Plots don't show automatically when PyPlot compiled with PackageCompiler #476

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1. marius311 commented on Apr 7, 2020

   

   marius311

   on Apr 7, 2020

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   Looks like the error goes away after upgrading matplotlib 3.1.1 -> 3.2.1 (as per #459 (comment)).

   The plot still is not showing automatically though. Any way to reset whatever has gone wrong to make them show?
2. xzackli commented on Apr 18, 2020

   

   xzackli

   on Apr 18, 2020

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   Hey @marius311, this happens because PyPlot.display_figs(), the function called at the end of an IJulia cell, thinks there is no available display. You can see this in the notebook, i.e.

   using PyPlot
   PyPlot.isjulia_display

   1-element Array{Bool,1}:
    0
   

   PyPlot sets this global when it runs its init, which I suppose has now been compiled into your sysimage.
   

   PyPlot.jl/src/init.jl

   Line 178 in c451315

   global isjulia_display = Bool[isdisplayok()]

   This kind of thing should happen to any PackageCompiler-ed package which relies on logic during package loading. You can manually show the figure for now, i.e.

   fig = plt.figure()
   plt.plot()
   fig
   

   I'll see if I can make a PR.
3. xzackli commented on Apr 18, 2020

   

   xzackli

   on Apr 18, 2020

   Last edited by xzackli

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   Probably all it takes is just to check if there are displays whenever a cell is requested. For example, this works in a sysimage,

   using PyCall
   using PyPlot
   
   function display_figs() # called after IJulia cell executes
       if PyPlot.isdisplayok()  # CHANGED FROM QUERYING GLOBAL
           for manager in PyPlot.Gcf."get_all_fig_managers"()
               f = manager."canvas"."figure"
               if f.number ∉ PyPlot.withfig_fignums
                   fig = Figure(f)
                   isempty(fig) || display(fig)
                   pycall(plt."close", PyAny, f)
               end
           end
       end
   end
   
   plt.plot()
   display_figs()

   One also needs to push the pre-executes (which don't seem to make it in the sysimage)

   Main.IJulia.push_preexecute_hook(PyPlot.force_new_fig)
   Main.IJulia.push_postexecute_hook(PyPlot.display_figs)
   Main.IJulia.push_posterror_hook(PyPlot.close_figs)
4. marius311 commented on Apr 18, 2020

   

   marius311

   on Apr 18, 2020

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   Thanks, yea I think you're on the right track. The thing is that PackageCompiler still runs PyPlot.__init__() when you open a new terminal rather than when its being compiled, but I think whenever its running it must be too early because PyPlot.isdisplayok() must be returning false, as evidenced by as show that PyPlot.isjulia_display is false. Its only later that PyPlot.isdisplayok() starts returning true. So you end up with this when you use the system image:

   
5. stevengj commented on Apr 19, 2020

   

   stevengj

   on Apr 19, 2020

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   I'm afraid that's going to mess up other aspects of the initialization, too.

   In particular, if a Julia display is detected when PyPlot is initialized, then it starts up Matplotlib in non-interactive mode, so that figures are only displayed when the cell finishes executing and the post-execute hook is called. Whereas if displayok() == false at the __init__ call, then it will start up the GUI event loop and display plots in the GUI by default (assuming you have a working Matplotlib GUI backend).

   Why is __init__ not being called when the user runsimport PyPlot?
6. xzackli commented on Apr 19, 2020

   

   xzackli

   on Apr 19, 2020

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   Why is init not being called when the user runsimport PyPlot?

   As you described in the PR, the best way to fix this is probably to do things in a lazy fashion within PyPlot. Here's an example of the order of init calls changing when using sysimages. Consider the following test where I just stick a print statement in the PyPlot init.

   normal order

   julia -e 'println("Julia started"); flush(stdout); sleep(1); import PyPlot;'
   

   Julia started
   INIT IS CALLED
   

   with sysimage

   julia --sysimage=mysys.dylib -e 'println("Julia started"); flush(stdout); sleep(1); import PyPlot;'
   

   INIT IS CALLED
   Julia started
   

   With the sysimage, PyPlot's init is called before the first line of Julia code is started. Presumably PyPlot wakes up and runs init, only to find a barren land without any IJulia loaded.

   I'd be interested in reading how Julia starts up, maybe it's in the docs.
7. tfiers commented on Sep 22, 2022

   

   tfiers

   on Sep 22, 2022

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   My current solution is calling a custom function autodisplay_figs() (see below) at the start of the notebook.
   You can call it manually; I call it in the __init__ of a custom package that gets using'd in the notebook, i.e. after IJulia has been initialized. I suppose you could call it in startup_ijulia.jl as well.

   This function simply sets PyPlot.isjulia_display[] manually to true, and adds the three IJulia hooks, as in xzackli's proposal above.

   This doesn't fix the fact that a GUI event loop is, presumably, unnecesarily spun up.
   But that is not noticeable (I suspect because the startup cost of that is in the sysimg?).

   using PyPlot is instant, and plots display automatically under cells again.

   `autodisplay_figs()`:

   """
   When using a sysimg with PyPlot in it, PyPlot's `__init__` gets called before IJulia is
   initialized. As a result, figures do not get automatically displayed in the notebook.
   (https://github.com/JuliaPy/PyPlot.jl/issues/476).
   Calling `autodisplay_figs()` after IJulia is initialized fixes that.
   """
   function autodisplay_figs()
       if (isdefined(Main, :PyPlot) && isdefined(Main, :IJulia) && Main.IJulia.inited
           && (Main.PyPlot.isjulia_display[] == false)
       )
           Main.PyPlot.isjulia_display[] = true
           Main.IJulia.push_preexecute_hook(Main.PyPlot.force_new_fig)
           Main.IJulia.push_postexecute_hook(Main.PyPlot.display_figs)
           Main.IJulia.push_posterror_hook(Main.PyPlot.close_figs)
       end
   end
8. stevengj commented on Sep 22, 2022

   

   stevengj

   on Sep 22, 2022

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   See also my #480 (comment) on how I think this should be fixed.
9. ufechner7 commented on Dec 8, 2023

   

   ufechner7

   on Dec 8, 2023

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   The following command works for me as a workaround when using the REPL:

   PyPlot.show(block=false)