1 files changed, 104 insertions, 0 deletions
diff --git a/tex/context/base/mkxl/attr-neg.lmt b/tex/context/base/mkxl/attr-neg.lmt
new file mode 100644
index 000000000..4739b736d
--- /dev/null
+++ b/tex/context/base/mkxl/attr-neg.lmt
@@ -0,0 +1,104 @@
+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, utilities, logs, backends = attributes, nodes, utilities, logs, backends
+local commands, context, interfaces = commands, context, interfaces
+local tex = tex
+
+local states            = attributes.states
+local enableaction      = nodes.tasks.enableaction
+local nodeinjections    = backends.nodeinjections
+local texsetattribute   = tex.setattribute
+local variables         = interfaces.variables
+local allocate          = utilities.storage.allocate
+local setmetatableindex = table.setmetatableindex
+
+--- negative / positive
+
+attributes.negatives    = attributes.negatives or { }
+local negatives         = attributes.negatives
+
+local a_negative        = attributes.private("negative")
+
+local v_none            = interfaces.variables.none
+
+negatives.data          = allocate()
+negatives.attribute     = a_negative
+
+negatives.registered = allocate {
+    [variables.positive] = 1,
+    [variables.negative] = 2,
+}
+
+local data       = negatives.data
+local registered = negatives.registered
+
+local function extender(negatives,key)
+    if key == "none" then -- v_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
+
+setmetatableindex(negatives,      extender)
+setmetatableindex(negatives.data, reviver)
+
+negatives.handler = nodes.installattributehandler {
+    name        = "negative",
+    namespace   = negatives,
+    initializer = states.initialize,
+    finalizer   = states.finalize,
+    processor   = states.process,
+}
+
+local function register(stamp)
+    return registered[stamp] or registered.positive
+end
+
+local function enable()
+    enableaction("shipouts","attributes.negatives.handler")
+end
+
+negatives.register = register
+negatives.enable   = enable
+
+-- interface
+
+local enabled = false
+
+function negatives.set(stamp)
+    if not enabled then
+        enable()
+        enabled = true
+    end
+    texsetattribute(a_negative,register(stamp))
+end
+
+interfaces.implement {
+    name      = "setnegative",
+    actions   = negatives.set,
+    arguments = "argument",
+}