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- Fix for x11 zoom bug now works for linestrings with more than

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one line segment.
- Slight reduce CPU effort for intersection calculations


git-svn-id: http://svn.osgeo.org/qgis/trunk@3006 c8812cc2-4d05-0410-92ff-de0c093fc19c
This commit is contained in:
g_j_m 2005-03-22 21:19:48 +00:00
parent 840ed7b7bf
commit 81c7a7de03
3 changed files with 47 additions and 38 deletions
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63
src/qgsmaptopixel.cpp
View File

@ -76,22 +76,18 @@ QString QgsMapToPixel::showParameters()
}
void QgsMapToPixel::trimLine(const QgsPoint& from, const QgsPoint& to,
bool QgsMapToPixel::trimLine(const QgsPoint& from, const QgsPoint& to,
QgsPoint& tFrom, QgsPoint& tTo)
{
// The limits for X11 screen coordinates. Actual value is 32767, but
// we allow a little bit if space of rounding errors in the
// we allow a little bit of space for rounding errors in the
// calculations below.
static const int minX = -32760;
static const int maxX = 32760;
static const int minY = -32760;
static const int maxY = 32760;
static const double minX = -32760;
static const double maxX = 32760;
static const double minY = -32760;
static const double maxY = 32760;
static const double SMALL_NUM = 1e-6;
// One thing in our favour is that if this function is called we
// already know that the line intersects the region that is visible
// on the screen, so there's no need to check for that intersection.
// To determine the intersection between a line given by the points
// A and B, and the line given by the points C and D, calculate
//
@ -122,6 +118,13 @@ void QgsMapToPixel::trimLine(const QgsPoint& from, const QgsPoint& to,
//
// P = A + r*(B-A)
//
// Also do a check to see if the line segment is inside or outside
// the limits. If outside, return false to let the caller know that
// the shouldn't plot the line segment.
//
// This function has more than one exit point - as soon as the code
// determines that it has trimmed the lines appropriately, it exits,
// to reduce CPU effort.
// Once we have adjusted both the to and from points, there is no
// point in doing further checks, so return from the function
@ -136,13 +139,14 @@ void QgsMapToPixel::trimLine(const QgsPoint& from, const QgsPoint& to,
tTo = to;
// Check the top boundary
double r_n = (from.y() - minY) * (maxX - minX);
double d = - (to.y() - from.y()) * (maxX - minX);
double s_n = (from.y() - minY) * (to.x() - from.x())
- (from.x() - minX) * (to.y() - from.y());
double r_n = (from.y() - minY) * (maxX - minX);
double d = - (to.y() - from.y()) * (maxX - minX);
double s_n;
if (fabs(d) > SMALL_NUM && fabs(r_n) > SMALL_NUM != 0.0)
if (fabs(d) > SMALL_NUM && fabs(r_n) > SMALL_NUM)
{
s_n = (from.y() - minY) * (to.x() - from.x())
- (from.x() - minX) * (to.y() - from.y());
double r_nOverd = r_n / d;
double s_nOverd = s_n / d;
if (r_nOverd >= 0.0 && r_nOverd <= 1.0 &&
@ -168,11 +172,11 @@ void QgsMapToPixel::trimLine(const QgsPoint& from, const QgsPoint& to,
// the right border
r_n = -(from.x() - maxX) * (maxY - minY);
d = (to.x() - from.x()) * (maxY - minY);
s_n = (from.y() - minY) * (to.x() - from.x())
- (from.x() - maxX) * (to.y() - from.y());
if (fabs(d) > SMALL_NUM && fabs(r_n) > SMALL_NUM != 0.0)
if (fabs(d) > SMALL_NUM && fabs(r_n) > SMALL_NUM)
{
s_n = (from.y() - minY) * (to.x() - from.x())
- (from.x() - maxX) * (to.y() - from.y());
double r_nOverd = r_n / d;
double s_nOverd = s_n / d;
if (r_nOverd >= 0.0 && r_nOverd <= 1.0 &&
@ -197,16 +201,16 @@ void QgsMapToPixel::trimLine(const QgsPoint& from, const QgsPoint& to,
// Done both ends of the line, so leave.
if (toDone && fromDone)
return;
return true;
// the left border
r_n = - (from.x() - minX) * (maxY - minY);
d = (to.x() - from.x()) * (maxY - minY);
s_n = (from.y() - minY) * (to.x() - from.x())
- (from.x() - minX) * (to.y() - from.y());
if (fabs(d) > SMALL_NUM && fabs(r_n) > SMALL_NUM != 0.0)
if (fabs(d) > SMALL_NUM && fabs(r_n) > SMALL_NUM)
{
s_n = (from.y() - minY) * (to.x() - from.x())
- (from.x() - minX) * (to.y() - from.y());
double r_nOverd = r_n / d;
double s_nOverd = s_n / d;
if (r_nOverd >= 0.0 && r_nOverd <= 1.0 &&
@ -231,16 +235,16 @@ void QgsMapToPixel::trimLine(const QgsPoint& from, const QgsPoint& to,
// Done both ends of the line, so leave.
if (toDone && fromDone)
return;
return true;
// the bottom border
r_n = (from.y() - maxY) * (maxX - minX);
d = - (to.y() - from.y()) * (maxX - minX);
s_n = (from.y() - maxY) * (to.x() - from.x())
- (from.x() - minX) * (to.y() - from.y());
if (fabs(d) > SMALL_NUM && fabs(r_n) > SMALL_NUM != 0.0)
if (fabs(d) > SMALL_NUM && fabs(r_n) > SMALL_NUM)
{
s_n = (from.y() - maxY) * (to.x() - from.x())
- (from.x() - minX) * (to.y() - from.y());
double r_nOverd = r_n/d;
double s_nOverd = s_n/d;
if (r_nOverd >= 0.0 && r_nOverd <= 1.0 &&
@ -262,6 +266,9 @@ void QgsMapToPixel::trimLine(const QgsPoint& from, const QgsPoint& to,
}
}
}
// If the line hasn't been trimmed yet, it is entirely outside the
// boundary, so tell the calling code.
return false;
}
else
{
@ -269,11 +276,13 @@ void QgsMapToPixel::trimLine(const QgsPoint& from, const QgsPoint& to,
tFrom = from;
tTo = to;
}
/*
// Too verbose for QGISDEBUG, but handy sometimes.
/*
std::cerr << "Point 1 trimmed from " << from.x() << ", " << from.y()
<< " to " << tFrom.x() << ", " << tFrom.y() << '\n'
<< "Point 2 trimmed from " << to.x() << ", " << to.y()
<< " to " << tTo.x() << ", " << tTo.y() << "\n\n";
*/
return true;
}

2
src/qgsmaptopixel.h
View File

@ -85,7 +85,7 @@ class QgsMapToPixel{
//! String representation of the parameters used in the transform
QString showParameters();
static void trimLine(const QgsPoint& from, const QgsPoint& to,
static bool trimLine(const QgsPoint& from, const QgsPoint& to,
QgsPoint& tFrom, QgsPoint& tTo);
private:
double mapUnitsPerPixel;

20
src/qgsvectorlayer.cpp
View File

@ -2306,11 +2306,11 @@ void QgsVectorLayer::drawFeature(QPainter* p, QgsFeature* fet, QgsMapToPixel * t
ptFrom = ptTo;
else
{
QgsMapToPixel::trimLine(ptFrom, ptTo, trimmedFrom, trimmedTo);
p->drawLine(static_cast<int>(trimmedFrom.x()),
static_cast<int>(trimmedFrom.y()),
static_cast<int>(trimmedTo.x()),
static_cast<int>(trimmedTo.y()));
if (QgsMapToPixel::trimLine(ptFrom, ptTo, trimmedFrom, trimmedTo))
p->drawLine(static_cast<int>(trimmedFrom.x()),
static_cast<int>(trimmedFrom.y()),
static_cast<int>(trimmedTo.x()),
static_cast<int>(trimmedTo.y()));
ptFrom = ptTo;
}
}
@ -2365,11 +2365,11 @@ void QgsVectorLayer::drawFeature(QPainter* p, QgsFeature* fet, QgsMapToPixel * t
ptFrom = ptTo;
else
{
QgsMapToPixel::trimLine(ptFrom, ptTo, trimmedFrom, trimmedTo);
p->drawLine(static_cast<int>(trimmedFrom.x()),
static_cast<int>(trimmedFrom.y()),
static_cast<int>(trimmedTo.x()),
static_cast<int>(trimmedTo.y()));
if (QgsMapToPixel::trimLine(ptFrom, ptTo, trimmedFrom, trimmedTo))
p->drawLine(static_cast<int>(trimmedFrom.x()),
static_cast<int>(trimmedFrom.y()),
static_cast<int>(trimmedTo.x()),
static_cast<int>(trimmedTo.y()));
ptFrom = ptTo;
}
}