feat(plotting): add Makie backend + share case layer via src/PlotCase

BREAKING.md

@@ -4,6 +4,27 @@
 
 This document describes breaking changes in CTModels releases and how to migrate your code.
 
+## [0.19.0-beta] - unreleased
+
+### Plotting case-layer helpers moved to `CTModels.PlotCase`
+
+The backend-free plotting helpers (`clean`, `do_plot`, `do_decorate`, the
+`__plot_*` defaults, the panel/decoration builders) moved out of the
+`CTModelsPlots` extension into a new `src` submodule, `CTModels.PlotCase`.
+
+**Who is affected**: only code reaching these *internal* helpers through
+`Base.get_extension(CTModels, :CTModelsPlots)`. The public `Plots.plot(sol)` /
+`plot!(sol)` API — signatures, keywords, defaults and behaviour — is unchanged.
+
+**Migration**: replace
+`Base.get_extension(CTModels, :CTModelsPlots).clean` (etc.) with
+`CTModels.PlotCase.clean`. These helpers are now available without loading `Plots`.
+
+### `CTBase` lower bound raised to 0.30
+
+The Makie backend needs `CTBase.Plotting.MakieBackend` (CTBase 0.30). `[compat]`
+is now `CTBase = "0.30"`.
+
 ## [0.18.0] - 2026-08-23
 
 ### `Components.times(sol)` returns the time grid instead of the times model

CHANGELOG.md

@@ -7,6 +7,30 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.19.0-beta] - unreleased
+
+### ✨ Added
+
+- **Makie plotting backend (proof of concept)**: new `CTModelsMakie` weak-dependency
+  extension (trigger: `Makie`). Load a Makie backend package (`CairoMakie`,
+  `GLMakie`, …) and `plot(sol)` renders a `Makie.Figure`; the backend is chosen by
+  which package is loaded (`Plots` → Plots, `Makie` → Makie), with identical
+  `description` and keyword arguments. Part of the plot-engine roadmap
+  ([#366](https://github.com/control-toolbox/CTModels.jl/issues/366)).
+  - Scope: `plot` only. Not yet handled (parity follow-up): `plot!` (overlay,
+    throws `NotImplemented`), the reference-line decorations (box bounds,
+    initial/final time markers), and step/scatter control curves — constant
+    controls render as lines.
+  - Requires `CTBase` ≥ 0.30 (`Plotting.MakieBackend` + `CTBaseMakie`).
+
+### ♻️ Internal
+
+- The backend-free plotting case layer (vocabulary, gating, panel/decoration
+  builders, layout assembly, `build_figure`) moved from the `CTModelsPlots`
+  extension into a new `src` submodule, `CTModels.PlotCase`, so the Plots and Makie
+  extensions share it. `Plots.plot(sol)` behaviour, signatures and defaults are
+  unchanged.
+
 ## [0.18.0] - 2026-08-23
 
 ### 💥 Changed

Project.toml

@@ -1,6 +1,6 @@
 name = "CTModels"
 uuid = "34c4fa32-2049-4079-8329-de33c2a22e2d"
-version = "0.18.0"
+version = "0.19.0-beta"
 authors = ["Olivier Cots <olivier.cots@toulouse-inp.fr>"]
 
 [deps]
@@ -16,23 +16,27 @@ RecipesBase = "3cdcf5f2-1ef4-517c-9805-6587b60abb01"
 [weakdeps]
 JLD2 = "033835bb-8acc-5ee8-8aae-3f567f8a3819"
 JSON3 = "0f8b85d8-7281-11e9-16c2-39a750bddbf1"
+Makie = "ee78f7c6-11fb-53f2-987a-cfe4a2b5a57a"
 Plots = "91a5bcdd-55d7-5caf-9e0b-520d859cae80"
 
 [extensions]
 CTModelsJLD = "JLD2"
 CTModelsJSON = "JSON3"
+CTModelsMakie = "Makie"
 CTModelsPlots = "Plots"
 
 [compat]
 Aqua = "0.8"
 BenchmarkTools = "1"
-CTBase = "0.29"
+CTBase = "0.30"
+CairoMakie = "0.15"
 DocStringExtensions = "0.9"
 JET = "0.9, 0.11, 0.12"
 JLD2 = "0.6"
 JSON3 = "1"
 LinearAlgebra = "1"
 MLStyle = "0.4"
+Makie = "0.24"
 MacroTools = "0.5"
 OrderedCollections = "1, 2"
 Parameters = "0.13"
@@ -45,6 +49,7 @@ julia = "1.10"
 [extras]
 Aqua = "4c88cf16-eb10-579e-8560-4a9242c79595"
 BenchmarkTools = "6e4b80f9-dd63-53aa-95a3-0cdb28fa8baf"
+CairoMakie = "13f3f980-e62b-5c42-98c6-ff1f3baf88f0"
 JET = "c3a54625-cd67-489e-a8e7-0a5a0ff4e31b"
 JLD2 = "033835bb-8acc-5ee8-8aae-3f567f8a3819"
 JSON3 = "0f8b85d8-7281-11e9-16c2-39a750bddbf1"
@@ -53,4 +58,4 @@ Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["Aqua", "BenchmarkTools", "JET", "JLD2", "JSON3", "Plots", "Random", "Test"]
+test = ["Aqua", "BenchmarkTools", "CairoMakie", "JET", "JLD2", "JSON3", "Plots", "Random", "Test"]

docs/Project.toml

@@ -11,7 +11,7 @@ MarkdownAST = "d0879d2d-cac2-40c8-9cee-1863dc0c7391"
 Plots = "91a5bcdd-55d7-5caf-9e0b-520d859cae80"
 
 [compat]
-CTBase = "0.29"
+CTBase = "0.30"
 Documenter = "1"
 DocumenterInterLinks = "1"
 DocumenterVitepress = "0.3"

docs/api_reference.jl

@@ -24,6 +24,7 @@ function generate_api_reference(src_dir::String, ext_dir::String)
         Symbol("@unpack_PreModel"),
         :is_empty,
         :time_ns,
+        :CTModels,   # PlotCase binds the parent module name for the moved case files
     ]
     EXCLUDE_INTERNALS = vcat(
         EXCLUDE_SYMBOLS,
@@ -102,6 +103,19 @@ function generate_api_reference(src_dir::String, ext_dir::String)
                 joinpath("Solutions", "show.jl"),
             ),
         ),
+        (
+            mod=CTModels.PlotCase,
+            title="PlotCase",
+            filename="plotcase",
+            files=src(
+                joinpath("PlotCase", "PlotCase.jl"),
+                joinpath("PlotCase", "vocabulary.jl"),
+                joinpath("PlotCase", "panels.jl"),
+                joinpath("PlotCase", "decorations.jl"),
+                joinpath("PlotCase", "assemble.jl"),
+                joinpath("PlotCase", "build.jl"),
+            ),
+        ),
         (
             mod=CTModels.Display,
             title="Display",
@@ -166,17 +180,8 @@ function generate_api_reference(src_dir::String, ext_dir::String)
 
     # Conditional extensions
     for (sym, files) in [
-        (
-            :CTModelsPlots,
-            ext(
-                "CTModelsPlots.jl",
-                joinpath("case", "vocabulary.jl"),
-                joinpath("case", "panels.jl"),
-                joinpath("case", "decorations.jl"),
-                joinpath("case", "assemble.jl"),
-                joinpath("case", "plot.jl"),
-            ),
-        ),
+        (:CTModelsPlots, ext("CTModelsPlots.jl", joinpath("case", "plot.jl"))),
+        (:CTModelsMakie, ext("CTModelsMakie.jl")),
         (:CTModelsJSON, ext("CTModelsJSON.jl")),
         (:CTModelsJLD, ext("CTModelsJLD.jl")),
     ]

docs/src/index.md

@@ -143,6 +143,12 @@ by the corresponding packages:
   display the trajectories of state, control, costate, constraints, and dual
   variables in a consistent, configurable way.
 
+- **CTModelsMakie.jl** (requires `Makie.jl`, e.g. via `CairoMakie` / `GLMakie`):
+  a second, backend-agnostic rendering path for the same figure —
+  `Makie.plot(sol::CTModels.Solution, ...)` returns a `Makie.Figure`. Proof of
+  concept ([#366](https://github.com/control-toolbox/CTModels.jl/issues/366)):
+  `plot` only, no reference lines or `plot!` yet.
+
 If the corresponding extension package is not loaded, the public wrappers
 `export_ocp_solution`, `import_ocp_solution`, and the generic `RecipesBase.plot`
 throw a descriptive `CTBase.ExtensionError`.

docs/src/serialization/plotting.md

@@ -72,3 +72,28 @@ plt
 Because the recipe reads the *typed* solution (its time grids, interpolation kind, and dual
 structure) rather than raw arrays, the same call works for unified- and multiple-grid
 solutions alike — see [Time grids](../solution/time_grids.md).
+
+## Makie backend (proof of concept)
+
+A second backend renders the same figure with [Makie.jl](https://docs.makie.org).
+Load a Makie backend package (`CairoMakie`, `GLMakie`, …) instead of `Plots`; the
+`CTModelsMakie` extension then provides `plot(sol)`:
+
+```julia
+using CTModels
+using CairoMakie          # activates the CTModelsMakie extension
+
+f = plot(sol)             # a Makie.Figure
+plot(sol; layout=:group, control=:all)
+```
+
+The backend is chosen by which package is loaded — `Plots.plot(sol)` renders with
+Plots, `Makie.plot(sol)` renders with Makie; the `description` and keyword
+arguments (`layout`, `control`, `time`, the `*_style` keywords, `color`, `size`)
+are identical. Loading both packages at once means `plot` must be qualified.
+
+This backend is a proof of concept (issue
+[#366](https://github.com/control-toolbox/CTModels.jl/issues/366)). It does not
+yet draw the reference lines (box bounds, initial/final time markers), renders
+constant-interpolation controls as lines rather than steps, and does not support
+`plot!` (overlay). A parity follow-up tracks these.

ext/CTModelsMakie.jl

@@ -0,0 +1,77 @@
+"""
+Weak-dependency extension of CTModels providing `Makie.plot` for solutions
+(proof of concept — issue #366).
+
+Loaded automatically when both `CTModels` and `Makie` are available (for example
+via `CairoMakie` or `GLMakie`). Thin plumbing on top of the backend-free case
+layer [`CTModels.PlotCase`](@extref): `Makie.plot` builds the figure with
+[`CTModels.PlotCase.build_figure`](@extref) and renders it through the
+`CTBase.Plotting` Makie backend.
+
+## Scope
+
+`plot` only. `plot!` overlay is not implemented (throws `NotImplemented`), and the
+Makie backend itself does not yet draw reference-line decorations (box bounds,
+initial/final time markers) or step/scatter control curves — see the parity
+follow-up of #366.
+"""
+module CTModelsMakie
+
+using DocStringExtensions: TYPEDSIGNATURES
+
+using CTBase: Plotting, Exceptions
+using CTModels: CTModels, PlotCase
+using Makie: Makie
+
+"""
+$(TYPEDSIGNATURES)
+
+Plot the components of an optimal control [`CTModels.Solution`](@extref) with a
+Makie backend.
+
+Same `description` and keyword arguments as `Plots.plot(::CTModels.Solution)`
+(`layout`, `control`, `time`, the `*_style` / `*_bounds_style` keywords, `color`,
+`size`). Returns a `Makie.Figure`.
+
+# Example
+```julia-repl
+julia> using CairoMakie
+
+julia> plot(sol)
+
+julia> plot(sol, :state, :control; layout=:group, control=:all)
+```
+"""
+function Makie.plot(
+    sol::CTModels.Solution, description::Symbol...; size=nothing, color=nothing, kwargs...
+)
+    build, render_kwargs = PlotCase.split_plot_kwargs(kwargs)
+    fig = PlotCase.build_figure(sol, description...; size=size, build...)
+    fig === nothing && return Makie.Figure()
+    return if color === nothing
+        Plotting.render(Plotting.MakieBackend(), fig; render_kwargs...)
+    else
+        Plotting.render(Plotting.MakieBackend(), fig; color=color, render_kwargs...)
+    end
+end
+
+"""
+$(TYPEDSIGNATURES)
+
+Overlay is not implemented by the Makie proof-of-concept backend.
+
+# Throws
+- `CTBase.Exceptions.NotImplemented`: always — use the Plots backend for overlays,
+  or wait for the parity follow-up of CTModels#366.
+"""
+function Makie.plot!(::CTModels.Solution, args...; kwargs...)
+    return throw(
+        Exceptions.NotImplemented(
+            "Makie.plot!(::CTModels.Solution) (overlay) is not implemented";
+            suggestion="use the Plots backend for overlays, or wait for the parity follow-up of CTModels#366",
+            context="CTModelsMakie",
+        ),
+    )
+end
+
+end # module CTModelsMakie

ext/CTModelsPlots.jl

@@ -1,23 +1,20 @@
 """
 Weak-dependency extension of CTModels providing `Plots.plot` / `plot!` for solutions.
 
-Loaded automatically when both `CTModels` and `Plots` are available. This is a thin
-**case layer**: it names and samples the optimal-control quantities (state, control,
-costate, path constraints, duals), chooses a layout template, and delegates all layout
-and rendering to the generic `CTBase.Plotting` engine.
+Loaded automatically when both `CTModels` and `Plots` are available. This is the thin
+plumbing on top of the backend-free case layer [`CTModels.PlotCase`](@extref): the
+public `Plots.plot` / `plot!` methods build the figure with
+[`CTModels.PlotCase.build_figure`](@extref) and render it through the
+`CTBase.Plotting` Plots backend.
 """
 module CTModelsPlots
 
 using DocStringExtensions: TYPEDSIGNATURES
 
-using CTBase: Plotting, Exceptions
-using CTModels: CTModels
+using CTBase: Plotting
+using CTModels: CTModels, PlotCase
 using Plots: Plots
 
-include(joinpath(@__DIR__, "case", "vocabulary.jl"))
-include(joinpath(@__DIR__, "case", "panels.jl"))
-include(joinpath(@__DIR__, "case", "decorations.jl"))
-include(joinpath(@__DIR__, "case", "assemble.jl"))
 include(joinpath(@__DIR__, "case", "plot.jl"))
 
 end