1/*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ANDROID_HWUI_PATH_TESSELLATOR_H
18#define ANDROID_HWUI_PATH_TESSELLATOR_H
19
20#include <utils/Vector.h>
21
22#include "Matrix.h"
23#include "Rect.h"
24#include "Vertex.h"
25#include "VertexBuffer.h"
26
27namespace android {
28namespace uirenderer {
29
30/**
31 * Structure used for threshold values in outline path tessellation.
32 *
33 * TODO: PaintInfo should store one of this object, and initialized all values in constructor
34 * depending on its type (point, line or path).
35 */
36struct PathApproximationInfo {
37    PathApproximationInfo(float invScaleX, float invScaleY, float pixelThreshold)
38        : thresholdSquared(pixelThreshold * pixelThreshold)
39        , sqrInvScaleX(invScaleX * invScaleX)
40        , sqrInvScaleY(invScaleY * invScaleY)
41        , thresholdForConicQuads(pixelThreshold * MathUtils::min(invScaleX, invScaleY) / 2.0f) {
42    };
43
44    const float thresholdSquared;
45    const float sqrInvScaleX;
46    const float sqrInvScaleY;
47    const float thresholdForConicQuads;
48};
49
50class PathTessellator {
51public:
52    /**
53     * Populates scaleX and scaleY with the 'tessellation scale' of the transform - the effective X
54     * and Y scales that tessellation will take into account when generating the 1.0 pixel thick
55     * ramp.
56     *
57     * Two instances of the same shape (size, paint, etc.) will only generate the same vertices if
58     * their tessellation scales are equal.
59     */
60    static void extractTessellationScales(const Matrix4& transform, float* scaleX, float* scaleY);
61
62    /**
63     * Populates a VertexBuffer with a tessellated approximation of the input convex path, as a single
64     * triangle strip. Note: joins are not currently supported.
65     *
66     * @param path The path to be approximated
67     * @param paint The paint the path will be drawn with, indicating AA, painting style
68     *        (stroke vs fill), stroke width, stroke cap & join style, etc.
69     * @param transform The transform the path is to be drawn with, used to drive stretch-aware path
70     *        vertex approximation, and correct AA ramp offsetting.
71     * @param vertexBuffer The output buffer
72     */
73    static void tessellatePath(const SkPath& path, const SkPaint* paint,
74            const mat4& transform, VertexBuffer& vertexBuffer);
75
76    /**
77     * Populates a VertexBuffer with a tessellated approximation of points as a single triangle
78     * strip (with degenerate tris separating), respecting the shape defined by the paint cap.
79     *
80     * @param points The center vertices of the points to be drawn
81     * @param count The number of floats making up the point vertices
82     * @param paint The paint the points will be drawn with indicating AA, stroke width & cap
83     * @param transform The transform the points will be drawn with, used to drive stretch-aware path
84     *        vertex approximation, and correct AA ramp offsetting
85     * @param vertexBuffer The output buffer
86     */
87    static void tessellatePoints(const float* points, int count, const SkPaint* paint,
88            const mat4& transform, VertexBuffer& vertexBuffer);
89
90    /**
91     * Populates a VertexBuffer with a tessellated approximation of lines as a single triangle
92     * strip (with degenerate tris separating).
93     *
94     * @param points Pairs of endpoints defining the lines to be drawn
95     * @param count The number of floats making up the line vertices
96     * @param paint The paint the lines will be drawn with indicating AA, stroke width & cap
97     * @param transform The transform the points will be drawn with, used to drive stretch-aware path
98     *        vertex approximation, and correct AA ramp offsetting
99     * @param vertexBuffer The output buffer
100     */
101    static void tessellateLines(const float* points, int count, const SkPaint* paint,
102            const mat4& transform, VertexBuffer& vertexBuffer);
103
104    /**
105     * Approximates a convex outline into a clockwise Vector of 2d vertices.
106     *
107     * @param path The outline to be approximated
108     * @param threshold The threshold of acceptable error (in pixels) when approximating
109     * @param outputVertices An empty Vector which will be populated with the output
110     */
111    static bool approximatePathOutlineVertices(const SkPath &path, float threshold,
112            Vector<Vertex> &outputVertices);
113
114private:
115    static bool approximatePathOutlineVertices(const SkPath &path, bool forceClose,
116            const PathApproximationInfo& approximationInfo, Vector<Vertex> &outputVertices);
117
118/*
119  endpoints a & b,
120  control c
121 */
122    static void recursiveQuadraticBezierVertices(
123            float ax, float ay,
124            float bx, float by,
125            float cx, float cy,
126            const PathApproximationInfo& approximationInfo,
127            Vector<Vertex> &outputVertices, int depth = 0);
128
129/*
130  endpoints p1, p2
131  control c1, c2
132 */
133    static void recursiveCubicBezierVertices(
134            float p1x, float p1y,
135            float c1x, float c1y,
136            float p2x, float p2y,
137            float c2x, float c2y,
138            const PathApproximationInfo& approximationInfo,
139            Vector<Vertex> &outputVertices, int depth = 0);
140};
141
142}; // namespace uirenderer
143}; // namespace android
144
145#endif // ANDROID_HWUI_PATH_TESSELLATOR_H
146