Switch to using display() to show the plots

This brings better compatibility with the Julia package ecosystem.
Now, if Gnuplot.jl is used in an environment capable of showing
multimedia content (IJulia, VS Code, Pluto), their internal viewer
will take precedence over using gnuplot's built-in viewer. In the
REPL, gnuplot viewer is still used by default.

In VS Code, for example, when the *Use Plot Pane* settings is enabled,
the plots show in that pane, but when it is disabled, gnuplot viewer is
automatically used.

For people who prefer to always use the gnuplot viewer, they can set
Gnuplot.options.gpviewer to true. This should result in the same
behaviour as before this commit.

docs/src/index.md

@@ -25,7 +25,7 @@ The **Gnuplot.jl** package allows easy and fast use of [gnuplot](http://gnuplot.
 
 - export to a huge number of formats such as `pdf`, `png`, `gif`, ``\LaTeX``, `svg`, etc. (actually all those supported by gnuplot);
 
-- compatibility with Jupyter and Juno;
+- compatibility with Jupyter, VS Code, Pluto, Juno, Weave.jl, etc.
 
 - save sessions into gnuplot scripts, to enable easy plot customization and reproducibility.
 

docs/src/options.md

@@ -13,13 +13,11 @@ saveas(file) = save(term="pngcairo size 550,350 fontscale 0.8", output="assets/$
 
 The display behaviour of **Gnuplot.jl** depends on the value of the `Gnuplot.options.gpviewer` flag:
 
-- if `true` the plot is displayed in a gnuplot window, using one of the interactive terminals such as `wxt`, `qt` or `aqua`.  This is the default setting when running a Julia REPL session; The terminal options can be customized using `Gnuplot.options.term`;
+- if `false` (the default) the plot is displayed through the Julia [multimedia interface](https://docs.julialang.org/en/v1/base/io-network/#Multimedia-I/O-1), i.e. depending on the current environment, it is displayed either in a gnuplot window (REPL) or exported as either a `png`, `svg` or `html` file, and displayed in an external viewer (IDE, notebook). The terminal options for the gnuplot window can be customized using `Gnuplot.options.term`; options for exporting can be customized using the `Gnuplot.options.mime` dictionary.
-
-- if `false` the plot is displayed through the Julia [multimedia interface](https://docs.julialang.org/en/v1/base/io-network/#Multimedia-I/O-1), i.e. it is exported as either a `png`, `svg` or `html` file, and displayed in an external viewer.  This is the default setting when running a Jupyter, JupyterLab or Juno session.  The terminal options can be customized using the `Gnuplot.options.mime` dictionary.
-
-The `Gnuplot.options.gpviewer` flag is automatically set when the package is first loaded according to the runtime environment, however the user can change its value at any time to fit specific needs.  Further informations and examples for both options are available in this Jupyter [notebook](https://github.com/gcalderone/Gnuplot.jl/blob/gh-pages/v1.3.0/options/display.ipynb).
 
+- if `true` the plot is always displayed in a gnuplot window, using one of the interactive terminals such as `wxt`, `qt` or `aqua`.  The terminal options can be customized using `Gnuplot.options.term`;
 
+Further information and examples for both options are available in this Jupyter [notebook](https://github.com/gcalderone/Gnuplot.jl/blob/gh-pages/v1.3.0/options/display.ipynb).
 
 
 # Package options and initialization

src/Gnuplot.jl

@@ -202,7 +202,7 @@ Structure containing the package global options, accessible through `Gnuplot.opt
 - `default::Symbol`: default session name (default: `:default`)
 - `term::String`: default terminal for interactive use (default: empty string, i.e. use gnuplot settings);
 - `mime::Dict{DataType, String}`: dictionary of MIME types and corresponding gnuplot terminals.  Used to export images with either [`save()`](@ref) or `show()` (see [Display options](@ref));
-- `gpviewer::Bool`: use a gnuplot terminal as main plotting device (if `true`) or an external viewer (if `false`);
+- `gpviewer::Bool`: force using a gnuplot terminal as main plotting device (if `true`) or use Julia multimedia I/O, which automatically selects between the gnuplot terminal and external viewers (if `false`);
 - `init::Vector{String}`: commands to initialize the session when it is created or reset (e.g., to set default palette);
 - `verbose::Bool`: verbosity flag (default: `false`)
 - `preferred_format::Symbol`: preferred format to send data to gnuplot.  Value must be one of:
@@ -236,14 +236,15 @@ const sessions = OrderedDict{Symbol, Session}()
 const options = Options()
 
 function __init__()
-    # Check whether we are running in an IJulia, Juno, VSCode or Pluto session.
+    # Copied from Plots - insert GnuplotDisplay before text displays,
-    # (copied from Gaston.jl).
+    # but after graphic displays such as IJulia.
-    options.gpviewer = !(
+    insert!(Base.Multimedia.displays, findlast(x -> x isa Base.TextDisplay || x isa REPL.REPLDisplay, Base.Multimedia.displays) + 1, GnuplotDisplay())
-        ((isdefined(Main, :IJulia)  &&  Main.IJulia.inited)  ||
+    atreplinit(i -> begin
-         (isdefined(Main, :Juno)    &&  Main.Juno.isactive()) ||
+        while GnuplotDisplay() in Base.Multimedia.displays
-         (isdefined(Main, :VSCodeServer)) ||
+            popdisplay(GnuplotDisplay())
-         (isdefined(Main, :PlutoRunner)) )
+        end
-    )
+        insert!(Base.Multimedia.displays, findlast(x -> x isa REPL.REPLDisplay, Base.Multimedia.displays) + 1, GnuplotDisplay())
+    end)
     if isdefined(Main, :VSCodeServer)
         # VS Code shows "dynamic" plots with fixed and small size :-(
         options.mime[MIME"image/svg+xml"] = replace(options.mime[MIME"image/svg+xml"], "dynamic" => "")
@@ -585,6 +586,10 @@ function gp_write_table(args...; kw...)
     reset(gp)
     gpexec(sid, "set term unknown")
     driver(sid, "set table '$tmpfile'", args...; kw...)
+    if !Gnuplot.options.gpviewer
+        # driver() did not send plots to the gnuplot process - do it now
+        execall(gp, term="unknown")
+    end
     gpexec(sid, "unset table")
     quit(sid)
     out = readlines(tmpfile)
@@ -766,8 +771,11 @@ function reset(gp::Session)
     gpexec(gp, "set output")
     gpexec(gp, "reset session")
 
-    if options.gpviewer
+    # Configure the gnuplot viewer. If options.gpviewer is false, it would be more
-        # Use gnuplot viewer
+    # appropriate to do this in display(), but doing so leads to hang of the gnuplot
+    # process in some situations (after manual close of the Qt window, gnuplot
+    # receives the CAPTURE_END marker, but does not print it back). Therefore, we do
+    # in here unconditionally.
     (options.term != "")  &&  gpexec(gp, "set term " * options.term)
 
     # Set window title (if not already set)
@@ -778,10 +786,6 @@ function reset(gp::Session)
             writeread(gp, "set term $term $opts title 'Gnuplot.jl: $(gp.sid)'")
         end
     end
-    else
-        # Use external viewer
-        gpexec(gp, "set term unknown")
-    end
 
     # Note: the reason to keep Options.term and .init separate are:
     # - .term can be overriden by "unknown" (if options.gpviewer is false);
@@ -1547,10 +1551,21 @@ end
 
 
 # ╭───────────────────────────────────────────────────────────────────╮
-# │                     Interfacing Julia's show                      │
+# │              Interfacing Julia's Multimedia I/O                   │
 # ╰───────────────────────────────────────────────────────────────────╯
 # --------------------------------------------------------------------
 
+struct GnuplotDisplay <: AbstractDisplay end
+
+function Base.display(d::GnuplotDisplay, obj::SessionID)
+    if !options.gpviewer && obj.dump
+        gp = getsession(obj.sid)
+        execall(gp)
+    else
+        throw(MethodError(display, (d, obj)))
+    end
+end
+
 function show(obj::SessionID)
     gp = getsession(obj.sid)
     @info "Gnuplot session" sid=gp.sid datasets=length(gp.datas) plots=length(gp.plots)

test/runtests.jl

@@ -5,7 +5,9 @@ try
 catch
     Gnuplot.options.dry = true
 end
-Gnuplot.options.gpviewer = true
+
+# Test the default, i.e. false
+#Gnuplot.options.gpviewer = true
 
 x = [1, 2, 3]
 y = [4, 5, 6]
@@ -110,6 +112,24 @@ dummy = terminals()
 # Force unknown on Travis CI
 Gnuplot.options.term = "unknown"
 
+if Gnuplot.options.gpviewer == false
+    # Wrap @gp and @gsp macrocalls in display() to ensure that the whole
+    # plot is sent to the gnuplot process during testing. In interactive
+    # sessions display() is called by the REPL.
+    macro gp(args...)
+        gpcall = :(Gnuplot.@gp)
+        push!(gpcall.args, args...)
+        out = :(display($gpcall))
+        return esc(out)
+    end
+    macro gsp(args...)
+        gpcall = :(Gnuplot.@gsp)
+        push!(gpcall.args, args...)
+        out = :(display($gpcall))
+        return esc(out)
+    end
+end
+
 @gp 1:9
 @info "using terminal: " terminal()
 #test_terminal("unknown")