[wxWidgets.git] / src / common / layout.cpp

/////////////////////////////////////////////////////////////////////////////
// Name:        layout.cpp
// Purpose:     Constraint layout system classes
// Author:      Julian Smart
// Modified by:
// Created:     04/01/98
// RCS-ID:      $Id$
// Copyright:   (c) Julian Smart and Markus Holzem
// Licence:       wxWindows license
/////////////////////////////////////////////////////////////////////////////

// =============================================================================
// declarations
// =============================================================================

// ----------------------------------------------------------------------------
// headers
// ----------------------------------------------------------------------------

#ifdef __GNUG__
    #pragma implementation "layout.h"
#endif

// For compilers that support precompilation, includes "wx.h".
#include "wx/wxprec.h"

#ifdef __BORLANDC__
  #pragma hdrstop
#endif

#ifndef WX_PRECOMP
  #include "wx/defs.h"
#endif

#if wxUSE_CONSTRAINTS

#ifndef WX_PRECOMP
  #include "wx/window.h"
  #include "wx/utils.h"
  #include "wx/dialog.h"
  #include "wx/msgdlg.h"
  #include "wx/intl.h"
#endif

#include "wx/layout.h"

#if !USE_SHARED_LIBRARY
    IMPLEMENT_DYNAMIC_CLASS(wxIndividualLayoutConstraint, wxObject)
    IMPLEMENT_DYNAMIC_CLASS(wxLayoutConstraints, wxObject)
    IMPLEMENT_DYNAMIC_CLASS(wxSizer, wxObject)
    IMPLEMENT_DYNAMIC_CLASS(wxRowColSizer, wxSizer)
    IMPLEMENT_DYNAMIC_CLASS(wxSpacingSizer, wxSizer)
#endif

/*
TODO:
 - Non shrink-to-fit row-col behaviour.
 - Give justification styles, so can e.g. centre
 the rows & cols, distribute the available space...
 - Shrink-to-fit: should resize outer window (e.g. dialog box)
 if directly associated with this kind of window.
 - How to deal with a rowcol that stretches in one direction
 but shrinks-to-fit in other. E.g. a horizontal toolbar: the width
 stretches to fit the frame, but the height is constant
 or wraps around contents. The algorithm currently assumes
 both dimensions have the same behaviour. Could assume a constant
 height (absolute value).
 - rowcol where each row or column is aligned (length of
   largest element determines spacing)
 - Groupbox sizer
 - Analyze aesthetic dialog boxes and implement using sizers.
 - What reuseable components can we provide? E.g. Ok/Cancel/Help
   group of buttons.
 - use wxStaticItems for aesthetic dialogs.

*/

// Find margin sizes if a sizer, or zero otherwise
int wxSizerMarginX(wxWindowBase *win)
{
    if ( win->IsKindOf(CLASSINFO(wxSizer)) )
    {
        wxSizer *sizer = (wxSizer *)win;
        return sizer->GetBorderX();
    }
    else
        return 0;
}

int wxSizerMarginY(wxWindowBase *win)
{
    if ( win->IsKindOf(CLASSINFO(wxSizer)) )
    {
        wxSizer *sizer = (wxSizer *)win;
        return sizer->GetBorderY();
    }
    else
        return 0;
}


wxIndividualLayoutConstraint::wxIndividualLayoutConstraint()
{
    myEdge = wxTop;
    relationship = wxUnconstrained;
    margin = 0;
    value = 0;
    percent = 0;
    otherEdge = wxTop;
    done = FALSE;
    otherWin = (wxWindowBase *) NULL;
}

wxIndividualLayoutConstraint::~wxIndividualLayoutConstraint()
{
}

void wxIndividualLayoutConstraint::Set(wxRelationship rel, wxWindowBase *otherW, wxEdge otherE, int val, int marg)
{
  relationship = rel;
  otherWin = otherW;
  otherEdge = otherE;
  value = val;
  margin = marg;
}

void wxIndividualLayoutConstraint::LeftOf(wxWindowBase *sibling, int marg)
{
    Set(wxLeftOf, sibling, wxLeft, 0, marg);
}

void wxIndividualLayoutConstraint::RightOf(wxWindowBase *sibling, int marg)
{
    Set(wxRightOf, sibling, wxRight, 0, marg);
}

void wxIndividualLayoutConstraint::Above(wxWindowBase *sibling, int marg)
{
    Set(wxAbove, sibling, wxTop, 0, marg);
}

void wxIndividualLayoutConstraint::Below(wxWindowBase *sibling, int marg)
{
    Set(wxBelow, sibling, wxBottom, 0, marg);
}

//
// 'Same edge' alignment
//
void wxIndividualLayoutConstraint::SameAs(wxWindowBase *otherW, wxEdge edge, int marg)
{ 
    Set(wxPercentOf, otherW, edge, 0, marg);
    percent = 100;
}

// The edge is a percentage of the other window's edge
void wxIndividualLayoutConstraint::PercentOf(wxWindowBase *otherW, wxEdge wh, int per)
{ 
    otherWin = otherW;
    relationship = wxPercentOf;
    percent = per;

    otherEdge = wh;
}

//
// Edge has absolute value
//
void wxIndividualLayoutConstraint::Absolute(int val)
{
    value = val; relationship = wxAbsolute;
}

// Reset constraint if it mentions otherWin
bool wxIndividualLayoutConstraint::ResetIfWin(wxWindowBase *otherW)
{
    if (otherW == otherWin)
    {
        myEdge = wxTop;
        relationship = wxAsIs;
        margin = 0;
        value = 0;
        percent = 0;
        otherEdge = wxTop;
        otherWin = (wxWindowBase *) NULL;
        return TRUE;
    }
    else
        return FALSE;
}

// Try to satisfy constraint
bool wxIndividualLayoutConstraint::SatisfyConstraint(wxLayoutConstraints *constraints, wxWindowBase *win)
{
    if (relationship == wxAbsolute)
    {
        done = TRUE;
        return TRUE;
    }

    switch (myEdge)
    {
        case wxLeft:
        {
            switch (relationship)
            {
                case wxLeftOf:
                {
                    // We can know this edge if: otherWin is win's
                    // parent, or otherWin has a satisfied constraint,
                    // or otherWin has no constraint.
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = edgePos - margin;
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxRightOf:
                {
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = edgePos + margin;
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxPercentOf:
                {
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = (int)(edgePos*(((float)percent)*0.01) + margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxUnconstrained:
                {
                    // We know the left-hand edge position if we know
                    // the right-hand edge and we know the width; OR if
                    // we know the centre and the width.
                    if (constraints->right.GetDone() && constraints->width.GetDone())
                    {
                        value = (constraints->right.GetValue() - constraints->width.GetValue() + margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else if (constraints->centreX.GetDone() && constraints->width.GetDone())
                    {
                        value = (int)(constraints->centreX.GetValue() - (constraints->width.GetValue()/2) + margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxAsIs:
                {
                    int y;
                    win->GetPosition(&value, &y);
                    done = TRUE;
                    return TRUE;
                }
                default:
                    break;
            }
            break;
        }
        case wxRight:
        {
            switch (relationship)
            {
                case wxLeftOf:
                {
                    // We can know this edge if: otherWin is win's
                    // parent, or otherWin has a satisfied constraint,
                    // or otherWin has no constraint.
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = edgePos - margin;
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxRightOf:
                {
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = edgePos + margin;
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxPercentOf:
                {
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = (int)(edgePos*(((float)percent)*0.01) - margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxUnconstrained:
                {
                    // We know the right-hand edge position if we know the
                    // left-hand edge and we know the width, OR if we know the
                    // centre edge and the width.
                    if (constraints->left.GetDone() && constraints->width.GetDone())
                    {
                        value = (constraints->left.GetValue() + constraints->width.GetValue() - margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else if (constraints->centreX.GetDone() && constraints->width.GetDone())
                    {
                        value = (int)(constraints->centreX.GetValue() + (constraints->width.GetValue()/2) - margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxAsIs:
                {
                    int x, y;
                    int w, h;
                    win->GetSize(&w, &h);
                    win->GetPosition(&x, &y);
                    value = x + w;
                    done = TRUE;
                    return TRUE;
                }
                default:
                    break;
            }
            break;
        }
        case wxTop:
        {
            switch (relationship)
            {
                case wxAbove:
                {
                    // We can know this edge if: otherWin is win's
                    // parent, or otherWin has a satisfied constraint,
                    // or otherWin has no constraint.
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = edgePos - margin;
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxBelow:
                {
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = edgePos + margin;
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxPercentOf:
                {
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = (int)(edgePos*(((float)percent)*0.01) + margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxUnconstrained:
                {
                    // We know the top edge position if we know the bottom edge
                    // and we know the height; OR if we know the centre edge and
                    // the height.
                    if (constraints->bottom.GetDone() && constraints->height.GetDone())
                    {
                        value = (constraints->bottom.GetValue() - constraints->height.GetValue() + margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else if (constraints->centreY.GetDone() && constraints->height.GetDone())
                    {
                        value = (constraints->centreY.GetValue() - (constraints->height.GetValue()/2) + margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxAsIs:
                {
                    int x;
                    win->GetPosition(&x, &value);
                    done = TRUE;
                    return TRUE;
                }
                default:
                    break;
            }
            break;
        }
        case wxBottom:
        {
            switch (relationship)
            {
                case wxAbove:
                {
                    // We can know this edge if: otherWin is win's parent,
                    // or otherWin has a satisfied constraint, or
                    // otherWin has no constraint.
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = edgePos + margin;
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxBelow:
                {
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = edgePos - margin;
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxPercentOf:
                {
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = (int)(edgePos*(((float)percent)*0.01) - margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxUnconstrained:
                {
                    // We know the bottom edge position if we know the top edge
                    // and we know the height; OR if we know the centre edge and
                    // the height.
                    if (constraints->top.GetDone() && constraints->height.GetDone())
                    {
                        value = (constraints->top.GetValue() + constraints->height.GetValue() - margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else if (constraints->centreY.GetDone() && constraints->height.GetDone())
                    {
                        value = (constraints->centreY.GetValue() + (constraints->height.GetValue()/2) - margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxAsIs:
                {
                    int x, y;
                    int w, h;
                    win->GetSize(&w, &h);
                    win->GetPosition(&x, &y);
                    value = h + y;
                    done = TRUE;
                    return TRUE;
                }
                default:
                    break;
            }
            break;
        }
        case wxCentreX:
        {
            switch (relationship)
            {
                case wxLeftOf:
                {
                    // We can know this edge if: otherWin is win's parent, or
                    // otherWin has a satisfied constraint, or otherWin has no
                    // constraint.
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = edgePos - margin;
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxRightOf:
                {
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = edgePos + margin;
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxPercentOf:
                {
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = (int)(edgePos*(((float)percent)*0.01) + margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxUnconstrained:
                {
                    // We know the centre position if we know
                    // the left-hand edge and we know the width, OR
                    // the right-hand edge and the width
                    if (constraints->left.GetDone() && constraints->width.GetDone())
                    {
                        value = (int)(constraints->left.GetValue() + (constraints->width.GetValue()/2) + margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else if (constraints->right.GetDone() && constraints->width.GetDone())
                    {
                        value = (int)(constraints->left.GetValue() - (constraints->width.GetValue()/2) + margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                default:
                    break;
            }
            break;
        }
        case wxCentreY:
        {
            switch (relationship)
            {
                case wxAbove:
                {
                    // We can know this edge if: otherWin is win's parent,
                    // or otherWin has a satisfied constraint, or otherWin
                    // has no constraint.
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = edgePos - margin;
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxBelow:
                {
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = edgePos + margin;
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxPercentOf:
                {
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = (int)(edgePos*(((float)percent)*0.01) + margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxUnconstrained:
                {
                    // We know the centre position if we know
                    // the top edge and we know the height, OR
                    // the bottom edge and the height.
                    if (constraints->bottom.GetDone() && constraints->height.GetDone())
                    {
                        value = (int)(constraints->bottom.GetValue() - (constraints->height.GetValue()/2) + margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else if (constraints->top.GetDone() && constraints->height.GetDone())
                    {
                        value = (int)(constraints->top.GetValue() + (constraints->height.GetValue()/2) + margin);
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                default:
                    break;
            }
            break;
        }
        case wxWidth:
        {
            switch (relationship)
            {
                case wxPercentOf:
                {
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = (int)(edgePos*(((float)percent)*0.01));
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxAsIs:
                {
                    if (win)
                    {
                        int h;
                        win->GetSize(&value, &h);
                        done = TRUE;
                        return TRUE;
                    }
                    else return FALSE;
                }
                case wxUnconstrained:
                {
                    // We know the width if we know the left edge and the right edge, OR
                    // if we know the left edge and the centre, OR
                    // if we know the right edge and the centre
                    if (constraints->left.GetDone() && constraints->right.GetDone())
                    {
                        value = constraints->right.GetValue() - constraints->left.GetValue();
                        done = TRUE;
                        return TRUE;
                    }
                    else if (constraints->centreX.GetDone() && constraints->left.GetDone())
                    {
                        value = (int)(2*(constraints->centreX.GetValue() - constraints->left.GetValue()));
                        done = TRUE;
                        return TRUE;
                    }
                    else if (constraints->centreX.GetDone() && constraints->right.GetDone())
                    {
                        value = (int)(2*(constraints->right.GetValue() - constraints->centreX.GetValue()));
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                default:
                    break;
            }
            break;
        }
        case wxHeight:
        {
            switch (relationship)
            {
                case wxPercentOf:
                {
                    int edgePos = GetEdge(otherEdge, win, otherWin);
                    if (edgePos != -1)
                    {
                        value = (int)(edgePos*(((float)percent)*0.01));
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                case wxAsIs:
                {
                    if (win)
                    {
                        int w;
                        win->GetSize(&w, &value);
                        done = TRUE;
                        return TRUE;
                    }
                    else return FALSE;
                }
                case wxUnconstrained:
                {
                    // We know the height if we know the top edge and the bottom edge, OR
                    // if we know the top edge and the centre, OR
                    // if we know the bottom edge and the centre
                    if (constraints->top.GetDone() && constraints->bottom.GetDone())
                    {
                        value = constraints->bottom.GetValue() - constraints->top.GetValue();
                        done = TRUE;
                        return TRUE;
                    }
                    else if (constraints->top.GetDone() && constraints->centreY.GetDone())
                    {
                        value = (int)(2*(constraints->centreY.GetValue() - constraints->top.GetValue()));
                        done = TRUE;
                        return TRUE;
                    }
                    else if (constraints->bottom.GetDone() && constraints->centreY.GetDone())
                    {
                        value = (int)(2*(constraints->bottom.GetValue() - constraints->centreY.GetValue()));
                        done = TRUE;
                        return TRUE;
                    }
                    else
                        return FALSE;
                }
                default:
                    break;
            }
            break;
        }
        default:
            break;
    }
    return FALSE;
}

// Get the value of this edge or dimension, or if this is not determinable, -1.
int wxIndividualLayoutConstraint::GetEdge(wxEdge which,
                                          wxWindowBase *thisWin,
                                          wxWindowBase *other) const
{
    // If the edge or dimension belongs to the parent, then we know the
    // dimension is obtainable immediately. E.g. a wxExpandSizer may contain a
    // button (but the button's true parent is a panel, not the sizer)
    if (other->GetChildren().Find(thisWin))
    {
        switch (which)
        {
            case wxLeft:
                {
                    return wxSizerMarginX(other);
                }
            case wxTop:
                {
                    return wxSizerMarginY(other);
                }
            case wxRight:
                {
                    int w, h;
                    other->GetClientSizeConstraint(&w, &h);
                    return w - wxSizerMarginX(other);
                }
            case wxBottom:
                {
                    int w, h;
                    other->GetClientSizeConstraint(&w, &h);
                    return h - wxSizerMarginY(other);
                }
            case wxWidth:
                {
                    int w, h;
                    other->GetClientSizeConstraint(&w, &h);
                    return w - 2*wxSizerMarginX(other);
                }
            case wxHeight:
                {
                    int w, h;
                    other->GetClientSizeConstraint(&w, &h);
                    return h - 2*wxSizerMarginY(other);
                }
            case wxCentreX:
            case wxCentreY:
                {
                    int w, h;
                    other->GetClientSizeConstraint(&w, &h);
                    if (which == wxCentreX)
                        return (int)(w/2);
                    else
                        return (int)(h/2);
                }
            default:
                return -1;
        }
    }
    switch (which)
    {
        case wxLeft:
            {
                wxLayoutConstraints *constr = other->GetConstraints();
                // If no constraints, it means the window is not dependent
                // on anything, and therefore we know its value immediately
                if (constr)
                {
                    if (constr->left.GetDone())
                        return constr->left.GetValue();
                    else
                        return -1;
                }
                else
                {
                    int x, y;
                    other->GetPosition(&x, &y);
                    return x;
                }
            }
        case wxTop:
            {
                wxLayoutConstraints *constr = other->GetConstraints();
                // If no constraints, it means the window is not dependent
                // on anything, and therefore we know its value immediately
                if (constr)
                {
                    if (constr->top.GetDone())
                        return constr->top.GetValue();
                    else
                        return -1;
                }
                else
                {
                    int x, y;
                    other->GetPosition(&x, &y);
                    return y;
                }
            }
        case wxRight:
            {
                wxLayoutConstraints *constr = other->GetConstraints();
                // If no constraints, it means the window is not dependent
                // on anything, and therefore we know its value immediately
                if (constr)
                {
                    if (constr->right.GetDone())
                        return constr->right.GetValue();
                    else
                        return -1;
                }
                else
                {
                    int x, y, w, h;
                    other->GetPosition(&x, &y);
                    other->GetSize(&w, &h);
                    return (int)(x + w);
                }
            }
        case wxBottom:
            {
                wxLayoutConstraints *constr = other->GetConstraints();
                // If no constraints, it means the window is not dependent
                // on anything, and therefore we know its value immediately
                if (constr)
                {
                    if (constr->bottom.GetDone())
                        return constr->bottom.GetValue();
                    else
                        return -1;
                }
                else
                {
                    int x, y, w, h;
                    other->GetPosition(&x, &y);
                    other->GetSize(&w, &h);
                    return (int)(y + h);
                }
            }
        case wxWidth:
            {
                wxLayoutConstraints *constr = other->GetConstraints();
                // If no constraints, it means the window is not dependent
                // on anything, and therefore we know its value immediately
                if (constr)
                {
                    if (constr->width.GetDone())
                        return constr->width.GetValue();
                    else
                        return -1;
                }
                else
                {
                    int w, h;
                    other->GetSize(&w, &h);
                    return w;
                }
            }
        case wxHeight:
            {
                wxLayoutConstraints *constr = other->GetConstraints();
                // If no constraints, it means the window is not dependent
                // on anything, and therefore we know its value immediately
                if (constr)
                {
                    if (constr->height.GetDone())
                        return constr->height.GetValue();
                    else
                        return -1;
                }
                else
                {
                    int w, h;
                    other->GetSize(&w, &h);
                    return h;
                }
            }
        case wxCentreX:
            {
                wxLayoutConstraints *constr = other->GetConstraints();
                // If no constraints, it means the window is not dependent
                // on anything, and therefore we know its value immediately
                if (constr)
                {
                    if (constr->centreX.GetDone())
                        return constr->centreX.GetValue();
                    else
                        return -1;
                }
                else
                {
                    int x, y, w, h;
                    other->GetPosition(&x, &y);
                    other->GetSize(&w, &h);
                    return (int)(x + (w/2));
                }
            }
        case wxCentreY:
            {
                wxLayoutConstraints *constr = other->GetConstraints();
                // If no constraints, it means the window is not dependent
                // on anything, and therefore we know its value immediately
                if (constr)
                {
                    if (constr->centreY.GetDone())
                        return constr->centreY.GetValue();
                    else
                        return -1;
                }
                else
                {
                    int x, y, w, h;
                    other->GetPosition(&x, &y);
                    other->GetSize(&w, &h);
                    return (int)(y + (h/2));
                }
            }
        default:
            break;
    }
    return -1;
}

wxLayoutConstraints::wxLayoutConstraints()
{
    left.SetEdge(wxLeft);
    top.SetEdge(wxTop);
    right.SetEdge(wxRight);
    bottom.SetEdge(wxBottom);
    centreX.SetEdge(wxCentreX);
    centreY.SetEdge(wxCentreY);
    width.SetEdge(wxWidth);
    height.SetEdge(wxHeight);
}

wxLayoutConstraints::~wxLayoutConstraints()
{
}

bool wxLayoutConstraints::SatisfyConstraints(wxWindowBase *win, int *nChanges)
{
    int noChanges = 0;

    bool done = width.GetDone();
    bool newDone = (done ? TRUE : width.SatisfyConstraint(this, win));
    if (newDone != done)
        noChanges ++;

    done = height.GetDone();
    newDone = (done ? TRUE : height.SatisfyConstraint(this, win));
    if (newDone != done)
        noChanges ++;

    done = left.GetDone();
    newDone = (done ? TRUE : left.SatisfyConstraint(this, win));
    if (newDone != done)
        noChanges ++;

    done = top.GetDone();
    newDone = (done ? TRUE : top.SatisfyConstraint(this, win));
    if (newDone != done)
        noChanges ++;

    done = right.GetDone();
    newDone = (done ? TRUE : right.SatisfyConstraint(this, win));
    if (newDone != done)
        noChanges ++;

    done = bottom.GetDone();
    newDone = (done ? TRUE : bottom.SatisfyConstraint(this, win));
    if (newDone != done)
        noChanges ++;

    done = centreX.GetDone();
    newDone = (done ? TRUE : centreX.SatisfyConstraint(this, win));
    if (newDone != done)
        noChanges ++;

    done = centreY.GetDone();
    newDone = (done ? TRUE : centreY.SatisfyConstraint(this, win));
    if (newDone != done)
        noChanges ++;

    *nChanges = noChanges;

    return AreSatisfied();
}

/*
 * Main constrained layout algorithm. Look at all the child
 * windows, and their constraints (if any).
 * The idea is to keep iterating through the constraints
 * until all left, right, bottom and top edges, and widths and heights,
 * are known (or no change occurs and we've failed to resolve all
 * constraints).
 *
 * If the user has not specified a dimension or edge, it will be
 * be calculated from the other known values. E.g. If we know
 * the right hand edge and the left hand edge, we now know the width.
 * The snag here is that this means we must specify absolute dimensions
 * twice (in constructor and in constraint), if we wish to use the
 * constraint notation to just set the position, for example.
 * Otherwise, if we only set ONE edge and no dimension, it would never
 * find the other edge.
 *
 * Algorithm:

  Mark all constraints as not done.

  iterations = 0;
  until no change or iterations >= max iterations
    For each child:
    {
      Calculate all constraints
    }
    iterations ++;

  For each child
    Set each calculated position and size

 */
 
#if WXWIN_COMPATIBILITY
bool wxOldDoLayout(wxWindowBase *win)
{
  // Make sure this isn't called recursively from below
  static wxList doneSoFar;

  if (doneSoFar.Member(win))
    return TRUE;

  doneSoFar.Append(win);

  wxNode *node = win->GetChildren().First();
  while (node)
  {
    wxWindowBase *child = (wxWindowBase *)node->Data();
    wxLayoutConstraints *constr = child->GetConstraints();
    if (constr)
    {
      constr->left.SetDone(FALSE);
      constr->top.SetDone(FALSE);
      constr->right.SetDone(FALSE);
      constr->bottom.SetDone(FALSE);
      constr->width.SetDone(FALSE);
      constr->height.SetDone(FALSE);
      constr->centreX.SetDone(FALSE);
      constr->centreY.SetDone(FALSE);
    }
    node = node->Next();
  }
  int noIterations = 0;
  int maxIterations = 500;
  int noChanges = 1;

  while ((noChanges > 0) && (noIterations < maxIterations))
  {
    noChanges = 0;
    wxNode *node = win->GetChildren().First();
    while (node)
    {
      wxWindowBase *child = (wxWindowBase *)node->Data();
      wxLayoutConstraints *constr = child->GetConstraints();
      if (constr)
      {
        int tempNoChanges = 0;
        (void)constr->SatisfyConstraints(child, &tempNoChanges);
        noChanges += tempNoChanges;
      }
      node = node->Next();
    }
    noIterations ++;
  }
/*
  // Would be nice to have a test here to see _which_ constraint(s)
  // failed, so we can print a specific diagnostic message.
  if (noFailures > 0)
  {
    wxDebugMsg(_("wxWindowBase::Layout() failed.\n"));
  }
*/
  // Now set the sizes and positions of the children, and
  // recursively call Layout().
  node = win->GetChildren().First();
  while (node)
  {
    wxWindowBase *child = (wxWindowBase *)node->Data();
    wxLayoutConstraints *constr = child->GetConstraints();
    if (constr && constr->left.GetDone() && constr->right.GetDone() &&
                  constr->width.GetDone() && constr->height.GetDone())
    {
      int x = constr->left.GetValue();
      int y = constr->top.GetValue();
      int w = constr->width.GetValue();
      int h = constr->height.GetValue();

      // If we don't want to resize this window, just move it...
      if ((constr->width.GetRelationship() != wxAsIs) ||
          (constr->height.GetRelationship() != wxAsIs))
      {
        // _Should_ call Layout() recursively.
        child->SetSize(x, y, w, h);
      }
      else
      {
        child->Move(x, y);
      }
    }
    else
      child->Layout();
    node = node->Next();
  }
  doneSoFar.DeleteObject(win);

  return TRUE;
}
#endif // WXWIN_COMPATIBILITY

wxSizer::wxSizer()
{
    sizerBehaviour = wxSizerNone;
    borderX = 2;
    borderY = 2;
    sizerX = 0;
    sizerY = 0;
    sizerWidth = 0;
    sizerHeight = 0;
}

wxSizer::wxSizer(wxWindowBase *parent, wxSizerBehaviour behav)
{
    Create(parent, behav);
}

bool wxSizer::Create(wxWindowBase *parent, wxSizerBehaviour behav)
{
    sizerBehaviour = behav;
    borderX = 2;
    borderY = 2;
    m_sizerParent = parent;
    sizerX = 0;
    sizerY = 0;
    sizerWidth = 0;
    sizerHeight = 0;

    // A normal window can have just one top-level sizer
    // associated with it.
    if (!parent->IsKindOf(CLASSINFO(wxSizer)))
    {
        parent->SetSizer(this);
    }
    else
        ((wxSizer *)parent)->AddSizerChild(this);

    switch (sizerBehaviour)
    {
        case wxSizerExpand:
            {
                // Defines a set of constraints
                // to expand the sizer to fit the parent window
                wxLayoutConstraints *c = new wxLayoutConstraints;

                c->left.SameAs(parent, wxLeft, 0);
                c->top.SameAs(parent, wxTop, 0);
                c->right.SameAs(parent, wxRight, 0);
                c->bottom.SameAs(parent, wxBottom, 0);

                SetConstraints(c);
                break;
            }
        case wxSizerShrink:
        case wxSizerNone:
        default:
            {
            }
    }
    return TRUE;
}

wxSizer::~wxSizer()
{
    // Remove all children without deleting them,
    // or ~wxbWindow will delete proper windows _twice_
    wxNode *node = GetChildren().First();
    while (node)
    {
        wxNode *next = node->Next();
        wxWindowBase *win = (wxWindowBase *)node->Data();
        if (!win->IsKindOf(CLASSINFO(wxSizer)))
        {
            delete node;
            win->SetSizerParent((wxWindowBase *) NULL);
        }
        else
        {
            RemoveSizerChild(win);
            delete win;
        }
        node = next;
    }

    if (m_sizerParent) // && !m_sizerParent->IsKindOf(CLASSINFO(wxSizer)))
    {
        m_sizerParent->SetSizer((wxSizer *) NULL);
        m_sizerParent = (wxWindowBase *) NULL;
    }

}

void wxSizer::SetBorder(int x, int y)
{
    borderX = x;
    borderY = y;
    /* No: the margin is for inside, not outside (expansion)

       if ( GetConstraints() )
       {
       GetConstraints()->left.SetMargin(x);
       GetConstraints()->right.SetMargin(x);
       GetConstraints()->top.SetMargin(y);
       GetConstraints()->bottom.SetMargin(y);
       }
     */

}

void wxSizer::AddSizerChild(wxWindowBase *child)
{
    child->SetSizerParent(this);
    GetChildren().Append(child);

    // Add some constraints for the purpose of storing
    // the relative position of the window/sizer
    // during layout calculations.
    if (!child->GetConstraints())
    {
        wxLayoutConstraints *c = new wxLayoutConstraints;
        c->left.AsIs();
        c->top.AsIs();
        c->width.AsIs();
        c->height.AsIs();
        int w, h;
        child->GetSize(&w, &h);
        c->width.SetValue(w);
        c->height.SetValue(h);

        child->SetConstraints(c);
    }
}

void wxSizer::RemoveSizerChild(wxWindowBase *child)
{
    GetChildren().DeleteObject(child);
}

void wxSizer::DoSetSize(int x, int y, int w, int h, int WXUNUSED(flags))
{
    wxLayoutConstraints *constr = GetConstraints();
    if (x != -1)
    {
        sizerX = x;
        if (constr)
            constr->left.SetValue(x);
    }
    if (y != -1)
    {
        sizerY = y;
        if (constr)
            constr->top.SetValue(y);
    }
    if (w != -1)
    {
        sizerWidth = w;
        if (constr)
            constr->width.SetValue(w);
    }
    if (h != -1)
    {
        sizerHeight = h;
        if (constr)
            constr->height.SetValue(h);
    }
}

void wxSizer::DoGetSize(int *w, int *h) const
{
    *w = sizerWidth;
    *h = sizerHeight;
}

void wxSizer::DoGetPosition(int *x, int *y) const
{
    *x = sizerX;
    *y = sizerY;
}

bool wxSizer::LayoutPhase1(int *noChanges)
{
    *noChanges = 0;
    switch (sizerBehaviour)
    {
        case wxSizerExpand:
            {
                if (!m_sizerParent)
                {
                    wxMessageBox(_("wxExpandSizer has no parent!"), _("Sizer error"), wxOK);
                    return TRUE;
                }

                // Set the size to fill the parent client area
                int pw, ph;
                m_sizerParent->GetClientSize(&pw, &ph);
                SetSize(GetBorderX(), GetBorderY(), pw - 2*GetBorderX(), ph - 2*GetBorderY());
                wxLayoutConstraints *constr = GetConstraints();

                // Fill in the constraints
                if (constr)
                {
                    constr->left.SetValue(0); constr->left.SetDone(TRUE);
                    constr->top.SetValue(0); constr->right.SetDone(TRUE);
                    constr->width.SetValue(pw); constr->width.SetDone(TRUE);
                    constr->height.SetValue(ph); constr->height.SetDone(TRUE);
                }

                return TRUE;
                break;
            }
        case wxSizerShrink:
            {
                wxLayoutConstraints *constr = GetConstraints();

                if (constr)
                {
                    // Force the constraint to have as-is width and height
                    // if we're in shrink-to-fit mode, because if left unconstrained,
                    // SatisfyConstraints will fail. The shrink-to-fit option
                    // essentially specifies the width and height as 'whatever I calculate'.
                    constr->width.AsIs();
                    constr->height.AsIs();
                }
                DoPhase(1);
                DoPhase(2);
                // Find the bounding box and set own size
                int maxX = 0;
                int maxY = 0;

                wxNode *node = GetChildren().First();
                while (node)
                {
                    int x, y, width, height;
                    wxWindowBase *win = (wxWindowBase *)node->Data();
                    win->GetSizeConstraint(&width, &height);
                    win->GetPositionConstraint(&x, &y);
                    if ((x+width) > maxX)
                        maxX = (x + width);
                    if ((y+height) > maxY)
                        maxY = (y + height);

                    node = node->Next();
                }
                SetSize(GetBorderX(), GetBorderY(), maxX, maxY);

                // If this is the only sizer for the parent, size the parent to this sizer.
                if ( m_sizerParent && (m_sizerParent->GetSizer() == this) )
                    m_sizerParent->SetClientSize(maxX + 2*GetBorderX(), maxY + 2*GetBorderY());

                return TRUE;
                break;
            }
        case wxSizerNone:
            {
                wxLayoutConstraints *constr = GetConstraints();
                if (constr)
                {
                    bool success = constr->SatisfyConstraints(this, noChanges);
                    if (success)
                    {
                        int x = constr->left.GetValue();
                        int y = constr->top.GetValue();
                        int w = constr->width.GetValue();
                        int h = constr->height.GetValue();
                        SetSize(x, y, w, h);
                    }
                    return success;
                }
                else
                    return TRUE;
                break;
            }
    }
    return TRUE;

}

bool wxSizer::LayoutPhase2(int *noChanges)
{
    *noChanges = 0;

    switch (sizerBehaviour)
    {
        case wxSizerExpand:
            {
                // Layout children
                DoPhase(1);
                DoPhase(2);
                return TRUE;
            }
        case wxSizerShrink:
            {
                wxLayoutConstraints *constr = GetConstraints();
                if (constr)
                {
                    bool success = constr->SatisfyConstraints(this, noChanges);
                    if (success)
                    {
                        int x = constr->left.GetValue();
                        int y = constr->top.GetValue();
                        Move(x, y);
                    }
                    return success;
                }
                break;
            }
        case wxSizerNone:
            {
                // Layout children
                DoPhase(1);
                DoPhase(2);

                // Is this a dumb fix for lack of constraint evaluation?
                wxLayoutConstraints *constr = GetConstraints();
                if (constr)
                {
                    bool success = constr->SatisfyConstraints(this, noChanges);
                    if (success)
                    {
                        int x = constr->left.GetValue();
                        int y = constr->top.GetValue();
                        int w = constr->width.GetValue();
                        int h = constr->height.GetValue();
                        SetSize(x, y, w, h);
                    }
                    return success;
                }
                else
                    return TRUE;
            }
    }
    return TRUE;
}

/*
 * wxRowColSizer
 */

wxRowColSizer::wxRowColSizer()
{
    rowOrCol = TRUE;
    rowOrColSize = 20;
    xSpacing = 2;
    ySpacing = 2;
}

wxRowColSizer::wxRowColSizer(wxWindowBase *parent, bool rc, int n, wxSizerBehaviour behav)
{
    Create(parent, rc, n, behav);
}

bool wxRowColSizer::Create(wxWindowBase *parent, bool rc, int n, wxSizerBehaviour behav)
{
    wxSizer::Create(parent, behav);

    rowOrCol = rc;
    rowOrColSize = n;
    xSpacing = 2;
    ySpacing = 2;

    return TRUE;
}

wxRowColSizer::~wxRowColSizer()
{
}

bool wxRowColSizer::LayoutPhase1(int *noChanges)
{
    *noChanges = 0;
    wxLayoutConstraints *constr = GetConstraints();

    if (constr)
    {
        // Force the constraint to have as-is width and height
        // if we're in shrink-to-fit mode, because if left unconstrained,
        // SatisfyConstraints will fail. The shrink-to-fit option
        // essentially specifies the width and height as 'whatever I calculate'.
        if (sizerBehaviour == wxSizerShrink)
        {
            constr->width.AsIs();
            constr->height.AsIs();
        }

        // Only evaluate the constraints FIRST if we're NOT
        // in shrink-to-fit mode, i.e. we want to size the rowcol
        // first, then lay the children out in the space we've calculated.
        if (sizerBehaviour != wxSizerShrink)
        {
            bool success = constr->SatisfyConstraints(this, noChanges);
            if (success)
            {
                int x = constr->left.GetValue();
                int y = constr->top.GetValue();
                int w = constr->width.GetValue();
                int h = constr->height.GetValue();
                SetSize(x, y, w, h);
            }
            else
                return FALSE;

            // Continue to do the rest of the phase when the constraints have been
            // satisfied, i.e. we're on the last iteration of phase 1 and
            // can now do the actual rowcol laying out.
        }
    }

    // If we ARE in shrink-to-fit mode, we must now
    // calculate the child sizes BEFORE laying out in rows or columns.
    if (sizerBehaviour == wxSizerShrink)
    {
        DoPhase(1);
        DoPhase(2);

        // WILL THE WINDOW BE SIZED CORRECTLY AT THIS POINT?
        // CHECK CONSTRAINTS IF ANY...
        int noRows = 0;
        int noCols = 0;
        int currentX = borderX;
        int currentY = borderY;
        int maxX = currentX;
        int maxY = currentY;

        wxNode *node = GetChildren().First();
        while (node)
        {
            wxWindowBase *win = (wxWindowBase *)node->Data();
            int childWidth, childHeight;
            if (win->GetConstraints() &&
                    win->GetConstraints()->width.GetDone() &&
                    win->GetConstraints()->height.GetDone())
            {
                childWidth = win->GetConstraints()->width.GetValue();
                childHeight = win->GetConstraints()->height.GetValue();
            }
            else
                win->GetSize(&childWidth, &childHeight);

            win->MoveConstraint(currentX, currentY);

            if ((currentX + childWidth) > maxX)
                maxX = (currentX + childWidth);
            if ((currentY + childHeight) > maxY)
                maxY = (currentY + childHeight);

            if (rowOrCol)
            {
                currentX += childWidth + xSpacing;
                noCols ++;

                // Reset to start of row
                if (noCols == rowOrColSize)
                {
                    currentX = borderX;
                    currentY += childHeight + ySpacing;
                    noCols = 0;
                }
            }
            else
            {
                currentY += childHeight + ySpacing;
                noRows ++;

                // Reset to start of col
                if (noRows == rowOrColSize)
                {
                    currentY = borderY;
                    currentX += childWidth + xSpacing;
                    noRows = 0;
                }
            }

            node = node->Next();
        }
        maxX += borderX;
        maxY += borderY;

        SetSize(-1, -1, maxX, maxY);
    }
    return TRUE;
}

bool wxRowColSizer::LayoutPhase2(int *noChanges)
{
    *noChanges = 0;

    // If shrink-to-fit, it's only at Phase 2 that we know the size of
    // the wxRowColSizer, and now we can evaluate the
    // constraints and pass result back up to parent.
    // This implements a depth-first strategy
    if (sizerBehaviour == wxSizerShrink)
    {
        wxLayoutConstraints *constr = GetConstraints();
        if (constr)
        {
            bool success = constr->SatisfyConstraints(this, noChanges);
            if (success)
            {
                int x = constr->left.GetValue();
                int y = constr->top.GetValue();
                Move(x, y);
            }
            return success;
        }
        else return TRUE;
    }
    else
    {
        // Lay out the children: breadth-first strategy.
        DoPhase(1);
        DoPhase(2);

        // Space them
    }
    return TRUE;
}


/*
 * wxSpacingSizer
 */

wxSpacingSizer::wxSpacingSizer()
{
}

wxSpacingSizer::wxSpacingSizer(wxWindowBase *parent)
{
    Create(parent);
}

wxSpacingSizer::wxSpacingSizer(wxWindowBase *parent, wxRelationship rel, wxWindowBase *other, int spacing)
{
    Create(parent, rel, other, spacing);
}

bool wxSpacingSizer::Create(wxWindowBase *parent)
{
    wxSizer::Create(parent);
    return TRUE;
}

bool wxSpacingSizer::Create(wxWindowBase *parent, wxRelationship rel, wxWindowBase *other, int spacing)
{
    wxLayoutConstraints *c = new wxLayoutConstraints;

    wxSizer::Create(parent);

    switch ( rel )
    {
        case wxLeftOf :
            c->width.Absolute    (spacing);
            c->top.SameAs        (other, wxTop);
            c->bottom.SameAs    (other, wxBottom);
            c->right.LeftOf        (other);
            break;
        case wxRightOf :
            c->width.Absolute    (spacing);
            c->top.SameAs        (other, wxTop);
            c->bottom.SameAs    (other, wxBottom);
            c->left.RightOf        (other);
            break;
        case wxBelow :
            c->height.Absolute    (spacing);
            c->left.SameAs        (other, wxLeft);
            c->right.SameAs        (other, wxRight);
            c->top.Below        (other);
            break;
        case wxAbove :
            c->height.Absolute    (spacing);
            c->left.SameAs        (other, wxLeft);
            c->right.SameAs        (other, wxRight);
            c->bottom.Above        (other);
            break;

        default :
            break;
    }
    SetConstraints(c);

    return TRUE;
}

wxSpacingSizer::~wxSpacingSizer()
{
}

#endif // wxUSE_CONSTRAINTS