contrib/src/ogl/oglmisc.cpp

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        misc.cpp
   3 // Purpose:     Miscellaneous OGL support functions
   4 // Author:      Julian Smart
   5 // Modified by:
   6 // Created:     12/07/98
   7 // RCS-ID:      $Id$
   8 // Copyright:   (c) Julian Smart
   9 // Licence:     wxWindows licence
  10 /////////////////////////////////////////////////////////////////////////////
  11
  12 #ifdef __GNUG__
  13 #pragma implementation "misc.h"
  14 #endif
  15
  16 // For compilers that support precompilation, includes "wx.h".
  17 #include "wx/wxprec.h"
  18
  19 #ifdef __BORLANDC__
  20 #pragma hdrstop
  21 #endif
  22
  23 #ifndef WX_PRECOMP
  24 #include <wx/wx.h>
  25 #endif
  26
  27 #include <wx/wxexpr.h>
  28
  29 #include <wx/types.h>
  30
  31 #ifdef new
  32 #undef new
  33 #endif
  34
  35 #include <ctype.h>
  36 #include <math.h>
  37 #include <stdlib.h>
  38
  39 #include <wx/ogl/basic.h>
  40 #include <wx/ogl/basicp.h>
  41 #include <wx/ogl/misc.h>
  42 #include <wx/ogl/constrnt.h>
  43 #include <wx/ogl/composit.h>
  44
  45 wxFont*         g_oglNormalFont;
  46 wxPen*          g_oglBlackPen;
  47 wxPen*          g_oglWhiteBackgroundPen;
  48 wxPen*          g_oglTransparentPen;
  49 wxBrush*        g_oglWhiteBackgroundBrush;
  50 wxPen*          g_oglBlackForegroundPen;
  51 wxCursor*       g_oglBullseyeCursor = NULL;
  52
  53 char*           oglBuffer = NULL;
  54
  55 wxList          oglObjectCopyMapping(wxKEY_INTEGER);
  56
  57
  58
  59 void wxOGLInitialize()
  60 {
  61   g_oglBullseyeCursor = new wxCursor(wxCURSOR_BULLSEYE);
  62
  63   g_oglNormalFont = new wxFont(10, wxSWISS, wxNORMAL, wxNORMAL);
  64
  65   g_oglBlackPen = new wxPen("BLACK", 1, wxSOLID);
  66
  67   g_oglWhiteBackgroundPen = new wxPen("WHITE", 1, wxSOLID);
  68   g_oglTransparentPen = new wxPen("WHITE", 1, wxTRANSPARENT);
  69   g_oglWhiteBackgroundBrush = new wxBrush("WHITE", wxSOLID);
  70   g_oglBlackForegroundPen = new wxPen("BLACK", 1, wxSOLID);
  71
  72   OGLInitializeConstraintTypes();
  73
  74   // Initialize big buffer used when writing images
  75   oglBuffer = new char[3000];
  76
  77 }
  78
  79 void wxOGLCleanUp()
  80 {
  81     if (oglBuffer)
  82     {
  83         delete[] oglBuffer;
  84         oglBuffer = NULL;
  85     }
  86     oglBuffer = NULL;
  87     if (g_oglBullseyeCursor)
  88     {
  89         delete g_oglBullseyeCursor;
  90         g_oglBullseyeCursor = NULL;
  91     }
  92
  93     if (g_oglNormalFont)
  94     {
  95         delete g_oglNormalFont;
  96         g_oglNormalFont = NULL;
  97     }
  98     if (g_oglBlackPen)
  99     {
 100         delete g_oglBlackPen;
 101         g_oglBlackPen = NULL;
 102     }
 103     if (g_oglWhiteBackgroundPen)
 104     {
 105         delete g_oglWhiteBackgroundPen;
 106         g_oglWhiteBackgroundPen = NULL;
 107     }
 108     if (g_oglTransparentPen)
 109     {
 110         delete g_oglTransparentPen;
 111         g_oglTransparentPen = NULL;
 112     }
 113     if (g_oglWhiteBackgroundBrush)
 114     {
 115         delete g_oglWhiteBackgroundBrush;
 116         g_oglWhiteBackgroundBrush = NULL;
 117     }
 118     if (g_oglBlackForegroundPen)
 119     {
 120         delete g_oglBlackForegroundPen;
 121         g_oglBlackForegroundPen = NULL;
 122     }
 123
 124     OGLCleanUpConstraintTypes();
 125 }
 126
 127 wxFont *oglMatchFont(int point_size)
 128 {
 129   wxFont *font = wxTheFontList->FindOrCreateFont(point_size, wxSWISS, wxNORMAL, wxNORMAL);
 130 #if 0
 131   switch (point_size)
 132   {
 133     case 4:
 134       font = swiss_font_4;
 135       break;
 136     case 6:
 137       font = swiss_font_6;
 138       break;
 139     case 8:
 140       font = swiss_font_8;
 141       break;
 142     case 12:
 143       font = swiss_font_12;
 144       break;
 145     case 14:
 146       font = swiss_font_14;
 147       break;
 148     case 18:
 149       font = swiss_font_18;
 150       break;
 151     case 24:
 152       font = swiss_font_24;
 153       break;
 154     default:
 155     case 10:
 156       font = swiss_font_10;
 157       break;
 158   }
 159 #endif
 160   return font;
 161 }
 162
 163 int FontSizeDialog(wxFrame *parent, int old_size)
 164 {
 165   if (old_size <= 0)
 166     old_size = 10;
 167   char buf[40];
 168   sprintf(buf, "%d", old_size);
 169   wxString ans = wxGetTextFromUser("Enter point size", "Font size", buf, parent);
 170   if (ans == "")
 171     return 0;
 172
 173   int new_size = atoi(ans);
 174   if ((new_size <= 0) || (new_size > 40))
 175   {
 176     wxMessageBox("Invalid point size!", "Error", wxOK);
 177     return 0;
 178   }
 179   return new_size;
 180 /*
 181   char *strings[8];
 182   strings[0] = "4";
 183   strings[1] = "6";
 184   strings[2] = "8";
 185   strings[3] = "10";
 186   strings[4] = "12";
 187   strings[5] = "14";
 188   strings[6] = "18";
 189   strings[7] = "24";
 190   char *ans = wxGetSingleChoice("Choose", "Choose a font size", 8, strings, parent);
 191   if (ans)
 192   {
 193     int size;
 194     sscanf(ans, "%d", &size);
 195     return oglMatchFont(size);
 196   }
 197   else return NULL;
 198 */
 199 }
 200
 201 // Centre a list of strings in the given box. xOffset and yOffset are the
 202 // the positions that these lines should be relative to, and this might be
 203 // the same as m_xpos, m_ypos, but might be zero if formatting from left-justifying.
 204 void oglCentreText(wxDC& dc, wxList *text_list,
 205                 double m_xpos, double m_ypos, double width, double height,
 206                 int formatMode)
 207 {
 208   int n = text_list->Number();
 209
 210   if (!text_list || (n == 0))
 211     return;
 212
 213   // First, get maximum dimensions of box enclosing text
 214
 215   long char_height = 0;
 216   long max_width = 0;
 217   long current_width = 0;
 218
 219   // Store text extents for speed
 220   double *widths = new double[n];
 221
 222   wxNode *current = text_list->First();
 223   int i = 0;
 224   while (current)
 225   {
 226     wxShapeTextLine *line = (wxShapeTextLine *)current->Data();
 227     dc.GetTextExtent(line->GetText(), &current_width, &char_height);
 228     widths[i] = current_width;
 229
 230     if (current_width > max_width)
 231       max_width = current_width;
 232     current = current->Next();
 233     i ++;
 234   }
 235
 236   double max_height = n*char_height;
 237
 238   double xoffset, yoffset, xOffset, yOffset;
 239
 240   if (formatMode & FORMAT_CENTRE_VERT)
 241   {
 242     if (max_height < height)
 243       yoffset = (double)(m_ypos - (height/2.0) + (height - max_height)/2.0);
 244     else
 245       yoffset = (double)(m_ypos - (height/2.0));
 246     yOffset = m_ypos;
 247   }
 248   else
 249   {
 250     yoffset = 0.0;
 251     yOffset = 0.0;
 252   }
 253
 254   if (formatMode & FORMAT_CENTRE_HORIZ)
 255   {
 256     xoffset = (double)(m_xpos - width/2.0);
 257     xOffset = m_xpos;
 258   }
 259   else
 260   {
 261     xoffset = 0.0;
 262     xOffset = 0.0;
 263   }
 264
 265   current = text_list->First();
 266   i = 0;
 267
 268   while (current)
 269   {
 270     wxShapeTextLine *line = (wxShapeTextLine *)current->Data();
 271
 272     double x;
 273     if ((formatMode & FORMAT_CENTRE_HORIZ) && (widths[i] < width))
 274       x = (double)((width - widths[i])/2.0 + xoffset);
 275     else
 276       x = xoffset;
 277     double y = (double)(i*char_height + yoffset);
 278
 279     line->SetX( x - xOffset ); line->SetY( y - yOffset );
 280     current = current->Next();
 281     i ++;
 282   }
 283
 284   delete widths;
 285 }
 286
 287 // Centre a list of strings in the given box
 288 void oglCentreTextNoClipping(wxDC& dc, wxList *text_list,
 289                               double m_xpos, double m_ypos, double width, double height)
 290 {
 291   int n = text_list->Number();
 292
 293   if (!text_list || (n == 0))
 294     return;
 295
 296   // First, get maximum dimensions of box enclosing text
 297
 298   long char_height = 0;
 299   long max_width = 0;
 300   long current_width = 0;
 301
 302   // Store text extents for speed
 303   double *widths = new double[n];
 304
 305   wxNode *current = text_list->First();
 306   int i = 0;
 307   while (current)
 308   {
 309     wxShapeTextLine *line = (wxShapeTextLine *)current->Data();
 310     dc.GetTextExtent(line->GetText(), &current_width, &char_height);
 311     widths[i] = current_width;
 312
 313     if (current_width > max_width)
 314       max_width = current_width;
 315     current = current->Next();
 316     i ++;
 317   }
 318
 319   double max_height = n*char_height;
 320
 321   double yoffset = (double)(m_ypos - (height/2.0) + (height - max_height)/2.0);
 322
 323   double xoffset = (double)(m_xpos - width/2.0);
 324
 325   current = text_list->First();
 326   i = 0;
 327
 328   while (current)
 329   {
 330     wxShapeTextLine *line = (wxShapeTextLine *)current->Data();
 331
 332     double x = (double)((width - widths[i])/2.0 + xoffset);
 333     double y = (double)(i*char_height + yoffset);
 334
 335     line->SetX( x - m_xpos ); line->SetY( y - m_ypos );
 336     current = current->Next();
 337     i ++;
 338   }
 339   delete widths;
 340 }
 341
 342 void oglGetCentredTextExtent(wxDC& dc, wxList *text_list,
 343                               double m_xpos, double m_ypos, double width, double height,
 344                               double *actual_width, double *actual_height)
 345 {
 346   int n = text_list->Number();
 347
 348   if (!text_list || (n == 0))
 349   {
 350     *actual_width = 0;
 351     *actual_height = 0;
 352     return;
 353   }
 354
 355   // First, get maximum dimensions of box enclosing text
 356
 357   long char_height = 0;
 358   long max_width = 0;
 359   long current_width = 0;
 360
 361   wxNode *current = text_list->First();
 362   int i = 0;
 363   while (current)
 364   {
 365     wxShapeTextLine *line = (wxShapeTextLine *)current->Data();
 366     dc.GetTextExtent(line->GetText(), &current_width, &char_height);
 367
 368     if (current_width > max_width)
 369       max_width = current_width;
 370     current = current->Next();
 371     i ++;
 372   }
 373
 374   *actual_height = n*char_height;
 375   *actual_width = max_width;
 376 }
 377
 378 // Format a string to a list of strings that fit in the given box.
 379 // Interpret %n and 10 or 13 as a new line.
 380 wxStringList *oglFormatText(wxDC& dc, const wxString& text, double width, double height, int formatMode)
 381 {
 382   // First, parse the string into a list of words
 383   wxStringList word_list;
 384
 385   // Make new lines into NULL strings at this point
 386   int i = 0; int j = 0; int len = strlen(text);
 387   char word[200]; word[0] = 0;
 388   bool end_word = FALSE; bool new_line = FALSE;
 389   while (i < len)
 390   {
 391     switch (text[i])
 392     {
 393       case '%':
 394       {
 395         i ++;
 396         if (i == len)
 397         { word[j] = '%'; j ++; }
 398         else
 399         {
 400           if (text[i] == 'n')
 401           { new_line = TRUE; end_word = TRUE; i++; }
 402           else
 403           { word[j] = '%'; j ++; word[j] = text[i]; j ++; i ++; }
 404         }
 405         break;
 406       }
 407       case 10:
 408       {
 409         new_line = TRUE; end_word = TRUE; i++;
 410         break;
 411       }
 412       case 13:
 413       {
 414         new_line = TRUE; end_word = TRUE; i++;
 415       }
 416       case ' ':
 417       {
 418         end_word = TRUE;
 419         i ++;
 420         break;
 421       }
 422       default:
 423       {
 424         word[j] = text[i];
 425         j ++; i ++;
 426         break;
 427       }
 428     }
 429     if (i == len) end_word = TRUE;
 430     if (end_word)
 431     {
 432       word[j] = 0;
 433       j = 0;
 434       word_list.Add(word);
 435       end_word = FALSE;
 436     }
 437     if (new_line)
 438     {
 439       word_list.Append(NULL);
 440       new_line = FALSE;
 441     }
 442   }
 443   // Now, make a list of strings which can fit in the box
 444   wxStringList *string_list = new wxStringList;
 445
 446   char buffer[400];
 447   buffer[0] = 0;
 448   wxNode *node = word_list.First();
 449   long x, y;
 450
 451   while (node)
 452   {
 453     wxString oldBuffer(buffer);
 454
 455     char *s = (char *)node->Data();
 456     if (!s)
 457     {
 458       // FORCE NEW LINE
 459       if (strlen(buffer) > 0)
 460         string_list->Add(buffer);
 461
 462       buffer[0] = 0;
 463     }
 464     else
 465     {
 466       if (buffer[0] != 0)
 467         strcat(buffer, " ");
 468
 469       strcat(buffer, s);
 470       dc.GetTextExtent(buffer, &x, &y);
 471
 472       // Don't fit within the bounding box if we're fitting shape to contents
 473       if ((x > width) && !(formatMode & FORMAT_SIZE_TO_CONTENTS))
 474       {
 475         // Deal with first word being wider than box
 476         if (oldBuffer.Length() > 0)
 477           string_list->Add(oldBuffer);
 478
 479         buffer[0] = 0;
 480         strcat(buffer, s);
 481       }
 482     }
 483
 484     node = node->Next();
 485   }
 486   if (buffer[0] != 0)
 487     string_list->Add(buffer);
 488
 489   return string_list;
 490 }
 491
 492 void oglDrawFormattedText(wxDC& dc, wxList *text_list,
 493                        double m_xpos, double m_ypos, double width, double height,
 494                        int formatMode)
 495 {
 496   double xoffset, yoffset;
 497   if (formatMode & FORMAT_CENTRE_HORIZ)
 498     xoffset = m_xpos;
 499   else
 500     xoffset = (double)(m_xpos - (width / 2.0));
 501
 502   if (formatMode & FORMAT_CENTRE_VERT)
 503     yoffset = m_ypos;
 504   else
 505     yoffset = (double)(m_ypos - (height / 2.0));
 506
 507   dc.SetClippingRegion(
 508                     (long)(m_xpos - width/2.0), (long)(m_ypos - height/2.0),
 509                     (long)width, (long)height);
 510
 511   wxNode *current = text_list->First();
 512   while (current)
 513   {
 514     wxShapeTextLine *line = (wxShapeTextLine *)current->Data();
 515
 516     dc.DrawText(line->GetText(), WXROUND(xoffset + line->GetX()), WXROUND(yoffset + line->GetY()));
 517     current = current->Next();
 518   }
 519
 520   dc.DestroyClippingRegion();
 521 }
 522
 523 /*
 524  * Find centroid given list of points comprising polyline
 525  *
 526  */
 527
 528 void oglFindPolylineCentroid(wxList *points, double *x, double *y)
 529 {
 530   double xcount = 0;
 531   double ycount = 0;
 532
 533   wxNode *node = points->First();
 534   while (node)
 535   {
 536     wxRealPoint *point = (wxRealPoint *)node->Data();
 537     xcount += point->x;
 538     ycount += point->y;
 539     node = node->Next();
 540   }
 541
 542   *x = (xcount/points->Number());
 543   *y = (ycount/points->Number());
 544 }
 545
 546 /*
 547  * Check that (x1, y1) -> (x2, y2) hits (x3, y3) -> (x4, y4).
 548  * If so, ratio1 gives the proportion along the first line
 549  * that the intersection occurs (or something like that).
 550  * Used by functions below.
 551  *
 552  */
 553 void oglCheckLineIntersection(double x1, double y1, double x2, double y2,
 554                              double x3, double y3, double x4, double y4,
 555                              double *ratio1, double *ratio2)
 556 {
 557   double denominator_term = (y4 - y3)*(x2 - x1) - (y2 - y1)*(x4 - x3);
 558   double numerator_term = (x3 - x1)*(y4 - y3) + (x4 - x3)*(y1 - y3);
 559
 560   double line_constant;
 561   double length_ratio = 1.0;
 562   double k_line = 1.0;
 563
 564   // Check for parallel lines
 565   if ((denominator_term < 0.005) && (denominator_term > -0.005))
 566     line_constant = -1.0;
 567   else
 568     line_constant = numerator_term/denominator_term;
 569
 570   // Check for intersection
 571   if ((line_constant < 1.0) && (line_constant > 0.0))
 572   {
 573     // Now must check that other line hits
 574     if (((y4 - y3) < 0.005) && ((y4 - y3) > -0.005))
 575       k_line = ((x1 - x3) + line_constant*(x2 - x1))/(x4 - x3);
 576     else
 577       k_line = ((y1 - y3) + line_constant*(y2 - y1))/(y4 - y3);
 578
 579     if ((k_line >= 0.0) && (k_line < 1.0))
 580       length_ratio = line_constant;
 581     else
 582       k_line = 1.0;
 583   }
 584   *ratio1 = length_ratio;
 585   *ratio2 = k_line;
 586 }
 587
 588 /*
 589  * Find where (x1, y1) -> (x2, y2) hits one of the lines in xvec, yvec.
 590  * (*x3, *y3) is the point where it hits.
 591  *
 592  */
 593 void oglFindEndForPolyline(double n, double xvec[], double yvec[],
 594                            double x1, double y1, double x2, double y2, double *x3, double *y3)
 595 {
 596   int i;
 597   double lastx = xvec[0];
 598   double lasty = yvec[0];
 599
 600   double min_ratio = 1.0;
 601   double line_ratio;
 602   double other_ratio;
 603
 604   for (i = 1; i < n; i++)
 605   {
 606     oglCheckLineIntersection(x1, y1, x2, y2, lastx, lasty, xvec[i], yvec[i],
 607                             &line_ratio, &other_ratio);
 608     lastx = xvec[i];
 609     lasty = yvec[i];
 610
 611     if (line_ratio < min_ratio)
 612       min_ratio = line_ratio;
 613   }
 614
 615   // Do last (implicit) line if last and first doubles are not identical
 616   if (!(xvec[0] == lastx && yvec[0] == lasty))
 617   {
 618     oglCheckLineIntersection(x1, y1, x2, y2, lastx, lasty, xvec[0], yvec[0],
 619                             &line_ratio, &other_ratio);
 620
 621     if (line_ratio < min_ratio)
 622       min_ratio = line_ratio;
 623   }
 624
 625   *x3 = (x1 + (x2 - x1)*min_ratio);
 626   *y3 = (y1 + (y2 - y1)*min_ratio);
 627
 628 }
 629
 630 /*
 631  * Find where the line hits the box.
 632  *
 633  */
 634
 635 void oglFindEndForBox(double width, double height,
 636                       double x1, double y1,         // Centre of box (possibly)
 637                       double x2, double y2,         // other end of line
 638                       double *x3, double *y3)       // End on box edge
 639 {
 640   double xvec[5];
 641   double yvec[5];
 642
 643   xvec[0] = (double)(x1 - width/2.0);
 644   yvec[0] = (double)(y1 - height/2.0);
 645   xvec[1] = (double)(x1 - width/2.0);
 646   yvec[1] = (double)(y1 + height/2.0);
 647   xvec[2] = (double)(x1 + width/2.0);
 648   yvec[2] = (double)(y1 + height/2.0);
 649   xvec[3] = (double)(x1 + width/2.0);
 650   yvec[3] = (double)(y1 - height/2.0);
 651   xvec[4] = (double)(x1 - width/2.0);
 652   yvec[4] = (double)(y1 - height/2.0);
 653
 654   oglFindEndForPolyline(5, xvec, yvec, x2, y2, x1, y1, x3, y3);
 655 }
 656
 657 /*
 658  * Find where the line hits the circle.
 659  *
 660  */
 661
 662 void oglFindEndForCircle(double radius,
 663                          double x1, double y1,  // Centre of circle
 664                          double x2, double y2,  // Other end of line
 665                          double *x3, double *y3)
 666 {
 667   double H = (double)sqrt((x2 - x1)*(x2 - x1) + (y2 - y1)*(y2 - y1));
 668
 669   if (H == 0.0)
 670   {
 671     *x3 = x1;
 672     *y3 = y1;
 673   }
 674   else
 675   {
 676    *y3 = radius * (y2 - y1)/H + y1;
 677    *x3 = radius * (x2 - x1)/H + x1;
 678   }
 679 }
 680
 681 /*
 682  * Given the line (x1, y1) -> (x2, y2), and an arrow size of given length and width,
 683  * return the position of the tip of the arrow and the left and right vertices of the arrow.
 684  *
 685  */
 686
 687 void oglGetArrowPoints(double x1, double y1, double x2, double y2,
 688                       double length, double width,
 689                       double *tip_x, double *tip_y,
 690                       double *side1_x, double *side1_y,
 691                       double *side2_x, double *side2_y)
 692 {
 693   double l = (double)sqrt((x2 - x1)*(x2 - x1) + (y2 - y1)*(y2 - y1));
 694
 695   if (l < 0.01)
 696     l = (double) 0.01;
 697
 698   double i_bar = (x2 - x1)/l;
 699   double j_bar = (y2 - y1)/l;
 700
 701   double x3 = (- length*i_bar) + x2;
 702   double y3 = (- length*j_bar) + y2;
 703
 704   *side1_x = width*(-j_bar) + x3;
 705   *side1_y = width*i_bar + y3;
 706
 707   *side2_x = -width*(-j_bar) + x3;
 708   *side2_y = -width*i_bar + y3;
 709
 710   *tip_x = x2; *tip_y = y2;
 711 }
 712
 713 /*
 714  * Given an ellipse and endpoints of a line, returns the point at which
 715  * the line touches the ellipse in values x4, y4.
 716  * This function assumes that the centre of the ellipse is at x1, y1, and the
 717  * ellipse has a width of width1 and a height of height1. It also assumes you are
 718  * wanting to draw an arc FROM point x2, y2 TOWARDS point x3, y3.
 719  * This function calculates the x,y coordinates of the intersection point of
 720  * the arc with the ellipse.
 721  * Author: Ian Harrison
 722  */
 723
 724 void oglDrawArcToEllipse(double x1, double y1, double width1, double height1, double x2, double y2, double x3, double y3,
 725   double *x4, double *y4)
 726 {
 727   double a1 = (double)(width1/2.0);
 728   double b1 = (double)(height1/2.0);
 729
 730   // These are required to give top left x and y coordinates for DrawEllipse
 731 //  double top_left_x1 = (double)(x1 - a1);
 732 //  double top_left_y1 = (double)(y1 - b1);
 733 /*
 734   // Check for vertical line
 735   if (fabs(x2 - x3) < 0.05)
 736   {
 737     *x4 = x3;
 738     if (y2 < y3)
 739       *y4 = (double)(y1 - b1);
 740     else
 741       *y4 = (double)(y1 + b1);
 742     return;
 743   }
 744 */
 745   // Check that x2 != x3
 746   if (fabs(x2 - x3) < 0.05)
 747   {
 748     *x4 = x2;
 749     if (y3 > y2)
 750       *y4 = (double)(y1 - sqrt((b1*b1 - (((x2-x1)*(x2-x1))*(b1*b1)/(a1*a1)))));
 751     else
 752       *y4 = (double)(y1 + sqrt((b1*b1 - (((x2-x1)*(x2-x1))*(b1*b1)/(a1*a1)))));
 753     return;
 754   }
 755
 756   // Calculate the x and y coordinates of the point where arc intersects ellipse
 757
 758   double A, B, C, D, E, F, G, H, K;
 759   double ellipse1_x, ellipse1_y;
 760
 761   A = (double)(1/(a1 * a1));
 762   B = (double)((y3 - y2) * (y3 - y2)) / ((x3 - x2) * (x3 - x2) * b1 * b1);
 763   C = (double)(2 * (y3 - y2) * (y2 - y1)) / ((x3 - x2) * b1 * b1);
 764   D = (double)((y2 - y1) * (y2 - y1)) / (b1 * b1);
 765   E = (double)(A + B);
 766   F = (double)(C - (2 * A * x1) - (2 * B * x2));
 767   G = (double)((A * x1 * x1) + (B * x2 * x2) - (C * x2) + D - 1);
 768   H = (double)((y3 - y2) / (x3 - x2));
 769   K = (double)((F * F) - (4 * E * G));
 770
 771   if (K >= 0)
 772   // In this case the line intersects the ellipse, so calculate intersection
 773   {
 774     if(x2 >= x1)
 775     {
 776       ellipse1_x = (double)(((F * -1) + sqrt(K)) / (2 * E));
 777       ellipse1_y = (double)((H * (ellipse1_x - x2)) + y2);
 778     }
 779     else
 780     {
 781       ellipse1_x = (double)(((F * -1) -  sqrt(K)) / (2 * E));
 782       ellipse1_y = (double)((H * (ellipse1_x - x2)) + y2);
 783     }
 784   }
 785   else
 786   // in this case, arc does not intersect ellipse, so just draw arc
 787   {
 788     ellipse1_x = x3;
 789     ellipse1_y = y3;
 790   }
 791   *x4 = ellipse1_x;
 792   *y4 = ellipse1_y;
 793
 794 /*
 795   // Draw a little circle (radius = 2) at the end of the arc where it hits
 796   // the ellipse .
 797
 798   double circle_x = ellipse1_x - 2.0;
 799   double circle_y = ellipse1_y - 2.0;
 800   m_canvas->DrawEllipse(circle_x, circle_y, 4.0, 4.0);
 801 */
 802 }
 803
 804 // Update a list item from a list of strings
 805 void UpdateListBox(wxListBox *item, wxList *list)
 806 {
 807   item->Clear();
 808   if (!list)
 809     return;
 810
 811   wxNode *node = list->First();
 812   while (node)
 813   {
 814     char *s = (char *)node->Data();
 815     item->Append(s);
 816     node = node->Next();
 817   }
 818 }
 819
 820 bool oglRoughlyEqual(double val1, double val2, double tol)
 821 {
 822     return ( (val1 < (val2 + tol)) && (val1 > (val2 - tol)) &&
 823              (val2 < (val1 + tol)) && (val2 > (val1 - tol)));
 824 }
 825
 826 /*
 827  * Hex<->Dec conversion
 828  */
 829
 830 // Array used in DecToHex conversion routine.
 831 static char sg_HexArray[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B',
 832   'C', 'D', 'E', 'F' };
 833
 834 // Convert 2-digit hex number to decimal
 835 unsigned int oglHexToDec(char* buf)
 836 {
 837   int firstDigit, secondDigit;
 838
 839   if (buf[0] >= 'A')
 840     firstDigit = buf[0] - 'A' + 10;
 841   else
 842     firstDigit = buf[0] - '0';
 843
 844   if (buf[1] >= 'A')
 845     secondDigit = buf[1] - 'A' + 10;
 846   else
 847     secondDigit = buf[1] - '0';
 848
 849   return firstDigit * 16 + secondDigit;
 850 }
 851
 852 // Convert decimal integer to 2-character hex string
 853 void oglDecToHex(unsigned int dec, char *buf)
 854 {
 855     int firstDigit = (int)(dec/16.0);
 856     int secondDigit = (int)(dec - (firstDigit*16.0));
 857     buf[0] = sg_HexArray[firstDigit];
 858     buf[1] = sg_HexArray[secondDigit];
 859     buf[2] = 0;
 860 }
 861
 862 // 3-digit hex to wxColour
 863 wxColour oglHexToColour(const wxString& hex)
 864 {
 865     if (hex.Length() == 6)
 866         {
 867         char buf[7];
 868         strncpy(buf, hex, 7);
 869         unsigned int r = oglHexToDec((char *)buf);
 870         unsigned int g = oglHexToDec((char *)(buf+2));
 871         unsigned int b = oglHexToDec((char *)(buf+4));
 872         return wxColour(r, g, b);
 873         }
 874         else
 875             return wxColour(0,0,0);
 876 }
 877
 878 // RGB to 3-digit hex
 879 wxString oglColourToHex(const wxColour& colour)
 880 {
 881     char buf[7];
 882     unsigned int red = colour.Red();
 883     unsigned int green = colour.Green();
 884     unsigned int blue = colour.Blue();
 885
 886     oglDecToHex(red, buf);
 887     oglDecToHex(green, buf+2);
 888     oglDecToHex(blue, buf+4);
 889
 890     return wxString(buf);
 891 }
 892
 893