# base.cpp

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    00001 /* $Id: base.cpp 22439 2011-05-08 18:20:21Z frosch $ */
    00002
    00003 /*
    00004  * This file is part of OpenTTD.
    00005  * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
    00006  * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
    00007  * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
    00008  */
    00009
    00012 #include "../stdafx.h"
    00013 #include "base.hpp"
    00014 #include "../core/math_func.hpp"
    00015
    00016 void Blitter::DrawLine(void *video, int x, int y, int x2, int y2, int screen_width, int screen_height, uint8 colour, int width)
    00017 {
    00018   int dy;
    00019   int dx;
    00020   int stepx;
    00021   int stepy;
    00022
    00023   dy = (y2 - y) * 2;
    00024   if (dy < 0) {
    00025     dy = -dy;
    00026     stepy = -1;
    00027   } else {
    00028     stepy = 1;
    00029   }
    00030
    00031   dx = (x2 - x) * 2;
    00032   if (dx < 0) {
    00033     dx = -dx;
    00034     stepx = -1;
    00035   } else {
    00036     stepx = 1;
    00037   }
    00038
    00039   if (dx == 0 && dy == 0) {
    00040     /* The algorithm below cannot handle this special case; make it work at least for line width 1 */
    00041     if (x >= 0 && x < screen_width && y >= 0 && y < screen_height) this->SetPixel(video, x, y, colour);
    00042     return;
    00043   }
    00044
    00045   int frac_diff = width * max(dx, dy);
    00046   if (width > 1) {
    00047     /* compute frac_diff = width * sqrt(dx*dx + dy*dy)
    00048      * Start interval:
    00049      *    max(dx, dy) <= sqrt(dx*dx + dy*dy) <= sqrt(2) * max(dx, dy) <= 3/2 * max(dx, dy) */
    00050     int frac_sq = width * width * (dx * dx + dy * dy);
    00051     int frac_max = 3 * frac_diff / 2;
    00052     while (frac_diff < frac_max) {
    00053       int frac_test = (frac_diff + frac_max) / 2;
    00054       if (frac_test * frac_test < frac_sq) {
    00055         frac_diff = frac_test + 1;
    00056       } else {
    00057         frac_max = frac_test - 1;
    00058       }
    00059     }
    00060   }
    00061
    00062   if (dx > dy) {
    00063     int y_low     = y;
    00064     int y_high    = y;
    00065     int frac_low  = dy - frac_diff / 2;
    00066     int frac_high = dy + frac_diff / 2;
    00067
    00068     while (frac_low + dx / 2 < 0) {
    00069       frac_low += dx;
    00070       y_low -= stepy;
    00071     }
    00072     while (frac_high - dx / 2 >= 0) {
    00073       frac_high -= dx;
    00074       y_high += stepy;
    00075     }
    00076     x2 += stepx;
    00077
    00078     while (x != x2) {
    00079       if (x >= 0 && x < screen_width) {
    00080         for (int y = y_low; y != y_high; y += stepy) {
    00081           if (y >= 0 && y < screen_height) this->SetPixel(video, x, y, colour);
    00082         }
    00083       }
    00084       if (frac_low >= 0) {
    00085         y_low += stepy;
    00086         frac_low -= dx;
    00087       }
    00088       if (frac_high >= 0) {
    00089         y_high += stepy;
    00090         frac_high -= dx;
    00091       }
    00092       x += stepx;
    00093       frac_low += dy;
    00094       frac_high += dy;
    00095     }
    00096   } else {
    00097     int x_low     = x;
    00098     int x_high    = x;
    00099     int frac_low  = dx - frac_diff / 2;
    00100     int frac_high = dx + frac_diff / 2;
    00101
    00102     while (frac_low + dy / 2 < 0) {
    00103       frac_low += dy;
    00104       x_low -= stepx;
    00105     }
    00106     while (frac_high - dy / 2 >= 0) {
    00107       frac_high -= dy;
    00108       x_high += stepx;
    00109     }
    00110     y2 += stepy;
    00111
    00112     while (y != y2) {
    00113       if (y >= 0 && y < screen_height) {
    00114         for (int x = x_low; x != x_high; x += stepx) {
    00115           if (x >= 0 && x < screen_width) this->SetPixel(video, x, y, colour);
    00116         }
    00117       }
    00118       if (frac_low >= 0) {
    00119         x_low += stepx;
    00120         frac_low -= dy;
    00121       }
    00122       if (frac_high >= 0) {
    00123         x_high += stepx;
    00124         frac_high -= dy;
    00125       }
    00126       y += stepy;
    00127       frac_low += dx;
    00128       frac_high += dx;
    00129     }
    00130   }
    00131 }