Clicking on TChart Causes BeforeSeries to Fire (but it didn't used to)
Posted: Fri Jun 27, 2025 6:25 am
I'm upgrading a 2008 app that uses TChart extensively.
When I draw the chart, it takes about 30 seconds to draw a bunch of custom lines on the canvas, which I do in the BeforeDrawSeries event, so the lines are under the stock prices.
In the old 2008 version of the app, clicking on the chart didn't trigger the BeforeDrawSeries event (or any of the 4 drawing events) to fire, so it didn't erase all the custom drawings, ie, it was very user-friendly.
The new version fires all 4 drawing events only if there's a price series on the chart (which there is). So if the user clicks on the chart, it takes 30 seconds for each click to redraw all the custom drawings.
In the 2008 version (using VB.NET), this behaviour didn't exist.
I opened a bug and thought I'd post the sample app here - notice that in the sample app if you remove the price series from the chart the problem goes away. No events fired when you click on the chart and custom drawing is not erased. But add a price series, and the 4 draw events that erase all the custom data are fired.
I hope there's a simple workaround besides telling my users they're young and 30 seconds each click won't kill them (well eventually it will, but not right away).
Thanks very much,
Joseph
When I draw the chart, it takes about 30 seconds to draw a bunch of custom lines on the canvas, which I do in the BeforeDrawSeries event, so the lines are under the stock prices.
In the old 2008 version of the app, clicking on the chart didn't trigger the BeforeDrawSeries event (or any of the 4 drawing events) to fire, so it didn't erase all the custom drawings, ie, it was very user-friendly.
The new version fires all 4 drawing events only if there's a price series on the chart (which there is). So if the user clicks on the chart, it takes 30 seconds for each click to redraw all the custom drawings.
In the 2008 version (using VB.NET), this behaviour didn't exist.
I opened a bug and thought I'd post the sample app here - notice that in the sample app if you remove the price series from the chart the problem goes away. No events fired when you click on the chart and custom drawing is not erased. But add a price series, and the 4 draw events that erase all the custom data are fired.
I hope there's a simple workaround besides telling my users they're young and 30 seconds each click won't kill them (well eventually it will, but not right away).
Thanks very much,
Joseph