Added mouse scroll events

src/main/scala/com/repocad/view/event/Event.scala

@@ -7,19 +7,64 @@ import com.repocad.geom.Vector2D
   */
 trait Event
 
+/**
+  * An event arriving from the interaction of a mouse.
+  */
 trait MouseEvent extends Event {
+  /**
+    * The position of the mouse event relative to the view coordinates.
+    *
+    * @return A [[Vector2D]] denoting the x and y coordinates in a 2-d space.
+    */
   def point: Vector2D
 }
 
 case class MouseDown(point: Vector2D) extends Event
+
 case class MouseMove(point: Vector2D) extends Event
+
 case class MouseLeave(point: Vector2D) extends Event
+
+case class MouseScroll(point: Vector2D, delta: ScrollDistance) extends Event
+
 case class MouseUp(point: Vector2D) extends Event
 
+/**
+  * An event arriving from the interaction of a keyboard.
+  */
 trait KeyboardEvent extends Event {
+
+  /**
+    * The string representation of the pressed key.
+    *
+    * @return
+    */
   def key: String
+
+  /**
+    * Descriptions of which modifier keys are currently pressed.
+    *
+    * @return A [[ModifierKeys]] object.
+    */
   def modifierKeys: ModifierKeys
+
 }
 
 case class KeyDown(key: String, modifierKeys: ModifierKeys) extends KeyboardEvent
+
 case class KeyUp(key: String, modifierKeys: ModifierKeys) extends KeyboardEvent
+
+/**
+  * A scrolling distance described by a double value.
+  *
+  * @param value The value the scroll event scrolls.
+  */
+sealed case class ScrollDistance(value: Double)
+
+case object ScrollDistance {
+  def apply(value: Double) = if (value >= 0) ScrollUp(value) else ScrollDown(value)
+}
+
+sealed case class ScrollUp(value: Double) extends ScrollDistance(value)
+
+sealed case class ScrollDown(value: Double) extends ScrollDistance(value)

src/main/scala/com/repocad/web/CanvasView.scala

@@ -4,7 +4,7 @@ import com.repocad.geom.{TransformationMatrix, Vector2D}
 import com.repocad.view.View
 import com.repocad.view.event.{Event, _}
 import org.scalajs.dom.MouseEvent
-import org.scalajs.dom.raw.HTMLCanvasElement
+import org.scalajs.dom.raw.{WheelEvent, HTMLCanvasElement}
 
 import scala.scalajs.js.annotation.JSExport
 
@@ -16,6 +16,7 @@ class CanvasView(canvas: HTMLCanvasElement) extends View {
   canvas.onmousemove = (e: MouseEvent) => enqueueMouseEvent(e, MouseMove)
   canvas.onmouseleave = (e: MouseEvent) => enqueueMouseEvent(e, MouseLeave)
   canvas.onmouseup = (e: MouseEvent) => enqueueMouseEvent(e, MouseUp)
+  canvas.onmousewheel = (e: WheelEvent) => enqueueMouseEvent(e, MouseScroll(_, ScrollDistance(e.deltaMode)))
 
   canvas.onkeydown = (e: org.scalajs.dom.KeyboardEvent) => enqueueKeyboardEvent(e, KeyDown)
   canvas.onkeyup = (e: org.scalajs.dom.KeyboardEvent) => enqueueKeyboardEvent(e, KeyUp)