Add OpenBuffer() function to View

Fixes #43

cmd/micro/micro.go

@@ -211,7 +211,7 @@ func main() {
 				case tcell.KeyCtrlQ:
 					// Make sure not to quit if there are unsaved changes
 					if helpOpen {
-						view.buf = buf
+						view.OpenBuffer(buf)
 						helpOpen = false
 					} else {
 						if view.CanClose("Quit anyway? (yes, no, save) ") {
@@ -234,9 +234,9 @@ func main() {
 						helpBuffer := NewBuffer(helpTxt, "")
 						helpBuffer.name = "Help"
 						helpOpen = true
-						view.buf = helpBuffer
+						view.OpenBuffer(helpBuffer)
 					} else {
-						view.buf = buf
+						view.OpenBuffer(buf)
 						helpOpen = false
 					}
 				}

cmd/micro/view.go

@@ -276,6 +276,29 @@ func (v *View) SelectAll() {
 	v.cursor.y = 0
 }
 
+// OpenBuffer opens a new buffer in this view.
+// This resets the topline, event handler and cursor.
+func (v *View) OpenBuffer(buf *Buffer) {
+	v.buf = buf
+	v.topline = 0
+	// Put the cursor at the first spot
+	v.cursor = Cursor{
+		x: 0,
+		y: 0,
+		v: v,
+	}
+	v.cursor.ResetSelection()
+
+	v.eh = NewEventHandler(v)
+
+	v.matches = Match(v)
+
+	// Set mouseReleased to true because we assume the mouse is not being pressed when
+	// the editor is opened
+	v.mouseReleased = true
+	v.lastClickTime = time.Time{}
+}
+
 // OpenFile opens a new file in the current view
 // It makes sure that the current buffer can be closed first (unsaved changes)
 func (v *View) OpenFile() {