| Qingqing Deng | 6f56a91 | 2019-05-13 10:10:37 -0700 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2019 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package androidx.ui.core.selection |
| 18 | |
| 19 | import androidx.compose.Ambient |
| 20 | import androidx.ui.core.LayoutCoordinates |
| 21 | import androidx.ui.core.PxPosition |
| 22 | import androidx.ui.core.gesture.DragObserver |
| 23 | import androidx.ui.core.px |
| 24 | import androidx.ui.engine.geometry.Rect |
| 25 | |
| 26 | /** |
| 27 | * An interface handling selection. Get selection from a widget by passing in the start and end of |
| 28 | * selection in a selection container as a pair, and the layout coordinates of the selection |
| 29 | * container. |
| 30 | */ |
| 31 | internal interface TextSelectionHandler { |
| 32 | fun getSelection( |
| 33 | selectionCoordinates: Pair<PxPosition, PxPosition>, |
| 34 | containerLayoutCoordinates: LayoutCoordinates |
| 35 | ): Selection? |
| 36 | } |
| 37 | |
| 38 | /** |
| 39 | * An interface allowing a Text composable to "register" and "unregister" itself with the class |
| 40 | * implementing the interface. |
| 41 | */ |
| 42 | internal interface SelectionRegistrar { |
| 43 | // TODO(qqd): Replace Any with a type in future. |
| 44 | fun subscribe(handler: TextSelectionHandler): Any |
| 45 | |
| 46 | fun unsubscribe(key: Any) |
| 47 | } |
| 48 | |
| 49 | internal class SelectionManager : SelectionRegistrar { |
| 50 | /** |
| 51 | * The current selection. |
| 52 | */ |
| 53 | var selection: Selection? = null |
| 54 | |
| 55 | /** |
| 56 | * The manager will invoke this every time it comes to the conclusion that the selection should |
| 57 | * change. The expectation is that this callback will end up causing `setSelection` to get |
| 58 | * called. This is what makes this a "controlled component". |
| 59 | */ |
| 60 | var onSelectionChange: (Selection?) -> Unit = {} |
| 61 | |
| 62 | /** |
| 63 | * Layout Coordinates of the selection container. |
| 64 | */ |
| 65 | lateinit var containerLayoutCoordinates: LayoutCoordinates |
| 66 | |
| 67 | /** |
| 68 | * This is essentially the list of registered components that want |
| 69 | * to handle text selection that are below the SelectionContainer. |
| 70 | */ |
| 71 | private val handlers = mutableSetOf<TextSelectionHandler>() |
| 72 | |
| 73 | /** |
| 74 | * The beginning position of the drag gesture. Every time a new drag gesture starts, it wil be |
| 75 | * recalculated. |
| 76 | */ |
| 77 | private var dragBeginPosition = PxPosition.Origin |
| 78 | |
| 79 | /** |
| 80 | * The total distance being dragged of the drag gesture. Every time a new drag gesture starts, |
| 81 | * it will be zeroed out. |
| 82 | */ |
| 83 | private var dragTotalDistance = PxPosition.Origin |
| 84 | |
| 85 | /** |
| 86 | * Allow a Text composable to "register" itself with the manager |
| 87 | */ |
| 88 | override fun subscribe(handler: TextSelectionHandler): Any { |
| 89 | handlers.add(handler) |
| 90 | return handler |
| 91 | } |
| 92 | |
| 93 | /** |
| 94 | * Allow a Text composable to "unregister" itself with the manager |
| 95 | */ |
| 96 | override fun unsubscribe(key: Any) { |
| 97 | handlers.remove(key as TextSelectionHandler) |
| 98 | } |
| 99 | |
| 100 | fun onPress(position: PxPosition) { |
| 101 | var result: Selection? = null |
| 102 | for (handler in handlers) { |
| 103 | result = handler.getSelection(Pair(position, position), containerLayoutCoordinates) |
| 104 | } |
| 105 | onSelectionChange(result) |
| 106 | } |
| 107 | |
| 108 | // Get the coordinates of a character. Currently, it's the middle point of the left edge of the |
| 109 | // bounding box of the character. This is a temporary solution. |
| 110 | // TODO(qqd): Read how Android solve this problem. |
| 111 | fun getCoordinatesForCharacter(box: Rect): PxPosition { |
| 112 | return PxPosition(box.left.px, box.top.px + (box.bottom.px - box.top.px) / 2) |
| 113 | } |
| 114 | |
| 115 | fun handleDragObserver(dragStartHandle: Boolean): DragObserver { |
| 116 | return object : DragObserver { |
| 117 | override fun onStart() { |
| 118 | // The LayoutCoordinates of the widget where the drag gesture should begin. This |
| 119 | // is used to convert the position of the beginning of the drag gesture from the |
| 120 | // widget coordinates to selection container coordinates. |
| 121 | val beginLayoutCoordinates = |
| 122 | if (dragStartHandle) { |
| 123 | selection!!.startLayoutCoordinates!! |
| 124 | } else { |
| 125 | selection!!.endLayoutCoordinates!! |
| 126 | } |
| 127 | // The position of the character where the drag gesture should begin. This is in |
| 128 | // the widget coordinates. |
| 129 | val beginCoordinates = |
| 130 | getCoordinatesForCharacter( |
| 131 | if (dragStartHandle) { |
| 132 | selection!!.startOffset |
| 133 | } else { |
| 134 | selection!!.endOffset |
| 135 | } |
| 136 | ) |
| 137 | // Convert the position where drag gesture begins from widget coordinates to |
| 138 | // selection container coordinates. |
| 139 | dragBeginPosition = containerLayoutCoordinates.childToLocal( |
| 140 | beginLayoutCoordinates, |
| 141 | beginCoordinates |
| 142 | ) |
| 143 | |
| 144 | // Zero out the total distance that being dragged. |
| 145 | dragTotalDistance = PxPosition.Origin |
| 146 | } |
| 147 | |
| 148 | override fun onDrag(dragDistance: PxPosition): PxPosition { |
| 149 | var result = selection |
| 150 | dragTotalDistance += dragDistance |
| 151 | |
| 152 | val currentStart = |
| 153 | if (dragStartHandle) { |
| 154 | dragBeginPosition + dragTotalDistance |
| 155 | } else { |
| 156 | containerLayoutCoordinates.childToLocal( |
| 157 | selection!!.startLayoutCoordinates!!, |
| 158 | getCoordinatesForCharacter(selection!!.startOffset) |
| 159 | ) |
| 160 | } |
| 161 | |
| 162 | val currentEnd = |
| 163 | if (dragStartHandle) { |
| 164 | containerLayoutCoordinates.childToLocal( |
| 165 | selection!!.endLayoutCoordinates!!, |
| 166 | getCoordinatesForCharacter(selection!!.endOffset) |
| 167 | ) |
| 168 | } else { |
| 169 | dragBeginPosition + dragTotalDistance |
| 170 | } |
| 171 | |
| 172 | for (handler in handlers) { |
| 173 | result = handler.getSelection( |
| 174 | Pair(currentStart, currentEnd), |
| 175 | containerLayoutCoordinates) |
| 176 | } |
| 177 | onSelectionChange(result) |
| 178 | return dragDistance |
| 179 | } |
| 180 | } |
| 181 | } |
| 182 | } |
| 183 | |
| 184 | /** Ambient of SelectionRegistrar for SelectionManager. */ |
| 185 | internal val SelectionRegistrarAmbient = Ambient.of<SelectionRegistrar> { SelectionManager() } |