Use cc.strings.wrap inside slowWrite

Means we don't end up re-wrapping text and producing incorrect results.
Fixes #865

src/main/resources/data/computercraft/lua/rom/apis/textutils.lua

@@ -5,35 +5,32 @@
 
 local expect = dofile("rom/modules/main/cc/expect.lua")
 local expect, field = expect.expect, expect.field
+local wrap = dofile("rom/modules/main/cc/strings.lua").wrap
 
 --- Slowly writes string text at current cursor position,
 -- character-by-character.
 --
 -- Like @{_G.write}, this does not insert a newline at the end.
 --
--- @tparam string sText The the text to write to the screen
--- @tparam[opt] number nRate The number of characters to write each second,
+-- @tparam string text The the text to write to the screen
+-- @tparam[opt] number rate The number of characters to write each second,
 -- Defaults to 20.
 -- @usage textutils.slowWrite("Hello, world!")
 -- @usage textutils.slowWrite("Hello, world!", 5)
-function slowWrite(sText, nRate)
-    expect(2, nRate, "number", "nil")
-    nRate = nRate or 20
-    if nRate < 0 then
+function slowWrite(text, rate)
+    expect(2, rate, "number", "nil")
+    rate = rate or 20
+    if rate < 0 then
         error("Rate must be positive", 2)
     end
-    local nSleep = 1 / nRate
+    local to_sleep = 1 / rate
 
-    sText = tostring(sText)
-    local x, y = term.getCursorPos()
-    local len = #sText
+    local wrapped_lines = wrap(tostring(text), (term.getSize()))
+    local wrapped_str = table.concat(wrapped_lines, "\n")
 
-    for n = 1, len do
-        term.setCursorPos(x, y)
-        sleep(nSleep)
-        local nLines = write(string.sub(sText, 1, n))
-        local _, newY = term.getCursorPos()
-        y = newY - nLines
+    for n = 1, #wrapped_str do
+        sleep(to_sleep)
+        write(wrapped_str:sub(n, n))
     end
 end
 

src/main/resources/data/computercraft/lua/rom/modules/main/cc/strings.lua

@@ -3,7 +3,7 @@
 -- @module cc.strings
 -- @see textutils For additional string related utilities.
 
-local expect = require "cc.expect".expect
+local expect = (require and require("cc.expect") or dofile("rom/modules/main/cc/expect.lua")).expect
 
 --[[- Wraps a block of text, so that each line fits within the given width.
 

src/test/resources/test-rom/spec/apis/textutils_spec.lua

@@ -1,8 +1,23 @@
+local helpers = require "test_helpers"
+
 describe("The textutils library", function()
     describe("textutils.slowWrite", function()
         it("validates arguments", function()
             expect.error(textutils.slowWrite, nil, false):eq("bad argument #2 (expected number, got boolean)")
         end)
+
+        it("wraps text correctly", function()
+            local count = 0
+            stub(_G, "sleep", function() count = count + 1 end)
+            local w = helpers.with_window(20, 3, function()
+                textutils.slowWrite("This is a long string which one would hope wraps.")
+            end)
+
+            expect(w.getLine(1)):eq "This is a long      "
+            expect(w.getLine(2)):eq "string which one    "
+            expect(w.getLine(3)):eq "would hope wraps.   "
+            expect(count):eq(51)
+        end)
     end)
 
     describe("textutils.formatTime", function()