[architektonas] / src / line.cpp

// line.cpp: Line object
//
// Part of the Architektonas Project
// (C) 2011 Underground Software
// See the README and GPLv3 files for licensing and warranty information
//
// JLH = James L. Hammons <jlhamm@acm.org>
//
// WHO  WHEN        WHAT
// ---  ----------  ------------------------------------------------------------
// JLH  03/22/2011  Created this file
// JLH  04/11/2011  Fixed attached dimensions to stay at correct length when
//                  "Fixed Length" button is down
// JLH  04/27/2011  Fixed attached dimension to stay a correct length when
//                  "Fixed Length" button is *not* down ;-)
// JLH  05/29/2011  Added (some) mouseover hints
//

#include "line.h"

#include <QtGui>
#include "dimension.h"
#include "painter.h"


Line::Line(Vector p1, Vector p2, Object * p/*= NULL*/): Object(p1, p), endpoint(p2),
        draggingLine(false), draggingHandle1(false), draggingHandle2(false), //needUpdate(false),
        length(Vector::Magnitude(p2, p1)), angle(Vector(endpoint - position).Unit()),
        hitPoint1(false), hitPoint2(false), hitLine(false)
{
}

Line::~Line()
{
        // If there are any attached Dimensions, we must set the attachment points
        // to NULL since they will no longer be valid.
        if (attachedDimension)
        {
                attachedDimension->SetPoint1(NULL);
                attachedDimension->SetPoint2(NULL);
        }
        // IT WOULD BE NICE to have any object points attached to this line automagically
        // connect to this dimension object at this point, instead of just becoming
        // detached.
}

/*virtual*/ void Line::Draw(Painter * painter)
{
        painter->SetPen(QPen(Qt::red, 2.0, Qt::DotLine));

        if ((state == OSSelected) || ((state == OSInactive) && hitPoint1))
                painter->DrawHandle(position);

        if ((state == OSSelected) || ((state == OSInactive) && hitPoint2))
                painter->DrawHandle(endpoint);

        if ((state == OSInactive) && !hitLine)
                painter->SetPen(QPen(Qt::black, 1.0, Qt::SolidLine));

        if (Object::fixedLength && (draggingHandle1 || draggingHandle2))
        {
                Vector point1 = (draggingHandle1 ? endpoint : position);
                Vector point2 = (draggingHandle1 ? position : endpoint);

                Vector current(point2 - point1);
                Vector v = current.Unit() * length;
                Vector v2 = point1 + v;
                painter->DrawLine((int)point1.x, (int)point1.y, (int)v2.x, (int)v2.y);

                if (current.Magnitude() > length)
                {
                        painter->SetPen(QPen(QColor(128, 0, 0), 1.0, Qt::DashLine));
                        painter->DrawLine((int)v2.x, (int)v2.y, (int)point2.x, (int)point2.y);
                }
        }
        else
                painter->DrawLine((int)position.x, (int)position.y, (int)endpoint.x, (int)endpoint.y);
}

/*virtual*/ Vector Line::Center(void)
{
        // Technically, this is the midpoint but who are we to quibble? :-)
        Vector v((position.x - endpoint.x) / 2.0, (position.y - endpoint.y) / 2.0);
        return endpoint + v;
}

/*virtual*/ bool Line::Collided(Vector point)
{
        // We can assume this, since this is a mouse down event here.
        objectWasDragged = false;
        HitTest(point);

/*
There's a small problem here with the implementation: You can have a dimension tied
to only one point while at the same time you can have a dimension sitting on this line.
Since there's only *one* dimPoint for each point, this can be problematic...

We solve this by allowing only *one* Dimension object to be attached to the Line,
Arc, etc. and by giving the Dimension object a pointer to our endpoints.

Problem still arises when we delete this object; The attached Dimension object will
then have bad pointers! What it *should* do is delete the object if and only if this
line is not attached to any other object. If it is, then one of those attachment
points should be sent to the dimension object (done for position & endpoint).

NOTE: The STL vector<T> *does not* take ownership of pointers, therefore is suitable
      for our purposes

Also: It would be nice to have a preview of the dimension being drawn, with a modifier
key to make it draw/show on the other side...

TODO: Make Dimension preview with modifier keys for showing on other side
*/
        // Is the dimension tool active? Let's use it:
        if (dimensionActive)
        {
                // User clicked on the line itself (endpoint checks should preceed this one):
                // (Priorities are taken care of in HitTest()...)
                if (hitLine)
                {
                        if (attachedDimension == NULL)
                        {
                                // How to get this object into the top level container???
/*
The real question is do we care. I think so, because if this isn't in the top
level container, it won't get drawn...
But we can fix that by making this object call any attached object's (like
a dimension only) Draw() function... :-/
*/
                                attachedDimension = new Dimension(&position, &endpoint, this);

                                if (parent != NULL)
                                        parent->Add(attachedDimension);
                        }
                        else
                        {
                                // If there's one already there, tell it to flip sides...
                                attachedDimension->FlipSides();
                        }

                        return true;
                }
        }


        if (state == OSInactive)
        {
//printf("Line: pp = %lf, length = %lf, distance = %lf\n", parameterizedPoint, lineSegment.Magnitude(), distance);
//printf("      v1.Magnitude = %lf, v2.Magnitude = %lf\n", v1.Magnitude(), v2.Magnitude());
//printf("      point = %lf,%lf,%lf; p1 = %lf,%lf,%lf; p2 = %lf,%lf,%lf\n", point.x, point.y, point.z, position.x, position.y, position.z, endpoint.x, endpoint.y, endpoint.z);
//printf("      \n", );
//How to translate this into pixels from Document space???
//Maybe we need to pass a scaling factor in here from the caller? That would make sense, as
//the caller knows about the zoom factor and all that good kinda crap
//I think what's needed is an Object class variable/method that can be changed by the TLC and
//called in derived classes to properly scale the location to the current zoom level. That *should* work.

// ALSO: Need to code a global (read: Object class) variable that tells use whether a modifier
//       key was pressed in addition to the mouse click, so we can do stuff like, say, hold
//       down CTRL and be able to do multiple selecting of objects (in that case, we would
//       keep the Object state from changing).
                if (hitPoint1)
                {
                        oldState = state;
                        state = OSSelected;
                        oldPoint = position; //maybe "position"?
                        draggingHandle1 = true;
                        return true;
                }
                else if (hitPoint2)
                {
                        oldState = state;
                        state = OSSelected;
                        oldPoint = endpoint; //maybe "position"?
                        draggingHandle2 = true;
                        return true;
                }
                else if (hitLine)
                {
                        oldState = state;
                        state = OSSelected;
                        oldPoint = point;
                        draggingLine = true;
                        return true;
                }
        }
        else if (state == OSSelected)
        {
                // Here we test for collision with handles as well! (SOON!) [I think it works...NOPE]
/*
Like so:
                if (v1.Magnitude() < 2.0) // Handle #1
                else if (v2.Magnitude() < 2.0) // Handle #2
*/
                if (hitLine)
                {
                        oldState = state;
//                      state = OSInactive;
                        oldPoint = point;
                        draggingLine = true;
                        return true;
                }
        }

        // If we got here, we clicked on nothing, so set the object to inactive.
        // (Once we can read key modifiers, we can override this to allow multiple selection.)
        state = OSInactive;
        return false;
}

/*virtual*/ void Line::PointerMoved(Vector point)
{
        // Hit test tells us what we hit (if anything) through boolean variables. It
        // also tells us whether or not the state changed.
        needUpdate = HitTest(point);

        objectWasDragged = (draggingLine | draggingHandle1 | draggingHandle2);

        if (objectWasDragged)
        {
                Vector delta = point - oldPoint;

                if (draggingHandle1 || draggingLine)
                        position += delta;

                if (draggingHandle2 || draggingLine)
                        endpoint += delta;

                oldPoint = point;
                needUpdate = true;
        }

/*
We can't count on any coupling between the dimension object and us, so how do we do this???
Also, there may be more than one Dimension object connected to a single endpoint!

Ugly ways to do it:
 - Keep track of the state of the connected dimension
 - Pass the Dimension the point that's being changed and the delta

More elegant ways:
 - Pass the point in a notification function (how?)
 - Pass the point as a reference to the class instance object (&endpoint). This way, the line
   doesn't have to care about keeping track of Dimensions connected to it. But still have to
   care about other connected entities (other Lines, Circles, Arcs, Splines, Texts, etc). I
   think I'd be OK with this.
   Since the Dimension has a pointer to our object, all we have to do is update our coordinates
   and the Dimension object will adjust itself on the next repaint. Problem solved, and we don't
   have to know anything about how many Dimensions are connected to us, or where! \o/
   The question then becomes, how do we do this kind of coupling???

We need to know about connected entities so that we can have them either move in expected ways
or constrain the movement of this Line object. This is how we will be a cut above all other CAD
software currently out there: the GUI will try to do the right thing, most of the time. :-)
*/
        if (needUpdate)
        {
// should only do this if "Fixed Length" is set... !!! FIX !!! [DONE]
                Vector point1 = (draggingHandle1 ? endpoint : position);
                Vector point2 = (draggingHandle1 ? position : endpoint);

#if 0
                Vector current(point2, point1);
                Vector v = current.Unit() * length;
                Vector v2 = point1 + v;

                //bleh
                if (!Object::fixedLength)
                        v2 = point2;
#endif

                if (Object::fixedAngle)
                {
                        // Here we calculate the component of the current vector along the fixed angle.
                        // A_compB = (A . Bu) * Bu
                        double magnitudeAlongB = Vector::Dot(Vector(point2 - point1), angle);
/*
Actually, this isn't quite right. What we want to do is look for the intersection along either
the horizontal line or vertical line that intersects from the current mouse position.
*/

                        if (draggingHandle1)
                                position = endpoint + (angle * magnitudeAlongB);

                        if (draggingHandle2)
                                endpoint = position + (angle * magnitudeAlongB);
                }
//              else
//                      v2 = point2;

//If we tell the dimension to flip sides, this is no longer a valid
//assumption. !!! FIX !!!
//Ideally, we should just send the point that's changing to the Dimension object
//and have it figure out which point needs to move... Or is it???
// Ideally, we shouldn't have to fuck around with this shit. We need to fix the rendering code
// so that we don't have to wait until the dragging is done to correct the position of the
// point in question, but we'd need another variable tho.
#if 0
                if (dimPoint1)
                        dimPoint1->SetPoint1(draggingHandle1 ? v2 : position);
                
                if (dimPoint2)
                        dimPoint2->SetPoint2(draggingHandle2 ? v2 : endpoint);
#endif
        }
}

/*virtual*/ void Line::PointerReleased(void)
{
        if (draggingHandle1 || draggingHandle2)
        {
                // Set the length (in case the global state was set to fixed (or not))
                if (Object::fixedLength)
                {
                        if (draggingHandle1)    // startpoint
                        {
                                Vector v = Vector(position - endpoint).Unit() * length;
                                position = endpoint + v;
                        }
                        else                                    // endpoint
                        {
//                              Vector v1 = endpoint - position;
                                Vector v = Vector(endpoint - position).Unit() * length;
                                endpoint = position + v;
                        }
                }
                else
                {
                        // Otherwise, we calculate the new length, just in case on the next move
                        // it turns out to have a fixed length. :-)
                        length = Vector(endpoint - position).Magnitude();
                }

                if (!Object::fixedAngle)
                {
                        // Calculate the new angle, just in case on the next move it turns out to
                        // be fixed. :-)
                        angle = Vector(endpoint - position).Unit();
                }
        }

        draggingLine = false;
        draggingHandle1 = false;
        draggingHandle2 = false;

//      hitPoint1 = hitPoint2 = hitLine = false;

        // Here we check for just a click: If object was clicked and dragged, then
        // revert to the old state (OSInactive). Otherwise, keep the new state that
        // we set.
/*Maybe it would be better to just check for "object was dragged" state and not have to worry
about keeping track of old states...
*/
        if (objectWasDragged)
                state = oldState;
}

#if 0
void Line::SetDimensionOnPoint1(Dimension * dimension)
{
        dimPoint1 = dimension;

        if (dimension)
                dimension->SetPoint1(position);
}

void Line::SetDimensionOnPoint2(Dimension * dimension)
{
        dimPoint2 = dimension;

        if (dimension)
                dimension->SetPoint2(endpoint);
}
#else
void Line::SetDimensionOnLine(Dimension * dimension/*=NULL*/)
{
        // If they don't pass one in, create it for the caller.
        if (dimension == NULL)
        {
                dimension = new Dimension(&position, &endpoint, this);

                if (parent)
                        parent->Add(dimension);
        }

        attachedDimension = dimension;

        // After we set the points here, we don't have to care about them anymore.
        if (dimension)
        {
                dimension->SetPoint1(&position);
                dimension->SetPoint2(&endpoint);
        }
}
#endif

bool Line::HitTest(Point point)
{
        SaveState();

        hitPoint1 = hitPoint2 = hitLine = false;
        Vector lineSegment = endpoint - position;
        Vector v1 = point - position;
        Vector v2 = point - endpoint;
        double parameterizedPoint = lineSegment.Dot(v1) / lineSegment.Magnitude(), distance;

        // Geometric interpretation:
        // The parameterized point on the vector lineSegment is where the perpendicular
        // intersects lineSegment. If pp < 0, then the perpendicular lies beyond the 1st
        // endpoint. If pp > length of ls, then the perpendicular lies beyond the 2nd endpoint.

        if (parameterizedPoint < 0.0)
                distance = v1.Magnitude();
        else if (parameterizedPoint > lineSegment.Magnitude())
                distance = v2.Magnitude();
        else
                // distance = ?Det?(ls, v1) / |ls|
                distance = fabs((lineSegment.x * v1.y - v1.x * lineSegment.y) / lineSegment.Magnitude());

        // Geometric interpretation of the above:
        // If the segment endpoints are s and e, and the point is p, then the test
        // for the perpendicular intercepting the segment is equivalent to insisting
        // that the two dot products {s-e}.{s-p} and {e-s}.{e-p} are both non-negative.
        // Perpendicular distance from the point to the segment is computed by first
        // computing the area of the triangle the three points form, then dividing by
        // the length of the segment.  Distances are done just by the Pythagorean
        // theorem. Twice the area of the triangle formed by three points is the
        // determinant of the following matrix:
        //
        // sx sy 1       0  0  1       0  0  0
        // ex ey 1  ==>  ex ey 1  ==>  ex ey 0
        // px py 1       px py 1       px py 0
        //
        // By translating the start point to the origin, and subtracting row 1 from
        // all other rows, we end up with the matrix on the right which greatly
        // simplifies the calculation of the determinant.

//How do we determine distance here? Especially if zoomed in or out???
#warning "!!! Distances tested for may not be valid if zoomed in or out !!!"
        if (v1.Magnitude() < 8.0)
                hitPoint1 = true;
        else if (v2.Magnitude() < 8.0)
                hitPoint2 = true;
        else if (distance < 5.0)
                hitLine = true;

        return StateChanged();
}

void Line::SaveState(void)
{
        oldHitPoint1 = hitPoint1;
        oldHitPoint2 = hitPoint2;
        oldHitLine = hitLine;
}

bool Line::StateChanged(void)
{
        if ((hitPoint1 != oldHitPoint1) || (hitPoint2 != oldHitPoint2) || (hitLine != oldHitLine))
                return true;

        return false;
}

/*
Intersection of two lines:

Find where the lines with equations r = i + j + t (3i - j) and r = -i + s (j) intersect.

When they intersect, we can set the equations equal to one another:

i + j + t (3i - j) = -i + s (j)

Equating coefficients:
1 + 3t = -1 and 1 - t = s
So t = -2/3 and s = 5/3

The position vector of the intersection point is therefore given by putting t = -2/3 or s = 5/3 into one of the above equations. This gives -i +5j/3 .


so, let's say we have two lines, l1 and l2. Points are v0(p0x, p0y), v1(p1x, p1y) for l1
and v2(p2x, p2y), v3(p3x, p3y) for l2.

d1 = v1 - v0, d2 = v3 - v2

Our parametric equations for the line then are:

r1 = v0 + t(d1)
r2 = v2 + s(d2)

Set r1 = r2, thus we have:

v0 + t(d1) = v2 + s(d2)

Taking coefficients, we have:

p0x + t(d1x) = p2x + s(d2x)
p0y + t(d1y) = p2y + s(d2y)

rearranging we get:

t(d1x) - s(d2x) = p2x - p0x
t(d1y) - s(d2y) = p2y - p0y

Determinant D is ad - bc where the matrix look like:

a b
c d

so D = (d1x)(d2y) - (d2x)(d1y)
if D = 0, the lines are parallel.
Dx = (p2x - p0x)(d2y) - (d2x)(p2y - p0y)
Dy = (d1x)(p2y - p0y) - (p2x - p0x)(d1y)
t = Dx/D, s = Dy/D

We only need to calculate t, as we can then multiply it by d1 to get the intersection point.

---------------------------------------------------------------------------------------------------

The first and most preferred method for intersection calculation is the perp-product calculation. There are two vectors, v1 and v2. Create a third vector vector between the starting points of these vectors, and calculate the perp product of v2 and the two other vectors. These two scalars have to be divided to get the mulitplication ratio of v1 to reach intersection point. So:

v1 ( bx1 , by1 );
v2 ( bx2 , by2 );
v3 ( bx3 , by3 );

Perp product is equal with dot product of normal of first vector and the second vector, so we need normals:

n1 ( -by1 , bx1 );
n3 ( -by3 , bx3 );

Dot products:

dp1 = n3 . v2 = -by3 * bx2 + bx3 * by2;
dp2 = n1 . v2 = -by1 * bx2 + bx1 * by2;

ratio = dp1 / dp2;
crossing vector = v1 * ratio;

And that's it.

-----------------------------------

So... to code this, let's say we have two Lines: l1 & l2.

Vector v1 = l1.endpoint - l1.position;
Vector v2 = l2.endpoint - l2.position;
Vector v3 = v2 - v1;

Vector normal1(-v1.y, v1.x);
Vector normal3(-v3.y, v3.x);

double dotProduct1 = v2.Dot(normal1);
double dotProduct2 = v2.Dot(normal3);

if (dotProduct2 == 0)
        return ParallelLines;
else
{
        // I think we'd still have to add the intersection to the position point to get the intersection...
        Point intersection = v1 * (dotProduct1 / dotProduct2);
        return intersection;
}
*/