fix colorbar corner cases (singleton)

src/basic_recipes/contourf.jl

@@ -74,9 +74,8 @@ function Makie.plot!(c::Contourf{<:Tuple{<:AbstractVector{<:Real}, <:AbstractVec
         _get_isoband_levels(Val(mode), levels, vec(zs))
     end
 
-    colorrange = lift(c, c._computed_levels) do levels
-        minimum(levels), maximum(levels)
-    end
+    colorrange = lift(distinct_extrema_nan, c._computed_levels)
+
     computed_colormap = lift(compute_contourf_colormap, c, c._computed_levels, c.colormap, c.extendlow,
                              c.extendhigh)
     c.attributes[:_computed_colormap] = computed_colormap
@@ -171,7 +170,6 @@ function _group_polys(points, ids)
         for p1 in polys_lastdouble, p2 in polys_lastdouble]
 
     unclassified_polyindices = collect(1:size(containment_matrix, 1))
-    # @show unclassified_polyindices
 
     # each group has first an outer polygon, and then its holes
     # TODO: don't specifically type this 2f0?

src/basic_recipes/tricontourf.jl

@@ -75,11 +75,14 @@ function Makie.convert_arguments(::Type{<:Tricontourf}, x::AbstractVector{<:Real
 end
 
 function compute_contourf_colormap(levels, cmap, elow, ehigh)
-    levels_scaled = (levels .- minimum(levels)) ./ (maximum(levels) - minimum(levels))
-    n = length(levels_scaled)
-
     _cmap = to_colormap(cmap)
 
+    lo, hi = extrema(levels)
+    lo == hi && return cgrad(_cmap, levels; categorical=true)
+
+    levels_scaled = (levels .- lo) ./ (hi - lo)
+    n = length(levels_scaled)
+
     if elow === :auto && ehigh !== :auto
         cm_base = cgrad(_cmap, n + 1; categorical=true)[2:end]
         cm = cgrad(cm_base, levels_scaled; categorical=true)
@@ -122,7 +125,7 @@ function Makie.plot!(c::Tricontourf{<:Tuple{<:DelTri.Triangulation, <:AbstractVe
         return _get_isoband_levels(Val(mode), levels, vec(zs))
     end
 
-    colorrange = lift(extrema_nan, c, c._computed_levels)
+    colorrange = lift(distinct_extrema_nan, c, c._computed_levels)
     computed_colormap = lift(compute_contourf_colormap, c, c._computed_levels, c.colormap, c.extendlow,
                              c.extendhigh)
     c.attributes[:_computed_colormap] = computed_colormap

src/colorsampler.jl

@@ -292,11 +292,14 @@ function _colormapping(
     end
 
     colorrange = lift(color_tight, colorrange; ignore_equal_values=true) do color, crange
-        return crange isa Automatic ? Vec2{Float64}(distinct_extrema_nan(color)) : Vec2{Float64}(crange)
+        if !(auto = crange isa Automatic)
+            crange[1] == crange[2] && error("Cannot use a colorrange with a single value ($crange): provide distinct values instead.")
+        end
+        return auto ? Vec2{Float64}(distinct_extrema_nan(color)) : Vec2{Float64}(crange)
     end
 
-    colorrange_scaled = lift(colorrange, colorscale; ignore_equal_values=true) do range, scale
-        return Vec2f(apply_scale(scale, range))
+    colorrange_scaled = lift(colorrange, colorscale; ignore_equal_values=true) do crange, cscale
+        return Vec2f(apply_scale(cscale, crange))
     end
 
     color_scaled = lift(color_tight, colorscale) do color, scale

src/layouting/data_limits.jl

@@ -32,7 +32,17 @@ end
 
 function distinct_extrema_nan(x)
     lo, hi = extrema_nan(x)
-    lo == hi ? (lo - 0.5f0, hi + 0.5f0) : (lo, hi)
+    δ⁻ = if lo == hi
+        iszero(lo) ? zero(lo) : one(lo)
+    else
+        zero(lo)
+    end
+    δ⁺ = if lo == hi
+        iszero(hi) ? one(hi) : zero(hi)
+    else
+        zero(hi)
+    end
+    (lo - δ⁻, hi + δ⁺)
 end
 
 function point_iterator(plot::Union{Scatter, MeshScatter, Lines, LineSegments})

src/makielayout/blocks/colorbar.jl

@@ -63,15 +63,15 @@ end
 
 function extract_colormap(plot::Union{Contourf,Tricontourf})
     levels = plot._computed_levels
-    limits = lift(l -> (l[1], l[end]), levels)
+    colorrange = lift(distinct_extrema_nan, levels)
     function extend_color(color, computed)
         color === nothing && return automatic
         color == :auto || color == automatic && return computed
         return computed
     end
     elow = lift(extend_color, plot.extendlow, plot._computed_extendlow)
     ehigh = lift(extend_color, plot.extendhigh, plot._computed_extendhigh)
-    return ColorMapping(levels[], levels, plot._computed_colormap, limits, plot.colorscale, Observable(1.0),
+    return ColorMapping(levels[], levels, plot._computed_colormap, colorrange, plot.colorscale, Observable(1.0),
                     elow, ehigh, plot.nan_color)
 end
 

src/makielayout/ticklocators/wilkinson.jl

@@ -7,7 +7,7 @@ function WilkinsonTicks(k_ideal::Int; k_min = 2, k_max = 10,
         min_px_dist = 50.0)
 
     if !(0 < k_min <= k_ideal <= k_max)
-        error("Invalid tick number specifications k_ideal $k_ideal, k_min $k_min, k_max $k_max")
+        error("Invalid tick number specifications k_ideal=$k_ideal, k_min=$k_min, k_max=$k_max")
     end
 
     WilkinsonTicks(k_ideal, k_min, k_max, Q, granularity_weight, simplicity_weight,
@@ -17,9 +17,8 @@ end
 get_tickvalues(ticks::WilkinsonTicks, vmin, vmax) = get_tickvalues(ticks, Float64(vmin), Float64(vmax))
 
 function get_tickvalues(ticks::WilkinsonTicks, vmin::Float64, vmax::Float64)
-
     tickvalues, _ = PlotUtils.optimize_ticks(Float64(vmin), Float64(vmax);
-        extend_ticks = false, strict_span=true, span_buffer = nothing,
+        extend_ticks = false, span_buffer = nothing, strict_span = vmin ≉ vmax,
         k_min = ticks.k_min,
         k_max = ticks.k_max,
         k_ideal = ticks.k_ideal,

test/makielayout.jl

@@ -33,7 +33,7 @@ end
     @test isempty(ax.scene.plots)
 end
 
-@testset "zero heatmap" begin
+@testset "Colorbar: zero heatmap" begin
     xs = LinRange(0, 20, 10)
     ys = LinRange(0, 15, 10)
     zs = zeros(length(xs), length(ys))
@@ -42,15 +42,48 @@ end
     _, hm = heatmap(fig[1, 1], xs, ys, zs)
     cb = Colorbar(fig[1, 2], hm)
 
-    @test hm.calculated_colors[].colorrange[] == Vec(-0.5, 0.5)
-    @test cb.limits[] == Vec(-.5, .5)
-
+    let (lo, hi) = hm.calculated_colors[].colorrange[]
+        @test lo ≉ hi
+    end
+    let (lo, hi) = cb.limits[]
+        @test lo ≉ hi
+    end
     hm.colorrange = Float32.((-1, 1))
     @test cb.limits[] == Vec(-1, 1)
+end
 
-    # TODO: This doesn't work anymore because colorbar doesn't use the same observable
-    # cb.limits[] = Float32.((-2, 2))
-    # @test hm.attributes[:colorrange][] == (-2, 2)
+@testset "Colorbar: invalid limits" begin
+    fig = Figure()
+    Axis(fig[1, 1])
+    @test_throws ErrorException Colorbar(fig[1, 2], limits = (1, 1))
+end
+
+@testset "Colorbar: zero contourf" begin
+    x = [0, 1]
+    y = [0, 2]
+    z = zeros(2, 2)
+
+    fig = Figure()
+    _, ct = contourf(fig[1, 1], x, y, z)
+    cb = Colorbar(fig[1, 2], ct)
+
+    let (lo, hi) = cb.limits[]
+        @test lo ≉ hi
+    end
+end
+
+@testset "Colorbar: zero tricontourf" begin
+    x = randn(10)
+    y = randn(10)
+    z = @. -sqrt(x^2 + y^2) + 0.1 * randn()
+
+    fig = Figure()
+    _, ct = tricontourf(fig[1, 1], x, y, z)
+    cb = Colorbar(fig[1, 2], ct)
+
+    let (lo, hi) = cb.limits[]
+        @test lo ≉ hi
+    end
 end
 
 @testset "Axis limits basics" begin