Improve CairoMakie's 2D mesh performance (#4132)

* Remove splats in draw_mesh2d inner loop

This also restores parity in the loop body with `draw_mesh3d`.

* Squash point type instability in project_position

This shaves ~20% runtime from mesh2d

* Fix types in function signature

* Add changelog entry

---------

Co-authored-by: Simon <sdanisch@protonmail.com>
Co-authored-by: Frederic Freyer <frederic481994@hotmail.de>

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## [Unreleased]
 
+- Improved CairoMakie's 2D mesh drawing performance by ~30% [#4132](https://github.com/MakieOrg/Makie.jl/pull/4132).
 - Allow `width` to be set per box in `boxplot` [#4447](https://github.com/MakieOrg/Makie.jl/pull/4447).
 - For `Textbox`es in which a fixed width is specified, the text is now scrolled
   if the width is exceeded [#4293](https://github.com/MakieOrg/Makie.jl/pull/4293)

CairoMakie/src/primitives.jl

@@ -908,11 +908,11 @@ function draw_atomic(scene::Scene, screen::Screen, @nospecialize(primitive::Maki
     return nothing
 end
 
-function draw_mesh2D(scene, screen, @nospecialize(plot), @nospecialize(mesh))
+function draw_mesh2D(scene, screen, @nospecialize(plot::Makie.Mesh), @nospecialize(mesh::GeometryBasics.Mesh))
     space = to_value(get(plot, :space, :data))::Symbol
     transform_func = Makie.transform_func(plot)
     model = plot.model[]::Mat4d
-    vs = project_position(scene, transform_func, space, decompose(Point, mesh), model)
+    vs = project_position(scene, transform_func, space, GeometryBasics.metafree(GeometryBasics.coordinates(mesh)), model)::Vector{Point2f}
     fs = decompose(GLTriangleFace, mesh)::Vector{GLTriangleFace}
     uv = decompose_uv(mesh)::Union{Nothing, Vector{Vec2f}}
     # Note: This assume the function is only called from mesh plots
@@ -943,9 +943,9 @@ function draw_mesh2D(screen, per_face_cols, vs::Vector{<: Point2}, fs::Vector{GL
 
         Cairo.mesh_pattern_begin_patch(pattern)
 
-        Cairo.mesh_pattern_move_to(pattern, t1...)
-        Cairo.mesh_pattern_line_to(pattern, t2...)
-        Cairo.mesh_pattern_line_to(pattern, t3...)
+        Cairo.mesh_pattern_move_to(pattern, t1[1], t1[2])
+        Cairo.mesh_pattern_line_to(pattern, t2[1], t2[2])
+        Cairo.mesh_pattern_line_to(pattern, t3[1], t3[2])
 
         mesh_pattern_set_corner_color(pattern, 0, c1)
         mesh_pattern_set_corner_color(pattern, 1, c2)