Why does my figure appear to be animated (when it shouldn't be)?

Question

Consider the following code which draws a figure:

figure('Renderer', 'opengl');
N = 50;
tL = linspace(0.5, 6, N).';
tB = sort(randi(100,N,20),1);
yyaxis right; plot(tL, tB);
xlim([2 6]);

When I run this code, I get a haunted figure with moving lines that should be static, for example (this one is using my real data which looks a bit nicer than the example):

Several additional observations:

• I noticed that without the xlim line nothing happens (i.e. the figure is static as expected).
• I couldn't get it to work on another computer running the same MATLAB version.
• The line "animation" seems to coincide with the appearing and disappearing of the axes' toolbar (the one on the top right with the zoom etc.).
• When I create the figure using figure('Renderer', 'painters') this doesn't happen.

Can somebody please explain why this is happening? Is this documented behavior? Any idea how to control it?

I'm working with R2018b on Windows 10 v1803. My screens are connected to the on-board GPU which is Intel HD Graphics 530 (driver version 22.20.16.4749).

September 2019 Update: This also happens for me on R2019b on Windows 10 v1903. As suggested in the comments, below is the output of opengl info:

                          Version: '4.5.0 - Build 25.20.100.6373'
                           Vendor: 'Intel'
                         Renderer: 'Intel(R) HD Graphics 530'
            RendererDriverVersion: '25.20.100.6373'
        RendererDriverReleaseDate: '18-Nov-2018'
                   MaxTextureSize: 16384
                           Visual: 'Visual 0x07, (RGBA 32 bits (8 8 8 8), Z depth 16 bits, Hardware acceleration, Double buffer, Antialias 8 samples)'
                         Software: 'false'
             HardwareSupportLevel: 'full'
        SupportsGraphicsSmoothing: 1
    SupportsDepthPeelTransparency: 1
       SupportsAlignVertexCenters: 1
                       Extensions: {223×1 cell}
               MaxFrameBufferSize: 16384

Answer 1

• Firstly, you should understand that a figure is not a static picture at all. It refreshes frequenctly. If one resize/move the container(figure), the figure will be redrawed just after the interaction.
• Secondly, All objects,including lines,annotations,legend... , are redrawed at the same time. The discontinuous line types will be captured easily. This why you could see a "animated" dashed line.
• Lastly, for matlab, there are some interaction differences on Linux/Mac and Windows. On Windows, Move Mouse on figure will not fire data tracking event. But on Linux, the Data Tracker will be activated on Mouse move. Events for data tracking, object selection etc will refresh the plot.

All in all, the "animation" you see is designed by the author, and it should be.

The following code disabled the current axes's hit test visibility, so the redraw event won't be fired during mouse move or click on axes. But with the resize event, all objects must be redraw (which is a intentionally designed behaviour).

figure('Renderer', 'opengl');
N = 50;
tL = linspace(0.5, 6, N).';
tB = sort(randi(100,N,20),1);
yyaxis right; h = plot(tL, tB,'ButtonDownFcn',@lineCallback); 
set(gca,'HitTest','off')
xlim([2 6]);

function lineCallback(Figure1,Structure1)
    disp('Button Down: redraw...'); 
end

This code snippet has been tested using MATLAB R2018B on Mac,window10 and Ubuntu 18.04. All works fines.