Chart Control - Mouse location to graph scale

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Mouse location to graph scale

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Category: Codejock Products
Forum Name: Chart Control
Forum Description: Topics Related to Codejock Chart Control
URL: http://forum.codejock.com/forum_posts.asp?TID=21729
Printed Date: 21 November 2024 at 9:32pm
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Topic: Mouse location to graph scale

Posted By: BLW
Subject: Mouse location to graph scale
Date Posted: 20 June 2013 at 10:10am

Hi, I'm trying to develop a drag-drop concept with a bar chart. We have a threshold parameter that we plot on the graph along with results. The idea is to allow the user to "grab" the threshold and drag it to a new setting directly on the graph.

I have figured out most of the steps involved. But I have not been able to locate a conversion between a mouse location on the screen and an X-Y graph scale value. I'm using "HitTest()" to figure out which series and element is being pointed at. But that isn't quite what I need. I believe that I found some internal logic that might work (see specifics below), but I do not see how to get access to that information.

In XTPChartStackedBarSeriesStyle.cpp, function GetScreenRect() they call a function GetScreenPoint() which converts a scaled XY value to image coordinates. From that I could compute the scale and get the drag-drop logic to work. But this is a Style operation and that appears to be dynamically created in OnPaint() and is not available to access.

What I really need is a function similar to HitTest() to get the conversion back and forth between a screen location and scales series value.

Thank you,

Brad