To the best of my knowledge, there isn't a single wxWidgets charting library that meets all the following criteria: (1) free with a permissive license, (2) a large user and knowledge base, (3) feature-rich and interactive, and (4) actively maintained. This is not surprising, as it appears that creating and maintaining such library is quite challenging if not outright impossible.
On the other hand, there are JavaScript charting libraries that meet all four criteria, such as Plotly.js, Chart.js, and Apache ECharts. wxWidgets provides a wxWebView control, which wraps a full web browser core, allowing these libraries to be used in a wxWidgets application.
While using wxWebView and a JavaScript library in a native C++ application might seem crazy to some, and certainly has some disadvantages, it may still be a viable approach for others. The wxECharts project presents a simple example of doing this using Apache ECharts. wxECharts does not provide a ready-to-use code for applications, it is not a JavaScript library wrapper for wxWidgets. Rather, it demonstrates how certain tasks can be approached. The actual implementation will depend on the charting library used and the application's requirements. wxECharts also shows how to access the native wxWebView backend, to customize it and display very handy DevTools.
The project consists of several C++ header and source files, with charthelper.cpp being the most important one. It handles almost all direct communication between the chart and the C++ code. The project also includes chart assets (see the chart-assets folder), which consist of an HTML file for wxWebView (wxecharts.html), a JavaScript file for two-way communication between the C++ and JavaScript code (wxecharts.js), and the charting library itself (echarts.min.js).
Structured data is exchanged between C++ and JavaScript in the JSON format (using JSON for Modern C++ library).
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Communicate with the chart from C++ code (e.g., to change data or visuals).
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Communicate with C++ code from the chart (e.g., when a chart data point is double-clicked).
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Export the chart (so it can be saved or printed).
This is accomplished using wxWebView::RunScriptAsync(), where the C++ code asks JavaScript code to either (a) create or modify the chart or (b) query the chart for certain information.
The C++ code registers a message handler with wxWebView::AddScriptMessageHandler("wxmsg") and then processes wxEVT_WEBVIEW_SCRIPT_MESSAGE_RECEIVED events sent by JavaScript with window.wxmsg.postMessage().
JavaScript charting libraries usually also provide the chart rendered as PNG and SVG. Since there is little that can be done with a non-trivial SVG in wxWidgets, PNG generally seems the better choice. While vector format would be preferable, a bitmap saved at a sufficiently high resolution should be adequate for most scenarios.
Tested on Windows (10, 11) and briefly on Linux (Mint 22 Cinnamon). wxECharts does not support the hopelessly outdated Internet Explorer wxWebView backend. It also does not support the recently introduced wxWebViewChromium, since this backend does not allow adding a script message handler.
See BUILD.md for build instructions.
Aside from meeting the four criteria mentioned earlier, popular JavaScript charting libraries are generally very easy to use and well-documented, with an active user community. Moreover, their charts look very pretty and come with all the bells and whistles (such as animations on data change). Obviously, they also do not suffer from the bane of (some) C++ libraries, i.e., being difficult to build and add to the application project.
Using wxWebView adds a large dependency to the application, increasing the application’s startup time and memory footprint. However, on modern systems, neither may be noticeable, let alone the deal-breaker. Another potential downside is sometimes not-so-seamless integration of wxWebView into the application; for an example, see the "Known Issues" section.
When focused, wxWebViewEdge consumes keyboard shortcuts from the parent frame, see wxWidgets Issue #24786.