TraceCanvas QML Type

A specialized Canvas type for rendering Trace objects. 更多...

import 语句：	import QtQuick.VirtualKeyboard.Styles
Since:	QtQuick.VirtualKeyboard 2.0
继承：	Canvas

所有成员列表，包括继承成员

特性

autoDestroy : bool
autoDestroyDelay : int
renderFunction : var
trace : Trace

信号

onRecycle (var traceCanvas ) (since QtQuick.VirtualKeyboard.Styles 6.1)

方法

recycle () (since QtQuick.VirtualKeyboard.Styles 6.1)
renderClear () (since QtQuick.VirtualKeyboard.Styles 6.1)
renderSmoothedLine ()

详细描述

This type provides capabilities for rendering Trace objects on the screen.

To make the Trace rendering available in the keyboard, this type must be declared as the KeyboardStyle.traceCanvasDelegate 组件。

traceCanvasDelegate: TraceCanvas {
}

Custom drawing attributes can be initialized in the Canvas.available signal. For example:

onAvailableChanged: {
    if (!available)
        return;
    var ctx = getContext("2d")
    ctx.lineWidth = 8 * scaleHint
    ctx.lineCap = "round"
    ctx.strokeStyle = Qt.rgba(0xFF, 0xFF, 0xFF)
    ctx.fillStyle = ctx.strokeStyle
}

The type offers built-in options for Trace rendering. Currently the following rendering options are available:

renderSmoothedLine Renders smoothed line with round corners (the default)

The rendering function can be changed with the renderFunction 特性。

renderFunction: renderSmoothedLine

Custom rendering function is also supported. Consider the following example:

renderFunction: renderCustomLine
function renderCustomLine() {
    getContext("2d")
    var points = trace.points()
    ...
}

特性文档编制

autoDestroy : bool

Enables auto destruction mode.

If enabled, this item will be destroyed when the trace 对象被销毁。

The default value is false. In this case the canvas can be reused after onRecycle signal is triggered.

autoDestroyDelay : int

Specifies the approximate delay in milliseconds, counted from the beginning of the auto destruction, before the object is to be destroyed or recycled.

This delay makes it possible, for example, to animate the item before destruction.

默认值为 0。

renderFunction : var

This property defines the rendering function.

默认值为 renderSmoothedLine

trace : Trace

提供访问 Trace 对象。

信号文档编制

[since QtQuick.VirtualKeyboard.Styles 6.1] onRecycle ( var traceCanvas )

Emitted when the traceCanvas is recycled.

注意： 相应处理程序是 onOnRecycle .

This signal was introduced in QtQuick.VirtualKeyboard.Styles 6.1.

方法文档编制

[since QtQuick.VirtualKeyboard.Styles 6.1] recycle ()

Recycles trace canvas by clearing all drawings and resetting the variables.

The function triggers onRecycle signal after completed (before the return).

The function returns true when recycling is successful.

This method was introduced in QtQuick.VirtualKeyboard.Styles 6.1.

[since QtQuick.VirtualKeyboard.Styles 6.1] renderClear ()

Clears screen and resets the rendering.

This method was introduced in QtQuick.VirtualKeyboard.Styles 6.1.

renderSmoothedLine ()

Renders smoothed line with round corners.

This function is incremental and renders only the new part added to the Trace.

This function does not alter any of the canvas attributes (i.e. they can be set elsewhere.)