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