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139 lines
3.4 KiB
C++
139 lines
3.4 KiB
C++
/* $Id$ */
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/*
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* This file is part of OpenTTD.
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* 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.
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* 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.
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* 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/>.
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*/
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/** @file base.cpp Implementation of the base for all blitters. */
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#include "../stdafx.h"
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#include "base.hpp"
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#include "../core/math_func.hpp"
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#include "../safeguards.h"
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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)
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{
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int dy;
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int dx;
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int stepx;
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int stepy;
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dy = (y2 - y) * 2;
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if (dy < 0) {
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dy = -dy;
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stepy = -1;
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} else {
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stepy = 1;
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}
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dx = (x2 - x) * 2;
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if (dx < 0) {
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dx = -dx;
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stepx = -1;
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} else {
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stepx = 1;
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}
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if (dx == 0 && dy == 0) {
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/* The algorithm below cannot handle this special case; make it work at least for line width 1 */
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if (x >= 0 && x < screen_width && y >= 0 && y < screen_height) this->SetPixel(video, x, y, colour);
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return;
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}
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int frac_diff = width * max(dx, dy);
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if (width > 1) {
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/* compute frac_diff = width * sqrt(dx*dx + dy*dy)
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* Start interval:
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* max(dx, dy) <= sqrt(dx*dx + dy*dy) <= sqrt(2) * max(dx, dy) <= 3/2 * max(dx, dy) */
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int frac_sq = width * width * (dx * dx + dy * dy);
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int frac_max = 3 * frac_diff / 2;
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while (frac_diff < frac_max) {
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int frac_test = (frac_diff + frac_max) / 2;
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if (frac_test * frac_test < frac_sq) {
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frac_diff = frac_test + 1;
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} else {
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frac_max = frac_test - 1;
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}
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}
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}
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int gap = dash;
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if (dash == 0) dash = 1;
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int dash_count = 0;
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if (dx > dy) {
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int y_low = y;
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int y_high = y;
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int frac_low = dy - frac_diff / 2;
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int frac_high = dy + frac_diff / 2;
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while (frac_low + dx / 2 < 0) {
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frac_low += dx;
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y_low -= stepy;
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}
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while (frac_high - dx / 2 >= 0) {
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frac_high -= dx;
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y_high += stepy;
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}
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x2 += stepx;
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while (x != x2) {
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if (dash_count < dash && x >= 0 && x < screen_width) {
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for (int y = y_low; y != y_high; y += stepy) {
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if (y >= 0 && y < screen_height) this->SetPixel(video, x, y, colour);
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}
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}
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if (frac_low >= 0) {
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y_low += stepy;
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frac_low -= dx;
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}
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if (frac_high >= 0) {
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y_high += stepy;
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frac_high -= dx;
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}
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x += stepx;
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frac_low += dy;
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frac_high += dy;
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if (++dash_count >= dash + gap) dash_count = 0;
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}
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} else {
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int x_low = x;
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int x_high = x;
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int frac_low = dx - frac_diff / 2;
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int frac_high = dx + frac_diff / 2;
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while (frac_low + dy / 2 < 0) {
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frac_low += dy;
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x_low -= stepx;
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}
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while (frac_high - dy / 2 >= 0) {
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frac_high -= dy;
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x_high += stepx;
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}
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y2 += stepy;
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while (y != y2) {
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if (dash_count < dash && y >= 0 && y < screen_height) {
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for (int x = x_low; x != x_high; x += stepx) {
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if (x >= 0 && x < screen_width) this->SetPixel(video, x, y, colour);
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}
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}
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if (frac_low >= 0) {
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x_low += stepx;
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frac_low -= dy;
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}
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if (frac_high >= 0) {
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x_high += stepx;
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frac_high -= dy;
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}
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y += stepy;
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frac_low += dx;
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frac_high += dx;
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if (++dash_count >= dash + gap) dash_count = 0;
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}
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}
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}
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