Steema Central

Posted: **Sun May 09, 2021 8:19 pm**

Steema version = Steema.TeeChart.NET.Xamarin.Forms v4.2021.4.22
Xamarin Forms version = v5.0.0.2012
Development platform = Visual Studio 2019 Pro v16.9.1
Target device = Android 6.0 (API 23) to API 10.0 (API 29) smallest res = 480x800

I am trying to write code to re-size aspects of a circular gauge control when the gauge itself is resized. My code does work, but only when the gauge control is pressed after being resized. I assume I am not calling my resize code in the correct event (currently calling in the AfterDraw event) but I cannot determine the best solution.

I have written a small test solution (attached) to demonstrate what I am trying to achieve.

In my test App whenever the SIZE button(s) are pressed, the gauge control does resize but the label font, line band & center point only size correctly when the gauge control is subsequently pressed.

Incorrect result

: ChartWrongSizeResult.png (46.36 KiB) Viewed 14752 times

Correct result (after gauge control pressed)

: ChartCorrectSizeResult.png (56.57 KiB) Viewed 14752 times

All feedback & assistance greatly appreciated

Posted: **Tue May 11, 2021 8:12 am**

Hello,
ok, let me take a look and check your project and back to you with a possible solution as soon as possible.

Posted: **Wed May 12, 2021 9:01 am**

Hello Scobie,

in order to fix this problem just add an InternalDraw at the end of the resize method :

Code: Select all

                // ### AXIS ###
                CircularGauge.Axis.Labels.Font.Size = 7.0D * (CircularGauge.XRadius / 100D);
                this.Chart.Chart.InternalDraw();

Posted: **Wed May 12, 2021 9:37 pm**

Thank you for your help.

I have added the Chart.Chart.InternalDraw() method call to the end of the Resize method & while it does re-draw the font, centre point & colour band in the correct size it leaves the original (incorrectly sized) chart elements in position, creating a "shadow" effect - see image.

: ChartFontShadowAfterInternalDraw.png (107.27 KiB) Viewed 14676 times

Should I be calling some sort of repaint or invalidate method before the InternalDraw method to remove the old graphics?

Posted: **Thu May 13, 2021 11:59 am**

Hello,
yes, you're correct, it seems to be a repaint problem. I'll add as a bug on our bug list in order to be addressed.
In meantime I found a solution, it's to use the OnBeforeDraw event to hide the axis labels and then make them visible again once these have been resized :

Code: Select all

        // Add the beforeDraw method at the CreateGauge method
        cv.Chart.BeforeDraw += Chart_BeforeDraw;

        private void Chart_BeforeDraw(object sender, Steema.TeeChart.Drawing.Graphics3D g)
        {
            CircularGauge.Axis.Labels.Visible = false;
        }
        // Add these lines at the end of the Resize method
        CircularGauge.Axis.Labels.Visible = true;
        this.Chart.Chart.InternalDraw();

Posted: **Thu May 13, 2021 9:13 pm**

Hello

I have implemented your suggestion, along with further lines to deal with the center, hand & green/red lines & the solution is working...

Code: Select all

	// Add the beforeDraw method at the CreateGauge method
	cv.Chart.BeforeDraw += Chart_BeforeDraw;

	private void Chart_BeforeDraw(object sender, Steema.TeeChart.Drawing.Graphics3D g)
	{
		CircularGauge.Axis.Labels.Visible = false;
		CircularGauge.Center.Visible = false;
		CircularGauge.Hand.Visible = false;
		CircularGauge.GreenLine.Visible = false;
		CircularGauge.RedLine.Visible = false;
	}
	
	// Add these lines at the end of the Resize method
	CircularGauge.Axis.Labels.Visible = true;
	CircularGauge.Center.Visible = true;
	CircularGauge.Hand.Visible = true;
	CircularGauge.GreenLine.Visible = true;
	CircularGauge.RedLine.Visible = true;
	this.Chart.Chart.InternalDraw();

Thankyou for your help to get this code working.

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