1/*
2 * Copyright (C) 2015 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#include "renderstate/TextureState.h"
17
18#include "Caches.h"
19#include "utils/TraceUtils.h"
20
21#include <GLES3/gl3.h>
22#include <SkBitmap.h>
23#include <SkCanvas.h>
24#include <memory>
25
26namespace android {
27namespace uirenderer {
28
29// Width of mShadowLutTexture, defines how accurate the shadow alpha lookup table is
30static const int SHADOW_LUT_SIZE = 128;
31
32// Must define as many texture units as specified by kTextureUnitsCount
33const GLenum kTextureUnits[] = {GL_TEXTURE0, GL_TEXTURE1, GL_TEXTURE2, GL_TEXTURE3};
34
35TextureState::TextureState() : mTextureUnit(0) {
36    glActiveTexture(kTextureUnits[0]);
37    resetBoundTextures();
38
39    GLint maxTextureUnits;
40    glGetIntegerv(GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS, &maxTextureUnits);
41    LOG_ALWAYS_FATAL_IF(maxTextureUnits < kTextureUnitsCount,
42                        "At least %d texture units are required!", kTextureUnitsCount);
43    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
44}
45
46TextureState::~TextureState() {
47    if (mShadowLutTexture != nullptr) {
48        mShadowLutTexture->deleteTexture();
49    }
50}
51
52/**
53 * Maps shadow geometry 'alpha' varying (1 for darkest, 0 for transparent) to
54 * darkness at that spot. Input values of 0->1 should be mapped within the same
55 * range, but can affect the curve for a different visual falloff.
56 *
57 * This is used to populate the shadow LUT texture for quick lookup in the
58 * shadow shader.
59 */
60static float computeShadowOpacity(float ratio) {
61    // exponential falloff function provided by UX
62    float val = 1 - ratio;
63    return exp(-val * val * 4.0) - 0.018;
64}
65
66void TextureState::constructTexture(Caches& caches) {
67    if (mShadowLutTexture == nullptr) {
68        mShadowLutTexture.reset(new Texture(caches));
69
70        unsigned char bytes[SHADOW_LUT_SIZE];
71        for (int i = 0; i < SHADOW_LUT_SIZE; i++) {
72            float inputRatio = i / (SHADOW_LUT_SIZE - 1.0f);
73            bytes[i] = computeShadowOpacity(inputRatio) * 255;
74        }
75        mShadowLutTexture->upload(GL_ALPHA, SHADOW_LUT_SIZE, 1, GL_ALPHA, GL_UNSIGNED_BYTE, &bytes);
76        mShadowLutTexture->setFilter(GL_LINEAR);
77        mShadowLutTexture->setWrap(GL_CLAMP_TO_EDGE);
78    }
79}
80
81void TextureState::activateTexture(GLuint textureUnit) {
82    LOG_ALWAYS_FATAL_IF(textureUnit >= kTextureUnitsCount,
83                        "Tried to use texture unit index %d, only %d exist", textureUnit,
84                        kTextureUnitsCount);
85    if (mTextureUnit != textureUnit) {
86        glActiveTexture(kTextureUnits[textureUnit]);
87        mTextureUnit = textureUnit;
88    }
89}
90
91void TextureState::resetActiveTexture() {
92    mTextureUnit = -1;
93}
94
95void TextureState::bindTexture(GLuint texture) {
96    if (mBoundTextures[mTextureUnit] != texture) {
97        glBindTexture(GL_TEXTURE_2D, texture);
98        mBoundTextures[mTextureUnit] = texture;
99    }
100}
101
102void TextureState::bindTexture(GLenum target, GLuint texture) {
103    if (target == GL_TEXTURE_2D) {
104        bindTexture(texture);
105    } else {
106        // GLConsumer directly calls glBindTexture() with
107        // target=GL_TEXTURE_EXTERNAL_OES, don't cache this target
108        // since the cached state could be stale
109        glBindTexture(target, texture);
110    }
111}
112
113void TextureState::deleteTexture(GLuint texture) {
114    // When glDeleteTextures() is called on a currently bound texture,
115    // OpenGL ES specifies that the texture is then considered unbound
116    // Consider the following series of calls:
117    //
118    // glGenTextures -> creates texture name 2
119    // glBindTexture(2)
120    // glDeleteTextures(2) -> 2 is now unbound
121    // glGenTextures -> can return 2 again
122    //
123    // If we don't call glBindTexture(2) after the second glGenTextures
124    // call, any texture operation will be performed on the default
125    // texture (name=0)
126
127    unbindTexture(texture);
128
129    glDeleteTextures(1, &texture);
130}
131
132void TextureState::resetBoundTextures() {
133    for (int i = 0; i < kTextureUnitsCount; i++) {
134        mBoundTextures[i] = 0;
135    }
136}
137
138void TextureState::unbindTexture(GLuint texture) {
139    for (int i = 0; i < kTextureUnitsCount; i++) {
140        if (mBoundTextures[i] == texture) {
141            mBoundTextures[i] = 0;
142        }
143    }
144}
145
146} /* namespace uirenderer */
147} /* namespace android */
148