Try to give more equal allocations to large terms

src/trunc_io.erl

@@ -40,8 +40,9 @@ format(String, Args, Max) ->
     Maxlen = Max - length(String),
     format(Parts, Args, Maxlen, [], []).
 
-format([], _Args, _Max, Acc, ArgAcc) ->
-    io_lib:format(lists:flatten(lists:reverse(Acc)), lists:reverse(ArgAcc));
+format([], _Args, Max, Acc, ArgAcc) ->
+    FmtArgs = resolve_futures(Max, ArgAcc),
+    io_lib:format(lists:flatten(lists:reverse(Acc)), lists:reverse(FmtArgs));
 format([[] | T], Args, Max, Acc, ArgAcc) ->
     % discard the null list generated by split
     format(T, Args, Max, Acc, ArgAcc);
@@ -62,21 +63,21 @@ format([[$~|H]| T], [AH | AT], Max, Acc, ArgAcc) when length(H) == 1 ->
     case H of
         _ when H == "p"; H == "w"; H == "s" ->
             %okay, these are prime candidates for rewriting
-            {String, Length} = case print(AH, Max) of
+            case print(AH, Max) of
                 {_Res, Max} when AT /= [] ->
-                    % this isn't the last argument, but it consumed all available space, give it half instead
-                    print(AH, Max div 2);
-                {Res, Len} ->;
-                    {Res, Len}
-            end,
-            {Value, RealLen} = case H of
-                "s" ->
-                    % strip off the doublequotes
-                    {string:substr(String, 2, length(String) -2), Length -2};
-                _ ->
-                    {String, Length}
-            end,
-            format(T, AT, Max + 2 - RealLen, ["~s" | Acc], [Value | ArgAcc]);
+                    % this isn't the last argument, but it consumed all available space
+                    % delay calculating the print size until the end
+                    format(T, AT, Max + 2, ["~s" | Acc], [{future, AH} | ArgAcc]);
+                {String, Length} ->
+                    {Value, RealLen} = case H of
+                        "s" ->
+                            % strip off the doublequotes
+                            {string:substr(String, 2, length(String) -2), Length -2};
+                        _ ->;
+                            {String, Length}
+                    end,
+                    format(T, AT, Max + 2 - RealLen, ["~s" | Acc], [Value | ArgAcc])
+            end;
         _ ->
             % whatever, just pass them on through
             format(T, AT, Max, [[$~ | H], Acc], [AH | ArgAcc])
@@ -87,22 +88,26 @@ format([[$~|H]| T], [AH | AT], Max, Acc, ArgAcc) ->
     case re:run(H, "^(?:-??(\\d+|\\*)\\.|)(?:-??(\\d+|\\*)\\.|)(-??\\d+|\\*|)(t|)([cfegswpWPBX#bx+ni])$", [{capture, all_but_first, list}]) of
         {match, [_F, _P, _Pad, _Mod, C]} when C == "p"; C=="w"; C=="s" ->
             %okay, these are prime candidates for rewriting
-            {String, Length} = case print(AH, Max) of
+            case print(AH, Max) of
                 {_Res, Max} when AT /= [] ->
-                    % this isn't the last argument, but it consumed all available space, give it half instead
-                    print(AH, Max div 2);
-                {Res, Len} ->;
-                    {Res, Len}
-            end,
-            {Value, RealLen} = case H of
-                "s" ->
-                    % strip off the doublequotes
-                    {string:substr(String, 2, length(String) -2), Length -2};
-                _ ->
-                    {String, Length}
-            end,
-            format(T, AT, Max + length(H) + 1 - RealLen, ["~s" | Acc], [Value | ArgAcc]);
+                    % this isn't the last argument, but it consumed all available space
+                    % delay calculating the print size until the end
+                    format(T, AT, Max + length(H) + 1, ["~s" | Acc], [{future, AH} | ArgAcc]);
+                {String, Length} ->
+                    {Value, RealLen} = case H of
+                        "s" ->
+                            % strip off the doublequotes
+                            {string:substr(String, 2, length(String) -2), Length -2};
+                        _ ->;
+                            {String, Length}
+                    end,
+                    format(T, AT, Max + length(H) + 1 - RealLen, ["~s" | Acc], [Value | ArgAcc])
+            end;
         {match, [_F, _P, _Pad, _Mod, C]} when C == "P"; C=="W" ->
+            % these crazy ones consume TWO arguments, just pass them through
+            % because W and P implicitly limit size so we trust the user knows
+            % what they're doing. Unfortunately we can't change Max at all because
+            % depth based limits are not of known length.
             [AH2 | AT2] = AT,
             format(T, AT2, Max, [[$~|H]|Acc], [AH2, AH |ArgAcc]);
         {match, _} ->
@@ -114,6 +119,17 @@ format([[$~|H]| T], [AH | AT], Max, Acc, ArgAcc) ->
 format([H | T], Args, Max, Acc, ArgAcc) ->
     format(T, Args, Max, [H | Acc], ArgAcc).
 
+%% for all the really big terms encountered in a format/3 call, try to give each of them an equal share
+resolve_futures(Max, Args) ->
+    Count = length(lists:filter(fun({future, _}) -> true; (_) -> false end, Args)),
+    case Count of
+        0 ->
+            Args;
+        _ ->
+            SingleFmt = Max div Count,
+            lists:map(fun({future, Value}) -> element(1, print(Value, SingleFmt)); (X) -> X end, Args)
+    end.
+
 %% @doc Returns an flattened list containing the ASCII representation of the given
 %% term.
 -spec fprint(term(), pos_integer()) -> string().