StockChart.qml Example File

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  import QtQuick 2.0
  import "."

  Rectangle {
      id: chart
      width: 320
      height: 200

      property var stockModel: null
      property var startDate: new Date()
      property var endDate: new Date()
      property string activeChart: "year"
      property var settings
      property int gridSize: 4
      property real gridStep: gridSize ? (width - canvas.tickMargin) / gridSize : canvas.xGridStep

      function update() {
          endDate = new Date();
          if (chart.activeChart === "year") {
              chart.startDate = new Date(chart.endDate.getFullYear() - 1,
                                         chart.endDate.getMonth(),
                                         chart.endDate.getDate());
              chart.gridSize = 12;
          }
          else if (chart.activeChart === "month") {
              chart.startDate = new Date(chart.endDate.getFullYear(),
                                         chart.endDate.getMonth() - 1,
                                         chart.endDate.getDate());
              gridSize = 0;
          }
          else if (chart.activeChart === "week") {
              chart.startDate = new Date(chart.endDate.getFullYear(),
                                         chart.endDate.getMonth(),
                                         chart.endDate.getDate() - 7);
              gridSize = 0;
          }
          else {
              chart.startDate = new Date(2005, 3, 25);
              gridSize = 4;
          }

          canvas.requestPaint();
      }

      Row {
          id: activeChartRow
          anchors.left: chart.left
          anchors.right: chart.right
          anchors.top: chart.top
          anchors.topMargin: 4
          spacing: 52
          onWidthChanged: {
              var buttonsLen = maxButton.width + yearButton.width + monthButton.width + weekButton.width;
              var space = (width - buttonsLen) / 3;
              spacing = Math.max(space, 10);
          }

          Button {
              id: maxButton
              text: "Max"
              buttonEnabled: chart.activeChart === "max"
              onClicked: {
                  chart.activeChart = "max";
                  chart.update();
              }
          }
          Button {
              id: yearButton
              text: "Year"
              buttonEnabled: chart.activeChart === "year"
              onClicked: {
                  chart.activeChart = "year";
                  chart.update();
              }
          }
          Button {
              id: monthButton
              text: "Month"
              buttonEnabled: chart.activeChart === "month"
              onClicked: {
                  chart.activeChart = "month";
                  chart.update();
              }
          }
          Button {
              id: weekButton
              text: "Week"
              buttonEnabled: chart.activeChart === "week"
              onClicked: {
                  chart.activeChart = "week";
                  chart.update();
              }
          }
      }

      Text {
          id: fromDate
          color: "#000000"
          font.family: Settings.fontFamily
          font.pointSize: 8
          anchors.left: parent.left
          anchors.bottom: parent.bottom
          text: "| " + startDate.toDateString()
      }

      Text {
          id: toDate
          color: "#000000"
          font.family: Settings.fontFamily
          font.pointSize: 8
          anchors.right: parent.right
          anchors.rightMargin: canvas.tickMargin
          anchors.bottom: parent.bottom
          text: endDate.toDateString() + " |"
      }

      Canvas {
          id: canvas

          // Uncomment below lines to use OpenGL hardware accelerated rendering.
          // See Canvas documentation for available options.
          // renderTarget: Canvas.FramebufferObject
          // renderStrategy: Canvas.Threaded

          anchors.top: activeChartRow.bottom
          anchors.left: parent.left
          anchors.right: parent.right
          anchors.bottom: fromDate.top

          property int pixelSkip: 1
          property int numPoints: 1
          property int tickMargin: 34

          property real xGridStep: (width - tickMargin) / numPoints
          property real yGridOffset: height / 26
          property real yGridStep: height / 12

          function drawBackground(ctx) {
              ctx.save();
              ctx.fillStyle = "#ffffff";
              ctx.fillRect(0, 0, canvas.width, canvas.height);
              ctx.strokeStyle = "#d7d7d7";
              ctx.beginPath();
              // Horizontal grid lines
              for (var i = 0; i < 12; i++) {
                  ctx.moveTo(0, canvas.yGridOffset + i * canvas.yGridStep);
                  ctx.lineTo(canvas.width, canvas.yGridOffset + i * canvas.yGridStep);
              }

              // Vertical grid lines
              var height = 35 * canvas.height / 36;
              var yOffset = canvas.height - height;
              var xOffset = 0;
              for (i = 0; i < chart.gridSize; i++) {
                  ctx.moveTo(xOffset + i * chart.gridStep, yOffset);
                  ctx.lineTo(xOffset + i * chart.gridStep, height);
              }
              ctx.stroke();

              // Right ticks
              ctx.strokeStyle = "#666666";
              ctx.beginPath();
              var xStart = canvas.width - tickMargin;
              ctx.moveTo(xStart, 0);
              ctx.lineTo(xStart, canvas.height);
              for (i = 0; i < 12; i++) {
                  ctx.moveTo(xStart, canvas.yGridOffset + i * canvas.yGridStep);
                  ctx.lineTo(canvas.width, canvas.yGridOffset + i * canvas.yGridStep);
              }
              ctx.moveTo(0, canvas.yGridOffset + 9 * canvas.yGridStep);
              ctx.lineTo(canvas.width, canvas.yGridOffset + 9 * canvas.yGridStep);
              ctx.closePath();
              ctx.stroke();

              ctx.restore();
          }

          // Returns a shortened, readable version of the potentially
          // large volume number.
          function volumeToString(value) {
              if (value < 1000)
                  return value;
              var exponent = parseInt(Math.log(value) / Math.log(1000));
              var shortVal = parseFloat(parseFloat(value) / Math.pow(1000, exponent)).toFixed(1);

              // Drop the decimal point on 3-digit values to make it fit
              if (shortVal >= 100.0) {
                  shortVal = parseFloat(shortVal).toFixed(0);
              }
              return shortVal + "KMBTG".charAt(exponent - 1);
          }

          function drawScales(ctx, high, low, vol)
          {
              ctx.save();
              ctx.strokeStyle = "#888888";
              ctx.font = "10px Open Sans"
              ctx.beginPath();

              // prices on y-axis
              var x = canvas.width - tickMargin + 3;
              var priceStep = (high - low) / 9.0;
              for (var i = 0; i < 10; i += 2) {
                  var price = parseFloat(high - i * priceStep).toFixed(1);
                  ctx.text(price, x, canvas.yGridOffset + i * yGridStep - 2);
              }

              // volume scale
              for (i = 0; i < 3; i++) {
                  var volume = volumeToString(vol - (i * (vol/3)));
                  ctx.text(volume, x, canvas.yGridOffset + (i + 9) * yGridStep + 10);
              }

              ctx.closePath();
              ctx.stroke();
              ctx.restore();
          }

          function drawPrice(ctx, from, to, color, price, points, highest, lowest)
          {
              ctx.save();
              ctx.globalAlpha = 0.7;
              ctx.strokeStyle = color;
              ctx.lineWidth = 3;
              ctx.beginPath();

              var end = points.length;

              var range = highest - lowest;
              if (range == 0) {
                  range = 1;
              }

              for (var i = 0; i < end; i += pixelSkip) {
                  var x = points[i].x;
                  var y = points[i][price];
                  var h = 9 * yGridStep;

                  y = h * (lowest - y)/range + h + yGridOffset;

                  if (i == 0) {
                      ctx.moveTo(x, y);
                  } else {
                      ctx.lineTo(x, y);
                  }
              }
              ctx.stroke();
              ctx.restore();
          }

          function drawVolume(ctx, from, to, color, price, points, highest)
          {
              ctx.save();
              ctx.fillStyle = color;
              ctx.globalAlpha = 0.8;
              ctx.lineWidth = 0;
              ctx.beginPath();

              var end = points.length;
              var margin = 0;

              if (chart.activeChart === "month" || chart.activeChart === "week") {
                  margin = 8;
                  ctx.shadowOffsetX = 4;
                  ctx.shadowBlur = 3.5;
                  ctx.shadowColor = Qt.darker(color);
              }

              // To match the volume graph with price grid, skip drawing the initial
              // volume of the first day on chart.
              for (var i = 1; i < end; i += pixelSkip) {
                  var x = points[i - 1].x;
                  var y = points[i][price];
                  y = canvas.height * (y / highest);
                  y = 3 * y / 12;
                  ctx.fillRect(x, canvas.height - y + yGridOffset,
                               canvas.xGridStep - margin, y);
              }

              ctx.stroke();
              ctx.restore();
          }

          function drawError(ctx, msg)
          {
              ctx.save();
              ctx.strokeStyle = "#888888";
              ctx.font = "24px Open Sans"
              ctx.textAlign = "center"
              ctx.shadowOffsetX = 4;
              ctx.shadowOffsetY = 4;
              ctx.shadowBlur = 1.5;
              ctx.shadowColor = "#aaaaaa";
              ctx.beginPath();

              ctx.fillText(msg, (canvas.width - tickMargin) / 2,
                                (canvas.height - yGridOffset - yGridStep) / 2);

              ctx.closePath();
              ctx.stroke();
              ctx.restore();
          }

          onPaint: {
              numPoints = stockModel.indexOf(chart.startDate);

              if (chart.gridSize == 0)
                  chart.gridSize = numPoints

              var ctx = canvas.getContext("2d");
              ctx.globalCompositeOperation = "source-over";
              ctx.lineWidth = 1;

              drawBackground(ctx);

              if (!stockModel.ready) {
                  drawError(ctx, "No data available.");
                  return;
              }

              var highestPrice = 0;
              var highestVolume = 0;
              var lowestPrice = -1;
              var points = [];
              for (var i = numPoints, j = 0; i >= 0 ; i -= pixelSkip, j += pixelSkip) {
                  var price = stockModel.get(i);
                  if (parseFloat(highestPrice) < parseFloat(price.high))
                      highestPrice = price.high;
                  if (parseInt(highestVolume, 10) < parseInt(price.volume, 10))
                      highestVolume = price.volume;
                  if (lowestPrice < 0 || parseFloat(lowestPrice) > parseFloat(price.low))
                      lowestPrice = price.low;
                  points.push({
                                  x: j * xGridStep,
                                  open: price.open,
                                  close: price.close,
                                  high: price.high,
                                  low: price.low,
                                  volume: price.volume
                              });
              }

              if (settings.drawHighPrice)
                  drawPrice(ctx, 0, numPoints, settings.highColor, "high", points, highestPrice, lowestPrice);
              if (settings.drawLowPrice)
                  drawPrice(ctx, 0, numPoints, settings.lowColor, "low", points, highestPrice, lowestPrice);
              if (settings.drawOpenPrice)
                  drawPrice(ctx, 0, numPoints,settings.openColor, "open", points, highestPrice, lowestPrice);
              if (settings.drawClosePrice)
                  drawPrice(ctx, 0, numPoints, settings.closeColor, "close", points, highestPrice, lowestPrice);

              drawVolume(ctx, 0, numPoints, settings.volumeColor, "volume", points, highestVolume);
              drawScales(ctx, highestPrice, lowestPrice, highestVolume);
          }
      }
  }