add saveLayer to lua

resources/slides_utils.lua

+function tostr(t)
+    local str = ""
+    for k, v in next, t do
+        if #str > 0 then
+            str = str .. ", "
+        end
+        if type(k) == "number" then
+            str = str .. "[" .. k .. "] = "
+        else
+            str = str .. tostring(k) .. " = "
+        end
+        if type(v) == "table" then
+            str = str .. "{ " .. tostr(v) .. " }"
+        elseif type(v) == "string" then
+            str = str .. '"' .. v .. '"'
+        else
+            str = str .. tostring(v)
+        end
+    end
+    return str
+end
+
+function trim_ws(s)
+    return s:match("^%s*(.*)")
+end
+
+function count_hypens(s)
+    local leftover = s:match("^-*(.*)")
+    return string.len(s) - string.len(leftover)
+end
+
+function parse_file(file)
+    local slides = {}
+    local block = {}
+
+    for line in file:lines() do
+        local s = trim_ws(line)
+        if #s == 0 then   -- done with a block
+            if #block > 0 then
+                slides[#slides + 1] = block
+                block = {}
+            end
+        else
+            local n = count_hypens(s)
+            block[#block + 1] = {
+                indent = n,
+                text = trim_ws(s:sub(n + 1, -1))
+            }
+        end
+    end
+    return slides
+end
+
+function pretty_print_slide(slide)
+    io.write("{\n")
+    for i = 1, #slide do
+        local node = slide[i]
+        for j = 0, node.indent do
+            io.write("   ")
+        end
+        io.write("{ ")
+        io.write(tostr(node))
+        io.write(" },\n")
+    end
+    io.write("},\n")
+end
+
+function pretty_print_slides(slides)
+    io.write("gSlides = {\n")
+    for i = 1, #slides do
+        pretty_print_slide(slides[i])
+    end
+    io.write("}\n")
+end
+