Support glow for text (fixes for #3858) (#3866)

* Support glow for text

* Add reference test

* Update examples3d.jl

* forward glowwidth + glowcolor in Text for WGLMakie

---------

Co-authored-by: Kipton Barros <kbarros@gmail.com>

MakieCore/src/basic_plots.jl

@@ -499,6 +499,10 @@ Plots one or multiple texts passed via the `text` keyword.
     markerspace = :pixel
     "Controls whether the model matrix (without translation) applies to the glyph itself, rather than just the positions. (If this is true, `scale!` and `rotate!` will affect the text glyphs.)"
     transform_marker = false
+    "Sets the color of the glow effect around the text."
+    glowcolor = (:black, 0.0)
+    "Sets the size of a glow effect around the text."
+    glowwidth = 0.0
     "The offset of the text from the given position in `markerspace` units."
     offset = (0.0, 0.0)
     "Specifies a linewidth limit for text. If a word overflows this limit, a newline is inserted before it. Negative numbers disable word wrapping."

ReferenceTests/src/tests/examples3d.jl

@@ -394,6 +394,15 @@ end
     meshscatter(positions, color=RGBAf(0.9, 0.2, 0.4, 1), markersize=0.05)
 end
 
+@reference_test "Text glow and overdraw" begin
+    p1 = Point3f(0,0,0)
+    p2 = Point3f(1,0,0)
+    f, ax, pl = meshscatter([p1, p2]; markersize=0.3, color=[:purple, :yellow])
+    text!(ax, p1; text="A", align=(:center, :center), glowwidth=10.0, glowcolor=:white, color=:black, fontsize=40, overdraw=true)
+    text!(ax, p2; text="B", align=(:center, :center), glowwidth=20.0, glowcolor=(:black, 0.6), color=:white, fontsize=40, overdraw=true)
+    f
+end
+
 @reference_test "Animated surface and wireframe" begin
     function xy_data(x, y)
         r = sqrt(x^2 + y^2)

WGLMakie/src/particles.jl

@@ -289,7 +289,9 @@ function create_shader(scene::Scene, plot::Makie.Text{<:Tuple{<:Union{<:Makie.Gl
         :uv_offset_width => uv_offset_width,
         :transform_marker => get(plot.attributes, :transform_marker, Observable(true)),
         :billboard => Observable(false),
-        :depth_shift => get(plot, :depth_shift, Observable(0f0))
+        :depth_shift => get(plot, :depth_shift, Observable(0f0)),
+        :glowwidth => plot.glowwidth,
+        :glowcolor => plot.glowcolor,
     )
 
     return scatter_shader(scene, uniforms, plot_attributes)