OpenTTD
base.cpp
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1 /* $Id: base.cpp 26482 2014-04-23 20:13:33Z rubidium $ */
2 
3 /*
4  * This file is part of OpenTTD.
5  * 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.
6  * 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.
7  * 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/>.
8  */
9 
12 #include "../stdafx.h"
13 #include "base.hpp"
14 #include "../core/math_func.hpp"
15 
16 #include "../safeguards.h"
17 
18 void Blitter::DrawLine(void *video, int x, int y, int x2, int y2, int screen_width, int screen_height, uint8 colour, int width, int dash)
19 {
20  int dy;
21  int dx;
22  int stepx;
23  int stepy;
24 
25  dy = (y2 - y) * 2;
26  if (dy < 0) {
27  dy = -dy;
28  stepy = -1;
29  } else {
30  stepy = 1;
31  }
32 
33  dx = (x2 - x) * 2;
34  if (dx < 0) {
35  dx = -dx;
36  stepx = -1;
37  } else {
38  stepx = 1;
39  }
40 
41  if (dx == 0 && dy == 0) {
42  /* The algorithm below cannot handle this special case; make it work at least for line width 1 */
43  if (x >= 0 && x < screen_width && y >= 0 && y < screen_height) this->SetPixel(video, x, y, colour);
44  return;
45  }
46 
47  int frac_diff = width * max(dx, dy);
48  if (width > 1) {
49  /* compute frac_diff = width * sqrt(dx*dx + dy*dy)
50  * Start interval:
51  * max(dx, dy) <= sqrt(dx*dx + dy*dy) <= sqrt(2) * max(dx, dy) <= 3/2 * max(dx, dy) */
52  int frac_sq = width * width * (dx * dx + dy * dy);
53  int frac_max = 3 * frac_diff / 2;
54  while (frac_diff < frac_max) {
55  int frac_test = (frac_diff + frac_max) / 2;
56  if (frac_test * frac_test < frac_sq) {
57  frac_diff = frac_test + 1;
58  } else {
59  frac_max = frac_test - 1;
60  }
61  }
62  }
63 
64  int gap = dash;
65  if (dash == 0) dash = 1;
66  int dash_count = 0;
67  if (dx > dy) {
68  int y_low = y;
69  int y_high = y;
70  int frac_low = dy - frac_diff / 2;
71  int frac_high = dy + frac_diff / 2;
72 
73  while (frac_low + dx / 2 < 0) {
74  frac_low += dx;
75  y_low -= stepy;
76  }
77  while (frac_high - dx / 2 >= 0) {
78  frac_high -= dx;
79  y_high += stepy;
80  }
81  x2 += stepx;
82 
83  while (x != x2) {
84  if (dash_count < dash && x >= 0 && x < screen_width) {
85  for (int y = y_low; y != y_high; y += stepy) {
86  if (y >= 0 && y < screen_height) this->SetPixel(video, x, y, colour);
87  }
88  }
89  if (frac_low >= 0) {
90  y_low += stepy;
91  frac_low -= dx;
92  }
93  if (frac_high >= 0) {
94  y_high += stepy;
95  frac_high -= dx;
96  }
97  x += stepx;
98  frac_low += dy;
99  frac_high += dy;
100  if (++dash_count >= dash + gap) dash_count = 0;
101  }
102  } else {
103  int x_low = x;
104  int x_high = x;
105  int frac_low = dx - frac_diff / 2;
106  int frac_high = dx + frac_diff / 2;
107 
108  while (frac_low + dy / 2 < 0) {
109  frac_low += dy;
110  x_low -= stepx;
111  }
112  while (frac_high - dy / 2 >= 0) {
113  frac_high -= dy;
114  x_high += stepx;
115  }
116  y2 += stepy;
117 
118  while (y != y2) {
119  if (dash_count < dash && y >= 0 && y < screen_height) {
120  for (int x = x_low; x != x_high; x += stepx) {
121  if (x >= 0 && x < screen_width) this->SetPixel(video, x, y, colour);
122  }
123  }
124  if (frac_low >= 0) {
125  x_low += stepx;
126  frac_low -= dy;
127  }
128  if (frac_high >= 0) {
129  x_high += stepx;
130  frac_high -= dy;
131  }
132  y += stepy;
133  frac_low += dx;
134  frac_high += dx;
135  if (++dash_count >= dash + gap) dash_count = 0;
136  }
137  }
138 }