jcs.org
Serenity Operating System
1/*
2 * Copyright (c) 2023, MacDue <macdue@dueutil.tech>
3 *
4 * SPDX-License-Identifier: BSD-2-Clause
5 */
6
7#include <LibGfx/Bitmap.h>
8#include <LibWeb/Bindings/Intrinsics.h>
9#include <LibWeb/HTML/CanvasPattern.h>
10#include <LibWeb/HTML/CanvasRenderingContext2D.h>
11
12namespace Web::HTML {
13
14void CanvasPatternPaintStyle::paint(Gfx::IntRect physical_bounding_box, PaintFunction paint) const
15{
16 // 1. Create an infinite transparent black bitmap.
17 // *waves magic wand 🪄*
18 // Done!
19
20 // 2. Place a copy of the image on the bitmap, anchored such that its top left corner
21 // is at the origin of the coordinate space, with one coordinate space unit per CSS pixel of the image,
22 // then place repeated copies of this image horizontally to the left and right, if the repetition behavior
23 // is "repeat-x", or vertically up and down, if the repetition behavior is "repeat-y", or in all four directions
24 // all over the bitmap, if the repetition behavior is "repeat".
25
26 // FIMXE: If the original image data is a bitmap image, then the value painted at a point in the area of
27 // the repetitions is computed by filtering the original image data. When scaling up, if the imageSmoothingEnabled
28 // attribute is set to false, then the image must be rendered using nearest-neighbor interpolation.
29 // Otherwise, the user agent may use any filtering algorithm (for example bilinear interpolation or nearest-neighbor).
30 // User agents which support multiple filtering algorithms may use the value of the imageSmoothingQuality attribute
31 // to guide the choice of filtering algorithm. When such a filtering algorithm requires a pixel value from outside
32 // the original image data, it must instead use the value from wrapping the pixel's coordinates to the original
33 // image's dimensions. (That is, the filter uses 'repeat' behavior, regardless of the value of the pattern's repetition behavior.)
34
35 // FIXME: 3. Transform the resulting bitmap according to the pattern's transformation matrix.
36
37 // FIXME: 4. Transform the resulting bitmap again, this time according to the current transformation matrix.
38
39 // 5. Replace any part of the image outside the area in which the pattern is to be rendered with transparent black.
40
41 // 6. The resulting bitmap is what is to be rendered, with the same origin and same scale.
42
43 auto const bitmap_width = m_bitmap->width();
44 auto const bitmap_height = m_bitmap->height();
45
46 paint([=, this](auto point) {
47 point.translate_by(physical_bounding_box.location());
48 point = [&]() -> Gfx::IntPoint {
49 switch (m_repetition) {
50 case Repetition::NoRepeat: {
51 return point;
52 }
53 case Repetition::Repeat: {
54 return {
55 point.x() % bitmap_width,
56 point.y() % bitmap_height
57 };
58 }
59 case Repetition::RepeatX: {
60 return {
61 point.x() % bitmap_width,
62 point.y()
63 };
64 }
65 case Repetition::RepeatY: {
66 return {
67 point.x(),
68 point.y() % bitmap_height
69 };
70 }
71 default:
72 VERIFY_NOT_REACHED();
73 }
74 }();
75 if (m_bitmap->rect().contains(point))
76 return m_bitmap->get_pixel(point);
77 return Gfx::Color();
78 });
79}
80
81CanvasPattern::CanvasPattern(JS::Realm& realm, CanvasPatternPaintStyle& pattern)
82 : PlatformObject(realm)
83 , m_pattern(pattern)
84{
85}
86
87CanvasPattern::~CanvasPattern() = default;
88
89// https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-createpattern
90WebIDL::ExceptionOr<JS::GCPtr<CanvasPattern>> CanvasPattern::create(JS::Realm& realm, CanvasImageSource const& image, StringView repetition)
91{
92 auto parse_repetition = [&](auto repetition) -> Optional<CanvasPatternPaintStyle::Repetition> {
93 if (repetition == "repeat"sv)
94 return CanvasPatternPaintStyle::Repetition::Repeat;
95 if (repetition == "repeat-x"sv)
96 return CanvasPatternPaintStyle::Repetition::RepeatX;
97 if (repetition == "repeat-y"sv)
98 return CanvasPatternPaintStyle::Repetition::RepeatY;
99 if (repetition == "no-repeat"sv)
100 return CanvasPatternPaintStyle::Repetition::NoRepeat;
101 return {};
102 };
103
104 // 1. Let usability be the result of checking the usability of image.
105 auto usability = TRY(check_usability_of_image(image));
106
107 // 2. If usability is bad, then return null.
108 if (usability == CanvasImageSourceUsability::Bad)
109 return JS::GCPtr<CanvasPattern> {};
110
111 // 3. Assert: usability is good.
112 VERIFY(usability == CanvasImageSourceUsability::Good);
113
114 // 4. If repetition is the empty string, then set it to "repeat".
115 if (repetition.is_empty())
116 repetition = "repeat"sv;
117
118 // 5. If repetition is not identical to one of "repeat", "repeat-x", "repeat-y", or "no-repeat",
119 // then throw a "SyntaxError" DOMException.
120 auto repetition_value = parse_repetition(repetition);
121 if (!repetition_value.has_value())
122 return WebIDL::SyntaxError::create(realm, "Repetition value is not valid");
123
124 // Note: Bitmap won't be null here, as if it were it would have "bad" usability.
125 auto const& bitmap = *image.visit([](auto const& source) -> Gfx::Bitmap const* { return source->bitmap(); });
126
127 // 6. Let pattern be a new CanvasPattern object with the image image and the repetition behavior given by repetition.
128 auto pattern = TRY_OR_THROW_OOM(realm.vm(), CanvasPatternPaintStyle::create(bitmap, *repetition_value));
129
130 // FIXME: 7. If image is not origin-clean, then mark pattern as not origin-clean.
131
132 // 8. Return pattern.
133 return MUST_OR_THROW_OOM(realm.heap().allocate<CanvasPattern>(realm, realm, *pattern));
134}
135
136JS::ThrowCompletionOr<void> CanvasPattern::initialize(JS::Realm& realm)
137{
138 MUST_OR_THROW_OOM(Base::initialize(realm));
139 set_prototype(&Bindings::ensure_web_prototype<Bindings::CanvasPatternPrototype>(realm, "CanvasPattern"));
140
141 return {};
142}
143
144}