test: add regression tests for issue #279 (facet_wrap spacing with custom height)

NEWS.md

@@ -1,3 +1,9 @@
+# Changes in version 2026.9.4 (PR#288)
+
+- Plot SVGs use `display: block` so browsers do not leave baseline whitespace below the plot (issue #279). Thanks @ANAMASGARD.
+
+# Changes in development (PR#339)
+
 # Changes in version 2026.9.5
 
 - geom_text() renders with .text(), instead of setMultilineText(), fixing interactive updates.

inst/htmljs/animint.js

@@ -401,7 +401,9 @@ var setMultilineText = function(textElement, text) {
     var svg = tdLeft.append("svg")
       .attr("id", p_info.plot_id)
       .attr("height", p_info.options.height)
-      .attr("width", p_info.options.width);
+      .attr("width", p_info.options.width)
+      // block avoids inline SVG baseline/descender gap below the plot (issue #279)
+      .style("display", "block");
 
     // divvy up width/height based on the panel layout
     var nrows = Math.max.apply(null, p_info.layout.ROW);

tests/testthat/test-issue-279-facet-wrap-custom-height-spacing.R

@@ -0,0 +1,43 @@
+test_that("facet_wrap SVG height is proportional to theme_animint height, no excess space (#279)", {
+  task_data <- data.frame(
+    x = rep(1:5, 5),
+    y = rep(1:5, 5),
+    task_id = rep(c("sonar", "spam", "vowel", "waveform", "zip"), each = 5)
+  )
+  n_facets <- length(unique(task_data$task_id))
+  default_theme_height <- 400
+  custom_theme_height <- 600
+  svg_xpath <- "//svg[@id='plot_plot']"
+  svg_sel <- "svg#plot_plot"
+  parent_sel <- "td:has(> svg#plot_plot)"
+  base_plot <- ggplot() +
+    geom_point(aes(x, y), data = task_data) +
+    facet_wrap(~ task_id, ncol = 1) +
+    theme_bw()
+  viz_list <- list(
+    default = animint(plot = base_plot),
+    custom = animint(plot = base_plot + theme_animint(height = custom_theme_height))
+  )
+  heights <- list()
+  for (viz_name in names(viz_list)) {
+    info <- animint2HTML(viz_list[[viz_name]])
+    svg_node <- getNodeSet(info$html, svg_xpath)
+    expect_equal(length(svg_node), 1L)
+    svg_attrs <- xmlAttrs(svg_node[[1]])
+    display <- getStyleValue(info$html, svg_xpath, "display")
+    expect_equal(display, "block",
+      label = "plot SVG should have inline display:block to prevent whitespace below it")
+    svg_box <- get_element_bbox(svg_sel)
+    parent_box <- get_element_bbox(parent_sel)
+    bottom_gap <- (parent_box$top + parent_box$height) - (svg_box$top + svg_box$height)
+    expect_lte(bottom_gap, 1,
+      label = "no excess rendered gap below plot SVG (issue #279)")
+    heights[[viz_name]] <- as.numeric(svg_attrs[["height"]])
+  }
+  expect_lt(heights$default, default_theme_height * n_facets)
+  expect_lt(heights$custom, custom_theme_height * n_facets,
+    label = sprintf(
+      "SVG height should not be %d*num_facets — regression from issue #279",
+      custom_theme_height))
+  expect_gt(heights$custom, heights$default)
+})

tests/testthat/test-renderer3-knit-print.R

@@ -44,10 +44,9 @@ test_that("segments and breakpoints are rendered", {
 })
 
 test_that("svg id property is unique", {
-  svg.list <- getNodeSet(html, "//svg")
-  attr.mat <- sapply(svg.list, xmlAttrs)
-  id.counts <- table(attr.mat["id",])
-  expect_true(all(id.counts==1))
+  id.vec <- getPropertyValue(html, "//svg", "id")
+  id.counts <- table(id.vec)
+  expect_equal(max(id.counts), 1L)
 })
 
 all.list <- getNodeSet(html, "//*")