How to plot with inverted Y axes

[jbcolme]

I'm trying to plot some data using an inverted Y axis.
Since this is the most recent working version of wxMathplot that I found, I checked it out and currently everything works great except this.

This issue was first mentioned here long time ago: https://forums.wxwidgets.org/viewtopic.php?f=1&t=45412
I left a comment there. If I understand correctly, there are two issues:

• get wxAutoBufferedPaintDC to also change the axis orientation. That's an issue in wxWidgets.
• do the required changes in wxMathplot to handle that change of axis direction.

I can change the axis orientation in a simple example using wxPaintDC, but I can't just change the orientation in mathplot. It has no effect.

I'll try go over the code, but if anyone can point me to where I should look / what to modify, that would be great. I'm new to the library. I'd gladly do the work and make a pull request.

One hack could be to use a "custom made" mpScaleY. But that's just a temporary hack which I would prefer to avoid.

[GitHubLionel]

Well, it is not evident since this is not the logical behaviour and the 0 of the screen is at top.
The changes I see for test are:
In p2y, multiply by -1 the return
return -1*(m_posY - pixelCoordY / m_scaleY);

In y2p, subtract the height of the screen
return (wxCoord)(m_plotBoundaries.endPy - (m_posY - y) * m_scaleY);

But it is not sufficient. You need to reverse the plot of the Y axis and correct the mouse ...