OpenTTD Source: src/blitter/common.hpp Source File

OpenTTD Source 12.2

common.hpp
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1 /*
2 * This file is part of OpenTTD.
3 * 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.
4 * 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.
5 * 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/>.
6 */
7
10 #ifndef BLITTER_COMMON_HPP
11 #define BLITTER_COMMON_HPP
12
13 #include "base.hpp"
14 #include "../core/math_func.hpp"
15
16 #include <utility>
17
18 template <typename SetPixelT>
19 void Blitter::DrawLineGeneric(int x1, int y1, int x2, int y2, int screen_width, int screen_height, int width, int dash, SetPixelT set_pixel)
20 {
21 int dy;
22 int dx;
23 int stepx;
24 int stepy;
25
26 dy = (y2 - y1) * 2;
27 if (dy < 0) {
28 dy = -dy;
29 stepy = -1;
30 } else {
31 stepy = 1;
32 }
33
34 dx = (x2 - x1) * 2;
35 if (dx < 0) {
36 dx = -dx;
37 stepx = -1;
38 } else {
39 stepx = 1;
40 }
41
42 if (dx == 0 && dy == 0) {
43 /* The algorithm below cannot handle this special case; make it work at least for line width 1 */
44 if (x1 >= 0 && x1 < screen_width && y1 >= 0 && y1 < screen_height) set_pixel(x1, y1);
45 return;
46 }
47
48 int frac_diff = width * std::max(dx, dy);
49 if (width > 1) {
50 /* compute frac_diff = width * sqrt(dx*dx + dy*dy)
51 * Start interval:
52 * max(dx, dy) <= sqrt(dx*dx + dy*dy) <= sqrt(2) * max(dx, dy) <= 3/2 * max(dx, dy) */
53 int64 frac_sq = ((int64) width) * ((int64) width) * (((int64) dx) * ((int64) dx) + ((int64) dy) * ((int64) dy));
54 int frac_max = 3 * frac_diff / 2;
55 while (frac_diff < frac_max) {
56 int frac_test = (frac_diff + frac_max) / 2;
57 if (((int64) frac_test) * ((int64) frac_test) < frac_sq) {
58 frac_diff = frac_test + 1;
59 } else {
60 frac_max = frac_test - 1;
61 }
62 }
63 }
64
65 int gap = dash;
66 if (dash == 0) dash = 1;
67 int dash_count = 0;
68 if (dx > dy) {
69 if (stepx < 0) {
70 std::swap(x1, x2);
71 std::swap(y1, y2);
72 stepy = -stepy;
73 }
74 if (x2 < 0 || x1 >= screen_width) return;
75
76 int y_low = y1;
77 int y_high = y1;
78 int frac_low = dy - frac_diff / 2;
79 int frac_high = dy + frac_diff / 2;
80
81 while (frac_low < -(dx / 2)) {
82 frac_low += dx;
83 y_low -= stepy;
84 }
85 while (frac_high >= dx / 2) {
86 frac_high -= dx;
87 y_high += stepy;
88 }
89
90 if (x1 < 0) {
91 dash_count = (-x1) % (dash + gap);
92 auto adjust_frac = [&](int64 frac, int &y_bound) -> int {
93 frac -= ((int64) dy) * ((int64) x1);
94 if (frac >= 0) {
95 int quotient = frac / dx;
96 int remainder = frac % dx;
97 y_bound += (1 + quotient) * stepy;
98 frac = remainder - dx;
99 }
100 return frac;
101 };
102 frac_low = adjust_frac(frac_low, y_low);
103 frac_high = adjust_frac(frac_high, y_high);
104 x1 = 0;
105 }
106 x2++;
107 if (x2 > screen_width) {
108 x2 = screen_width;
109 }
110
111 while (x1 != x2) {
112 if (dash_count < dash) {
113 for (int y = y_low; y != y_high; y += stepy) {
114 if (y >= 0 && y < screen_height) set_pixel(x1, y);
115 }
116 }
117 if (frac_low >= 0) {
118 y_low += stepy;
119 frac_low -= dx;
120 }
121 if (frac_high >= 0) {
122 y_high += stepy;
123 frac_high -= dx;
124 }
125 x1++;
126 frac_low += dy;
127 frac_high += dy;
128 if (++dash_count >= dash + gap) dash_count = 0;
129 }
130 } else {
131 if (stepy < 0) {
132 std::swap(x1, x2);
133 std::swap(y1, y2);
134 stepx = -stepx;
135 }
136 if (y2 < 0 || y1 >= screen_height) return;
137
138 int x_low = x1;
139 int x_high = x1;
140 int frac_low = dx - frac_diff / 2;
141 int frac_high = dx + frac_diff / 2;
142
143 while (frac_low < -(dy / 2)) {
144 frac_low += dy;
145 x_low -= stepx;
146 }
147 while (frac_high >= dy / 2) {
148 frac_high -= dy;
149 x_high += stepx;
150 }
151
152 if (y1 < 0) {
153 dash_count = (-y1) % (dash + gap);
154 auto adjust_frac = [&](int64 frac, int &x_bound) -> int {
155 frac -= ((int64) dx) * ((int64) y1);
156 if (frac >= 0) {
157 int quotient = frac / dy;
158 int remainder = frac % dy;
159 x_bound += (1 + quotient) * stepx;
160 frac = remainder - dy;
161 }
162 return frac;
163 };
164 frac_low = adjust_frac(frac_low, x_low);
165 frac_high = adjust_frac(frac_high, x_high);
166 y1 = 0;
167 }
168 y2++;
169 if (y2 > screen_height) {
170 y2 = screen_height;
171 }
172
173 while (y1 != y2) {
174 if (dash_count < dash) {
175 for (int x = x_low; x != x_high; x += stepx) {
176 if (x >= 0 && x < screen_width) set_pixel(x, y1);
177 }
178 }
179 if (frac_low >= 0) {
180 x_low += stepx;
181 frac_low -= dy;
182 }
183 if (frac_high >= 0) {
184 x_high += stepx;
185 frac_high -= dy;
186 }
187 y1++;
188 frac_low += dx;
189 frac_high += dx;
190 if (++dash_count >= dash + gap) dash_count = 0;
191 }
192 }
193 }
194
195 #endif /* BLITTER_COMMON_HPP */
base.hpp