Add better docs for Axis3 protrusions (#3139)

* Add better docs for Axis3 protrusions

* remove 100

* add background color for easier understanding

src/makielayout/blocks/axis3d.jl

@@ -1137,5 +1137,28 @@ function attribute_examples(::Type{Axis3})
                     """
             ),
         ],
+        :protrusions => [
+            Example(
+                name = "Single protrusion",
+                code = """
+                    fig = Figure(backgroundcolor = :gray97)
+                    Box(fig[1, 1], strokewidth = 0) # visualizes the layout cell
+                    Axis3(fig[1, 1], protrusions = 100, viewmode = :stretch,
+                        title = "protrusions = 100")
+                    fig
+                """
+            ),
+            Example(
+                name = "Removing protrusions",
+                code = """
+                    fig = Figure(backgroundcolor = :gray97)
+                    Box(fig[1, 1], strokewidth = 0) # visualizes the layout cell
+                    ax = Axis3(fig[1, 1], protrusions = (0, 0, 0, 20), viewmode = :stretch,
+                        title = "protrusions = (0, 0, 0, 20)")
+                    hidedecorations!(ax)
+                    fig
+                """
+            ),
+        ]
     )
 end

src/makielayout/types.jl

@@ -1547,7 +1547,19 @@ end
         ygridvisible = true
         "Controls if the z grid is visible"
         zgridvisible = true
-        "The protrusions on the sides of the axis, how much gap space is reserved for labels etc."
+        """
+        The protrusions control how much gap space is reserved for labels etc. on the sides of the `Axis3`.
+        Unlike `Axis`, `Axis3` currently does not set these values automatically depending on the properties
+        of ticks and labels. This is because the effective protrusions also depend on the rotation and scaling
+        of the axis cuboid, which changes whenever the `Axis3` shifts in the layout. Therefore, auto-updating
+        protrusions could lead to an endless layout update cycle.
+
+        The default value of `30` for all sides is just a heuristic and might lead to collisions of axis
+        decorations with the `Figure` boundary or other plot elements. If that's the case, you can try increasing
+        the value(s).
+
+        The `protrusions` attribute accepts a single number for all sides, or a tuple of `(left, right, bottom, top)`.
+        """
         protrusions = 30
         "The x ticks"
         xticks = WilkinsonTicks(5; k_min = 3)