Reimplement TextInput's selection state

src/main/scala/ocelot/desktop/ui/event/MouseEvent.scala

@@ -1,5 +1,8 @@
 package ocelot.desktop.ui.event
 
+case class MouseEvent(state: MouseEvent.State.Value, button: MouseEvent.Button.Value)(val stateChanged: Boolean)
+  extends CapturingEvent
+
 object MouseEvent {
   object State extends Enumeration {
     val Pressed, Released = Value
@@ -10,6 +13,14 @@ object MouseEvent {
     val Right: Button.Value = Value(1)
     val Middle: Button.Value = Value(2)
   }
-}
 
-case class MouseEvent(state: MouseEvent.State.Value, button: MouseEvent.Button.Value) extends CapturingEvent
+  object StateChanged {
+    def unapply(event: MouseEvent): Option[(State.Value, Button.Value)] = {
+      if (event.stateChanged) {
+        MouseEvent.unapply(event)
+      } else {
+        None
+      }
+    }
+  }
+}

src/main/scala/ocelot/desktop/ui/event/handlers/MouseHandler.scala

@@ -24,7 +24,7 @@ trait MouseHandler extends Widget {
   protected def receiveDragEvents: Boolean = false
 
   /**
-    * If `true`, drag events, once they start, will be sent on every update cycle when if the mouse does not move.
+    * If `true`, drag events, once they start, will be sent on every update cycle even if the mouse does not move.
     */
   protected def spamDragEvents: Boolean = true
 

src/main/scala/ocelot/desktop/ui/event/sources/MouseEvents.scala

@@ -26,13 +26,13 @@ object MouseEvents {
       if (MouseEvent.Button.values.map(_.id).contains(buttonIdx)) {
         val button = MouseEvent.Button(buttonIdx)
         val state = if (Mouse.getEventButtonState) MouseEvent.State.Pressed else MouseEvent.State.Released
-        _events += MouseEvent(state, button)
+        val changed = state match {
-        state match {
           case MouseEvent.State.Pressed =>
-            _pressedButtons += button
+            _pressedButtons.add(button)
           case MouseEvent.State.Released =>
-            _pressedButtons -= button
+            _pressedButtons.remove(button)
         }
+        _events += MouseEvent(state, button)(changed)
       }
 
       val delta = Mouse.getEventDWheel
@@ -49,7 +49,7 @@ object MouseEvents {
 
   def releaseButtons(): Unit = {
     for (button <- pressedButtons) {
-      _events += MouseEvent(MouseEvent.State.Released, button)
+      _events += MouseEvent(MouseEvent.State.Released, button)(stateChanged = true)
     }
 
     _pressedButtons.clear()

src/main/scala/ocelot/desktop/ui/widget/TextInput.scala

@@ -17,7 +17,6 @@ import org.lwjgl.input.Keyboard
 
 import java.lang.Character.isWhitespace
 
-
 class TextInput(val initialText: String = "") extends Widget with MouseHandler with HoverAnimation {
   private val CursorBlinkTime = 2f
   private val PlaceholderForegroundColor: Color = ColorScheme("TextInputForegroundDisabled")
@@ -29,33 +28,44 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
   // model
   private val _text: Text = new Text(initialText.codePoints().toArray)
   private val cursor: Cursor = new Cursor()
-  private val selection: Selection = new Selection()
+  private val selectionWatcher = new Watcher[Option[Selection]](None)
+
+  // updated after all events are processed so that event handlers can refer to the previous position.
+  private val prevCursorPosition = Register.sampling(cursor.position)
 
   // view
   private var isFocused = false
   private var scroll = 0f
   private var blinkTimer = 0f
   private var cursorOffset = 0f
-  private var selectionStartOffset = 0f
+  private var selectionOffsets: Option[(Int, Int)] = None
-  private var selectionEndOffset = 0f
 
   private val enabledRegister = Register.sampling(enabled)
 
+  private def selection: Option[Selection] = selectionWatcher.value
+  private def selection_=(newValue: Option[Selection]): Unit = {
+    selectionWatcher.value = newValue
+  }
+
   cursor.onChange(position => {
     cursorOffset = charsWidth(_text.chars, 0, position)
     blinkTimer = 0
     adjustScroll()
   })
 
-  selection.onChange((from, to) => {
+  selectionWatcher.onChange(newValue => {
-    selectionStartOffset = charsWidth(_text.chars, 0, from min to)
+    selectionOffsets = newValue.map {
-    selectionEndOffset = charsWidth(_text.chars, 0, from max to)
+      case Selection.Ordered(start, end) =>
+        (
+          charsWidth(_text.chars, 0, start),
+          charsWidth(_text.chars, 0, end),
+        )
+    }
   })
 
   private val foregroundAnimation = new ColorAnimation(targetForegroundColor, 7f)
   private val borderAnimation = new ColorAnimation(targetBorderColor, 7f)
 
-
   // public API
   // -------------------------------------------------------------------------------------------------------------------
   def onInput(text: String): Unit = {}
@@ -70,11 +80,14 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
   def text: String = new String(_text.chars, 0, _text.chars.length)
   def text_=(value: String): Unit = {
     _text.chars = value.codePoints().toArray
-    selection.active = false
+    selection = None
     cursor.position = cursor.position max 0 min _text.chars.length
   }
 
-  private def selectedText: String = new String(_text.chars, selection.start, selection.length)
+  private def selectedText: String = selection match {
+    case Some(Selection.Ordered(start, end)) => new String(_text.chars, start, end)
+    case None => ""
+  }
 
   protected var placeholder: Array[Int] = Array.empty
   def placeholder_=(value: String): Unit = placeholder = value.codePoints().toArray
@@ -96,7 +109,6 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
     }
   }
 
-
   // widget management
   // -------------------------------------------------------------------------------------------------------------------
   override def minimumSize: Size2D = Size2D(200, 24)
@@ -128,79 +140,77 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
   }
 
   eventHandlers += {
-    case MouseEvent(MouseEvent.State.Pressed, button) if enabled =>
+    case MouseEvent.StateChanged(MouseEvent.State.Pressed, _) if enabled =>
       val inBounds = mouseInBounds
       if (isFocused && !inBounds) unfocus()
       if (!isFocused && inBounds) focus()
+
       if (isFocused) {
         val pos = pixelToCursorPosition(UiHandler.mousePosition.x - bounds.x)
-        val clamped = _text.chars.length.min(pos).max(0)
+        cursor.position = pos
-        // a bit of special logic: right click moves cursor position, but only if we clicked outside the current selection
-        // otherwise it would be impossible to do context operations on the selected text
-        if (button != MouseEvent.Button.Right || !selection.active || clamped < selection.from || clamped > selection.to) {
-          setCursorAndSelectionPosition(clamped)
-        }
       }
   }
 
   eventHandlers += {
-    case MouseEvent(MouseEvent.State.Pressed, MouseEvent.Button.Right) if isFocused && mouseInBounds =>
+    case MouseEvent.StateChanged(MouseEvent.State.Pressed, MouseEvent.Button.Right) if isFocused && mouseInBounds =>
       val menu = new ContextMenu
-      if (selection.active) {
+
+      if (selection.nonEmpty) {
         menu.addEntry(ContextMenuEntry("Cut", IconSource.Icons.Cut) { cutSelection() })
         menu.addEntry(ContextMenuEntry("Copy", IconSource.Icons.Copy) { copySelection() })
       }
+
       if (UiHandler.clipboard.nonEmpty) {
         menu.addEntry(ContextMenuEntry("Paste", IconSource.Icons.Paste) { pasteSelection() })
       }
+
+      if (_text.chars.nonEmpty) {
         if (menu.children.nonEmpty) {
           menu.addSeparator()
         }
+
         menu.addEntry(ContextMenuEntry("Select all") { selectAll() })
+      }
+
       root.get.contextMenus.open(menu)
 
+    case MouseEvent.StateChanged(MouseEvent.State.Pressed, _) if isFocused && mouseInBounds =>
+      selection = None
+
     case DoubleClickEvent(MouseEvent.Button.Left, _) if isFocused && mouseInBounds =>
       selectWord()
 
-    case event @ DragEvent(DragEvent.State.Start, MouseEvent.Button.Left, mouse) if isFocused =>
+    case DragEvent(DragEvent.State.Start | DragEvent.State.Drag, MouseEvent.Button.Left, mouse) if isFocused =>
       val pos = pixelToCursorPosition(mouse.x - bounds.x)
-      selection.active = true
+      selection = Selection(selection.fold(prevCursorPosition.value)(_.start), pos)
-      selection.to = pos
       cursor.position = pos
-      event.consume()
-
-    case event @ DragEvent(DragEvent.State.Drag, MouseEvent.Button.Left, mouse) if isFocused =>
-      val pos = pixelToCursorPosition(mouse.x - bounds.x)
-      selection.to = pos
-      cursor.position = pos
-      event.consume()
 
     case event @ KeyEvent(KeyEvent.State.Press | KeyEvent.State.Repeat, Keyboard.KEY_LEFT, _) if isFocused =>
-      if (selection.active && !KeyEvents.isShiftDown) {
+      handleKeyMovement(selection match {
-        setCursorAndSelectionPosition(selection.start)
+        case Some(Selection.Ordered(start, _)) if !KeyEvents.isShiftDown => start
-      } else if (cursor.position > 0) {
+        case _ => cursor.position - 1
-        setCursorAndSelectionPosition(cursor.position - 1)
+      })
-      }
+
       event.consume()
 
     case event @ KeyEvent(KeyEvent.State.Press | KeyEvent.State.Repeat, Keyboard.KEY_RIGHT, _) if isFocused =>
-      if (selection.active && !KeyEvents.isShiftDown) {
+      handleKeyMovement(selection match {
-        setCursorAndSelectionPosition(selection.end)
+        case Some(Selection.Ordered(_, end)) if !KeyEvents.isShiftDown => end
-      } else if (cursor.position < _text.chars.length) {
+        case _ => cursor.position + 1
-        setCursorAndSelectionPosition(cursor.position + 1)
+      })
-      }
+
       event.consume()
 
     case event @ KeyEvent(KeyEvent.State.Press, Keyboard.KEY_HOME, _) if isFocused =>
-      setCursorAndSelectionPosition(0)
+      handleKeyMovement(0)
       event.consume()
 
     case event @ KeyEvent(KeyEvent.State.Press, Keyboard.KEY_END, _) if isFocused =>
-      setCursorAndSelectionPosition(_text.chars.length)
+      handleKeyMovement(_text.chars.length)
       event.consume()
 
     case event @ KeyEvent(KeyEvent.State.Press | KeyEvent.State.Repeat, Keyboard.KEY_BACK, _) if isFocused =>
-      if (selection.active) {
+      if (selection.nonEmpty) {
         deleteSelection()
       } else {
         val (lhs, rhs) = _text.chars.splitAt(cursor.position)
@@ -209,10 +219,11 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
           cursor.position -= 1
         }
       }
+
       event.consume()
 
     case event @ KeyEvent(KeyEvent.State.Press | KeyEvent.State.Repeat, Keyboard.KEY_DELETE, _) if isFocused =>
-      if (selection.active) {
+      if (selection.nonEmpty) {
         deleteSelection()
       } else {
         val (lhs, rhs) = _text.chars.splitAt(cursor.position)
@@ -220,6 +231,7 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
           _text.chars = lhs ++ rhs.drop(1)
         }
       }
+
       event.consume()
 
     case event @ KeyEvent(KeyEvent.State.Press, Keyboard.KEY_A, _)
@@ -233,12 +245,12 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
       event.consume()
 
     case event @ KeyEvent(KeyEvent.State.Press, Keyboard.KEY_C, _)
-        if isFocused && KeyEvents.isControlDown && selection.active =>
+        if isFocused && KeyEvents.isControlDown && selection.nonEmpty =>
       copySelection()
       event.consume()
 
     case event @ KeyEvent(KeyEvent.State.Press, Keyboard.KEY_X, _)
-        if isFocused && KeyEvents.isControlDown && selection.active =>
+        if isFocused && KeyEvents.isControlDown && selection.nonEmpty =>
       cutSelection()
       event.consume()
 
@@ -256,7 +268,10 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
       event.consume()
 
     case event @ KeyEvent(KeyEvent.State.Press | KeyEvent.State.Repeat, _, char) if isFocused && !char.isControl =>
-      if (selection.active) deleteSelection()
+      if (selection.nonEmpty) {
+        deleteSelection()
+      }
+
       writeChar(char)
       event.consume()
   }
@@ -276,36 +291,25 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
     pos
   }
 
-  /**
+  private def handleKeyMovement(position: Int): Unit = {
-    * Generally you can just do `cursor.position = x`.
+    selection = if (KeyEvents.isShiftDown) {
-    * But this method will take care of correctly repositioning the selection as well.
+      Selection(selection.fold(cursor.position)(_.start), position)
-    */
-  private def setCursorAndSelectionPosition(position: Int): Unit = {
-    if (!selection.active && KeyEvents.isShiftDown && cursor.position != position) {
-      selection.active = true
-      selection.from = cursor.position
-    } else if (selection.active && !KeyEvents.isShiftDown) {
-      selection.active = false
-    }
-    cursor.position = position
-    if (selection.active) {
-      selection.to = cursor.position
     } else {
-      selection.from = cursor.position
+      None
     }
+
+    cursor.position = position
   }
 
   private def selectAll(): Unit = {
-    selection.active = true
+    selection = Selection(0, _text.chars.length)
-    selection.from = 0
-    selection.to = _text.chars.length
   }
 
   private def selectWord(): Unit = {
-    selection.active = true
+    val from = 0 max (_text.chars.lastIndexWhere(isWhitespace, cursor.position - 1) + 1)
-    selection.from = 0 max (_text.chars.lastIndexWhere(isWhitespace, cursor.position - 1) + 1)
     val to = _text.chars.indexWhere(isWhitespace, cursor.position)
-    selection.to = if (to >= 0 && to < _text.chars.length) to else _text.chars.length
+    val clampedTo = if (to >= 0 && to < _text.chars.length) to else _text.chars.length
+    selection = Selection(from, clampedTo)
   }
 
   private def copySelection(): Unit = {
@@ -318,14 +322,15 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
   }
 
   private def pasteSelection(): Unit = {
-    if (selection.active) deleteSelection()
+    if (selection.nonEmpty) deleteSelection()
     writeString(UiHandler.clipboard)
   }
 
   private def deleteSelection(): Unit = {
-    selection.active = false
+    for (Selection.Ordered(start, end) <- selection) {
-    _text.chars = _text.chars.take(selection.start) ++ _text.chars.drop(selection.end)
+      _text.chars = _text.chars.take(start) ++ _text.chars.drop(end)
-    cursor.position = selection.start
+      cursor.position = start
+    }
   }
 
   private def writeString(string: String): Unit = {
@@ -354,7 +359,6 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
     if (fullTextWidth > areaWidth && fullTextWidth - scroll < areaWidth) scroll = fullTextWidth - areaWidth
   }
 
-
   override def update(): Unit = {
     super.update()
 
@@ -373,12 +377,12 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
     }
 
     // update everything
+    prevCursorPosition.update()
     foregroundAnimation.update()
     borderAnimation.update()
     blinkTimer = (blinkTimer + UiHandler.dt) % CursorBlinkTime
   }
 
-
   private def updateAnimationTargets(): Unit = {
     foregroundAnimation.goto(targetForegroundColor)
     borderAnimation.goto(targetBorderColor)
@@ -406,9 +410,9 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
 
     g.setScissor(position.x + 4, position.y, size.width - 8f, size.height)
 
-    if (selection.active) {
+    for ((start, end) <- selectionOffsets) {
-      val width = selectionEndOffset - selectionStartOffset
+      val width = end - start
-      g.rect(position.x + selectionStartOffset + 8 - scroll, position.y + 4, width, size.height - 8, BackgroundSelectedColor)
+      g.rect(position.x + start + 8 - scroll, position.y + 4, width, size.height - 8, BackgroundSelectedColor)
     }
 
     g.background = Color.Transparent
@@ -418,9 +422,10 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
     var charOffset = 0
     val charsToDisplay = if (_text.chars.nonEmpty || isFocused) _text.chars else placeholder
     for (char <- charsToDisplay) {
-      if (selection.active) {
+      for ((start, end) <- selectionOffsets) {
-        g.foreground = if (charOffset >= selectionStartOffset && charOffset < selectionEndOffset) ForegroundSelectedColor else foreground
+        g.foreground = if (charOffset >= start && charOffset < end) ForegroundSelectedColor else foreground
       }
+
       g.char(position.x + 8 + charOffset - scroll, position.y + 4, char)
       charOffset += g.font.charWidth(char)
     }
@@ -436,29 +441,29 @@ object TextInput {
     def chars: Array[Int] = value
     def chars_=(newValue: Array[Int]): Unit = value = newValue
   }
+
   class Cursor(initialValue: Int = 0) extends Watcher(initialValue) {
     def position: Int = value
     def position_=(newValue: Int): Unit = value = newValue
   }
-  class Selection {
-    private val fromWatcher = Watcher(0)
-    private val toWatcher = Watcher(0)
 
-    def from: Int = fromWatcher.value
+  case class Selection(start: Int, end: Int) {
-    def from_=(x: Int): Unit = fromWatcher.value = x
+    require(start != end)
+  }
 
-    def to: Int = toWatcher.value
+  object Selection {
-    def to_=(x: Int): Unit = toWatcher.value = x
+    def apply(start: Int, end: Int): Option[Selection] = {
+      Option.when(start != end) {
+        new Selection(start, end)
+      }
+    }
 
-    def start: Int = from min to
+    object Ordered {
-    def end: Int = from max to
+      def unapply(selection: Selection): Some[(Int, Int)] = {
-    def length: Int = end - start
+        val Selection(start, end) = selection
 
-    var active: Boolean = false
+        Some((start min end, start max end))
-
+      }
-    def onChange(callback: (Int, Int) => Unit): Unit = {
-      fromWatcher.onChange(callback(_, to))
-      toWatcher.onChange(callback(from, _))
     }
   }
 }