HitTestPenData
2.0
Determines if
a given point lies on or near the pen-down strokes contained in an HPENDATA
object.
int HitTestPenData( HPENDATA hpndt,
LPPOINT lppt, UINT dThresh, UINT FAR* lpiStrk,
UINT FAR* lpiPnt )
Parameters
hpndt
Handle to the
HPENDATA object. HitTestPenData does not alter the data in the HPENDATA
object.
lppt
Address of a POINT structure containing the
point to test.
dThresh
Threshold
around the point given in lppt. The point lies at the center of a square
with sides of length dThresh. If HitTestPenData finds a point in
the HPENDATA object that lies in the square, it indicates a hit. dThresh
must have the same scaling units as the points in the HPENDATA or the
result will not be correct. If dThresh is 0, HitTestPenData
assumes a default threshold value of 3.
lpiStrk
Stroke index
from which to begin testing. After HitTestPenData returns from a
successful test, the variable that lpiStrk points to contains the index
of the hit stroke.
lpiPnt
Point index
from which to begin testing. After HitTestPenData returns from a
successful test, the variable that lpiPnt points to contains the index
of the hit point in the stroke indicated by lpiStrk.
Return Value
Returns one
of the following if successful:
|
Constant |
Description |
|
PDR_HIT |
The point
hits (intersects) the pen data or falls within the provided threshold around
a particular point in the pen data as specified by the stroke and the point
indices. The stroke and point values are returned in lpiStrk and lpiPnt,
respectively. |
|
PDR_NOHIT |
The point
does not hit (intersect) the pen data nor does it fall within the provided
threshold around a particular point in the pen data as specified by the
stroke and the point indices. |
Otherwise,
the function returns one of the following negative values:
|
Constant |
Description |
|
PDR_COMPRESSED |
Pen data is
compressed. |
|
PDR_ERROR |
Parameter
or other unspecified error. |
|
PDR_MEMERR |
Memory
error. |
|
PDR_PNDTERR |
Invalid pen
data. |
|
PDR_PNTINDEXERR |
Invalid
point index. |
|
PDR_STRKINDEXERR |
Invalid
stroke index. |
|
PDR_VERSIONERR |
Could not
convert old pen data. |
Comments
HitTestPenData checks whether the point specified by lppt
falls within the threshold specified by dThresh around a point in the
pen data, depending on the zero-based starting stroke and point indices
specified by lpiStrk and lpiPnt. This function tests only down
strokes in the pen data. If lpiStrk is greater than the number of
strokes in the pen data, testing starts from the first stroke.
Similarly, if
lpiPnt is greater than the number of points in the stroke, testing
starts from the first point in that stroke. The first point in the first stroke
(from the specified indices) that meets the test condition is returned via lpiPnt
and lpiStrk, respectively.
In any case, HitTestPenData
accounts for the width of the ink trail. If the value given in dThresh
is less than the ink width, HitTestPenData ignores the specified value of
dThresh and instead uses the ink width as the threshold.
HitTestPenData does not consider pen-up strokes.