fix: Extraneous blank pages are sometimes inserted before chapters or…

… parts.

Or anything that tries to check whether a page break is needed

packages/resilient/sectioning/init.lua

@@ -14,6 +14,24 @@ function package:_init (options)
  self.class:loadPackage("counters")
 end
 
+local function hasContent()
+ -- Important, flushes nodes to output queue.
+ SILE.typesetter:leaveHmode()
+ -- The frame breaking logic is a bit messy:
+ -- It's not enough to check if the output queue is empty, because in some
+ -- cases where horizontal mode was already left, the output queue might still
+ -- contain vglue nodes. These are ignored afterwards at the top of a frame,
+ -- so do not count.
+ local hasNonGlueContent = false
+ for _, vnode in ipairs(SILE.typesetter.state.outputQueue) do
+ if not vnode.is_vglue then
+ hasNonGlueContent = true
+ break
+ end
+ end
+ return hasNonGlueContent
+end
+
 function package:registerCommands ()
 
  local resolveSectionStyleDef = function (name)
@@ -141,15 +159,15 @@ function package:registerCommands ()
  -- I really had hard times to make this work correctly. It now
  -- seems ok, but it might be fragile.
  SILE.typesetter:leaveHmode() -- Important, flushes nodes to output queue.
- if #SILE.typesetter.state.outputQueue ~= 0 then
+ if hasContent() then
  -- We are not at the top of a page, eject the current content.
  SILE.call("supereject")
  end
  SILE.typesetter:leaveHmode() -- Important again...
  -- ... so now we are at the top of a page, and only need
  -- to add a blank page if we have not landed on an odd page.
  if not SILE.documentState.documentClass:oddPage() then
- SILE.typesetter:typeset("")
+ SILE.typesetter:typeset("") -- Some non glue empty content to force a page break.
  SILE.typesetter:leaveHmode()
  -- Disable headers and footers if we can... i.e. the
  -- supporting class loaded all the necessary commands.
@@ -166,7 +184,7 @@ function package:registerCommands ()
 
  self:registerCommand("open-on-any-page", function (_, _)
  SILE.typesetter:leaveHmode() -- Important, flushes nodes to output queue.
- if #SILE.typesetter.state.outputQueue ~= 0 then
+ if hasContent() then
  -- We are not at the top of a page, eject the current content.
  SILE.call("supereject")
  end