Place graph vertex labels in circles

Question

Consider the following code:

vsh[{xc_, yc_}, name_, {w_, h_}] := {LightYellow, 
   Rectangle[{xc - w, yc - h}, {xc + w, yc + h}], 
   Inset[Style[Text[name], 14, Black, Bold], {xc, yc}]};
options = 
  Sequence[VertexSize -> 0.1, VertexShapeFunction -> vsh, 
   GraphLayout -> "CircularEmbedding", ImageSize -> 350, 
   EdgeStyle -> Blue];

g1 = Graph[{1 -> 2, 1 -> 3, 2 -> 4, 3 -> 4}, options];
g1

The output will be a simple graph with vertex labels depicted in rectangles (as can be inferred from vsh):

My question is: how can I encapsulate the vertex labels in circles instead? Nothing I've tried seems to be working.

Answer 1

You can change Rectangle[...] to Disk[{xc, yc}, Min[w, h]] or use any other function of w and h to control the disk radius.

But ... you can also get the same result without having to define a custom VertexShapeFunction using the options:

 options = Sequence[VertexStyle -> LightYellow,
 VertexSize -> 0.15,
 VertexLabels -> Placed["Name", {1/2, 1/2}], 
 VertexLabelStyle -> Directive[20, Red, Bold, Italic], 
 GraphLayout -> "CircularEmbedding", ImageSize -> 350, 
 EdgeStyle -> Blue];
 Graph[{1 \[UndirectedEdge] 2, 2 \[UndirectedEdge] 3, 3 \[UndirectedEdge] 1}, options]

Answer 2

Try:

Rectangle[{xc - w, yc - h}, {xc + w, yc + h}, RoundingRadius -> 1000]

Rounded corners rather than circles can be had with smaller values.

Answer 3

According to google you are supposed to use VertexRenderingFunction.