ggplot2 geom_point and geom_text prevent exceeding plot area in R

I have a graph to plot points, texts and edges to export in png. Here is current codes.

node <- data.frame(id=c(1,2,3), x=c(1,2,1), y=c(1,1,2), label=c("a","b","c"))
edge <- data.frame(from=c(1,1,2), to=c(2,3,3))
g <- graph_from_data_frame(d=edge, vertices=node, directed=F)


cor <- matrix(c(V(g)$x, y=V(g)$y), ncol=2)

p <- g %>% ggraph(layout=cor) +
## Base settings
  geom_edge_link(width=3, color="gray70") +
  geom_node_point(size=22, aes(x=x, y=y)) +
  geom_node_text(size=16, color="white", fontface=2, vjust=0.4, aes(x=x, y=y, label=label)) +
## Set axis
  expand_limits(x=1, y=1) +
  coord_fixed() +
## Set legend
  scale_color_manual(name=tname, labels=plabel, values=pname) +
## Theme
theme(
  ## Font size
  plot.title=element_blank(),
  axis.title.y=element_blank(),
  axis.title.x.top=element_blank(),
  axis.text=element_blank(),
  legend.title=element_blank(),
  legend.text=element_blank(),
  legend.position="none",
  ## Appearance
  panel.background=element_rect(fill="transparent"),
  panel.grid.major=element_blank(),
  legend.key=element_blank()
  )

ggsave(p, file="test.png", width=5, height=5, dpi=100)

It generates the following image. Nodes and texts are cut off, thus I changed width and height in ggsave larger value so it fit into the plot area. But node size became smaller.

As I need to put lots of graphs in a document within limited space, I do not want to make node and text size small. Also, it may not suite changing values in expand_limits(x=1, y=1) dinamically as I need to export graphs into images as bigger as possible within fixed and limited size (in this example, 'width=5, height=5'). Is there any ways or parameters to plot nodes and texts within plot area? I've tried margin() in theme() but it can set marging outside plot area.

One option would be to

1. remove the default expansion of the x and y scale,
2. set the length of the (even if invisible) axis ticks to zero,
3. use clip="off" to prevent the points and text to be clipped off when hitting the panel border
4. and finally to set the plot.margin according to the size of your points, e.g. a margin of 9mm works fine for the point size of 22. (Actually I expected that 22 / 2 = 11 should work fine.).

library(ggraph)
library(tidygraph)
library(igraph)

p <- g %>% 
  ggraph(layout = cor) +
  ## Base settings
  geom_edge_link(width = 3, color = "gray70") +
  geom_node_point(size = 22, aes(x = x, y = y)) +
  geom_node_text(
    size = 16, color = "white", fontface = 2, vjust = 0.4,
    aes(x = x, y = y, label = label)
  ) +
  scale_x_continuous(expand = c(0, 0)) +
  scale_y_continuous(expand = c(0, 0)) +
  ## Set axis
  expand_limits(x = 1, y = 1) +
  coord_fixed(clip = "off") +
  ## Set legend
  # scale_color_manual(name = tname, labels = plabel, values = pname) +
  ## Theme
  theme(
    ## Font size
    plot.title = element_blank(),
    axis.title.y = element_blank(),
    axis.title.x.top = element_blank(),
    axis.text = element_blank(),
    axis.ticks = element_blank(),
    axis.line = element_blank(),
    axis.ticks.length = unit(0, "pt"),
    legend.title = element_blank(),
    legend.text = element_blank(),
    legend.position = "none",
    ## Appearance
    panel.background = element_rect(fill = "transparent"),
    panel.grid.major = element_blank(),
    legend.key = element_blank(),
    plot.margin = unit(rep(9, 4), units = "mm")
  )

ggsave(p, file = "test.png", width = 5, height = 5, dpi = 100)

And for a larger size

ggsave(p, file = "test.png", width = 20, height = 20, dpi = 100, scale = .5)