1 files changed, 71 insertions, 0 deletions
diff --git a/tex/context/base/attr-neg.lua b/tex/context/base/attr-neg.lua
new file mode 100644
index 000000000..ab62fbab5
--- /dev/null
+++ b/tex/context/base/attr-neg.lua
@@ -0,0 +1,71 @@
+if not modules then modules = { } end modules ['attr-neg'] = {
+    version   = 1.001,
+    comment   = "companion to attr-neg.mkiv",
+    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
+    copyright = "PRAGMA ADE / ConTeXt Development Team",
+    license   = "see context related readme files"
+}
+
+-- this module is being reconstructed and code will move to other places
+-- we can also do the nsnone via a metatable and then also se index 0
+
+local format = string.format
+
+local attributes, nodes = attributes, nodes
+
+local states         = attributes.states
+local tasks          = nodes.tasks
+local nodeinjections = backends.nodeinjections
+
+--- negative / positive
+
+attributes.negatives = attributes.negatives or { }
+local negatives      = attributes.negatives
+negatives.data       = negatives.data or { }
+negatives.attribute  = attributes.private("negative")
+
+negatives.registered = {
+    positive = 1,
+    negative = 2,
+}
+
+local data, registered = negatives.data, negatives.registered
+
+local function extender(negatives,key)
+    if key == "none" then
+        local d = data[1]
+        negatives.none = d
+        return d
+    end
+end
+
+local function reviver(data,n)
+    if n == 1 then
+        local d = nodeinjections.positive() -- called once
+        data[1] = d
+        return d
+    elseif n == 2 then
+        local d = nodeinjections.negative() -- called once
+        data[2] = d
+        return d
+    end
+end
+
+setmetatable(negatives,      { __index = extender })
+setmetatable(negatives.data, { __index = reviver  })
+
+function negatives.register(stamp)
+    return registered[stamp] or registered.positive
+end
+
+attributes.negatives.handler = nodes.install_attribute_handler {
+    name        = "negative",
+    namespace   = negatives,
+    initializer = states.initialize,
+    finalizer   = states.finalize,
+    processor   = states.process,
+}
+
+function negatives.enable()
+    tasks.enableaction("shipouts","attributes.negatives.handler")
+end