- skins2/utils/bezier.*: Added support for curves made of one point

 - skins2/theme/skin.dtd: Removed Event and Rectangle tags
 - skins2/src/theme.cpp: Destroy curves explicitely
 - ALL: Anchors can be defined using a Bezier curve, which allows
   rectilinear anchors (but it is still possible to define anchors
   reduced to a single point).
   A "curved anchor" only attracts "single point anchors"

modules/gui/skins2/controls/ctrl_slider.cpp

@@ -2,7 +2,7 @@
  * ctrl_slider.cpp
  *****************************************************************************
  * Copyright (C) 2003 VideoLAN
- * $Id: ctrl_slider.cpp,v 1.4 2004/02/29 16:49:55 asmax Exp $
+ * $Id: ctrl_slider.cpp,v 1.5 2004/03/02 21:45:15 ipkiss Exp $
  *
  * Authors: Cyril Deguet     <asmax@via.ecp.fr>
  *          Olivier Teulire <ipkiss@via.ecp.fr>
@@ -55,7 +55,7 @@ CtrlSliderCursor::CtrlSliderCursor( intf_thread_t *pIntf,
     m_cmdUpOver( this, &transUpOver ), m_cmdMove( this, &transMove ),
     m_cmdScroll( this, &transScroll ),
     m_lastPercentage( 0 ), m_xOffset( 0 ), m_yOffset( 0 ),
-    m_pEvt( NULL ), m_curve( rCurve )
+    m_pEvt( NULL ), m_rCurve( rCurve )
 {
     // Build the images of the cursor
     OSFactory *pOsFactory = OSFactory::instance( getIntf() );
@@ -120,7 +120,7 @@ bool CtrlSliderCursor::mouseOver( int x, int y ) const
     {
         // Compute the position of the cursor
         int xPos, yPos;
-        m_curve.getPoint( m_rVariable.get(), xPos, yPos );
+        m_rCurve.getPoint( m_rVariable.get(), xPos, yPos );
 
         // Compute the resize factors
         float factorX, factorY;
@@ -144,7 +144,7 @@ void CtrlSliderCursor::draw( OSGraphics &rImage, int xDest, int yDest )
     {
         // Compute the position of the cursor
         int xPos, yPos;
-        m_curve.getPoint( m_rVariable.get(), xPos, yPos );
+        m_rCurve.getPoint( m_rVariable.get(), xPos, yPos );
 
         // Compute the resize factors
         float factorX, factorY;
@@ -181,7 +181,7 @@ void CtrlSliderCursor::transOverDown( SkinObject *pCtrl )
 
     // Compute the offset
     int tempX, tempY;
-    pThis->m_curve.getPoint( pThis->m_rVariable.get(), tempX, tempY );
+    pThis->m_rCurve.getPoint( pThis->m_rVariable.get(), tempX, tempY );
     pThis->m_xOffset = pEvtMouse->getXPos() - pPos->getLeft()
                        - (int)(tempX * factorX);
     pThis->m_yOffset = pEvtMouse->getYPos() - pPos->getTop()
@@ -244,10 +244,10 @@ void CtrlSliderCursor::transMove( SkinObject *pCtrl )
     int relYPond = (int)(relY / factorY);
 
     // Update the position
-    if( pThis->m_curve.getMinDist( relXPond, relYPond ) < RANGE )
+    if( pThis->m_rCurve.getMinDist( relXPond, relYPond ) < RANGE )
     {
-        float percentage = pThis->m_curve.getNearestPercent( relXPond,
-                                                             relYPond );
+        float percentage = pThis->m_rCurve.getNearestPercent( relXPond,
+                                                              relYPond );
         pThis->m_rVariable.set( percentage );
     }
     else
@@ -304,7 +304,7 @@ CtrlSliderBg::CtrlSliderBg( intf_thread_t *pIntf, CtrlSliderCursor &rCursor,
                             int thickness, VarBool *pVisible,
                             const UString &rHelp ):
     CtrlGeneric( pIntf, rHelp, pVisible ), m_rCursor( rCursor ),
-    m_rVariable( rVariable ), m_thickness( thickness ), m_curve( rCurve ),
+    m_rVariable( rVariable ), m_thickness( thickness ), m_rCurve( rCurve ),
     m_width( rCurve.getWidth() ), m_height( rCurve.getHeight() )
 {
 }
@@ -316,8 +316,8 @@ bool CtrlSliderBg::mouseOver( int x, int y ) const
     float factorX, factorY;
     getResizeFactors( factorX, factorY );
 
-    return (m_curve.getMinDist( (int)(x / factorX),
-                                (int)(y / factorY) ) < m_thickness );
+    return (m_rCurve.getMinDist( (int)(x / factorX),
+                                 (int)(y / factorY) ) < m_thickness );
 }
 
 
@@ -336,7 +336,7 @@ void CtrlSliderBg::handleEvent( EvtGeneric &rEvent )
         EvtMouse &rEvtMouse = (EvtMouse&)rEvent;
         int x = rEvtMouse.getXPos();
         int y = rEvtMouse.getYPos();
-        m_rVariable.set( m_curve.getNearestPercent(
+        m_rVariable.set( m_rCurve.getNearestPercent(
                             (int)((x - pPos->getLeft()) / factorX),
                             (int)((y - pPos->getTop()) / factorY) ) );
 

modules/gui/skins2/controls/ctrl_slider.hpp

@@ -2,7 +2,7 @@
  * ctrl_slider.hpp
  *****************************************************************************
  * Copyright (C) 2003 VideoLAN
- * $Id: ctrl_slider.hpp,v 1.3 2004/02/29 16:49:55 asmax Exp $
+ * $Id: ctrl_slider.hpp,v 1.4 2004/03/02 21:45:15 ipkiss Exp $
  *
  * Authors: Cyril Deguet     <asmax@via.ecp.fr>
  *          Olivier Teulire <ipkiss@via.ecp.fr>
@@ -92,7 +92,7 @@ class CtrlSliderCursor: public CtrlGeneric, public Observer<VarPercent>
         /// Current image
         OSGraphics *m_pImg;
         /// Bezier curve of the slider
-        const Bezier m_curve;
+        const Bezier &m_rCurve;
 
         /// Callback functions
         static void transOverDown( SkinObject *pCtrl );
@@ -133,7 +133,7 @@ class CtrlSliderBg: public CtrlGeneric
         /// Thickness of the curve
         int m_thickness;
         /// Bezier curve of the slider
-        const Bezier m_curve;
+        const Bezier &m_rCurve;
         /// Initial size of the control
         int m_width, m_height;
 

modules/gui/skins2/parser/builder.cpp

@@ -2,7 +2,7 @@
  * builder.cpp
  *****************************************************************************
  * Copyright (C) 2003 VideoLAN
- * $Id: builder.cpp,v 1.8 2004/03/01 18:33:31 asmax Exp $
+ * $Id: builder.cpp,v 1.9 2004/03/02 21:45:15 ipkiss Exp $
  *
  * Authors: Cyril Deguet     <asmax@via.ecp.fr>
  *          Olivier Teulire <ipkiss@via.ecp.fr>
@@ -182,8 +182,18 @@ void Builder::addAnchor( const BuilderData::Anchor &rData )
         return;
     }
 
+    Bezier *pCurve = getPoints( rData.m_points.c_str() );
+    if( pCurve == NULL )
+    {
+        msg_Err( getIntf(), "Invalid format in tag points=\"%s\"",
+                 rData.m_points.c_str() );
+        return;
+    }
+    m_pTheme->m_curves.push_back( BezierPtr( pCurve ) );
+
     Anchor *pAnc = new Anchor( getIntf(), rData.m_xPos, rData.m_yPos,
-                               rData.m_range, rData.m_priority, *pWin );
+                               rData.m_range, rData.m_priority,
+                               *pCurve, *pWin );
     pWin->addAnchor( pAnc );
 }
 
@@ -615,16 +625,18 @@ Bezier *Builder::getPoints( const char *pTag ) const
     int x, y, n;
     while( 1 )
     {
-        if( sscanf( pTag, "(%d,%d)%n", &x, &y, &n ) < 2 )
+        if( sscanf( pTag, "(%d,%d)%n", &x, &y, &n ) < 1 )
         {
             return NULL;
         }
+#if 0
         if( x < 0 || y < 0 )
         {
             msg_Err( getIntf(),
                      "Slider points cannot have negative coordinates!" );
             return NULL;
         }
+#endif
         xBez.push_back( x );
         yBez.push_back( y );
         pTag += n;

modules/gui/skins2/parser/builder_data.def

@@ -3,7 +3,7 @@ Bitmap id:string fileName:string alphaColor:uint32_t
 Font id:string fontName:string size:int
 Window id:string xPos:int yPos:int visible:bool dragDrop:bool playOnDrop:bool
 Layout id:string width:int height:int minWidth:int maxWidth:int minHeight:int maxHeight:int windowId:string
-Anchor xPos:int yPos:int range:int priority:int windowId:string
+Anchor xPos:int yPos:int range:int priority:int points:string windowId:string
 Button id:string xPos:int yPos:int leftTop:string rightBottom:string upId:string downId:string overId:string actionId:string tooltip:string help:string layer:int windowId:string layoutId:string
 Checkbox id:string xPos:int yPos:int leftTop:string rightBottom:string up1Id:string down1Id:string over1Id:string up2Id:string down2Id:string over2Id:string state:string action1:string action2:string tooltip1:string tooltip2:string help:string layer:int windowId:string layoutId:string
 Image id:string xPos:int yPos:int leftTop:string rightBottom:string visible:bool bmpId:string onclickId:string help:string layer:int windowId:string layoutId:string

modules/gui/skins2/parser/builder_data.hpp

@@ -2,7 +2,7 @@
  * builder_data.hpp
  *****************************************************************************
  * Copyright (C) 2003 VideoLAN
- * $Id: builder_data.hpp,v 1.5 2004/02/29 16:49:55 asmax Exp $
+ * $Id: builder_data.hpp,v 1.6 2004/03/02 21:45:15 ipkiss Exp $
  *
  * Authors: Cyril Deguet     <asmax@via.ecp.fr>
  *          Olivier Teulière <ipkiss@via.ecp.fr>
@@ -116,13 +116,14 @@ m_id( id ), m_width( width ), m_height( height ), m_minWidth( minWidth ), m_maxW
     /// Type definition
     struct Anchor
     {
-        Anchor( int xPos, int yPos, int range, int priority, const string & windowId ):
-m_xPos( xPos ), m_yPos( yPos ), m_range( range ), m_priority( priority ), m_windowId( windowId ) {}
+        Anchor( int xPos, int yPos, int range, int priority, const string & points, const string & windowId ):
+m_xPos( xPos ), m_yPos( yPos ), m_range( range ), m_priority( priority ), m_points( points ), m_windowId( windowId ) {}
 
         int m_xPos;
         int m_yPos;
         int m_range;
         int m_priority;
+        const string m_points;
         const string m_windowId;
     };
     /// List

modules/gui/skins2/parser/gen_builder.py

@@ -15,7 +15,7 @@ hppfile.write(
  * builder_data.hpp
  *****************************************************************************
  * Copyright (C) 2003 VideoLAN
- * $Id: gen_builder.py,v 1.1 2004/01/03 23:31:33 asmax Exp $
+ * $Id: gen_builder.py,v 1.2 2004/03/02 21:45:15 ipkiss Exp $
  *
  * Authors: Cyril Deguet     <asmax@via.ecp.fr>
  *          Olivier Teulire <ipkiss@via.ecp.fr>
@@ -41,13 +41,13 @@ hppfile.write(
 #ifndef BUILDER_DATA_HPP
 #define BUILDER_DATA_HPP
 
-using namespace std;
-
 #include <vlc/vlc.h>
 #include <list>
 #include <map>
 #include <string>
 
+using namespace std;
+
 /// Structure for mapping data from XML file
 struct BuilderData
 {

modules/gui/skins2/parser/skin_parser.cpp

@@ -2,7 +2,7 @@
  * skin_parser.cpp
  *****************************************************************************
  * Copyright (C) 2004 VideoLAN
- * $Id: skin_parser.cpp,v 1.4 2004/03/01 19:36:43 asmax Exp $
+ * $Id: skin_parser.cpp,v 1.5 2004/03/02 21:45:15 ipkiss Exp $
  *
  * Authors: Cyril Deguet     <asmax@via.ecp.fr>
  *
@@ -40,7 +40,7 @@ void SkinParser::handleBeginElement( const string &rName, AttrList_t &attr )
     {
         const BuilderData::Anchor anchor( atoi( attr["x"] ) + m_xOffset,
                 atoi( attr["y"] ) + m_yOffset, atoi( attr["range"] ),
-                atoi( attr["priority"] ), m_curWindowId );
+                atoi( attr["priority"] ), attr["points"], m_curWindowId );
         m_data.m_listAnchor.push_back( anchor );
     }
 

modules/gui/skins2/src/anchor.cpp

@@ -2,7 +2,7 @@
  * anchor.cpp
  *****************************************************************************
  * Copyright (C) 2003 VideoLAN
- * $Id: anchor.cpp,v 1.1 2004/01/03 23:31:33 asmax Exp $
+ * $Id: anchor.cpp,v 1.2 2004/03/02 21:45:15 ipkiss Exp $
  *
  * Authors: Cyril Deguet     <asmax@via.ecp.fr>
  *          Olivier Teulière <ipkiss@via.ecp.fr>
@@ -27,20 +27,47 @@
 
 bool Anchor::isHanging( const Anchor &rOther ) const
 {
-    return (getXPosAbs() == rOther.getXPosAbs() &&
-            getYPosAbs() == rOther.getYPosAbs() &&
-            m_priority > rOther.m_priority );
+    if( m_priority <= rOther.m_priority )
+        return false;
+
+    // Compute delta coordinates between anchors, since the Bezier class
+    // uses coordinates relative to (0;0)
+    int deltaX = getXPosAbs() - rOther.getXPosAbs();
+    int deltaY = getYPosAbs() - rOther.getYPosAbs();
+
+    // One of the anchors (at least) must be a point, else it has no meaning
+    return (isPoint() && rOther.m_rCurve.getMinDist( deltaX, deltaY ) == 0) ||
+           (rOther.isPoint() && m_rCurve.getMinDist( -deltaX, -deltaY ) == 0);
 }
 
 
 bool Anchor::canHang( const Anchor &rOther, int &xOffset, int &yOffset ) const
 {
-    int xDist = getXPosAbs() - (rOther.getXPosAbs() + xOffset);
-    int yDist = getYPosAbs() - (rOther.getYPosAbs() + yOffset);
-    if( m_range > 0 && xDist*xDist + yDist*yDist <= m_range*m_range )
+    int deltaX = getXPosAbs() - (rOther.getXPosAbs() + xOffset);
+    int deltaY = getYPosAbs() - (rOther.getYPosAbs() + yOffset);
+
+    // One of the anchors (at least) must be a point, else it has no meaning
+    if( (isPoint() && rOther.m_rCurve.getMinDist( deltaX, deltaY ) < m_range) )
     {
-        xOffset = getXPosAbs() - rOther.getXPosAbs();
-        yOffset = getYPosAbs() - rOther.getYPosAbs();
+        // Compute the coordinates of the nearest point of the curve
+        int xx, yy;
+        float p = rOther.m_rCurve.getNearestPercent( deltaX, deltaY );
+        rOther.m_rCurve.getPoint( p, xx, yy );
+
+        xOffset = getXPosAbs() - (rOther.getXPosAbs() + xx);
+        yOffset = getYPosAbs() - (rOther.getYPosAbs() + yy);
+        return true;
+    }
+    else if( (rOther.isPoint() &&
+              m_rCurve.getMinDist( -deltaX, -deltaY ) < m_range) )
+    {
+        // Compute the coordinates of the nearest point of the curve
+        int xx, yy;
+        float p = m_rCurve.getNearestPercent( -deltaX, -deltaY );
+        m_rCurve.getPoint( p, xx, yy );
+
+        xOffset = (getXPosAbs() + xx) - rOther.getXPosAbs();
+        yOffset = (getYPosAbs() + yy) - rOther.getYPosAbs();
         return true;
     }
     else

modules/gui/skins2/src/anchor.hpp

@@ -2,7 +2,7 @@
  * anchor.hpp
  *****************************************************************************
  * Copyright (C) 2003 VideoLAN
- * $Id: anchor.hpp,v 1.1 2004/01/03 23:31:33 asmax Exp $
+ * $Id: anchor.hpp,v 1.2 2004/03/02 21:45:15 ipkiss Exp $
  *
  * Authors: Cyril Deguet     <asmax@via.ecp.fr>
  *          Olivier Teulière <ipkiss@via.ecp.fr>
@@ -27,6 +27,7 @@
 
 #include "skin_common.hpp"
 #include "generic_window.hpp"
+#include "../utils/bezier.hpp"
 
 
 /// Class for the windows anchors
@@ -34,9 +35,10 @@ class Anchor: public SkinObject
 {
     public:
         Anchor( intf_thread_t *pIntf, int xPos, int yPos, int range,
-                int priority, GenericWindow &rWindow ):
+                int priority, const Bezier &rCurve, GenericWindow &rWindow ):
             SkinObject( pIntf ), m_xPos( xPos ), m_yPos( yPos ),
-            m_range( range ), m_priority( priority ), m_rWindow( rWindow ) {}
+            m_rCurve( rCurve ), m_range( range ), m_priority( priority ),
+            m_rWindow( rWindow ) {}
         virtual ~Anchor() {}
 
         /// Return true if the given anchor is hanged by this one
@@ -56,6 +58,9 @@ class Anchor: public SkinObject
         /// doesn't "jump" in a strange way).
         bool canHang( const Anchor &rOther, int &xOffset, int &yOffset ) const;
 
+        // Indicate whether this anchor is reduced to a single point
+        bool isPoint() const { return m_rCurve.getNbCtrlPoints() == 1; }
+
         // Getters
         int getXPosAbs() const { return (m_xPos + m_rWindow.getLeft()); }
         int getYPosAbs() const { return (m_yPos + m_rWindow.getTop()); }
@@ -64,6 +69,9 @@ class Anchor: public SkinObject
         /// Coordinates relative to the window
         int m_xPos, m_yPos;
 
+        /// Curve of the anchor
+        const Bezier &m_rCurve;
+
         /// Range of action
         int m_range;
 

modules/gui/skins2/src/theme.cpp

@@ -2,7 +2,7 @@
  * theme.cpp
  *****************************************************************************
  * Copyright (C) 2003 VideoLAN
- * $Id: theme.cpp,v 1.3 2004/02/08 11:23:17 gbazin Exp $
+ * $Id: theme.cpp,v 1.4 2004/03/02 21:45:15 ipkiss Exp $
  *
  * Authors: Cyril Deguet     <asmax@via.ecp.fr>
  *          Olivier Teulire <ipkiss@via.ecp.fr>
@@ -37,6 +37,7 @@ Theme::~Theme()
     m_fonts.clear();
     m_commands.clear();
     m_vars.clear();
+    m_curves.clear();
 }
 
 

modules/gui/skins2/theme/skin.dtd

@@ -2,7 +2,7 @@
 -->
 
 
-<!ELEMENT Theme (ThemeInfo,(Bitmap|Font|Window|Event)*)>
+<!ELEMENT Theme (ThemeInfo,(Bitmap|Font|Window)*)>
     <!ATTLIST Theme
         version     CDATA   "1.0"
         magnet      CDATA   "15"
@@ -18,12 +18,6 @@
         file        CDATA   #REQUIRED
         alphacolor  CDATA   #REQUIRED
     >
-<!ELEMENT Event EMPTY>
-    <!ATTLIST Event
-        id          CDATA   #REQUIRED
-        event       CDATA   #REQUIRED
-        key         CDATA   "none"
-    >
 <!ELEMENT Font EMPTY>
     <!ATTLIST Font
         id          CDATA   #REQUIRED
@@ -61,7 +55,7 @@
         maxheight   CDATA   "-1"
     >
 <!ELEMENT Group (Group|Image|Button|Playlist|Slider|RadialSlider|Text|CheckBox|
-                 Rectangle|Anchor)+>
+                 Anchor)+>
     <!ATTLIST Group
         x           CDATA   "0"
         y           CDATA   "0"
@@ -73,6 +67,7 @@
         x           CDATA   "0"
         y           CDATA   "0"
         priority    CDATA   #REQUIRED
+        points      CDATA   "(0,0)"
         range       CDATA   "10"
     >
 
@@ -89,18 +84,6 @@
         onclick     CDATA   "none"
         help        CDATA   "\0"
     >
-<!ELEMENT Rectangle EMPTY>
-    <!ATTLIST Rectangle
-        id          CDATA   "none"
-        visible     CDATA   "true"
-        x           CDATA   "0"
-        y           CDATA   "0"
-        w           CDATA   "50"
-        h           CDATA   "50"
-        color       CDATA   "#C0C0C0"
-        onclick     CDATA   "none"
-        help        CDATA   "\0"
-    >
 <!ELEMENT Button EMPTY>
     <!ATTLIST Button
         id          CDATA   "none"

modules/gui/skins2/utils/bezier.cpp

@@ -2,7 +2,7 @@
  * bezier.cpp
  *****************************************************************************
  * Copyright (C) 2003 VideoLAN
- * $Id: bezier.cpp,v 1.3 2004/02/01 21:13:04 ipkiss Exp $
+ * $Id: bezier.cpp,v 1.4 2004/03/02 21:45:15 ipkiss Exp $
  *
  * Authors: Cyril Deguet     <asmax@via.ecp.fr>
  *          Olivier Teulire <ipkiss@via.ecp.fr>
@@ -30,13 +30,13 @@ Bezier::Bezier( intf_thread_t *p_intf, const vector<float> &rAbscissas,
                 const vector<float> &rOrdinates, Flag_t flag )
     : SkinObject( p_intf )
 {
-    // We expect rAbscissas and rOrdinates to have the same size, of course
-    m_nbCtrlPt = rAbscissas.size();
-
     // Copy the control points coordinates
     m_ptx.assign( rAbscissas.begin(), rAbscissas.end() );
     m_pty.assign( rOrdinates.begin(), rOrdinates.end() );
 
+    // We expect m_ptx and m_pty to have the same size, of course
+    m_nbCtrlPt = m_ptx.size();
+
     // Precalculate the factoriels
     m_ft.push_back( 1 );
     for( int i = 1; i < m_nbCtrlPt; i++ )
@@ -44,18 +44,16 @@ Bezier::Bezier( intf_thread_t *p_intf, const vector<float> &rAbscissas,
         m_ft.push_back( i * m_ft[i - 1] );
     }
 
-    // Initialization
-    int cx, cy, oldx, oldy;
-    m_leftVect.reserve( MAX_BEZIER_POINT + 1 );
-    m_topVect.reserve( MAX_BEZIER_POINT + 1 );
-
     // Calculate the first point
+    int oldx, oldy;
     computePoint( 0, oldx, oldy );
-    m_leftVect[0] = oldx;
-    m_topVect[0]  = oldy;
+    m_leftVect.push_back( oldx );
+    m_topVect.push_back( oldy );
+    m_percVect.push_back( 0 );
 
     // Calculate the other points
     float percentage;
+    int cx, cy;
     for( float j = 1; j <= MAX_BEZIER_POINT; j++ )
     {
         percentage = j / MAX_BEZIER_POINT;
@@ -71,9 +69,19 @@ Bezier::Bezier( intf_thread_t *p_intf, const vector<float> &rAbscissas,
             oldy = cy;
         }
     }
-    m_nbPoints = m_percVect.size();
+    m_nbPoints = m_leftVect.size();
+
+    // If we have only one control point, we duplicate it
+    // This allows to simplify the algorithms used in the class
+    if( m_nbPoints == 1 )
+    {
+        m_leftVect.push_back( m_leftVect[0] );
+        m_topVect.push_back( m_topVect[0] );
+        m_percVect.push_back( 1 );
+        m_nbPoints = 2;
+   }
 
-    // Small hack to ensure that the percentage of the last point is always 1
+    // Ensure that the percentage of the last point is always 1
     m_percVect[m_nbPoints - 1] = 1;
 }
 

modules/gui/skins2/utils/bezier.hpp

@@ -2,7 +2,7 @@
  * bezier.hpp
  *****************************************************************************
  * Copyright (C) 2003 VideoLAN
- * $Id: bezier.hpp,v 1.4 2004/02/01 21:13:04 ipkiss Exp $
+ * $Id: bezier.hpp,v 1.5 2004/03/02 21:45:15 ipkiss Exp $
  *
  * Authors: Cyril Deguet     <asmax@via.ecp.fr>
  *          Olivier Teulière <ipkiss@via.ecp.fr>
@@ -51,6 +51,9 @@ class Bezier: public SkinObject
                 Flag_t flag = kCoordsBoth );
         ~Bezier() {}
 
+        /// Get the number of control points used to define the curve
+        int getNbCtrlPoints() const { return m_nbCtrlPt; }
+
         /// Return the percentage (between 0 and 1) of the curve point nearest
         /// from (x, y)
         float getNearestPercent( int x, int y ) const;