add backend and update_state kwargs to show (#4558)

* add backend kwarg to show

* added CHANGELOG entry

* add minimal test

* add kwarg to update state or not

* fix CHANGELOG

* add test

* refactor per ffreyer's review

* fix test

---------

Co-authored-by: Frederic Freyer <[email protected]>
Co-authored-by: Simon <[email protected]>

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ## [0.21.17] - 2024-12-05
 
+- Added `backend` and `update` kwargs to `show` [#4558](https://github.com/MakieOrg/Makie.jl/pull/4558)
 - Disabled unit prefix conversions for compound units (e.g. `u"m/s"`) to avoid generating incorrect units. [#4583](https://github.com/MakieOrg/Makie.jl/pull/4583)
 - Added kwarg to rotate Toggle [#4445](https://github.com/MakieOrg/Makie.jl/pull/4445)
 - Fixed orientation of environment light textures in RPRMakie [#4629](https://github.com/MakieOrg/Makie.jl/pull/4629).

src/display.jl

@@ -244,17 +244,16 @@ function Base.show(io::IO, m::MIME"text/markdown", fig::FigureLike)
     throw(MethodError(show, io, m, fig))
 end
 
-function Base.show(io::IO, m::MIME, figlike::FigureLike)
+function Base.show(io::IO, m::MIME, figlike::FigureLike; backend = current_backend(), update=true)
     if ALWAYS_INLINE_PLOTS[] == false && m isa MIME_TO_TRICK_VSCODE
         # We use this mime to display the figure in a window here.
         # See declaration of MIME_TO_TRICK_VSCODE for more info
         display(figlike)
         return () # this is a diagnostic vscode mime, so we can just return nothing
     end
     scene = get_scene(figlike)
-    backend = current_backend()
     # get current screen the scene is already displayed on, or create a new screen
-    update_state_before_display!(figlike)
+    update && update_state_before_display!(figlike)
     screen = getscreen(backend, scene, Dict(:visible=>false), io, m)
     backend_show(screen, io, m, scene)
     return screen

test/figures.jl

@@ -171,3 +171,10 @@ end
     @test_throws ArgumentError lines(f[1, 1], 1:10, axis = (aspect = DataAspect()))
     @test_throws ArgumentError lines(f[1, 1][2, 2], 1:10, axis = (aspect = DataAspect()))
 end
+
+@testset "show with a backend" begin
+    fig = Figure()
+    io = IOBuffer()
+    # if there were no show method with backend and update kwargs then MethodError would be thrown instead
+    @test_throws ErrorException show(io, MIME"text/plain"(), fig, backend=missing, update=false)
+end