mirror of
https://github.com/flutter/flutter
synced 2024-09-28 20:44:26 +00:00
2b4c960885
* Remove more references to dart:ui.window * two more doc referenes * revert icon_color_test.dart
103 lines
4.2 KiB
Dart
103 lines
4.2 KiB
Dart
// Copyright 2014 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.
|
|
|
|
// This example shows how to draw some bi-directional text using the raw
|
|
// interface to the engine.
|
|
|
|
import 'dart:typed_data';
|
|
import 'dart:ui' as ui;
|
|
|
|
// The FlutterView into which this example will draw; set in the main method.
|
|
late final ui.FlutterView view;
|
|
|
|
// A paragraph represents a rectangular region that contains some text.
|
|
late ui.Paragraph paragraph;
|
|
|
|
ui.Picture paint(ui.Rect paintBounds) {
|
|
final ui.PictureRecorder recorder = ui.PictureRecorder();
|
|
final ui.Canvas canvas = ui.Canvas(recorder, paintBounds);
|
|
|
|
final double devicePixelRatio = view.devicePixelRatio;
|
|
final ui.Size logicalSize = view.physicalSize / devicePixelRatio;
|
|
|
|
canvas.translate(logicalSize.width / 2.0, logicalSize.height / 2.0);
|
|
canvas.drawRect(
|
|
const ui.Rect.fromLTRB(-100.0, -100.0, 100.0, 100.0),
|
|
ui.Paint()..color = const ui.Color.fromARGB(255, 0, 255, 0),
|
|
);
|
|
|
|
// The paint method of Paragraph draws the contents of the paragraph onto the
|
|
// given canvas.
|
|
canvas.drawParagraph(paragraph, ui.Offset(-paragraph.width / 2.0, (paragraph.width / 2.0) - 125.0));
|
|
|
|
return recorder.endRecording();
|
|
}
|
|
|
|
ui.Scene composite(ui.Picture picture, ui.Rect paintBounds) {
|
|
final double devicePixelRatio = view.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 & (view.physicalSize / view.devicePixelRatio);
|
|
final ui.Picture picture = paint(paintBounds);
|
|
final ui.Scene scene = composite(picture, paintBounds);
|
|
view.render(scene);
|
|
}
|
|
|
|
void main() {
|
|
// TODO(goderbauer): Create a window if embedder doesn't provide an implicit view to draw into.
|
|
assert(ui.PlatformDispatcher.instance.implicitView != null);
|
|
view = ui.PlatformDispatcher.instance.implicitView!;
|
|
|
|
// To create a paragraph of text, we use ParagraphBuilder.
|
|
final ui.ParagraphBuilder builder = ui.ParagraphBuilder(
|
|
// The text below has a primary direction of left-to-right.
|
|
// The embedded text has other directions.
|
|
// If this was TextDirection.rtl, the "Hello, world" text would end up on
|
|
// the other side of the right-to-left text.
|
|
ui.ParagraphStyle(textDirection: ui.TextDirection.ltr),
|
|
)
|
|
// We first push a style that turns the text blue.
|
|
..pushStyle(ui.TextStyle(color: const ui.Color(0xFF0000FF)))
|
|
..addText('Hello, ')
|
|
// The next run of text will be bold.
|
|
..pushStyle(ui.TextStyle(fontWeight: ui.FontWeight.bold))
|
|
..addText('world. ')
|
|
// The pop() command signals the end of the bold styling.
|
|
..pop()
|
|
// We add text to the paragraph in logical order. The paragraph object
|
|
// understands bi-directional text and will compute the visual ordering
|
|
// during layout.
|
|
..addText('هذا هو قليلا طويلة من النص الذي يجب التفاف .')
|
|
// The second pop() removes the blue color.
|
|
..pop()
|
|
// We can add more text with the default styling.
|
|
..addText(' و أكثر قليلا لجعله أطول. ')
|
|
..addText('สวัสดี');
|
|
// When we're done adding styles and text, we build the Paragraph object, at
|
|
// which time we can apply styling that affects the entire paragraph, such as
|
|
// left, right, or center alignment. Once built, the contents of the paragraph
|
|
// cannot be altered, but sizing and positioning information can be updated.
|
|
paragraph = builder.build()
|
|
// Next, we supply a width that the text is permitted to occupy and we ask
|
|
// the paragraph to the visual position of each its glyphs as well as its
|
|
// overall size, subject to its sizing constraints.
|
|
..layout(const ui.ParagraphConstraints(width: 180.0));
|
|
|
|
// Finally, we register our beginFrame callback and kick off the first frame.
|
|
ui.PlatformDispatcher.instance
|
|
..onBeginFrame = beginFrame
|
|
..scheduleFrame();
|
|
}
|