Difference between revisions of "GrePartialArc"
(Created page with "GrePartialArc draws a straight line from the current position to the starting point of a partial arc and draws the specified partial arc. This function can be hooked by the ...") 
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Latest revision as of 03:05, 16 January 2020
GrePartialArc draws a straight line from the current position to the starting point of a partial arc and draws the specified partial arc.
This function can be hooked by the presentation driver.
 Simulation support
 This function is simulated by a handling routine in the graphics engine.
Contents
Syntax
GrePartialArc(hdc, pptlCenter, fxMultiplier, fxStart, fxSweep, pInstance, lFunction);
Parameters
 hdc (HDC)  input
 Device context handle.
 pptlCenter (PPOINTL)  input
 Pointer to (X,Y) coordinates for center of arc.
 If COM_TRANSFORM is not set, the function expects the center of the arc position to be in screen coordinates.
 fxMultiplier (FIXED)  input
 Multiplier.
 This parameter defines the size of the full arc in relation to an arc drawn with the current arc parameters. The multiplier is a fixedpoint value. The highorder WORD contains the integer portion; the loworder WORD contains the fractional portion. A value of 64KB gives a multiplier of 1. There is an implementation limit of 255 for this value, which must not be negative.
 fxStart (FIXED)  input
 Start angle.
 Start angle that defines the starting point on the curve. Start and sweep angles are measured counterclockwise from the Xaxis at the center of the arc before the arc parameters are applied. If the current arc parameters do not specify a circle, the angles are skewed to the same degree that the full arc is a skewed circle.
 The angles are specified as doubleword values in fixedpoint format. The highorder WORD contains the integer portion; the loworder WORD contains the fractional portion. A value of 6553 gives an angle of 1°. Both angles must be positive. Whether the arc is drawn in a clockwise or counterclockwise direction is determined by the arc parameters. An angle greater than 360° is also valid. In this case, after the initial line, a full arc is drawn followed by a partial arc of (lSweep MOD 360)°. See also the function "GpiPartialArc" in the Presentation Manager Programming Reference.
 fxSweep (FIXED)  input
 Sweep angle.
 Sweep angle that defines the extent of the curve to be drawn. Start and sweep angles are measured counterclockwise from the Xaxis at the center of the arc before the arc parameters are applied. If the current arc parameters do not specify a circle, the angles are skewed to the same degree that the full arc is a skewed circle.
 The angles are specified as doubleword values in fixedpoint format. The highorder WORD contains the integer portion; the loworder WORD contains the fractional portion. A value of 6553 gives an angle of 1°. Both angles must be positive. Whether the arc is drawn in a clockwise or counterclockwise direction is determined by the arc parameters. An angle greater than 360° is also valid. In this case, after the initial line, a full arc is drawn followed by a partial arc of (lSweep MOD 360)°. See also the function "GpiPartialArc" in the Presentation Manager Programming Reference.
 pInstance (PVOID)  input
 Pointer to instance data.
 lFunction (ULONG)  input
 Highorder WORD=flags; loworder WORD=NGrePartialArc.
Returns
 rc (LONG)  returns
 Return codes.
 This function returns an integer (cHits) indicating, where appropriate, whether correlation hits were detected:
 GPI_OK Successful
 GPI_HITS Successful with correlate hit (returned by display drivers when the correlate flag is ON, and a hit is detected)
 GPI_ERROR Error
 Possible Errors Detected: When an error is detected, the handling routine must call WinSetErrorInfo to post the condition. Error codes for conditions that the handling routine is expected to check include:
 PMERR_BASE_ERROR
 PMERR_BITMAP_NOT_SELECTED
 PMERR_COORDINATE_OVERFLOW
 PMERR_DEV_FUNC_NOT_INSTALLED
 PMERR_HDC_BUSY
 PMERR_INV_ANGLE_PARM
 PMERR_INV_COLOR_DATA
 PMERR_INV_COLOR_INDEX
 PMERR_INV_COORD_SPACE
 PMERR_INV_HDC
 PMERR_INV_IN_AREA
 PMERR_INV_IN_PATH
 PMERR_INV_LENGTH_OR_COUNT
 PMERR_INV_MULTIPLIER
 PMERR_INV_PICK_APERTURE_POSN
 PMERR_INV_RECT
 PMERR_PATH_LIMIT_EXCEEDED
 PMERR_PATH_UNKNOWN
 Refer to the "Error Explanations" section in the Presentation Manager Programming Reference for further explanation.
Sample
#define INCL_GRE_ARCS #include <os2.h> HDC hdc; /* Device context handle. */ PPOINTL pptlCenter; /* Pointer to (X,Y) coordinates for center of arc. */ FIXED fxMultiplier; /* Multiplier. */ FIXED fxStart; /* Start angle. */ FIXED fxSweep; /* Sweep angle. */ PVOID pInstance; /* Pointer to instance data. */ ULONG lFunction; /* Highorder WORD=flags; loworder WORD=NGrePartialArc. */ LONG rc; /* Return codes. */ rc = GrePartialArc(hdc, pptlCenter, fxMultiplier, fxStart, fxSweep, pInstance, lFunction);
Remarks
Upon completion, the current (X,Y) position is the end of the partial arc. The dimensions of the full arc are defined as a multiplier, which is applied to the current arc parameters. The partial arc that is drawn is the section of the full arc that is enclosed by the specified start and sweep angles.
If GrePartialArc is used within a path or an area definition to continue a figure following a GreBoxxxx or GreFullArcxxx function, the error PMERR_INV_NESTED_FIGURES is posted. This error occurs because GreBoxxxx and GreFullArcxxx generate a closed figure within an area or path definition.