Zooming with ZoomRect

[moelski.net]

Hi !

I have a problem in using the ZoomRect function.

For reproduction just place a chart on a form, add one FastLine Series and this code in FormLoad:

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            ((FastLine)this.tChart1[0]).DrawAllPoints = true;
            ((FastLine)this.tChart1[0]).FillSampleValues(10000);

Add a Button and insert this buttonclick code:

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            var strgPressed = ModifierKeys == Keys.Control;

            var addon = -5;
            if (strgPressed)
            {
                addon = 5;
            }

            var r = new Rectangle(
                        this.tChart1.DisplayRectangle.Left + addon,
                        this.tChart1.DisplayRectangle.Top + addon,
                        this.tChart1.DisplayRectangle.Right - addon,
                        this.tChart1.DisplayRectangle.Bottom - addon);

            this.tChart1.Zoom.ZoomRect(r);

What I want to do is zoom in (or zoom out) the chart.

leftright.png (44.87 KiB) Viewed 13015 times

If you click the button (without pressing STRG) you will zoom out. First question ... Why is the left space bigger then the right one (marked with red). Why is it not the same on both sides. Mayby DisplayRectangle is the wrong rectangle I should use for calculation?

Now hold the STRG key and press the button again. Now it should be zoom in (to the previous position). But now it Zooms out again.

Actually I have no idea what happend here

Dominik

[Christopher]

If you click the button (without pressing STRG) you will zoom out. First question ... Why is the left space bigger then the right one (marked with red). Why is it not the same on both sides. Mayby DisplayRectangle is the wrong rectangle I should use for calculation?

Instead of:

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this.tChart1.DisplayRectangle

Try:

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this.tChart1.Chart.ChartRect

[moelski.net]

Hi Christopher,

u made my day

Just in case someone else need a working sample:

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            var strgPressed = ModifierKeys == Keys.Control;

            var addon = -5;
            if (strgPressed)
            {
                addon = 5;
            }

            var x = this.tChart1.Chart.ChartRect.Left + addon;
            var y = this.tChart1.Chart.ChartRect.Top + addon;
            var w = (this.tChart1.Chart.ChartRect.Right - addon) - x;
            var h = (this.tChart1.Chart.ChartRect.Bottom - addon) - y;
            
            var r = new Rectangle(x, y, w, h);

            this.tChart1.Zoom.ZoomRect(r);

Dominik

[moelski.net]

Hi Christopher,

I have one question left. I use the zoomed Event from the chart to Zoom, the custom Axes, too.
Now we have a layout where we stack the Y axes. The sample app has a TEE file for demonstrating.

If you use the Zoom button the X axis works like expected. But the Y Axes always do a Zoom out.
Any hint why this happens?

ProblemZoomout.png (20.24 KiB) Viewed 12985 times

Very strange zooming

[Christopher]

Very strange zooming

This is because the call to:

this.tChart1.Zoom.ZoomRect(r);

does not use custom axes. You will have to set the Axis.SetMinMax() "manually" for each axes you want to zoom in the case of using custom axes.

[moelski.net]

Hi Christopher,

You will have to set the Axis.SetMinMax() "manually" for each axes you want to zoom in the case of using custom axes.

That is whar I did. Take a look at my code / or my sample:

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        private void tChart1_Zoomed(object sender, EventArgs e)
        {
            if (this.tChart1.Zoom.Direction == ZoomDirections.Both ||
                this.tChart1.Zoom.Direction == ZoomDirections.Vertical)
            {
                for (int i = 0; i < this.tChart1.Axes.Count; i++)
                {
                    var axis = this.tChart1.Axes[i];
                    if (!axis.Horizontal && axis.IsCustom())
                    {
                        axis.SetMinMax(
                            axis.CalcPosPoint(((TChart)sender).Zoom.y1),
                            axis.CalcPosPoint(((TChart)sender).Zoom.y0));
                    }
                }
            }
        }

But it did not work as expected for me. Maybe the calculation for the SetMinMax values is wrong?

Dominik

[Christopher]

Hello Dominik,

But it did not work as expected for me. Maybe the calculation for the SetMinMax values is wrong?

You can try something like:

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        void tChart1_UndoneZoom(object sender, EventArgs e)
        {
          for (int i = 0; i < this.tChart1.Axes.Count; i++)
          {
            var axis = this.tChart1.Axes[i];


            if (!axis.Horizontal && axis.IsCustom())
            {
              axis.Automatic = true;
            }
          }
        }


        private void tChart1_Zoomed(object sender, EventArgs e)
        {
            if (this.tChart1.Zoom.Direction == ZoomDirections.Both ||
                this.tChart1.Zoom.Direction == ZoomDirections.Vertical)
            {
              Rectangle rect = Utils.FromLTRB(((TChart)sender).Zoom.x0, ((TChart)sender).Zoom.y0, ((TChart)sender).Zoom.x1, ((TChart)sender).Zoom.y1);

              Rectangle chartRect = tChart1.Chart.ChartRect;

              double ratio = 1.0 / ((double)chartRect.Height / (double)rect.Height);


              for (int i = 0; i < this.tChart1.Axes.Count; i++)
              {
                var axis = this.tChart1.Axes[i];
                if (!axis.Horizontal && axis.IsCustom() && (axis.IStartPos < rect.Bottom))
                {
                  axis.Automatic = false;
                  axis.Maximum *= ratio;
                  axis.Minimum *= ratio;
                }
              }
            }
        }

Here the axis is only being zoom if the bottom of the zoom rectangle is below the beginning of the axis. More "intelligence" can be added here to ensure the right axes are being zoomed at the right time.