ui/framework/src/main/java/androidx/ui/core/Text.kt - platform/frameworks/support - Git at Google

 /*
  * Copyright 2018 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 package androidx.ui.core

 import android.content.Context
 import androidx.ui.engine.geometry.Offset
 import androidx.ui.engine.text.TextAlign
 import androidx.ui.engine.text.TextDirection
 import androidx.ui.engine.text.TextPosition
 import androidx.ui.graphics.Color
 import androidx.ui.painting.TextSpan
 import androidx.ui.painting.TextStyle
 import androidx.ui.rendering.paragraph.RenderParagraph
 import androidx.ui.rendering.paragraph.TextOverflow
 import androidx.ui.services.text_editing.TextSelection
 import androidx.compose.Ambient
 import androidx.compose.Children
 import androidx.compose.Composable
 import androidx.compose.ambient
 import androidx.compose.composer
 import androidx.compose.compositionReference
 import androidx.compose.effectOf
 import androidx.compose.onCommit
 import androidx.compose.state
 import androidx.compose.memo
 import androidx.compose.onDispose
 import androidx.compose.unaryPlus

 private val DefaultTextAlign: TextAlign = TextAlign.Start
 private val DefaultTextDirection: TextDirection = TextDirection.Ltr
 private val DefaultSoftWrap: Boolean = true
 private val DefaultOverflow: TextOverflow = TextOverflow.Clip
 private val DefaultMaxLines: Int? = null

 /** The default selection color if none is specified. */
 private val DefaultSelectionColor = Color(0x6633B5E5)


 @Composable
 fun Text(
     /** How the text should be aligned horizontally. */
     textAlign: TextAlign = DefaultTextAlign,
     /** The directionality of the text. */
     textDirection: TextDirection = DefaultTextDirection,
     /**
      *  Whether the text should break at soft line breaks.
      *  If false, the glyphs in the text will be positioned as if there was unlimited horizontal
      *  space.
      *  If [softWrap] is false, [overflow] and [textAlign] may have unexpected effects.
      */
     softWrap: Boolean = DefaultSoftWrap,
     /** How visual overflow should be handled. */
     overflow: TextOverflow = DefaultOverflow,
     /** The number of font pixels for each logical pixel. */
     textScaleFactor: Float = 1.0f,
     /**
      *  An optional maximum number of lines for the text to span, wrapping if necessary.
      *  If the text exceeds the given number of lines, it will be truncated according to [overflow]
      *  and [softWrap].
      *  The value may be null. If it is not null, then it must be greater than zero.
      */
     maxLines: Int? = DefaultMaxLines,
     /**
      *  The color used to draw selected region.
      */
     selectionColor: Color = DefaultSelectionColor,
     /**
      * Composable TextSpan attached after [text].
      */
     @Children child: @Composable TextSpanScope.() -> Unit
 ) {
     val rootTextSpan = +memo { TextSpan() }
     val ref = +compositionReference()
     compose(rootTextSpan, ref, child)
     +onDispose { disposeComposition(rootTextSpan, ref) }

     // TODO This is a temporary workaround due to lack of textStyle parameter of Text.
     val textSpan = if (rootTextSpan.children.size == 1) {
         rootTextSpan.children[0]
     } else {
         rootTextSpan
     }
     Text(
         textAlign = textAlign,
         textDirection = textDirection,
         softWrap = softWrap,
         overflow = overflow,
         textScaleFactor = textScaleFactor,
         maxLines = maxLines,
         selectionColor = selectionColor,
         text = textSpan
     )
 }

 /**
  * Text Widget Crane version.
  *
  * The Text widget displays text that uses multiple different styles. The text to display is
  * described using a tree of [TextSpan] objects, each of which has an associated style that is used
  * for that subtree. The text might break across multiple lines or might all be displayed on the
  * same line depending on the layout constraints.
  */
 // TODO(migration/qqd): Add tests when text widget system is mature and testable.
 @Composable
 internal fun Text(
     /** How the text should be aligned horizontally. */
     textAlign: TextAlign = DefaultTextAlign,
     /** The directionality of the text. */
     textDirection: TextDirection = DefaultTextDirection,
     /**
      *  Whether the text should break at soft line breaks.
      *  If false, the glyphs in the text will be positioned as if there was unlimited horizontal
      *  space.
      *  If [softWrap] is false, [overflow] and [textAlign] may have unexpected effects.
      */
     softWrap: Boolean = DefaultSoftWrap,
     /** How visual overflow should be handled. */
     overflow: TextOverflow = DefaultOverflow,
     /** The number of font pixels for each logical pixel. */
     textScaleFactor: Float = 1.0f,
     /**
      *  An optional maximum number of lines for the text to span, wrapping if necessary.
      *  If the text exceeds the given number of lines, it will be truncated according to [overflow]
      *  and [softWrap].
      *  The value may be null. If it is not null, then it must be greater than zero.
      */
     maxLines: Int? = DefaultMaxLines,
     /**
      *  The color used to draw selected region.
      */
     selectionColor: Color = DefaultSelectionColor,
     /**
      * Composable TextSpan attached after [text].
      */
     text: TextSpan
 ) {
     val context = composer.composer.context
     val internalSelection = +state<TextSelection?> { null }
     val registrar = +ambient(SelectionRegistrarAmbient)
     val layoutCoordinates = +state<LayoutCoordinates?> { null }

     fun attachContextToFont(
         text: TextSpan,
         context: Context
     ) {
         text.visitTextSpan() {
             it.style?.fontFamily?.let {
                 it.context = context
             }
             true
         }
     }

     val style = +ambient(CurrentTextStyleAmbient)
     val mergedStyle = style.merge(text.style)
     // Make a wrapper to avoid modifying the style on the original element
     val styledText = TextSpan(style = mergedStyle, children = mutableListOf(text))

     Semantics(
         label = styledText.toPlainText()
     ) {
         val renderParagraph = RenderParagraph(
             text = styledText,
             textAlign = textAlign,
             textDirection = textDirection,
             softWrap = softWrap,
             overflow = overflow,
             textScaleFactor = textScaleFactor,
             maxLines = maxLines,
             selectionColor = selectionColor
         )
         // TODO(Migration/siyamed): This is temporary and should be removed when resource
         // system is resolved.
         attachContextToFont(styledText, context)

         val children = @Composable {
             // Get the layout coordinates of the text widget. This is for hit test of cross-widget
             // selection.
             OnPositioned(onPositioned = { layoutCoordinates.value = it })
             Draw { canvas, _ ->
                 internalSelection.value?.let { renderParagraph.paintSelection(canvas, it) }
                 renderParagraph.paint(canvas, Offset(0.0f, 0.0f))
             }
         }
         Layout(children = children, layoutBlock = { _, constraints ->
             renderParagraph.performLayout(constraints)
             layout(renderParagraph.width.px.round(), renderParagraph.height.px.round()) {}
         })

         +onCommit(renderParagraph) {
             val id = registrar.subscribe(object : TextSelectionHandler {
                 // Get selection for the start and end coordinates pair.
                 override fun getSelection(
                     selectionCoordinates: Pair<PxPosition, PxPosition>,
                     containerLayoutCoordinates: LayoutCoordinates
                 ): Selection? {
                     val relativePosition = containerLayoutCoordinates.childToLocal(
                         layoutCoordinates.value!!, PxPosition.Origin
                     )
                     val startPx = selectionCoordinates.first - relativePosition
                     val endPx = selectionCoordinates.second - relativePosition

                     val start = Offset(startPx.x.value, startPx.y.value)
                     val end = Offset(endPx.x.value, endPx.y.value)

                     var selectionStart = renderParagraph.getPositionForOffset(start)
                     var selectionEnd = renderParagraph.getPositionForOffset(end)

                     if (selectionStart.offset == selectionEnd.offset) {
                         val wordBoundary = renderParagraph.getWordBoundary(selectionStart)
                         selectionStart =
                             TextPosition(wordBoundary.start, selectionStart.affinity)
                         selectionEnd = TextPosition(wordBoundary.end, selectionEnd.affinity)
                     }

                     internalSelection.value =
                         TextSelection(selectionStart.offset, selectionEnd.offset)

                     // TODO(qqd): Determine a set of coordinates around a character that we need.
                     // Clean up the lower layer's getCaretForTextPosition methods.
                     // Currently the left bottom corner of a character is returned.
                     return Selection(
                         startOffset =
                         renderParagraph.getCaretForTextPosition(selectionStart).second,
                         endOffset =
                         renderParagraph.getCaretForTextPosition(selectionEnd).second,
                         startLayoutCoordinates = layoutCoordinates.value!!,
                         endLayoutCoordinates = layoutCoordinates.value!!
                     )
                 }
             })
             onDispose {
                 registrar.unsubscribe(id)
             }
         }
     }
 }

 /**
  * Simplified version of [Text] component with minimal set of customizations.
  *
  * @param text The text to display.
  * @param style The text style for the text.
  */
 @Composable
 fun Text(
     text: String,
     style: TextStyle? = null,
     textAlign: TextAlign = DefaultTextAlign,
     textDirection: TextDirection = DefaultTextDirection,
     softWrap: Boolean = DefaultSoftWrap,
     overflow: TextOverflow = DefaultOverflow,
     maxLines: Int? = DefaultMaxLines
 ) {
     Text(
         textAlign = textAlign,
         textDirection = textDirection,
         softWrap = softWrap,
         overflow = overflow,
         textScaleFactor = 1.0f,
         maxLines = maxLines,
         selectionColor = DefaultSelectionColor,
         text = TextSpan(text = text, style = style)
     )
 }

 internal val CurrentTextStyleAmbient = Ambient.of<TextStyle>("current text style") {
     TextStyle()
 }

 /**
  * This component is used to set the current value of the Text style ambient. The given style will
  * be merged with the current style values for any missing attributes. Any [Text]
  * components included in this component's children will be styled with this style unless
  * styled explicitly.
  */
 @Composable
 fun CurrentTextStyleProvider(value: TextStyle, @Children children: @Composable() () -> Unit) {
     val style = +ambient(CurrentTextStyleAmbient)
     val mergedStyle = style.merge(value)
     CurrentTextStyleAmbient.Provider(value = mergedStyle) {
         children()
     }
 }

 /**
  * This effect is used to read the current value of the Text style ambient. Any [Text]
  * components included in this component's children will be styled with this style unless
  * styled explicitly.
  */
 fun currentTextStyle() =
     effectOf<TextStyle> { +ambient(CurrentTextStyleAmbient) }
	/*
	* Copyright 2018 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/
	package androidx.ui.core

	import android.content.Context
	import androidx.ui.engine.geometry.Offset
	import androidx.ui.engine.text.TextAlign
	import androidx.ui.engine.text.TextDirection
	import androidx.ui.engine.text.TextPosition
	import androidx.ui.graphics.Color
	import androidx.ui.painting.TextSpan
	import androidx.ui.painting.TextStyle
	import androidx.ui.rendering.paragraph.RenderParagraph
	import androidx.ui.rendering.paragraph.TextOverflow
	import androidx.ui.services.text_editing.TextSelection
	import androidx.compose.Ambient
	import androidx.compose.Children
	import androidx.compose.Composable
	import androidx.compose.ambient
	import androidx.compose.composer
	import androidx.compose.compositionReference
	import androidx.compose.effectOf
	import androidx.compose.onCommit
	import androidx.compose.state
	import androidx.compose.memo
	import androidx.compose.onDispose
	import androidx.compose.unaryPlus

	private val DefaultTextAlign: TextAlign = TextAlign.Start
	private val DefaultTextDirection: TextDirection = TextDirection.Ltr
	private val DefaultSoftWrap: Boolean = true
	private val DefaultOverflow: TextOverflow = TextOverflow.Clip
	private val DefaultMaxLines: Int? = null

	/** The default selection color if none is specified. */
	private val DefaultSelectionColor = Color(0x6633B5E5)


	@Composable
	fun Text(
	/** How the text should be aligned horizontally. */
	textAlign: TextAlign = DefaultTextAlign,
	/** The directionality of the text. */
	textDirection: TextDirection = DefaultTextDirection,
	/**
	* Whether the text should break at soft line breaks.
	* If false, the glyphs in the text will be positioned as if there was unlimited horizontal
	* space.
	* If [softWrap] is false, [overflow] and [textAlign] may have unexpected effects.
	*/
	softWrap: Boolean = DefaultSoftWrap,
	/** How visual overflow should be handled. */
	overflow: TextOverflow = DefaultOverflow,
	/** The number of font pixels for each logical pixel. */
	textScaleFactor: Float = 1.0f,
	/**
	* An optional maximum number of lines for the text to span, wrapping if necessary.
	* If the text exceeds the given number of lines, it will be truncated according to [overflow]
	* and [softWrap].
	* The value may be null. If it is not null, then it must be greater than zero.
	*/
	maxLines: Int? = DefaultMaxLines,
	/**
	* The color used to draw selected region.
	*/
	selectionColor: Color = DefaultSelectionColor,
	/**
	* Composable TextSpan attached after [text].
	*/
	@Children child: @Composable TextSpanScope.() -> Unit
	) {
	val rootTextSpan = +memo { TextSpan() }
	val ref = +compositionReference()
	compose(rootTextSpan, ref, child)
	+onDispose { disposeComposition(rootTextSpan, ref) }

	// TODO This is a temporary workaround due to lack of textStyle parameter of Text.
	val textSpan = if (rootTextSpan.children.size == 1) {
	rootTextSpan.children[0]
	} else {
	rootTextSpan
	}
	Text(
	textAlign = textAlign,
	textDirection = textDirection,
	softWrap = softWrap,
	overflow = overflow,
	textScaleFactor = textScaleFactor,
	maxLines = maxLines,
	selectionColor = selectionColor,
	text = textSpan
	)
	}

	/**
	* Text Widget Crane version.
	*
	* The Text widget displays text that uses multiple different styles. The text to display is
	* described using a tree of [TextSpan] objects, each of which has an associated style that is used
	* for that subtree. The text might break across multiple lines or might all be displayed on the
	* same line depending on the layout constraints.
	*/
	// TODO(migration/qqd): Add tests when text widget system is mature and testable.
	@Composable
	internal fun Text(
	/** How the text should be aligned horizontally. */
	textAlign: TextAlign = DefaultTextAlign,
	/** The directionality of the text. */
	textDirection: TextDirection = DefaultTextDirection,
	/**
	* Whether the text should break at soft line breaks.
	* If false, the glyphs in the text will be positioned as if there was unlimited horizontal
	* space.
	* If [softWrap] is false, [overflow] and [textAlign] may have unexpected effects.
	*/
	softWrap: Boolean = DefaultSoftWrap,
	/** How visual overflow should be handled. */
	overflow: TextOverflow = DefaultOverflow,
	/** The number of font pixels for each logical pixel. */
	textScaleFactor: Float = 1.0f,
	/**
	* An optional maximum number of lines for the text to span, wrapping if necessary.
	* If the text exceeds the given number of lines, it will be truncated according to [overflow]
	* and [softWrap].
	* The value may be null. If it is not null, then it must be greater than zero.
	*/
	maxLines: Int? = DefaultMaxLines,
	/**
	* The color used to draw selected region.
	*/
	selectionColor: Color = DefaultSelectionColor,
	/**
	* Composable TextSpan attached after [text].
	*/
	text: TextSpan
	) {
	val context = composer.composer.context
	val internalSelection = +state<TextSelection?> { null }
	val registrar = +ambient(SelectionRegistrarAmbient)
	val layoutCoordinates = +state<LayoutCoordinates?> { null }

	fun attachContextToFont(
	text: TextSpan,
	context: Context
	) {
	text.visitTextSpan() {
	it.style?.fontFamily?.let {
	it.context = context
	}
	true
	}
	}

	val style = +ambient(CurrentTextStyleAmbient)
	val mergedStyle = style.merge(text.style)
	// Make a wrapper to avoid modifying the style on the original element
	val styledText = TextSpan(style = mergedStyle, children = mutableListOf(text))

	Semantics(
	label = styledText.toPlainText()
	) {
	val renderParagraph = RenderParagraph(
	text = styledText,
	textAlign = textAlign,
	textDirection = textDirection,
	softWrap = softWrap,
	overflow = overflow,
	textScaleFactor = textScaleFactor,
	maxLines = maxLines,
	selectionColor = selectionColor
	)
	// TODO(Migration/siyamed): This is temporary and should be removed when resource
	// system is resolved.
	attachContextToFont(styledText, context)

	val children = @Composable {
	// Get the layout coordinates of the text widget. This is for hit test of cross-widget
	// selection.
	OnPositioned(onPositioned = { layoutCoordinates.value = it })
	Draw { canvas, _ ->
	internalSelection.value?.let { renderParagraph.paintSelection(canvas, it) }
	renderParagraph.paint(canvas, Offset(0.0f, 0.0f))
	}
	}
	Layout(children = children, layoutBlock = { _, constraints ->
	renderParagraph.performLayout(constraints)
	layout(renderParagraph.width.px.round(), renderParagraph.height.px.round()) {}
	})

	+onCommit(renderParagraph) {
	val id = registrar.subscribe(object : TextSelectionHandler {
	// Get selection for the start and end coordinates pair.
	override fun getSelection(
	selectionCoordinates: Pair<PxPosition, PxPosition>,
	containerLayoutCoordinates: LayoutCoordinates
	): Selection? {
	val relativePosition = containerLayoutCoordinates.childToLocal(
	layoutCoordinates.value!!, PxPosition.Origin
	)
	val startPx = selectionCoordinates.first - relativePosition
	val endPx = selectionCoordinates.second - relativePosition

	val start = Offset(startPx.x.value, startPx.y.value)
	val end = Offset(endPx.x.value, endPx.y.value)

	var selectionStart = renderParagraph.getPositionForOffset(start)
	var selectionEnd = renderParagraph.getPositionForOffset(end)

	if (selectionStart.offset == selectionEnd.offset) {
	val wordBoundary = renderParagraph.getWordBoundary(selectionStart)
	selectionStart =
	TextPosition(wordBoundary.start, selectionStart.affinity)
	selectionEnd = TextPosition(wordBoundary.end, selectionEnd.affinity)
	}

	internalSelection.value =
	TextSelection(selectionStart.offset, selectionEnd.offset)

	// TODO(qqd): Determine a set of coordinates around a character that we need.
	// Clean up the lower layer's getCaretForTextPosition methods.
	// Currently the left bottom corner of a character is returned.
	return Selection(
	startOffset =
	renderParagraph.getCaretForTextPosition(selectionStart).second,
	endOffset =
	renderParagraph.getCaretForTextPosition(selectionEnd).second,
	startLayoutCoordinates = layoutCoordinates.value!!,
	endLayoutCoordinates = layoutCoordinates.value!!
	)
	}
	})
	onDispose {
	registrar.unsubscribe(id)
	}
	}
	}
	}

	/**
	* Simplified version of [Text] component with minimal set of customizations.
	*
	* @param text The text to display.
	* @param style The text style for the text.
	*/
	@Composable
	fun Text(
	text: String,
	style: TextStyle? = null,
	textAlign: TextAlign = DefaultTextAlign,
	textDirection: TextDirection = DefaultTextDirection,
	softWrap: Boolean = DefaultSoftWrap,
	overflow: TextOverflow = DefaultOverflow,
	maxLines: Int? = DefaultMaxLines
	) {
	Text(
	textAlign = textAlign,
	textDirection = textDirection,
	softWrap = softWrap,
	overflow = overflow,
	textScaleFactor = 1.0f,
	maxLines = maxLines,
	selectionColor = DefaultSelectionColor,
	text = TextSpan(text = text, style = style)
	)
	}

	internal val CurrentTextStyleAmbient = Ambient.of<TextStyle>("current text style") {
	TextStyle()
	}

	/**
	* This component is used to set the current value of the Text style ambient. The given style will
	* be merged with the current style values for any missing attributes. Any [Text]
	* components included in this component's children will be styled with this style unless
	* styled explicitly.
	*/
	@Composable
	fun CurrentTextStyleProvider(value: TextStyle, @Children children: @Composable() () -> Unit) {
	val style = +ambient(CurrentTextStyleAmbient)
	val mergedStyle = style.merge(value)
	CurrentTextStyleAmbient.Provider(value = mergedStyle) {
	children()
	}
	}

	/**
	* This effect is used to read the current value of the Text style ambient. Any [Text]
	* components included in this component's children will be styled with this style unless
	* styled explicitly.
	*/
	fun currentTextStyle() =
	effectOf<TextStyle> { +ambient(CurrentTextStyleAmbient) }