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// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// This example shows how to use the ui.Canvas interface to draw various shapes
// with gradients and transforms.
import 'dart:math' as math;
import 'dart:typed_data';
import 'dart:ui' as ui;
ui.Picture paint(ui.Rect paintBounds) {
// First we create a PictureRecorder to record the commands we're going to
// feed in the canvas. The PictureRecorder will eventually produce a Picture,
// which is an immutable record of those commands.
final ui.PictureRecorder recorder = ui.PictureRecorder();
// Next, we create a canvas from the recorder. The canvas is an interface
// which can receive drawing commands. The canvas interface is modeled after
// the SkCanvas interface from Skia. The paintBounds establishes a "cull rect"
// for the canvas, which lets the implementation discard any commands that
// are entirely outside this rectangle.
final ui.Canvas canvas = ui.Canvas(recorder, paintBounds);
final ui.Paint paint = ui.Paint();
canvas.drawPaint(ui.Paint()..color = const ui.Color(0xFFFFFFFF));
final ui.Size size = paintBounds.size;
final ui.Offset mid = size.center(ui.Offset.zero);
final double radius = size.shortestSide / 2.0;
final double devicePixelRatio = ui.window.devicePixelRatio;
final ui.Size logicalSize = ui.window.physicalSize / devicePixelRatio;
canvas.save();
canvas.translate(-mid.dx / 2.0, logicalSize.height * 2.0);
canvas.clipRect(ui.Rect.fromLTRB(0.0, -logicalSize.height, logicalSize.width, radius));
canvas.translate(mid.dx, mid.dy);
paint.color = const ui.Color.fromARGB(128, 255, 0, 255);
canvas.rotate(math.pi/4.0);
final ui.Gradient yellowBlue = ui.Gradient.linear(
ui.Offset(-radius, -radius),
const ui.Offset(0.0, 0.0),
<ui.Color>[const ui.Color(0xFFFFFF00), const ui.Color(0xFF0000FF)],
);
canvas.drawRect(ui.Rect.fromLTRB(-radius, -radius, radius, radius),
ui.Paint()..shader = yellowBlue);
// Scale x and y by 0.5.
final Float64List scaleMatrix = Float64List.fromList(<double>[
0.5, 0.0, 0.0, 0.0,
0.0, 0.5, 0.0, 0.0,
0.0, 0.0, 1.0, 0.0,
0.0, 0.0, 0.0, 1.0,
]);
canvas.transform(scaleMatrix);
paint.color = const ui.Color.fromARGB(128, 0, 255, 0);
canvas.drawCircle(ui.Offset.zero, radius, paint);
canvas.restore();
paint.color = const ui.Color.fromARGB(128, 255, 0, 0);
canvas.drawCircle(const ui.Offset(150.0, 300.0), radius, paint);
// When we're done issuing painting commands, we end the recording an receive
// a Picture, which is an immutable record of the commands we've issued. You
// can draw a Picture into another canvas or include it as part of a
// composited scene.
return recorder.endRecording();
}
ui.Scene composite(ui.Picture picture, ui.Rect paintBounds) {
final double devicePixelRatio = ui.window.devicePixelRatio;
final Float64List deviceTransform = Float64List(16)
..[0] = devicePixelRatio
..[5] = devicePixelRatio
..[10] = 1.0
..[15] = 1.0;
final ui.SceneBuilder sceneBuilder = ui.SceneBuilder()
..pushTransform(deviceTransform)
..addPicture(ui.Offset.zero, picture)
..pop();
return sceneBuilder.build();
}
void beginFrame(Duration timeStamp) {
final ui.Rect paintBounds = ui.Offset.zero & (ui.window.physicalSize / ui.window.devicePixelRatio);
final ui.Picture picture = paint(paintBounds);
final ui.Scene scene = composite(picture, paintBounds);
ui.window.render(scene);
}
void main() {
ui.window.onBeginFrame = beginFrame;
ui.window.scheduleFrame();
}