, Win32s, and Windows 95
Article: Q125693
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:1.3,3.1,95; winnt:
Operating System(s):
Keyword(s): kbOSWin2000 kbSDKWin32 kbOSWin95 kbDSupport
Last Modified: 11-MAY-2001
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The information in this article applies to:
- Microsoft Windows Software Development Kit (SDK) 3.1
- Microsoft Win32 Application Programming Interface (API), used with:
- Microsoft Win32s version 1.3
- Microsoft Windows 2000 Advanced Server
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SUMMARY
=======
In Windows version 3.1, Win32s, and Windows 95, you may want to use the
functionality provided by the Win32 API AngleArc(). AngleArc() is only supported
on Windows NT.
MORE INFORMATION
================
The AngleArc() function draws a line segment and an arc. The line segment is
drawn from the current position to the beginning of the arc. The arc is drawn
along the perimeter of a circle with the given radius and center. The length of
the arc is defined by the given start and sweep angles. The starting point of
the sweep is determined by measuring counterclockwise from the x-axis of the
circle by the number of degrees in the start angle. The ending point is
similarly located by measuring counterclockwise from the starting point by the
number of degrees in the sweep angle.
The code below provides two possible ways of getting functionality similar to
that of the AngleArc() function. While both of these methods will work on any
Windows platform, the second (AngleArc2) will be substantially faster due to the
fact that it uses the Arc() function to draw the sweep rather than calculating
each of the segments on the perimeter of the arc.
NOTE: One limitation of the second method is that if the sweep angle is greater
than 360 degrees, the arc will not be swept multiple times. In most cases this
will not be a problem but in certain cases (constructing paths, for example)
this can be a problem.
Sample Code #1
--------------
BOOL AngleArc1(HDC hdc, int X, int Y, DWORD dwRadius,
float fStartDegrees, float fSweepDegrees)
{
float fCurrentAngle; // Current angle in radians
float fStepAngle = 0.03f; // The sweep increment value in radians
float fStartRadians; // Start angle in radians
float fEndRadians; // End angle in radians
int ix, iy; // Current point on arc
float fTwoPi = 2.0f * 3.141592f;
/* Get the starting and ending angle in radians */
if (fSweepDegrees > 0.0f) {
fStartRadians = ((fStartDegrees / 360.0f) * fTwoPi);
fEndRadians = (((fStartDegrees + fSweepDegrees) / 360.0f) *
fTwoPi);
} else {
fStartRadians = (((fStartDegrees + fSweepDegrees) / 360.0f) *
fTwoPi);
fEndRadians = ((fStartDegrees / 360.0f) * fTwoPi);
}
/* Calculate the starting point for the sweep via */
/* polar -> cartesian conversion */
ix = X + (int)((float)dwRadius * (float)cos(fStartRadians));
iy = Y - (int)((float)dwRadius * (float)sin(fStartRadians));
/* Draw a line to the starting point */
LineTo(hdc, ix, iy);
/* Calculate and draw the sweep */
for (fCurrentAngle = fStartRadians;
fCurrentAngle <= fEndRadians;
fCurrentAngle += fStepAngle) {
/* Calculate the current point in the sweep via */
/* polar -> cartesian conversion */
ix = X + (int)((float)dwRadius * (float)cos(fCurrentAngle));
iy = Y - (int)((float)dwRadius * (float)sin(fCurrentAngle));
/* Draw a line segment to current point */
LineTo(hdc, ix, iy);
}
return TRUE;
}
Sample Code 2
-------------
BOOL AngleArc2(HDC hdc, int X, int Y, DWORD dwRadius,
float fStartDegrees, float fSweepDegrees)
{
int iXStart, iYStart; // End point of starting radial line.
int iXEnd, iYEnd; // End point of ending radial line.
float fStartRadians; // Start angle in radians.
float fEndRadians; // End angle in radians.
BOOL bResult; // Function result.
float fTwoPi = 2.0f * 3.141592f;
/* Get the starting and ending angle in radians. */
if (fSweepDegrees > 0.0f) {
fStartRadians = ((fStartDegrees / 360.0f) * fTwoPi);
fEndRadians = (((fStartDegrees + fSweepDegrees) / 360.0f) * fTwoPi);
} else {
fStartRadians = (((fStartDegrees + fSweepDegrees) / 360.0f) *
fTwoPi);
fEndRadians = ((fStartDegrees / 360.0f) * fTwoPi);
}
/* Calculate a point on the starting radial line via */
/* polar -> cartesian conversion. */
iXStart = X + (int)((float)dwRadius * (float)cos(fStartRadians));
iYStart = Y - (int)((float)dwRadius * (float)sin(fStartRadians));
/* Calculate a point on the ending radial line via */
/* polar -> cartesian conversion. */
iXEnd = X + (int)((float)dwRadius * (float)cos(fEndRadians));
iYEnd = Y - (int)((float)dwRadius * (float)sin(fEndRadians));
/* Draw a line to the starting point. */
if (fSweepDegrees > 0.0f)
LineTo(hdc, iXStart, iYStart);
else
LineTo(hdc, iXEnd, iYEnd);
/* Draw the arc. */
bResult = Arc(hdc, X - dwRadius, Y - dwRadius,
X + dwRadius, Y + dwRadius,
iXStart, iYStart,
iXEnd, iYEnd);
/* Move to the ending point. Arc() will not do this and ArcTo() */
/* will not work on Win32s or Win16. */
if (fSweepDegrees < 0.0f)
MoveToEx(hdc, iXStart, iYStart, NULL);
else
MoveToEx(hdc, iXEnd, iYEnd, NULL);
return bResult;
}
Additional query words:
======================================================================
Keywords : kbOSWin2000 kbSDKWin32 kbOSWin95 kbDSupport
Technology : kbAudDeveloper kbSDKSearch kbWin32sSearch kbWin32API kbWinSDKSearch
Version : WINDOWS:1.3,3.1,95; winnt:
Issue type : kbhowto
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