Support parsing Q/q in BezierPath (#4413)

CHANGELOG.md

@@ -6,6 +6,7 @@
 - Show DataInspector tooltip on NaN values if `nan_color` has been set to other than `:transparent` [#4310](https://github.com/MakieOrg/Makie.jl/pull/4310)
 - Fix `linestyle` not being used in `triplot` [#4332](https://github.com/MakieOrg/Makie.jl/pull/4332)
 - Fix voxel clipping not being based on voxel centers [#4397](https://github.com/MakieOrg/Makie.jl/pull/4397)
+- Parsing `Q` and `q` commands in svg paths with `BezierPath` is now supported [#4413](https://github.com/MakieOrg/Makie.jl/pull/4413)
 
 ## [0.21.11] - 2024-09-13
 

src/bezier.jl

@@ -40,6 +40,19 @@ CurveTo(cx1, cy1, cx2, cy2, p1, p2) = CurveTo(
     Point2d(cx1, cy1), Point2d(cx2, cy2), Point2d(p1, p2)
 )
 
+"""
+    quadratic_curve_to(x0::Real, y0::Real, cx1::Real, cy1::Real, p1::Real, p2::Real)
+
+A path command for use within a `BezierPath` which continues the current subpath with a quadratic
+bezier curve to point `p`, with the control point `c`. The curve is converted into a cubic bezier
+curve internally.
+"""
+quadratic_curve_to(x0, y0, cx1, cy1, p1, p2) = CurveTo(
+    x0 + 2/3 * (cx1 - x0), y0 + 2/3 * (cy1 - y0),
+    p1 + 2/3 * (cx1 - p1), p2 + 2/3 * (cy1 - p2),
+    p1, p2
+)
+
 """
     EllipticalArc(c::VecTypes, r1::Real, r2::Real, angle::Real, a1::Real, a2::Real)
     EllipticalArc(cx::Real, cy::Real, r1::Real, r2::Real, angle::Real, a1::Real, a2::Real)
@@ -492,6 +505,16 @@ function parse_bezier_commands(svg)
             l = lastp()
             push!(commands, LineTo(Point2d(l[1], y)))
             i += 2
+        elseif comm == "Q"
+            x0, y0 = lastp()
+            x1, y1, x2, y2 = parse.(Float64, args[i+1:i+4])
+            push!(commands, quadratic_curve_to(x0, y0, x1, y1, x2, y2))
+            i += 5
+        elseif comm == "q"
+            x0, y0 = lastp()
+            x1, y1, x2, y2 = parse.(Float64, args[i+1:i+4])
+            push!(commands, quadratic_curve_to(x0, y0, x1 + x0, y1 + y0, x2 + x0, y2 + y0))
+            i += 5
         else
             for c in commands
                 println(c)

test/bezier.jl

@@ -5,6 +5,20 @@ using Makie, Test
     @test_nowarn BezierPath("m 0,9 L 0,5138 0,9 z")
     @test_broken BezierPath("m 0,1e-5 L 0,5138 0,9 z") isa BezierPath
     @test_nowarn BezierPath("M 100,100 C 100,200 200,100 200,200 z")
-    @test_broken BezierPath("M 100,100 Q 50,150,100,100 z") isa BezierPath
+    @test_nowarn BezierPath("M 100,100 Q 50,150,100,100 z") isa BezierPath
     @test_broken BezierPath("M 3.0 10.0 A 10.0 7.5 0.0 0.0 0.0 20.0 15.0 z") isa BezierPath
 end
+
+@testset "Parsing Q/q" begin
+    x0, y0, x1, y1, x, y = 5.0, 0.0, 14.6, 5.2, 13.0, 15.9
+    C = Makie.quadratic_curve_to(x0, y0, x1, y1, x, y)
+    C2 = Makie.CurveTo(x0 + 2 / 3 * (x1 - x0), y0 + 2 / 3 * (y1 - y0), x + 2 / 3 * (x1 - x),
+                       y + 2 / 3 * (y1 - y),
+                       x, y)
+    @test C == C2
+    path = BezierPath("M 5.0 0.0 Q 14.6 5.2 13.0 15.9")
+    @test path.commands[2] == C2
+    path = BezierPath("M 5.0 0.0 q 0.2 2.3 1.0 -2.0")
+    C = Makie.quadratic_curve_to(x0, y0, x0 + 0.2, y0 + 2.3, x0 + 1.0, y0 - 2.0)
+    @test path.commands[2] == C
+end