GR: Draw all gridlines before axis (v2) (#4960)

* GR: Draw all gridlines before axis

Separates grid drawing from the remainder of gr_draw_axis, so that all
gridlines are drawn below the axis. Previously, y-axis gridlines were
drawn after the x-axis and could overlap it.

Fixes issue #4202 for GR.

* Added qualified PlotsBase names missing from v1 port

PlotsBase/ext/GRExt.jl

@@ -1585,26 +1585,52 @@ function gr_draw_axes(sp, vp)
         x_bg, y_bg = RecipesPipeline.unzip(GR.wc3towc.(area_x, area_y, area_z))
         GR.fillarea(x_bg, y_bg)
 
+        foreach(letter -> gr_draw_axis_minorgrid_3d(sp, letter, vp), (:x, :y, :z))
+        foreach(letter -> gr_draw_axis_grid_3d(sp, letter, vp), (:x, :y, :z))
         foreach(letter -> gr_draw_axis_3d(sp, letter, vp), (:x, :y, :z))
     elseif ispolar(sp)
         r = gr_set_viewport_polar(vp)
         # rmin, rmax = GR.adjustrange(ignorenan_minimum(r), ignorenan_maximum(r))
         rmin, rmax = axis_limits(sp, :y)
         gr_polaraxes(rmin, rmax, sp)
     elseif sp[:framestyle] ≢ :none
+        foreach(letter -> gr_draw_axis_minorgrid(sp, letter, vp), (:x, :y))
+        foreach(letter -> gr_draw_axis_grid(sp, letter, vp), (:x, :y))
         foreach(letter -> gr_draw_axis(sp, letter, vp), (:x, :y))
     end
     GR.settransparency(1.0)
     nothing
 end
 
+function gr_draw_axis_minorgrid_3d(sp, letter, vp)
+    ax = PlotsBase.axis_drawing_info_3d(sp, letter)
+    axis = sp[get_attr_symbol(letter, :axis)]
+    gr_draw_minorgrid(sp, axis, ax.minorgrid_segments, gr_polyline3d)
+end
+
+function gr_draw_axis_grid_3d(sp, letter, vp)
+    ax = PlotsBase.axis_drawing_info_3d(sp, letter)
+    axis = sp[get_attr_symbol(letter, :axis)]
+    gr_draw_grid(sp, axis, ax.grid_segments, gr_polyline3d)
+end
+
+function gr_draw_axis_minorgrid(sp, letter, vp)
+    ax = PlotsBase.axis_drawing_info(sp, letter)
+    axis = sp[get_attr_symbol(letter, :axis)]
+    gr_draw_minorgrid(sp, axis, ax.minorgrid_segments)
+end
+
+function gr_draw_axis_grid(sp, letter, vp)
+    ax = PlotsBase.axis_drawing_info(sp, letter)
+    axis = sp[get_attr_symbol(letter, :axis)]
+    gr_draw_grid(sp, axis, ax.grid_segments)
+end
+
 function gr_draw_axis(sp, letter, vp)
     ax = PlotsBase.axis_drawing_info(sp, letter)
     axis = sp[get_attr_symbol(letter, :axis)]
 
     # draw segments
-    gr_draw_grid(sp, axis, ax.grid_segments)
-    gr_draw_minorgrid(sp, axis, ax.minorgrid_segments)
     gr_draw_spine(sp, axis, ax.segments)
     gr_draw_border(sp, axis, ax.border_segments)
     gr_draw_ticks(sp, axis, ax.tick_segments)
@@ -1620,8 +1646,6 @@ function gr_draw_axis_3d(sp, letter, vp)
     axis = sp[get_attr_symbol(letter, :axis)]
 
     # draw segments
-    gr_draw_grid(sp, axis, ax.grid_segments, gr_polyline3d)
-    gr_draw_minorgrid(sp, axis, ax.minorgrid_segments, gr_polyline3d)
     gr_draw_spine(sp, axis, ax.segments, gr_polyline3d)
     gr_draw_border(sp, axis, ax.border_segments, gr_polyline3d)
     gr_draw_ticks(sp, axis, ax.tick_segments, gr_polyline3d)