Make the cost offset configurable

docs/manual/lwc-manual.tex

@@ -525,8 +525,13 @@ \subsection{Maximum Cost}
 
 \subsection{Draft Mode}
 
-You can use the draft mode to visualize how \lwc/ processes pages. Any \color[failure]{remaining widows and orphans will be coloured red}, any \color[expanded]{expanded paragraphs will be coloured green}, and any \color[moved]{lines moved to the next page will be coloured blue}. In addition, the cost of each paragraph is shown in the right margin.
+\setuplwc[draft=start]
+\definecolor[lwc_expanded][s=0]
+\definecolor[lwc_failure][s=0]
+\definecolor[lwc_moved][s=0]
+You can use the draft mode to visualize how \lwc/ processes pages. Any \color[failure]{remaining widows and orphans will be coloured red}, any \color[expanded]{expanded paragraphs will be coloured green}, and any \color[moved]{lines moved to the next page will be coloured blue}. In addition, the cost of each paragraph is shown in the right margin as it is here.
 
+\setuplwc[draft=stop]
 \startTABLE[setups=commandtable]
     \NC \plainop/
     \NC\inlineTEX{\lwcdraft 1}
@@ -539,8 +544,30 @@ \subsection{Draft Mode}
     \NC\NR
 \stopTABLE
 
+\setuplwc[draft=start]
 Advanced users may also customize the colours used by modifying the \inlineLUA{lwc.colours} table. The table keys are currently \type{expanded}, \type{failure}, and \type{moved}. The table values are \acronym{RGB} 3-tuples, where each element is a float between zero and one.
 
+\subsection{Draft Offset}
+
+In draft mode, the paragraph costs are printed in the right margin, offset a certain distance from the right edge of the paragraph. By default, this offset is the same length as the paragraph indent; however, you can change this to any value that you want:
+
+\setuplwc[draft=stop]
+\startTABLE[setups=commandtable]
+    \NC \plainop/
+    \NC\inlineTEX{\lwcdraftoffset = $\meta{dimension}$}
+    \NC\NR
+    \NC \LaTeX{}
+    \NC\inlineTEX{\lwcsetup{draftoffset = $\meta{dimension}$}}
+    \NC\NR
+    \NC \ConTeXt{}
+    \NC\inlineTEX{\setuplwc[draftoffset = $\meta{dimension}$]}
+    \NC\NR
+\stopTABLE
+
+\setuplwc[draft=start, draftoffset=-1em]
+If you set the \q{draft offset} to a negative value, the paragraph costs will instead be printed to the left of the paragraph, as it is here.
+
+\setuplwc[draft=stop]
 \subsection{Debug Mode}
 
 \Lwc/ offers a \q{debug} mode that prints extra information in the log files. This may be helpful to understand how \lwc/ is processing paragraphs and pages, although the information is likely inscrutable unless you are the package's author. If you are reporting an issue with \lwc/ make sure to compile your document with debug mode enabled!

source/lua-widow-control.lua

@@ -119,7 +119,6 @@ local iftrue = token.create("iftrue")
 local INFINITY = 10000
 local INSERT_CLASS_MULTIPLE = 1000 * 1000
 local INSERT_FIRST_MULTIPLE = 1000
-local llap_offset = math.max(tex.dimen.parindent, tex.sp("12pt"))
 local min_col_width = tex.sp("250pt")
 local PAGE_MULTIPLE = 100
 local SINGLE_LINE = 50
@@ -137,6 +136,7 @@ lwc.colours = {
      worrying about any format/engine differences.
   ]]
 local contrib_head,
+      draft_offset,
       emergencystretch,
       hold_head,
       info,
@@ -181,16 +181,19 @@ if context then
 
     -- Dimen names
     emergencystretch = "lwc_emergency_stretch"
+    draft_offset = "lwc_draft_offset"
     max_cost = "lwc_max_cost"
 elseif plain or latex or optex then
     pagenum = function() return tex_count[0] end
 
     -- Dimen names
     if tex.isdimen("g__lwc_emergencystretch_dim") then
         emergencystretch = "g__lwc_emergencystretch_dim"
+        draft_offset = "g__lwc_draftoffset_dim"
         max_cost = "g__lwc_maxcost_int"
     else
         emergencystretch = "lwcemergencystretch"
+        draft_offset = "lwcdraftoffset"
         max_cost = "lwcmaxcost"
     end
 
@@ -446,35 +449,6 @@ local function colour_list(head, colour)
 end
 
 
---- Generate an \\llap'ed box containing the provided string
----
---- @param str string The string to typeset
---- @return node head The box node
-local function llap_string(str)
-    local first = new_node("glue")
-    first.width = llap_offset
-
-    local m = first
-    for letter in str:gmatch(".")  do
-        local n = new_node("glyph")
-        n.font = SMALL_FONT
-        n.char = string.byte(letter)
-
-        m.next = n
-        m = n
-    end
-
-    local hss = new_node("glue")
-    hss.stretch = 1
-    hss[stretch_order] = 1
-    hss.shrink = 1
-    hss[shrink_order] = 1
-    m.next = hss
-
-    return node.hpack(first, 0, "exactly")
-end
-
-
 --- Typesets the cost of a paragraph beside it in draft mode
 ---
 --- @param paragraph node
@@ -485,11 +459,11 @@ local function show_cost(paragraph, cost)
         return
     end
 
-    local last_hlist_end = last(next_of_type(
+    local last_hlist = next_of_type(
         last(paragraph),
         hlist_id,
         { subtype = line_subid, reverse = true }
-    ).list)
+    )
 
     local cost_str
     if cost < math.maxinteger then
@@ -498,7 +472,42 @@ local function show_cost(paragraph, cost)
         cost_str = "infinite"
     end
 
-    last_hlist_end.next = llap_string(cost_str)
+    local m, first
+    for letter in cost_str:gmatch(".")  do
+        local n = new_node("glyph")
+        n.font = SMALL_FONT
+        n.char = string.byte(letter)
+
+        if not first then
+            first = n
+        else
+            m.next = n
+        end
+        m = n
+    end
+
+    local hss = new_node("glue")
+    hss.stretch = 1
+    hss[stretch_order] = 1
+    hss.shrink = 1
+    hss[shrink_order] = 1
+
+    local hbox
+    local offset = new_node("glue")
+    local offset_width = tex_dimen[draft_offset]
+
+    if offset_width >= 0 then
+        offset.width = offset_width
+        m.next = hss
+        hbox = node.hpack(first, 0, "exactly")
+    else
+        offset.width = offset_width - last_hlist.width
+        hss.next = first
+        hbox = node.hpack(hss, 0, "exactly")
+    end
+
+    last(last_hlist.list).next = offset
+    offset.next = hbox
 end
 
 

source/lua-widow-control.opm

@@ -14,6 +14,9 @@
 \_newdimen\lwcemergencystretch
 \lwcemergencystretch=3em
 
+\_newdimen\lwcdraftoffset
+\lwcdraftoffset=\parindent
+
 \_newcount\lwcmaxcost
 \lwcmaxcost=2147483647
 

source/lua-widow-control.sty

@@ -76,6 +76,10 @@
     emergencystretch .value_required:n = true,
     emergencystretch .initial:x        = \dim_max:nn { 3em } { 30pt },
 
+    draftoffset .dim_gset:N       = \g__lwc_draftoffset_dim,
+    draftoffset .value_required:n = true,
+    draftoffset .initial:x        = \dim_max:nn { \parindent } { 12pt },
+
     max-cost .int_gset:N       = \g__lwc_maxcost_int,
     max-cost .value_required:n = true,
     max-cost .initial:x        = \c_max_int,

source/lua-widow-control.tex

@@ -24,6 +24,9 @@
 \newdimen\lwcemergencystretch
 \lwcemergencystretch=3em
 
+\newdimen\lwcdraftoffset
+\lwcdraftoffset=\parindent
+
 \newcount\lwcmaxcost
 \lwcmaxcost=2147483647
 

source/t-lua-widow-control.mkxl

@@ -18,10 +18,12 @@
 
 % Set up the options
 \newdimen\lwc_emergency_stretch
+\newdimen\lwc_draft_offset
 \newcount\lwc_max_cost
 
 \starttexdefinition lwc_set_parameters
     \lwc_emergency_stretch=\lwcparameter{emergencystretch}
+    \lwc_draft_offset=\lwcparameter{draftoffset}
 
     \doifelse{\lwcparameter{\c!state}}\v!start{
         \lwc_enable
@@ -96,6 +98,7 @@
     \c!state=\v!start,
     debug=\v!stop,
     draft=\v!stop,
+    draftoffset=12pt,
 ]
 
 \setuplwc[default]

tests/latex/draft-offset.lvtext

@@ -0,0 +1,24 @@
+\documentclass{article}
+
+\usepackage[draft]{lua-widow-control}
+
+\parindent=0pt
+\parskip=\baselineskip
+
+\begin{document}
+
+One \hfill one.
+
+\lwcsetup{draftoffset=0pt} Two \hfill two.
+
+\lwcsetup{draftoffset=1in} Three \hfill three.
+
+\lwcsetup{draftoffset=-1sp} Four \hfill four.
+
+\lwcsetup{draftoffset=-1in} Five \hfill five.
+
+\lwcsetup{draftoffset=1em} Six \hfill six \hfill six.
+
+Seven \hfill seven \hfill seven.
+
+\end{document}