FastLineClip.cpp

/*--------------------------------------------------- V_FCclip * Realization of line clipping algorithm FC (Fast Clipping) * Sobkow-Pospisil-Yang, with line encoding * * int LineClip (double *x0, double *y0, double *x1, double *y1) * * Clips the line defined with (x0,y0)-(x1,y1), by clipping * window defined with global scalars Wxlef, Wytop, Wxrig, Wybot * (top of screen is 0) * * Returns: * -1 - clipping window error * 0 - line is invisible * 1 - line is visible */ #include "FastLineClip.h" namespace OpenXcom { void FastLineClip::Clip0_Bottom(void) { FC_xn = FC_xn + (FC_xk-FC_xn)*(Wybot-FC_yn)/(FC_yk-FC_yn); FC_yn = Wybot; } void FastLineClip::Clip0_Top(void) { FC_xn = FC_xn + (FC_xk-FC_xn)*(Wytop-FC_yn)/(FC_yk-FC_yn); FC_yn = Wytop; } void FastLineClip::Clip0_Right(void) { FC_yn = FC_yn + (FC_yk-FC_yn)*(Wxrig-FC_xn)/(FC_xk-FC_xn); FC_xn = Wxrig; } void FastLineClip::Clip0_Left(void) { FC_yn = FC_yn + (FC_yk-FC_yn)*(Wxlef-FC_xn)/(FC_xk-FC_xn); FC_xn = Wxlef; } void FastLineClip::Clip1_Bottom(void) { FC_xk = FC_xk + (FC_xn-FC_xk)*(Wybot-FC_yk)/(FC_yn-FC_yk); FC_yk = Wybot; } void FastLineClip::Clip1_Top(void) { FC_xk = FC_xk + (FC_xn-FC_xk)*(Wytop-FC_yk)/(FC_yn-FC_yk); FC_yk = Wytop; } void FastLineClip::Clip1_Right(void) { FC_yk = FC_yk + (FC_yn-FC_yk)*(Wxrig-FC_xk)/(FC_xn-FC_xk); FC_xk = Wxrig; } void FastLineClip::Clip1_Left(void) { FC_yk = FC_yk + (FC_yn-FC_yk)*(Wxlef-FC_xk)/(FC_xn-FC_xk); FC_xk = Wxlef; } int FastLineClip::LineClip(double *x0, double *y0, double *x1, double *y1) { int Code= 0; int visible= 0; // visible state FC_xn= *x0; FC_yn= *y0; FC_xk= *x1; FC_yk= *y1; // "Code" evaluation - bits 0..3 - end point, bits 4..7 - start point. //start point is if (FC_yk > Wybot) Code|= 0x08; else //lower if (FC_yk < Wytop) Code|= 0x04; //higher if (FC_xk > Wxrig) Code|= 0x02; else //righter if (FC_xk < Wxlef) Code|= 0x01; //lefter //end point is if (FC_yn > Wybot) Code|= 0x80; else //lower if (FC_yn < Wytop) Code|= 0x40; //higher if (FC_xn > Wxrig) Code|= 0x20; else //righter if (FC_xn < Wxlef) Code|= 0x10; //lefter // Clipping for each of 81 cases. switch (Code) { // From center case 0x00: ++visible; break; case 0x01: Clip1_Left() ; ++visible; break; case 0x02: Clip1_Right(); ++visible; break; case 0x04: Clip1_Top(); ++visible; break; case 0x05: Clip1_Left() ; if (FC_yk < Wytop) Clip1_Top(); ++visible; break; case 0x06: Clip1_Right(); if (FC_yk < Wytop) Clip1_Top(); ++visible; break; case 0x08: Clip1_Bottom(); ++visible; break; case 0x09: Clip1_Left() ; if (FC_yk > Wybot) Clip1_Bottom(); ++visible; break; case 0x0A: Clip1_Right(); if (FC_yk > Wybot) Clip1_Bottom(); ++visible; break; //From left case 0x10: Clip0_Left(); ++visible; case 0x11: break; case 0x12: Clip0_Left(); Clip1_Right(); ++visible; break; case 0x14: Clip0_Left(); if (FC_yn < Wytop) break; Clip1_Top(); ++visible; case 0x15: break; case 0x16: Clip0_Left(); if (FC_yn < Wytop) break; Clip1_Top(); if (FC_xk > Wxrig) Clip1_Right(); ++visible; break; case 0x18: Clip0_Left(); if (FC_yn > Wybot) break; Clip1_Bottom(); ++visible; case 0x19: break; case 0x1A: Clip0_Left(); if (FC_yn > Wybot) break; Clip1_Bottom(); if (FC_xk > Wxrig) Clip1_Right(); ++visible; break; // From right case 0x20: Clip0_Right(); ++visible; break; case 0x21: Clip0_Right(); Clip1_Left(); ++visible; case 0x22: break; case 0x24: Clip0_Right(); if (FC_yn < Wytop) break; Clip1_Top(); ++visible; break; case 0x25: Clip0_Right(); if (FC_yn < Wytop) break; Clip1_Top(); if (FC_xk < Wxlef) Clip1_Left(); ++visible; case 0x26: break; case 0x28: Clip0_Right(); if (FC_yn > Wybot) break; Clip1_Bottom(); ++visible; break; case 0x29: Clip0_Right(); if (FC_yn > Wybot) break; Clip1_Bottom(); if (FC_xk < Wxlef) Clip1_Left(); ++visible; case 0x2A: break; // From down case 0x40: Clip0_Top(); ++visible; break; case 0x41: Clip0_Top(); if (FC_xn < Wxlef) break; Clip1_Left() ; if (FC_yk < Wytop) Clip1_Top(); ++visible; break; case 0x42: Clip0_Top(); if (FC_xn > Wxrig) break; Clip1_Right(); ++visible; case 0x44: case 0x45: case 0x46: break; case 0x48: Clip0_Top(); Clip1_Bottom(); ++visible; break; case 0x49: Clip0_Top(); if (FC_xn < Wxlef) break; Clip1_Left() ; if (FC_yk > Wybot) Clip1_Bottom(); ++visible; break; case 0x4A: Clip0_Top(); if (FC_xn > Wxrig) break; Clip1_Right(); if (FC_yk > Wybot) Clip1_Bottom(); ++visible; break; // From bottom-left case 0x50: Clip0_Left(); if (FC_yn < Wytop) Clip0_Top(); ++visible; case 0x51: break; case 0x52: Clip1_Right(); if (FC_yk < Wytop) break; Clip0_Top(); if (FC_xn < Wxlef) Clip0_Left(); ++visible; case 0x54: case 0x55: case 0x56: break; case 0x58: Clip1_Bottom(); if (FC_xk < Wxlef) break; Clip0_Top(); if (FC_xn < Wxlef) Clip0_Left(); ++visible; case 0x59: break; case 0x5A: Clip0_Left(); if (FC_yn > Wybot) break; Clip1_Right(); if (FC_yk < Wytop) break; if (FC_yn < Wytop) Clip0_Top(); if (FC_yk > Wybot) Clip1_Bottom(); ++visible; break; // From bottom-right case 0x60: Clip0_Right(); if (FC_yn < Wytop) Clip0_Top(); ++visible; break; case 0x61: Clip1_Left() ; if (FC_yk < Wytop) break; Clip0_Top(); if (FC_xn > Wxrig) Clip0_Right(); ++visible; case 0x62: case 0x64: case 0x65: case 0x66: break; case 0x68: Clip1_Bottom(); if (FC_xk > Wxrig) break; Clip0_Right(); if (FC_yn < Wytop) Clip0_Top(); ++visible; break; case 0x69: Clip1_Left() ; if (FC_yk < Wytop) break; Clip0_Right(); if (FC_yn > Wybot) break; if (FC_yk > Wybot) Clip1_Bottom(); if (FC_yn < Wytop) Clip0_Top(); ++visible; case 0x6A: break; // From top case 0x80: Clip0_Bottom(); ++visible; break; case 0x81: Clip0_Bottom(); if (FC_xn < Wxlef) break; Clip1_Left() ; ++visible; break; case 0x82: Clip0_Bottom(); if (FC_xn > Wxrig) break; Clip1_Right(); ++visible; break; case 0x84: Clip0_Bottom(); Clip1_Top(); ++visible; break; case 0x85: Clip0_Bottom(); if (FC_xn < Wxlef) break; Clip1_Left() ; if (FC_yk < Wytop) Clip1_Top(); ++visible; break; case 0x86: Clip0_Bottom(); if (FC_xn > Wxrig) break; Clip1_Right(); if (FC_yk < Wytop) Clip1_Top(); ++visible; case 0x88: case 0x89: case 0x8A: break; // From top-left case 0x90: Clip0_Left(); if (FC_yn > Wybot) Clip0_Bottom(); ++visible; case 0x91: break; case 0x92: Clip1_Right(); if (FC_yk > Wybot) break; Clip0_Bottom(); if (FC_xn < Wxlef) Clip0_Left(); ++visible; break; case 0x94: Clip1_Top(); if (FC_xk < Wxlef) break; Clip0_Left(); if (FC_yn > Wybot) Clip0_Bottom(); ++visible; case 0x95: break; case 0x96: Clip0_Left(); if (FC_yn < Wytop) break; Clip1_Right(); if (FC_yk > Wybot) break; if (FC_yn > Wybot) Clip0_Bottom(); if (FC_yk < Wytop) Clip1_Top(); ++visible; case 0x98: case 0x99: case 0x9A: break; // From top-right case 0xA0: Clip0_Right(); if (FC_yn > Wybot) Clip0_Bottom(); ++visible; break; case 0xA1: Clip1_Left() ; if (FC_yk > Wybot) break; Clip0_Bottom(); if (FC_xn > Wxrig) Clip0_Right(); ++visible; case 0xA2: break; case 0xA4: Clip1_Top(); if (FC_xk > Wxrig) break; Clip0_Right(); if (FC_yn > Wybot) Clip0_Bottom(); ++visible; break; case 0xA5: Clip1_Left() ; if (FC_yk > Wybot) break; Clip0_Right(); if (FC_yn < Wytop) break; if (FC_yk < Wytop) Clip1_Top(); if (FC_yn > Wybot) Clip0_Bottom(); ++visible; case 0xA6: case 0xA8: case 0xA9: case 0xAA: break; // Error default: visible= -1; break; } //Switch if (visible > 0) { *x0= FC_xn; *y0= FC_yn; *x1= FC_xk; *y1= FC_yk; } return (visible); } }

↑ V525 The code contains the collection of similar blocks. Check items 'Clip1_Left', 'Clip1_Right', 'Clip1_Top', 'Clip1_Left' in lines 105, 106, 107, 108.