ggplot2 vs grrr: SVG Comparison

This vignette compares ggplot2 output rendered directly with svglite against the same built plot converted through ggbuild_to_scene() and rendered by grrr::device_svg().

1) Empty ggplot (baseline)

p_empty <- ggplot() +
  theme_minimal(base_size = 8)

cmp_empty <- comparison_block("empty", p_empty)

ggplot2 + svglite

ggbuild_to_scene() + device_svg()

cat(sprintf("<p><strong>SVG signature differences:</strong> %s</p>\n", cmp_empty$diff_text))

SVG signature differences: line: 0 vs 12 | rect: 4 vs 1 | text: 0 vs 12 | chars: 1329 vs 2948

2) Faceted points example (README-style)

p_points <- ggplot(mtcars, aes(wt, mpg, colour = factor(cyl))) +
  geom_point() +
  facet_wrap(~am) +
  theme_minimal(base_size = 5) +
  theme(
    panel.spacing = grid::unit(4, "mm"),
    strip.text = element_text(size = 4),
    axis.title = element_text(size = 4.5),
    axis.text = element_text(size = 4),
    legend.title = element_text(size = 4.5),
    legend.text = element_text(size = 4)
  )

cmp_points <- comparison_block("points", p_points)

ggplot2 + svglite

ggbuild_to_scene() + device_svg()

cat(sprintf("<p><strong>SVG signature differences:</strong> %s</p>\n", cmp_points$diff_text))

SVG signature differences: polyline: 40 vs 0 | line: 0 vs 70 | rect: 7 vs 4 | text: 22 vs 18 | chars: 12964 vs 13322

What I looked for and found

# Compare key counts in a compact table for both examples.
summary_tbl <- function(label, cmp) {
  data.frame(
    example = label,
    metric = names(cmp$svglite_sig),
    svglite = as.numeric(cmp$svglite_sig),
    grrr = as.numeric(cmp$grrr_sig),
    delta = as.numeric(cmp$grrr_sig) - as.numeric(cmp$svglite_sig)
  )
}

tbl <- rbind(
  summary_tbl("empty", cmp_empty),
  summary_tbl("points", cmp_points)
)
knitr::kable(tbl, align = "lrrrr")

example	metric	svglite	grrr	delta
empty	circle	0	0	0
empty	polyline	0	0	0
empty	polygon	0	0	0
empty	line	0	12	12
empty	rect	4	1	-3
empty	text	0	12	12
empty	chars	1329	2948	1619
points	circle	35	35	0
points	polyline	40	0	-40
points	polygon	0	0	0
points	line	0	70	70
points	rect	7	4	-3
points	text	22	18	-4
points	chars	12964	13322	358

cat("\n")
cat("- In the empty baseline, layout primitives (rect/line/text) are present on both sides but not necessarily with the same counts due to different internal decomposition.\n")

• In the empty baseline, layout primitives (rect/line/text) are present on both sides but not necessarily with the same counts due to different internal decomposition.

cat("- In the faceted points example, circle counts should now be non-zero in grrr and visually present; if not, it indicates a remaining point-shape/size translation issue.\n")

• In the faceted points example, circle counts should now be non-zero in grrr and visually present; if not, it indicates a remaining point-shape/size translation issue.

cat("- Gridline density, label placement, and legend drawing can still differ because ggplot's gtable layout and guides are only approximated in the current bridge.\n")

• Gridline density, label placement, and legend drawing can still differ because ggplot’s gtable layout and guides are only approximated in the current bridge.