Fix JuliaGraphs#160 make self-loop edges curved

behavior is regardless of the linetype

src/GraphPlot.jl

@@ -2,6 +2,8 @@ module GraphPlot
 
 using Compose  # for plotting features
 using Graphs
+using LinearAlgebra
+using SparseArrays
 
 const gadflyjs = joinpath(dirname(Base.source_path()), "gadfly.js")
 

src/lines.jl

@@ -201,3 +201,49 @@ function curveedge(x1, y1, x2, y2, θ, outangle, d; k=0.5)
 
     return [(x1,y1) (xc1, yc1) (xc2, yc2) (x2, y2)]
 end
+
+function build_curved_edges(g, locs_x, locs_y, nodesize, arrowlengthfrac, arrowangleoffset, outangle)
+    if arrowlengthfrac > 0.0
+        curves_cord, arrows_cord = graphcurve(g, locs_x, locs_y, nodesize, arrowlengthfrac, arrowangleoffset, outangle)
+        curves = curve(curves_cord[:,1], curves_cord[:,2], curves_cord[:,3], curves_cord[:,4])
+        carrows = line(arrows_cord)
+    else
+        curves_cord = graphcurve(g, locs_x, locs_y, nodesize, outangle)
+        curves = curve(curves_cord[:,1], curves_cord[:,2], curves_cord[:,3], curves_cord[:,4])
+        carrows = nothing
+    end
+
+    return curves, carrows
+end
+
+function build_straight_edges(g, locs_x, locs_y, nodesize, arrowlengthfrac, arrowangleoffset)
+    if arrowlengthfrac > 0.0
+        lines_cord, arrows_cord = graphline(g, locs_x, locs_y, nodesize, arrowlengthfrac, arrowangleoffset)
+        lines = line(lines_cord)
+        larrows = line(arrows_cord)
+    else
+        lines_cord = graphline(g, locs_x, locs_y, nodesize)
+        lines = line(lines_cord)
+        larrows = nothing
+    end
+
+    return lines, larrows
+end
+
+function build_straight_curved_edges(g, locs_x, locs_y, nodesize, arrowlengthfrac, arrowangleoffset, outangle)
+    A = adjacency_matrix(g) #adjacency matrix
+    B = spdiagm(diag(A)) #diagonal matrix (self-loops)
+    A[diagind(A)] .= 0 #set diagonal elements to 0 (remove self-loops)
+    if is_directed(g)
+        g1 = SimpleDiGraph(A)
+        g2 = SimpleDiGraph(B)
+    else
+        g1 = SimpleGraph(A)
+        g2 = SimpleGraph(B)
+    end
+
+    lines, larrows = build_straight_edges(g1, locs_x, locs_y, nodesize, arrowlengthfrac, arrowangleoffset)
+    curves, carrows = build_curved_edges(g2, locs_x, locs_y, nodesize, arrowlengthfrac, arrowangleoffset, outangle)
+
+    return lines, larrows, curves, carrows
+end

src/plot.jl

@@ -206,33 +206,24 @@ function gplot(g::AbstractGraph{T},
     end
 
     # Create lines and arrow heads
-    lines, arrows = nothing, nothing
+    lines, larrows = nothing, nothing
+    curves, carrows = nothing, nothing
     if linetype == "curve"
-        if arrowlengthfrac > 0.0
-            curves_cord, arrows_cord = graphcurve(g, locs_x, locs_y, nodesize, arrowlengthfrac, arrowangleoffset, outangle)
-            lines = curve(curves_cord[:,1], curves_cord[:,2], curves_cord[:,3], curves_cord[:,4])
-            arrows = line(arrows_cord)
-        else
-            curves_cord = graphcurve(g, locs_x, locs_y, nodesize, outangle)
-            lines = curve(curves_cord[:,1], curves_cord[:,2], curves_cord[:,3], curves_cord[:,4])
-        end
+        curves, carrows = build_curved_edges(g, locs_x, locs_y, nodesize, arrowlengthfrac, arrowangleoffset, outangle)
+    elseif has_self_loops(g)
+        lines, larrows, curves, carrows = build_straight_curved_edges(g, locs_x, locs_y, nodesize, arrowlengthfrac, arrowangleoffset, outangle)
     else
-        if arrowlengthfrac > 0.0
-            lines_cord, arrows_cord = graphline(g, locs_x, locs_y, nodesize, arrowlengthfrac, arrowangleoffset)
-            lines = line(lines_cord)
-            arrows = line(arrows_cord)
-        else
-            lines_cord = graphline(g, locs_x, locs_y, nodesize)
-            lines = line(lines_cord)
-        end
+        lines, larrows = build_straight_edges(g, locs_x, locs_y, nodesize, arrowlengthfrac, arrowangleoffset)
     end
 
     compose(context(units=UnitBox(-1.2, -1.2, +2.4, +2.4)),
             compose(context(), texts, fill(nodelabelc), stroke(nothing), fontsize(nodelabelsize)),
             compose(context(), nodes, fill(nodefillc), stroke(nodestrokec), linewidth(nodestrokelw)),
             compose(context(), edgetexts, fill(edgelabelc), stroke(nothing), fontsize(edgelabelsize)),
-            compose(context(), arrows, stroke(edgestrokec), linewidth(edgelinewidth)),
-            compose(context(), lines, stroke(edgestrokec), fill(nothing), linewidth(edgelinewidth)))
+            compose(context(), larrows, stroke(edgestrokec), linewidth(edgelinewidth)),
+            compose(context(), carrows, stroke(edgestrokec), linewidth(edgelinewidth)),
+            compose(context(), lines, stroke(edgestrokec), fill(nothing), linewidth(edgelinewidth)),
+            compose(context(), curves, stroke(edgestrokec), fill(nothing), linewidth(edgelinewidth)))
 end
 
 function gplot(g; layout::Function=spring_layout, keyargs...)