make colorrange_scaled computation safe for inverting / sort-order-breaking scales

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 - Added `font` attribute and fixed faulty selection in `scatter`. Scatter fonts can now be themed with `markerfont`. [#4832](https://github.com/MakieOrg/Makie.jl/pull/4832)
 - Fixed categorical `cgrad` interpolating at small enough steps [#4858](https://github.com/MakieOrg/Makie.jl/pull/4858)
+- Fixed the computed `colorrange` being out of order with `colorscale = -` or similar colorscale functions that break sorting [#4884](https://github.com/MakieOrg/Makie.jl/pull/4884)
 
 ## [0.22.2] - 2025-02-26
 

src/colorsampler.jl

@@ -135,6 +135,13 @@ function sampler(cmap::Matrix{<: Colorant}, uv::AbstractVector{Vec2f};
     return Sampler(cmap, uv, alpha, interpolation, Scaling())
 end
 
+"""
+    apply_scale(scale, x)
+
+Applies the scale function / callable `scale` to each element of `x`.  
+If `scale` is an Observable then this returns an Observable via `lift`,
+otherwise simply returns `broadcast(scale, x)`.
+"""
 apply_scale(scale::AbstractObservable, x) = lift(apply_scale, scale, x)
 apply_scale(::Union{Nothing,typeof(identity)}, x) = x  # noop
 apply_scale(scale, x) = broadcast(scale, x)
@@ -166,8 +173,7 @@ function numbers_to_colors(
     )::Union{Array{RGBAf, N},RGBAf} where {N}
 
     cmin, cmax = colorrange
-    scaled_cmin = apply_scale(colorscale, cmin)
-    scaled_cmax = apply_scale(colorscale, cmax)
+    scaled_cmin, scaled_cmax = extrema(apply_scale(colorscale, (cmin, cmax)))
 
     return map(numbers) do number
         scaled_number = apply_scale(colorscale, Float64(number))  # ints don't work in interpolated_getindex
@@ -307,7 +313,7 @@ function _colormapping(
     end
 
     colorrange_scaled = lift(colorrange, colorscale; ignore_equal_values=true) do range, scale
-        return Vec2f(apply_scale(scale, range))
+        return Vec2f(extrema(apply_scale(scale, range)))
     end
 
     color_scaled = Observable(el32convert(apply_scale(colorscale[], color_tight[])))

test/issues.jl

@@ -46,4 +46,12 @@
         @test p.plots[1].plots[1].transformation.model[][3, 4] == 10.0
         @test p.plots[1].plots[2].transformation.model[][3, 4] == 10.0
     end
+
+    @testset "#4883 colorscale that breaks sort" begin
+        data = Float32.(Makie.peaks())
+        f, a, p = image(data; colorscale = -)
+        @test p.calculated_colors[].colorrange_scaled[][1] == -maximum(data)
+        @test p.calculated_colors[].colorrange_scaled[][2] == -minimum(data)
+        @test issorted(p.calculated_colors[].colorrange_scaled[])
+    end
 end