Display.qml Example File

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  import QtQuick 2.0
  import QtQuick.Window 2.0

  Item {
      id: display
      property real fontSize: Math.floor(Screen.pixelDensity * 5.0)
      property bool enteringDigits: false
      property int maxDigits: (width / fontSize) + 1
      property string displayedOperand
      property string errorString: qsTr("ERROR")
      property bool isError: displayedOperand === errorString

      function displayOperator(operator)
      {
          listView.model.append({ "operator": operator, "operand": "" })
          enteringDigits = true
          listView.positionViewAtEnd()
      }

      function newLine(operator, operand)
      {
          displayedOperand = displayNumber(operand)
          listView.model.append({ "operator": operator, "operand": displayedOperand })
          enteringDigits = false
          listView.positionViewAtEnd()
      }

      function appendDigit(digit)
      {
          if (!enteringDigits)
              listView.model.append({ "operator": "", "operand": "" })
          var i = listView.model.count - 1;
          listView.model.get(i).operand = listView.model.get(i).operand + digit;
          enteringDigits = true
          listView.positionViewAtEnd()
      }

      function setDigit(digit)
      {
          var i = listView.model.count - 1;
          listView.model.get(i).operand = digit;
          listView.positionViewAtEnd()
      }

      function clear()
      {
          displayedOperand = ""
          if (enteringDigits) {
              var i = listView.model.count - 1
              if (i >= 0)
                  listView.model.remove(i)
              enteringDigits = false
          }
      }

      // Returns a string representation of a number that fits in
      // display.maxDigits characters, trying to keep as much precision
      // as possible. If the number cannot be displayed, returns an
      // error string.
      function displayNumber(num) {
          if (typeof(num) != "number")
              return errorString;

          var intNum = parseInt(num);
          var intLen = intNum.toString().length;

          // Do not count the minus sign as a digit
          var maxLen = num < 0 ? maxDigits + 1 : maxDigits;

          if (num.toString().length <= maxLen) {
              if (isFinite(num))
                  return num.toString();
              return errorString;
          }

          // Integer part of the number is too long - try
          // an exponential notation
          if (intNum == num || intLen > maxLen - 3) {
              var expVal = num.toExponential(maxDigits - 6).toString();
              if (expVal.length <= maxLen)
                  return expVal;
          }

          // Try a float presentation with fixed number of digits
          var floatStr = parseFloat(num).toFixed(maxDigits - intLen - 1).toString();
          if (floatStr.length <= maxLen)
              return floatStr;

          return errorString;
      }

      Item {
          id: theItem
          width: parent.width + 32
          height: parent.height

          Rectangle {
              id: rect
              x: 16
              color: "white"
              height: parent.height
              width: display.width - 16
          }
          Image {
              anchors.right: rect.left
              source: "images/paper-edge-left.png"
              height: parent.height
              fillMode: Image.TileVertically
          }
          Image {
              anchors.left: rect.right
              source: "images/paper-edge-right.png"
              height: parent.height
              fillMode: Image.TileVertically
          }

          Image {
              id: grip
              source: "images/paper-grip.png"
              anchors.horizontalCenter: parent.horizontalCenter
              anchors.bottom: parent.bottom
              anchors.bottomMargin: 20
          }

          ListView {
              id: listView
              x: 16; y: 30
              width: display.width
              height: display.height - 50 - y
              delegate: Item {
                  height: display.fontSize * 1.1
                  width: parent.width
                  Text {
                      id: operator
                      x: 6
                      font.pixelSize: display.fontSize
                      color: "#6da43d"
                      text: model.operator
                  }
                  Text {
                      id: operand
                      font.pixelSize: display.fontSize
                      anchors.right: parent.right
                      anchors.rightMargin: 22
                      text: model.operand
                  }
              }
              model: ListModel { }
          }

      }

  }