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render_vertices.dart
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render_vertices.dart
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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
part of engine;
_GlRenderer _glRenderer;
void initWebGl() {
_glRenderer ??= _WebGlRenderer();
}
void disposeWebGl() {
_OffscreenCanvas.dispose();
_glRenderer = null;
}
abstract class _GlRenderer {
void drawVertices(
html.CanvasRenderingContext2D context,
int canvasWidthInPixels,
int canvasHeightInPixels,
Matrix4 transform,
ui.Vertices vertices,
ui.BlendMode blendMode,
SurfacePaintData paint);
void drawHairline(html.CanvasRenderingContext2D _ctx, Float32List positions);
}
/// Treeshakeable backend for rendering webgl on canvas.
///
/// This class gets instantiated on demand by Vertices constructor. For apps
/// that don't use Vertices WebGlRenderer will be removed from release binary.
class _WebGlRenderer implements _GlRenderer {
// Vertex shader transforms pixel space [Vertices.positions] to
// final clipSpace -1..1 coordinates with inverted Y Axis.
static const _vertexShaderTriangle = '''
#version 300 es
layout (location=0) in vec4 position;
layout (location=1) in vec4 color;
uniform mat4 u_ctransform;
uniform vec4 u_scale;
uniform vec4 u_shift;
out vec4 vColor;
void main() {
gl_Position = ((u_ctransform * position) * u_scale) + u_shift;
vColor = color.zyxw;
}''';
// This fragment shader enables Int32List of colors to be passed directly
// to gl context buffer for rendering by decoding RGBA8888.
static const _fragmentShaderTriangle = '''
#version 300 es
precision highp float;
in vec4 vColor;
out vec4 fragColor;
void main() {
fragColor = vColor;
}''';
// WebGL 1 version of shaders above for compatibility with Safari.
static const _vertexShaderTriangleEs1 = '''
attribute vec4 position;
attribute vec4 color;
uniform mat4 u_ctransform;
uniform vec4 u_scale;
uniform vec4 u_shift;
varying vec4 vColor;
void main() {
gl_Position = ((u_ctransform * position) * u_scale) + u_shift;
vColor = color.zyxw;
}''';
// WebGL 1 version of shaders above for compatibility with Safari.
static const _fragmentShaderTriangleEs1 = '''
precision highp float;
varying vec4 vColor;
void main() {
gl_FragColor = vColor;
}''';
@override
void drawVertices(
html.CanvasRenderingContext2D context,
int canvasWidthInPixels,
int canvasHeightInPixels,
Matrix4 transform,
ui.Vertices vertices,
ui.BlendMode blendMode,
SurfacePaintData paint) {
// Compute bounds of vertices.
final Float32List positions = vertices.positions;
ui.Rect bounds = _computeVerticesBounds(positions, transform);
double minValueX = bounds.left;
double minValueY = bounds.top;
double maxValueX = bounds.right;
double maxValueY = bounds.bottom;
double offsetX = 0;
double offsetY = 0;
int widthInPixels = canvasWidthInPixels;
int heightInPixels = canvasHeightInPixels;
// If vertices fall outside the bitmap area, cull.
if (maxValueX < 0 || maxValueY < 0) {
return;
}
if (minValueX > widthInPixels || minValueY > heightInPixels) {
return;
}
// If Vertices are is smaller than hosting canvas, allocate minimal
// offscreen canvas to reduce readPixels data size.
if ((maxValueX - minValueX) < widthInPixels &&
(maxValueY - minValueY) < heightInPixels) {
widthInPixels = maxValueX.ceil() - minValueX.floor();
heightInPixels = maxValueY.ceil() - minValueY.floor();
offsetX = minValueX.floor().toDouble();
offsetY = minValueY.floor().toDouble();
}
if (widthInPixels == 0 || heightInPixels == 0) {
return;
}
_GlContext gl =
_OffscreenCanvas.createGlContext(widthInPixels, heightInPixels);
final bool isWebKit = (browserEngine == BrowserEngine.webkit);
_GlProgram glProgram = isWebKit
? gl.useAndCacheProgram(
_vertexShaderTriangleEs1, _fragmentShaderTriangleEs1)
: gl.useAndCacheProgram(
_vertexShaderTriangle, _fragmentShaderTriangle);
Object transformUniform = gl.getUniformLocation(glProgram.program, 'u_ctransform');
Matrix4 transformAtOffset = transform.clone()..translate(-offsetX, -offsetY);
gl.setUniformMatrix4fv(transformUniform, false, transformAtOffset.storage);
// Set uniform to scale 0..width/height pixels coordinates to -1..1
// clipspace range and flip the Y axis.
Object resolution = gl.getUniformLocation(glProgram.program, 'u_scale');
gl.setUniform4f(resolution, 2.0 / widthInPixels.toDouble(),
-2.0 / heightInPixels.toDouble(), 1, 1);
Object shift = gl.getUniformLocation(glProgram.program, 'u_shift');
gl.setUniform4f(shift, -1, 1, 0, 0);
// Setup geometry.
Object positionsBuffer = gl.createBuffer();
assert(positionsBuffer != null);
gl.bindArrayBuffer(positionsBuffer);
gl.bufferData(positions, gl.kStaticDraw);
js_util.callMethod(
gl.glContext, 'vertexAttribPointer', [0, 2, gl.kFloat, false, 0, 0]);
gl.enableVertexAttribArray(0);
// Setup color buffer.
Object colorsBuffer = gl.createBuffer();
gl.bindArrayBuffer(colorsBuffer);
// Buffer kBGRA_8888.
gl.bufferData(vertices.colors, gl.kStaticDraw);
js_util.callMethod(gl.glContext, 'vertexAttribPointer',
[1, 4, gl.kUnsignedByte, true, 0, 0]);
gl.enableVertexAttribArray(1);
gl.clear();
final int vertexCount = positions.length ~/ 2;
gl.drawTriangles(vertexCount, vertices.mode);
context.save();
context.resetTransform();
gl.drawImage(context, offsetX, offsetY);
context.restore();
}
@override
void drawHairline(html.CanvasRenderingContext2D _ctx, Float32List positions) {
assert(positions != null);
final int pointCount = positions.length ~/ 2;
_ctx.lineWidth = 1.0;
_ctx.beginPath();
for (int i = 0, len = pointCount * 2; i < len;) {
for (int triangleVertexIndex = 0;
triangleVertexIndex < 3;
triangleVertexIndex++, i += 2) {
final double dx = positions[i];
final double dy = positions[i + 1];
switch (triangleVertexIndex) {
case 0:
_ctx.moveTo(dx, dy);
break;
case 1:
_ctx.lineTo(dx, dy);
break;
case 2:
_ctx.lineTo(dx, dy);
_ctx.closePath();
_ctx.stroke();
}
}
}
}
}
ui.Rect _computeVerticesBounds(Float32List positions, Matrix4 transform) {
double minValueX, maxValueX, minValueY, maxValueY;
minValueX = maxValueX = positions[0];
minValueY = maxValueY = positions[1];
for (int i = 2, len = positions.length; i < len; i += 2) {
final double x = positions[i];
final double y = positions[i + 1];
if (x.isNaN || y.isNaN) {
// Follows skia implementation that sets bounds to empty
// and aborts.
return ui.Rect.zero;
}
minValueX = math.min(minValueX, x);
maxValueX = math.max(maxValueX, x);
minValueY = math.min(minValueY, y);
maxValueY = math.max(maxValueY, y);
}
return _transformBounds(
transform, minValueX, minValueY, maxValueX, maxValueY);
}
ui.Rect _transformBounds(
Matrix4 transform, double left, double top, double right, double bottom) {
final Float64List storage = transform.storage;
final double m0 = storage[0];
final double m1 = storage[1];
final double m4 = storage[4];
final double m5 = storage[5];
final double m12 = storage[12];
final double m13 = storage[13];
final double x0 = (m0 * left) + (m4 * top) + m12;
final double y0 = (m1 * left) + (m5 * top) + m13;
final double x1 = (m0 * right) + (m4 * top) + m12;
final double y1 = (m1 * right) + (m5 * top) + m13;
final double x2 = (m0 * right) + (m4 * bottom) + m12;
final double y2 = (m1 * right) + (m5 * bottom) + m13;
final double x3 = (m0 * left) + (m4 * bottom) + m12;
final double y3 = (m1 * left) + (m5 * bottom) + m13;
return ui.Rect.fromLTRB(
math.min(x0, math.min(x1, math.min(x2, x3))),
math.min(y0, math.min(y1, math.min(y2, y3))),
math.max(x0, math.max(x1, math.max(x2, x3))),
math.max(y0, math.max(y1, math.max(y2, y3))));
}
// Converts from [VertexMode] triangleFan and triangleStrip to triangles.
Float32List _convertVertexPositions(ui.VertexMode mode, Float32List positions) {
assert(mode != ui.VertexMode.triangles);
if (mode == ui.VertexMode.triangleFan) {
final int coordinateCount = positions.length ~/ 2;
final int triangleCount = coordinateCount - 2;
final Float32List triangleList = Float32List(triangleCount * 3 * 2);
double centerX = positions[0];
double centerY = positions[1];
int destIndex = 0;
int positionIndex = 2;
for (int triangleIndex = 0;
triangleIndex < triangleCount;
triangleIndex++, positionIndex += 2) {
triangleList[destIndex++] = centerX;
triangleList[destIndex++] = centerY;
triangleList[destIndex++] = positions[positionIndex];
triangleList[destIndex++] = positions[positionIndex + 1];
triangleList[destIndex++] = positions[positionIndex + 2];
triangleList[destIndex++] = positions[positionIndex + 3];
}
return triangleList;
} else {
assert(mode == ui.VertexMode.triangleStrip);
// Set of connected triangles. Each triangle shares 2 last vertices.
final int vertexCount = positions.length ~/ 2;
int triangleCount = vertexCount - 2;
double x0 = positions[0];
double y0 = positions[1];
double x1 = positions[2];
double y1 = positions[3];
final Float32List triangleList = Float32List(triangleCount * 3 * 2);
int destIndex = 0;
for (int i = 0, positionIndex = 4; i < triangleCount; i++) {
final double x2 = positions[positionIndex++];
final double y2 = positions[positionIndex++];
triangleList[destIndex++] = x0;
triangleList[destIndex++] = y0;
triangleList[destIndex++] = x1;
triangleList[destIndex++] = y1;
triangleList[destIndex++] = x2;
triangleList[destIndex++] = y2;
x0 = x1;
y0 = y1;
x1 = x2;
y1 = y2;
}
return triangleList;
}
}
/// Compiled and cached gl program.
class _GlProgram {
final Object program;
_GlProgram(this.program);
}
/// JS Interop helper for webgl apis.
class _GlContext {
final Object glContext;
final bool isOffscreen;
dynamic _kCompileStatus;
dynamic _kArrayBuffer;
dynamic _kStaticDraw;
dynamic _kFloat;
dynamic _kColorBufferBit;
dynamic _kTriangles;
dynamic _kLinkStatus;
dynamic _kUnsignedByte;
dynamic _kRGBA;
Object _canvas;
int _widthInPixels;
int _heightInPixels;
static Map<String, _GlProgram> _programCache;
_GlContext.fromOffscreenCanvas(html.OffscreenCanvas canvas)
: glContext = canvas.getContext('webgl2', {'premultipliedAlpha': false}),
isOffscreen = true {
_programCache = <String, _GlProgram>{};
_canvas = canvas;
}
_GlContext.fromCanvas(html.CanvasElement canvas, bool useWebGl1)
: glContext = canvas.getContext(useWebGl1 ? 'webgl' : 'webgl2',
{'premultipliedAlpha': false}),
isOffscreen = false {
_programCache = <String, _GlProgram>{};
_canvas = canvas;
}
void setViewportSize(int width, int height) {
_widthInPixels = width;
_heightInPixels = height;
}
/// Draws Gl context contents to canvas context.
void drawImage(html.CanvasRenderingContext2D context,
double left, double top) {
// Actual size of canvas may be larger than viewport size. Use
// source/destination to draw part of the image data.
js_util.callMethod(context, 'drawImage',
[_canvas, 0, 0, _widthInPixels, _heightInPixels,
left, top, _widthInPixels, _heightInPixels]);
}
_GlProgram useAndCacheProgram(
String vertexShaderSource, String fragmentShaderSource) {
String cacheKey = '$vertexShaderSource||$fragmentShaderSource';
_GlProgram cachedProgram = _programCache[cacheKey];
if (cachedProgram == null) {
// Create and compile shaders.
Object vertexShader = compileShader('VERTEX_SHADER', vertexShaderSource);
Object fragmentShader =
compileShader('FRAGMENT_SHADER', fragmentShaderSource);
// Create a gl program and link shaders.
Object program = createProgram();
attachShader(program, vertexShader);
attachShader(program, fragmentShader);
linkProgram(program);
cachedProgram = _GlProgram(program);
_programCache[cacheKey] = cachedProgram;
useProgram(program);
}
return cachedProgram;
}
Object compileShader(String shaderType, String source) {
Object shader = _createShader(shaderType);
if (shader == null) {
throw Exception(error);
}
js_util.callMethod(glContext, 'shaderSource', [shader, source]);
js_util.callMethod(glContext, 'compileShader', [shader]);
bool shaderStatus = js_util
.callMethod(glContext, 'getShaderParameter', [shader, compileStatus]);
if (!shaderStatus) {
throw Exception('Shader compilation failed: ${getShaderInfoLog(shader)}');
}
return shader;
}
Object createProgram() =>
js_util.callMethod(glContext, 'createProgram', const []);
void attachShader(Object program, Object shader) {
js_util.callMethod(glContext, 'attachShader', [program, shader]);
}
void linkProgram(Object program) {
js_util.callMethod(glContext, 'linkProgram', [program]);
if (!js_util
.callMethod(glContext, 'getProgramParameter', [program, kLinkStatus])) {
throw Exception(getProgramInfoLog(program));
}
}
void useProgram(Object program) {
js_util.callMethod(glContext, 'useProgram', [program]);
}
Object createBuffer() =>
js_util.callMethod(glContext, 'createBuffer', const []);
void bindArrayBuffer(Object buffer) {
js_util.callMethod(glContext, 'bindBuffer', [kArrayBuffer, buffer]);
}
void deleteBuffer(Object buffer) {
js_util.callMethod(glContext, 'deleteBuffer', [buffer]);
}
void bufferData(TypedData data, dynamic type) {
js_util.callMethod(glContext, 'bufferData', [kArrayBuffer, data, type]);
}
void enableVertexAttribArray(int index) {
js_util.callMethod(glContext, 'enableVertexAttribArray', [index]);
}
/// Clear background.
void clear() {
js_util.callMethod(glContext, 'clear', [kColorBufferBit]);
}
/// Destroys gl context.
void dispose() {
js_util.callMethod(_getExtension('WEBGL_lose_context'), 'loseContext', []);
}
void deleteProgram(Object program) {
js_util.callMethod(glContext, 'deleteProgram', [program]);
}
void deleteShader(Object shader) {
js_util.callMethod(glContext, 'deleteShader', [shader]);
}
dynamic _getExtension(String extensionName) =>
js_util.callMethod(glContext, 'getExtension', [extensionName]);
void drawTriangles(int triangleCount, ui.VertexMode vertexMode) {
dynamic mode = _triangleTypeFromMode(vertexMode);
js_util.callMethod(glContext, 'drawArrays', [mode, 0, triangleCount]);
}
/// Sets affine transformation from normalized device coordinates
/// to window coordinates
void viewport(double x, double y, double width, double height) {
js_util.callMethod(glContext, 'viewport', [x, y, width, height]);
}
dynamic _triangleTypeFromMode(ui.VertexMode mode) {
switch (mode) {
case ui.VertexMode.triangles:
return kTriangles;
break;
case ui.VertexMode.triangleFan:
return kTriangleFan;
break;
case ui.VertexMode.triangleStrip:
return kTriangleStrip;
break;
}
}
Object _createShader(String shaderType) => js_util.callMethod(
glContext, 'createShader', [js_util.getProperty(glContext, shaderType)]);
/// Error state of gl context.
dynamic get error => js_util.callMethod(glContext, 'getError', const []);
/// Shader compiler error, if this returns [kFalse], to get details use
/// [getShaderInfoLog].
dynamic get compileStatus =>
_kCompileStatus ??= js_util.getProperty(glContext, 'COMPILE_STATUS');
dynamic get kArrayBuffer =>
_kArrayBuffer ??= js_util.getProperty(glContext, 'ARRAY_BUFFER');
dynamic get kLinkStatus =>
_kLinkStatus ??= js_util.getProperty(glContext, 'LINK_STATUS');
dynamic get kFloat => _kFloat ??= js_util.getProperty(glContext, 'FLOAT');
dynamic get kRGBA => _kRGBA ??= js_util.getProperty(glContext, 'RGBA');
dynamic get kUnsignedByte =>
_kUnsignedByte ??= js_util.getProperty(glContext, 'UNSIGNED_BYTE');
dynamic get kStaticDraw =>
_kStaticDraw ??= js_util.getProperty(glContext, 'STATIC_DRAW');
dynamic get kTriangles =>
_kTriangles ??= js_util.getProperty(glContext, 'TRIANGLES');
dynamic get kTriangleFan =>
_kTriangles ??= js_util.getProperty(glContext, 'TRIANGLE_FAN');
dynamic get kTriangleStrip =>
_kTriangles ??= js_util.getProperty(glContext, 'TRIANGLE_STRIP');
dynamic get kColorBufferBit =>
_kColorBufferBit ??= js_util.getProperty(glContext, 'COLOR_BUFFER_BIT');
/// Returns reference to uniform in program.
Object getUniformLocation(Object program, String uniformName) {
return js_util
.callMethod(glContext, 'getUniformLocation', [program, uniformName]);
}
/// Sets vec2 uniform values.
void setUniform2f(Object uniform, double value1, double value2) {
return js_util
.callMethod(glContext, 'uniform2f', [uniform, value1, value2]);
}
/// Sets vec4 uniform values.
void setUniform4f(Object uniform, double value1, double value2, double value3,
double value4) {
return js_util.callMethod(
glContext, 'uniform4f', [uniform, value1, value2, value3, value4]);
}
/// Sets mat4 uniform values.
void setUniformMatrix4fv(Object uniform, bool transpose, Float64List value) {
return js_util.callMethod(
glContext, 'uniformMatrix4fv', [uniform, transpose, value]);
}
/// Shader compile error log.
dynamic getShaderInfoLog(Object glShader) {
return js_util.callMethod(glContext, 'getShaderInfoLog', [glShader]);
}
/// Errors that occurred during failed linking or validation of program
/// objects. Typically called after [linkProgram].
String getProgramInfoLog(Object glProgram) {
return js_util.callMethod(glContext, 'getProgramInfoLog', [glProgram]);
}
int get drawingBufferWidth =>
js_util.getProperty(glContext, 'drawingBufferWidth');
int get drawingBufferHeight =>
js_util.getProperty(glContext, 'drawingBufferWidth');
html.ImageData readImageData() {
if (browserEngine == BrowserEngine.webkit ||
browserEngine == BrowserEngine.firefox) {
const int kBytesPerPixel = 4;
final int bufferWidth = _widthInPixels;
final int bufferHeight = _heightInPixels;
final Uint8List pixels =
Uint8List(bufferWidth * bufferHeight * kBytesPerPixel);
js_util.callMethod(glContext, 'readPixels',
[0, 0, bufferWidth, bufferHeight, kRGBA, kUnsignedByte, pixels]);
return html.ImageData(
Uint8ClampedList.fromList(pixels), bufferWidth, bufferHeight);
} else {
const int kBytesPerPixel = 4;
final int bufferWidth = _widthInPixels;
final int bufferHeight = _heightInPixels;
final Uint8ClampedList pixels =
Uint8ClampedList(bufferWidth * bufferHeight * kBytesPerPixel);
js_util.callMethod(glContext, 'readPixels',
[0, 0, bufferWidth, bufferHeight, kRGBA, kUnsignedByte, pixels]);
return html.ImageData(pixels, bufferWidth, bufferHeight);
}
}
}
/// Shared Cached OffscreenCanvas for webgl rendering to image.
class _OffscreenCanvas {
static html.OffscreenCanvas _canvas;
static int _maxPixelWidth = 0;
static int _maxPixelHeight = 0;
static html.CanvasElement _glCanvas;
static _GlContext _cachedContext;
_OffscreenCanvas(int width, int height) {
assert(width > 0 && height > 0);
if (width > _maxPixelWidth || height > _maxPixelHeight) {
// Allocate bigger offscreen canvas.
_canvas = html.OffscreenCanvas(width, height);
_maxPixelWidth = width;
_maxPixelHeight = height;
_cachedContext?.dispose();
_cachedContext = null;
}
}
static void dispose() {
_canvas = null;
_maxPixelWidth = 0;
_maxPixelHeight = 0;
_glCanvas = null;
_cachedContext = null;
}
html.OffscreenCanvas get canvas => _canvas;
static _GlContext createGlContext(int widthInPixels, int heightInPixels) {
final bool isWebKit = (browserEngine == BrowserEngine.webkit);
if (_OffscreenCanvas.supported) {
final _OffscreenCanvas offScreenCanvas =
_OffscreenCanvas(widthInPixels, heightInPixels);
_cachedContext ??= _GlContext.fromOffscreenCanvas(offScreenCanvas.canvas);
_cachedContext.setViewportSize(widthInPixels, heightInPixels);
return _cachedContext;
} else {
// Allocate new canvas element is size is larger.
if (widthInPixels > _maxPixelWidth || heightInPixels > _maxPixelHeight) {
_glCanvas = html.CanvasElement(
width: widthInPixels,
height: heightInPixels,
);
_glCanvas.className = 'gl-canvas';
final double cssWidth = widthInPixels / EngineWindow.browserDevicePixelRatio;
final double cssHeight = heightInPixels / EngineWindow.browserDevicePixelRatio;
_glCanvas.style
..position = 'absolute'
..width = '${cssWidth}px'
..height = '${cssHeight}px';
_maxPixelWidth = widthInPixels;
_maxPixelHeight = heightInPixels;
_cachedContext?.dispose();
_cachedContext = null;
}
_cachedContext ??= _GlContext.fromCanvas(_glCanvas, isWebKit);
_cachedContext.setViewportSize(widthInPixels, heightInPixels);
return _cachedContext;
}
}
/// Feature detects OffscreenCanvas.
static bool get supported =>
js_util.hasProperty(html.window, 'OffscreenCanvas');
}