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93 lines
3.9 KiB
Dart
93 lines
3.9 KiB
Dart
// Copyright 2015 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// This example shows how to draw some bi-directional text using the raw
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// interface to the engine.
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import 'dart:typed_data';
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import 'dart:ui' as ui;
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// A paragraph represents a rectangular region that contains some text.
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ui.Paragraph paragraph;
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ui.Picture paint(ui.Rect paintBounds) {
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final ui.PictureRecorder recorder = new ui.PictureRecorder();
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final ui.Canvas canvas = new ui.Canvas(recorder, paintBounds);
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final double devicePixelRatio = ui.window.devicePixelRatio;
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final ui.Size logicalSize = ui.window.physicalSize / devicePixelRatio;
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canvas.translate(logicalSize.width / 2.0, logicalSize.height / 2.0);
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canvas.drawRect(new ui.Rect.fromLTRB(-100.0, -100.0, 100.0, 100.0),
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new ui.Paint()..color = const ui.Color.fromARGB(255, 0, 255, 0));
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// The paint method of Paragraph draws the contents of the paragraph onto the
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// given canvas.
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canvas.drawParagraph(paragraph, new ui.Offset(-paragraph.width / 2.0, (paragraph.width / 2.0) - 125.0));
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return recorder.endRecording();
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}
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ui.Scene composite(ui.Picture picture, ui.Rect paintBounds) {
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final double devicePixelRatio = ui.window.devicePixelRatio;
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final Float64List deviceTransform = new Float64List(16)
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..[0] = devicePixelRatio
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..[5] = devicePixelRatio
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..[10] = 1.0
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..[15] = 1.0;
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final ui.SceneBuilder sceneBuilder = new ui.SceneBuilder()
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..pushTransform(deviceTransform)
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..addPicture(ui.Offset.zero, picture)
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..pop();
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return sceneBuilder.build();
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}
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void beginFrame(Duration timeStamp) {
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final ui.Rect paintBounds = ui.Offset.zero & (ui.window.physicalSize / ui.window.devicePixelRatio);
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final ui.Picture picture = paint(paintBounds);
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final ui.Scene scene = composite(picture, paintBounds);
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ui.window.render(scene);
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}
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void main() {
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// To create a paragraph of text, we use ParagraphBuilder.
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final ui.ParagraphBuilder builder = new ui.ParagraphBuilder(
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// The text below has a primary direction of left-to-right.
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// The embedded text has other directions.
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// If this was TextDirection.rtl, the "Hello, world" text would end up on
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// the other side of the right-to-left text.
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new ui.ParagraphStyle(textDirection: ui.TextDirection.ltr),
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)
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// We first push a style that turns the text blue.
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..pushStyle(new ui.TextStyle(color: const ui.Color(0xFF0000FF)))
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..addText('Hello, ')
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// The next run of text will be bold.
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..pushStyle(new ui.TextStyle(fontWeight: ui.FontWeight.bold))
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..addText('world. ')
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// The pop() command signals the end of the bold styling.
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..pop()
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// We add text to the paragraph in logical order. The paragraph object
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// understands bi-directional text and will compute the visual ordering
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// during layout.
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..addText('هذا هو قليلا طويلة من النص الذي يجب التفاف .')
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// The second pop() removes the blue color.
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..pop()
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// We can add more text with the default styling.
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..addText(' و أكثر قليلا لجعله أطول. ')
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..addText('สวัสดี');
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// When we're done adding styles and text, we build the Paragraph object, at
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// which time we can apply styling that affects the entire paragraph, such as
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// left, right, or center alignment. Once built, the contents of the paragraph
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// cannot be altered, but sizing and positioning information can be updated.
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paragraph = builder.build()
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// Next, we supply a width that the text is permitted to occupy and we ask
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// the paragraph to the visual position of each its glyphs as well as its
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// overall size, subject to its sizing constraints.
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..layout(new ui.ParagraphConstraints(width: 180.0));
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// Finally, we register our beginFrame callback and kick off the first frame.
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ui.window.onBeginFrame = beginFrame;
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ui.window.scheduleFrame();
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}
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