2016-03-12 16:45:00

1 files changed, 69 insertions, 0 deletions

diff --git a/tex/context/base/mkiv/cldf-stp.lua b/tex/context/base/mkiv/cldf-stp.lua
new file mode 100644
index 000000000..7b5225dd3
--- /dev/null
+++ b/tex/context/base/mkiv/cldf-stp.lua
@@ -0,0 +1,69 @@
+if not modules then modules = { } end modules ['cldf-stp'] = {
+    version   = 1.001,
+    comment   = "companion to cldf-ini.mkiv",
+    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
+    copyright = "PRAGMA ADE / ConTeXt Development Team",
+    license   = "see context related readme files"
+}
+
+-- limitation: input levels
+
+-- context.stepwise (function()
+--     ...
+--     context.step(nil|...)
+--     ...
+--     context.step(nil|...)
+--     ...
+--     context.stepwise (function()
+--         ...
+--         context.step(nil|...)
+--         ...
+--     context.step(nil|...)
+--     ...
+--     end)
+--     ...
+--     context.step(nil|...)
+--     ...
+--     context.step(nil|...)
+--     ...
+-- end)
+
+local create   = coroutine.create
+local yield    = coroutine.yield
+local resume   = coroutine.resume
+local status   = coroutine.status
+
+local stepper  = nil
+local stack    = { } -- will never be deep so no gc needed
+local depth    = 0
+
+local nextstep = function()
+    if status(stepper) == "dead" then
+        stepper      = stack[depth]
+        depth        = depth - 1
+        stack[depth] = false
+    end
+    resume(stepper)
+end
+
+interfaces.implement {
+    name    = "step",
+    actions = nextstep,
+}
+
+local cldresume = context.constructcsonly("clf_step")
+
+function context.step(first,...)
+    if first ~= nil then
+        context(first,...)
+    end
+    cldresume()
+    yield()
+end
+
+function context.stepwise(f)
+    depth = depth + 1
+    stack[depth] = stepper
+    stepper = create(f)
+    resume(stepper)
+end