1/*
2 * Copyright (C) 2004 Red Hat, Inc.
3 * Copyright (C) 2010 Brent Fulgham <bfulgham@webkit.org>
4 *
5 * Based on Pango sources (see pangocairo-render.c)
6 *
7 * This library is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Library General Public
9 * License as published by the Free Software Foundation; either
10 * version 2 of the License, or (at your option) any later version.
11 *
12 * This library is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15 * Library General Public License for more details.
16 *
17 * You should have received a copy of the GNU Library General Public
18 * License along with this library; if not, write to the
19 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
20 * Boston, MA 02111-1307, USA.
21 *
22 */
23
24#if USE(CAIRO)
25
26#ifndef DrawErrorUnderline_h
27#define DrawErrorUnderline_h
28
29#include <cairo.h>
30
31//
32// Draws an error underline that looks like one of:
33//
34//              H       E                H
35//     /\      /\      /\        /\      /\               -
36//   A/  \    /  \    /  \     A/  \    /  \              |
37//    \   \  /    \  /   /D     \   \  /    \             |
38//     \   \/  C   \/   /        \   \/   C  \            | height = heightSquares * square
39//      \      /\  F   /          \  F   /\   \           |
40//       \    /  \    /            \    /  \   \G         |
41//        \  /    \  /              \  /    \  /          |
42//         \/      \/                \/      \/           -
43//         B                         B
44//         |---|
45//       unitWidth = (heightSquares - 1) * square
46//
47// The x, y, width, height passed in give the desired bounding box;
48// x/width are adjusted to make the underline a integer number of units
49// wide.
50//
51static inline void drawErrorUnderline(cairo_t* cr, double x, double y, double width, double height)
52{
53    static const double heightSquares = 2.5;
54
55    double square = height / heightSquares;
56    double halfSquare = 0.5 * square;
57
58    double unitWidth = (heightSquares - 1.0) * square;
59    int widthUnits = static_cast<int>((width + 0.5 * unitWidth) / unitWidth);
60
61    x += 0.5 * (width - widthUnits * unitWidth);
62    width = widthUnits * unitWidth;
63
64    double bottom = y + height;
65    double top = y;
66
67    // Bottom of squiggle
68    cairo_move_to(cr, x - halfSquare, top + halfSquare); // A
69
70    int i = 0;
71    for (i = 0; i < widthUnits; i += 2) {
72        double middle = x + (i + 1) * unitWidth;
73        double right = x + (i + 2) * unitWidth;
74
75        cairo_line_to(cr, middle, bottom); // B
76
77        if (i + 2 == widthUnits)
78            cairo_line_to(cr, right + halfSquare, top + halfSquare); // D
79        else if (i + 1 != widthUnits)
80            cairo_line_to(cr, right, top + square); // C
81    }
82
83    // Top of squiggle
84    for (i -= 2; i >= 0; i -= 2) {
85        double left = x + i * unitWidth;
86        double middle = x + (i + 1) * unitWidth;
87        double right = x + (i + 2) * unitWidth;
88
89        if (i + 1 == widthUnits)
90            cairo_line_to(cr, middle + halfSquare, bottom - halfSquare); // G
91        else {
92            if (i + 2 == widthUnits)
93                cairo_line_to(cr, right, top); // E
94
95            cairo_line_to(cr, middle, bottom - halfSquare); // F
96        }
97
98        cairo_line_to(cr, left, top); // H
99    }
100
101    cairo_fill(cr);
102}
103
104#endif // DrawErrorUnderline_h
105
106#endif
107