From a1d85a1d9ef9ab7397f8197937622634eacb1c8d Mon Sep 17 00:00:00 2001
From: t-bltg <tf.bltg@gmail.com>
Date: Sun, 24 Dec 2023 10:26:57 +0100
Subject: [PATCH] fix spurious minor tick (#3505)

---
 ReferenceTests/src/tests/examples2d.jl |  9 ++++++++-
 src/makielayout/lineaxis.jl            | 15 ++++++++-------
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/ReferenceTests/src/tests/examples2d.jl b/ReferenceTests/src/tests/examples2d.jl
index 8cc85e7e075..735be7bb507 100644
--- a/ReferenceTests/src/tests/examples2d.jl
+++ b/ReferenceTests/src/tests/examples2d.jl
@@ -1354,7 +1354,7 @@ function ppu_test_plot(resolution, px_per_unit, scalefactor)
     fig, ax, pl = scatter(1:4, markersize=100, color=1:4, figure=(; size=resolution), axis=(; titlesize=50, title="ppu: $px_per_unit, sf: $scalefactor"))
     DataInspector(ax)
     hidedecorations!(ax)
-    return fig
+    fig
 end
 
 @reference_test "px_per_unit and scalefactor" begin
@@ -1373,3 +1373,10 @@ end
         st
     end
 end
+
+@reference_test "spurious minor tick (#3487)" begin
+    fig = Figure(size=(227, 170))
+    ax = Axis(fig[1, 1]; yticks = 0:.2:1, yminorticksvisible = true)
+    ylims!(ax, 0, 1)
+    fig
+end
diff --git a/src/makielayout/lineaxis.jl b/src/makielayout/lineaxis.jl
index 38ec8004042..de5d3600d5b 100644
--- a/src/makielayout/lineaxis.jl
+++ b/src/makielayout/lineaxis.jl
@@ -187,6 +187,10 @@ function update_tick_obs(tick_obs, horizontal::Observable{Bool}, flipped::Observ
     return
 end
 
+# if labels are given manually, it's possible that some of them are outside the displayed limits
+# we only check approximately because otherwise because of floating point errors, ticks can be dismissed sometimes
+is_within_limits(tv, limits) = (limits[1] ≤ tv || limits[1] ≈ tv) && (tv ≤ limits[2] || tv ≈ limits[2])
+
 function update_tickpos_string(closure_args, tickvalues_labels_unfiltered, reversed::Bool, scale)
 
     tickstrings, tickpositions, tickvalues, pos_extents_horizontal, limits_obs = closure_args
@@ -204,12 +208,7 @@ function update_tickpos_string(closure_args, tickvalues_labels_unfiltered, rever
     lim_o = limits[1]
     lim_w = limits[2] - limits[1]
 
-    # if labels are given manually, it's possible that some of them are outside the displayed limits
-    # we only check approximately because otherwise because of floating point errors, ticks can be dismissed sometimes
-    i_values_within_limits = findall(tickvalues_unfiltered) do tv
-        return (limits[1] <= tv || limits[1] ≈ tv) &&
-                (tv <= limits[2] || tv ≈ limits[2])
-    end
+    i_values_within_limits = findall(tv -> is_within_limits(tv, limits), tickvalues_unfiltered)
 
     tickvalues[] = tickvalues_unfiltered[i_values_within_limits]
 
@@ -231,7 +230,7 @@ function update_tickpos_string(closure_args, tickvalues_labels_unfiltered, rever
     return
 end
 
-function update_minor_ticks(minortickpositions, limits::NTuple{2, Float32}, pos_extents_horizontal, minortickvalues, scale, reversed::Bool)
+function update_minor_ticks(minortickpositions, limits::NTuple{2, Float32}, pos_extents_horizontal, minortickvalues_unfiltered, scale, reversed::Bool)
     position::Float32, extents_uncorrected::NTuple{2, Float32}, horizontal::Bool = pos_extents_horizontal
 
     extents = reversed ? reverse(extents_uncorrected) : extents_uncorrected
@@ -239,6 +238,8 @@ function update_minor_ticks(minortickpositions, limits::NTuple{2, Float32}, pos_
     px_o = extents[1]
     px_width = extents[2] - extents[1]
 
+    minortickvalues = filter(tv -> is_within_limits(tv, limits), minortickvalues_unfiltered)
+
     tickvalues_scaled = scale.(minortickvalues)
 
     tick_fractions = (tickvalues_scaled .- scale(limits[1])) ./ (scale(limits[2]) - scale(limits[1]))