MATLAB: Background Color of UIAxes

app designerbackgroundcolorcolorguideMATLABtransparentuiaxes

I am trying to use the new html style ui graphics as it looks that Matlab will soon be moving away from the Java-based graphics. With the Java-based graphics, it is possible to stack multiple axes on top of each other — all with transparent backgrounds so as to be able to see through all the curves plotted on all the axes. This is the standard way of displaying more than 2 curves with the same x-axis but different y-axes. The commands are quite simple:
hf = figure;
ha1 = axes(hf,'Position',[0.1 0.2 0.7 0.5]);
ha2 = axes(hf,'Position',[0.2 0.25 0.7 0.5]); % This axes position is offset from previous for illustration.
set(ha2,'Color','none')
The last command makes the back of axes ha2 transparent. Now a curve in ha1 (using a plot command) will be visible together with a curve in ha2.
I have tried to do the same with the new style ui graphics both using App Designer as well as programmatically and have thus been unsuccessful. Specifically, I've used the following commands:
uihf = uifigure;
uiha1 = uiaxes(uihf,'Position',[50 50 400 300]);
uiha2 = uiaxes(uihf,'Position',[100 100 400 300]);
set(uiha2,'Color','none')
Unlike with the Java-based graphics, the last command makes the plot area transparent; but the color seen is now that specified in the BackgroundColor property of the uiaxes defined as the "Color of margin around plot area". That property does not exist for the old style axes. Apparently, when the Color property of uiaxes is set to 'none' the BackgroundColor property color is assigned to the entire area of the uiaxes object. From within App Designer, clicking on the color pull down menu of the BackgroundColor shows "None" as one of the selections, indicating that this option should be selectable (unless it's there as a placeholder for future versions). However, clicking on it generates an error message: "Cannot set UIAxes BackgroundColor to 'none'". The same error occurs, if I were to type command 
set(uiha2,'BackgroundColor','none')
I searched the KB and did a general google search on this topic and found close to nothing on this topic (for typical plot commands — I am not interested in other types of graphs/images). So, is this a known limitation of the new style graphics, or is there another way to stack multiple axes on top of each and see through all of them?
Thanks for the help.

Best Answer

This behavior of uiaxes has changed in MATLAB R2020b.
If you check the release notes for R2020b:
BackgroundColor property of UIAxes has no effect
Behavior change
Setting the BackgroundColor property on a UIAxes object no longer has any effect. The area around the plot box is transparent regardless of the value of the BackgroundColor property.
To produce the same effect as setting the background color in previous releases, create a panel with the desired BackgroundColor value, and then place the UIAxes in the panel.
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