Simplify TextInput and fix few small bugs

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

@@ -52,9 +52,8 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
   def text: String = chars.mkString
   def text_=(value: String): Unit = {
     chars = value.toCharArray
-    cursorPos = 0
-    cursorOffset = 0
-    textChanged = true
+    adjustCursor(0)
+    // note: we are not setting `textChanged = true` here to avoid potential recursion with `onInput` callback
   }
 
   protected var placeholder: Array[Char] = "".toCharArray
@@ -96,7 +95,7 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
 
   private def charsWidth(chars: Array[Char], first: Int, last: Int): Int = {
     var width = 0
-    for (index <- first to last) {
+    for (index <- (first max 0) to (last min (chars.length - 1))) {
       width += font().charWidth(chars(index))
     }
     width
@@ -117,53 +116,32 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
         width += charWidth(chars(pos))
         if (width < absoluteX) pos += 1
       }
-      cursorPos = chars.length.min(pos).max(0)
-      cursorOffset = if (cursorPos > 0) charsWidth(chars, 0, (cursorPos - 1).max(0)) else 0
-      blinkTimer = 0
-      adjustScroll()
+      adjustCursor(chars.length.min(pos).max(0))
 
     case event @ KeyEvent(KeyEvent.State.Press | KeyEvent.State.Repeat, Keyboard.KEY_LEFT, _) if isFocused =>
-      if (cursorPos != 0) {
-        cursorOffset -= charWidth(chars(cursorPos - 1))
-        cursorPos -= 1
-        blinkTimer = 0
-        adjustScroll()
-      }
+      if (cursorPos > 0) adjustCursor(cursorPos - 1)
       event.consume()
 
     case event @ KeyEvent(KeyEvent.State.Press | KeyEvent.State.Repeat, Keyboard.KEY_RIGHT, _) if isFocused =>
-      if (cursorPos < chars.length) {
-        cursorOffset += charWidth(chars(cursorPos))
-        cursorPos += 1
-        blinkTimer = 0
-        adjustScroll()
-      }
+      if (cursorPos < chars.length) adjustCursor(cursorPos + 1)
       event.consume()
 
     case event @ KeyEvent(KeyEvent.State.Press, Keyboard.KEY_HOME, _) if isFocused =>
-      cursorPos = 0
-      cursorOffset = 0
-      blinkTimer = 0
-      scroll = 0
+      adjustCursor(0)
       event.consume()
 
     case event @ KeyEvent(KeyEvent.State.Press, Keyboard.KEY_END, _) if isFocused =>
-      val textWidth = charsWidth(chars)
-      cursorPos = chars.length
-      cursorOffset = textWidth
-      blinkTimer = 0
-      scroll = (textWidth - size.width + 16).max(0)
+      adjustCursor(chars.length)
       event.consume()
 
     case event @ KeyEvent(KeyEvent.State.Press | KeyEvent.State.Repeat, Keyboard.KEY_BACK, _) if isFocused =>
       val (lhs, rhs) = chars.splitAt(cursorPos)
       if (!lhs.isEmpty) {
-        val cw = charWidth(lhs.last)
         chars = lhs.take(lhs.length - 1) ++ rhs
         textChanged = true
-        cursorOffset -= cw
-        cursorPos -= 1
-        blinkTimer = 0
+        adjustCursor(cursorPos - 1)
+        // if the text overflows - scroll it into visibility, it will feel nicer
+        val cw = charWidth(lhs.last)
         scroll = (scroll - cw).max(0)
       }
       event.consume()
@@ -182,18 +160,12 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
       event.consume()
 
     case event @ KeyEvent(KeyEvent.State.Press | KeyEvent.State.Repeat, Keyboard.KEY_INSERT, _) if isFocused =>
-      // TODO: insert the whole clipboard string at once instead of going char-by-char.
-      for (char <- UiHandler.clipboard.toCharArray) {
-        writeChar(char)
-      }
+      writeString(UiHandler.clipboard)
       event.consume()
 
     case event @ KeyEvent(KeyEvent.State.Press | KeyEvent.State.Repeat, Keyboard.KEY_V, _)
         if isFocused && KeyEvents.isControlDown =>
-      // TODO: insert the whole clipboard string at once instead of going char-by-char.
-      for (char <- UiHandler.clipboard.toCharArray) {
-        writeChar(char)
-      }
+      writeString(UiHandler.clipboard)
       event.consume()
 
     case event @ KeyEvent(KeyEvent.State.Press, Keyboard.KEY_RETURN, _) if isFocused =>
@@ -206,13 +178,26 @@ class TextInput(val initialText: String = "") extends Widget with MouseHandler w
   }
 
 
+  private def writeString(string: String): Unit = {
+    val (lhs, rhs) = chars.splitAt(cursorPos)
+    val array = string.toCharArray
+    chars = lhs ++ array ++ rhs
+    textChanged = true
+    adjustCursor(cursorPos + string.length)
+  }
+
   private def writeChar(char: Char): Unit = {
     val (lhs, rhs) = chars.splitAt(cursorPos)
     chars = lhs ++ Array(char) ++ rhs
     textChanged = true
-    cursorOffset += charWidth(chars(cursorPos))
-    cursorPos += 1
+    adjustCursor(cursorPos + 1)
+  }
+
+  private def adjustCursor(position: Int): Unit = {
+    cursorPos = position
+    cursorOffset = charsWidth(chars, 0, cursorPos - 1)
     blinkTimer = 0
+    adjustScroll()
   }
 
   private def adjustScroll(): Unit = {