1 files changed, 75 insertions, 0 deletions
diff --git a/tex/generic/context/luatex/luatex-gadgets.lua b/tex/generic/context/luatex/luatex-gadgets.lua
new file mode 100644
index 000000000..9bf423fda
--- /dev/null
+++ b/tex/generic/context/luatex/luatex-gadgets.lua
@@ -0,0 +1,75 @@
+if not modules then modules = { } end modules ['luatex-gadgets'] = {
+    version   = 1.001,
+    comment   = "companion to luatex-gadgets.tex",
+    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
+    copyright = "PRAGMA ADE / ConTeXt Development Team",
+    license   = "see context related readme files"
+}
+
+if context then return end
+
+-- This module contains some maybe useful gadgets. More might show up here
+-- as side effect of tutorials or articles. Don't use this file in ConTeXt
+-- because we often have similar mechanisms already.
+
+gadgets = gadgets or { } -- global namespace
+
+-- marking content for optional removal
+
+local marking   = { }
+gadgets.marking = marking
+
+local marksignal   = 5001 -- will be set in the tex module
+local lastmarked   = 0
+local marked       = { }
+local local_par    = 6
+local whatsit_node = 8
+
+function marking.setsignal(n)
+    marksignal = tonumber(n) or marksignal
+end
+
+function marking.mark(str)
+    local currentmarked = marked[str]
+    if not currentmarked then
+        lastmarked    = lastmarked + 1
+        currentmarked = lastmarked
+        marked[str]   = currentmarked
+    end
+    tex.setattribute(marksignal,currentmarked)
+end
+
+function marking.remove(str)
+    local attr = marked[str]
+    if not attr then
+        return
+    end
+    local list = tex.nest[tex.nest.ptr]
+    if list then
+        local head = list.head
+        local tail = list.tail
+        local last = tail
+        if last[marksignal] == attr then
+            local first = last
+            while true do
+                local prev = first.prev
+                if not prev
+                        or prev[marksignal] ~= attr
+                        or (prev.id == whatsit_node and prev.subtype == local_par) then
+                    break
+                else
+                    first = prev
+                end
+            end
+            if first == head then
+                list.head = nil
+                list.tail = nil
+            else
+                local prev = first.prev
+                list.tail  = prev
+                prev.next  = nil
+            end
+            node.flush_list(first)
+        end
+    end
+end