From ebf64ca35df03737e9850ab940125b21ba64ff16 Mon Sep 17 00:00:00 2001
From: Nick Cameron <ncameron@mozilla.com>
Date: Thu, 24 Sep 2015 11:00:14 +1200
Subject: [PATCH] Heuristic max width for function calls

---
 src/config.rs |  7 +++++--
 src/items.rs  |  2 +-
 src/lists.rs  | 22 ++++++++++++++++++++++
 src/types.rs  |  2 +-
 4 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/src/config.rs b/src/config.rs
index c5b777e1d81c..4779d0e9b98c 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -215,9 +215,11 @@ macro_rules! create_config {
 
 create_config! {
     max_width: usize, "Maximum width of each line",
-    ideal_width: usize, "Ideal width of each line",
-    leeway: usize, "Leeway of line width",
+    ideal_width: usize, "Ideal width of each line (only used for comments)",
+    leeway: usize, "Leeway of line width (deprecated)",
     tab_spaces: usize, "Number of spaces per tab",
+    list_width: usize, "Maximum width in a struct literal or function \
+                        call before faling back to vertical formatting",
     newline_style: NewlineStyle, "Unix or Windows line endings",
     fn_brace_style: BraceStyle, "Brace style for functions",
     fn_return_indent: ReturnIndent, "Location of return type in function declaration",
@@ -256,6 +258,7 @@ impl Default for Config {
             ideal_width: 80,
             leeway: 5,
             tab_spaces: 4,
+            list_width: 50,
             newline_style: NewlineStyle::Unix,
             fn_brace_style: BraceStyle::SameLineWhere,
             fn_return_indent: ReturnIndent::WithArgs,
diff --git a/src/items.rs b/src/items.rs
index c2a8f46b3db1..3656fcdf982b 100644
--- a/src/items.rs
+++ b/src/items.rs
@@ -948,7 +948,7 @@ impl<'a> FmtVisitor<'a> {
             item.item = ty;
         }
 
-        let fmt = ListFormatting::for_fn(h_budget, offset, self.config);
+        let fmt = ListFormatting::for_item(h_budget, offset, self.config);
         let list_str = try_opt!(write_list(&items, &fmt));
 
         Some(format!("<{}>", list_str))
diff --git a/src/lists.rs b/src/lists.rs
index cccb8d37b081..cf1d433a25c2 100644
--- a/src/lists.rs
+++ b/src/lists.rs
@@ -26,6 +26,8 @@ pub enum ListTactic {
     Horizontal,
     // Try Horizontal layout, if that fails then vertical
     HorizontalVertical,
+    // HorizontalVertical with a soft limit.
+    LimitedHorizontalVertical(usize),
     // Pack as many items as possible per row over (possibly) many rows.
     Mixed,
 }
@@ -59,6 +61,19 @@ pub struct ListFormatting<'a> {
 
 impl<'a> ListFormatting<'a> {
     pub fn for_fn(width: usize, offset: Indent, config: &'a Config) -> ListFormatting<'a> {
+        ListFormatting {
+            tactic: ListTactic::LimitedHorizontalVertical(config.list_width),
+            separator: ",",
+            trailing_separator: SeparatorTactic::Never,
+            indent: offset,
+            h_width: width,
+            v_width: width,
+            ends_with_newline: false,
+            config: config,
+        }
+    }
+
+    pub fn for_item(width: usize, offset: Indent, config: &'a Config) -> ListFormatting<'a> {
         ListFormatting {
             tactic: ListTactic::HorizontalVertical,
             separator: ",",
@@ -118,6 +133,13 @@ pub fn write_list<'b>(items: &[ListItem], formatting: &ListFormatting<'b>) -> Op
     let fits_single = total_width + total_sep_len <= formatting.h_width;
 
     // Check if we need to fallback from horizontal listing, if possible.
+    if let ListTactic::LimitedHorizontalVertical(limit) = tactic {
+        if total_width > limit {
+            tactic = ListTactic::Vertical;
+        } else {
+            tactic = ListTactic::HorizontalVertical;
+        }
+    }
     if tactic == ListTactic::HorizontalVertical {
         debug!("write_list: total_width: {}, total_sep_len: {}, h_width: {}",
                total_width,
diff --git a/src/types.rs b/src/types.rs
index 284654049887..b1af98afbda6 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -230,7 +230,7 @@ fn rewrite_segment(segment: &ast::PathSegment,
                                      list_lo,
                                      span_hi);
 
-            let fmt = ListFormatting::for_fn(list_width, offset + extra_offset, context.config);
+            let fmt = ListFormatting::for_item(list_width, offset + extra_offset, context.config);
             let list_str = try_opt!(write_list(&items.collect::<Vec<_>>(), &fmt));
 
             // Update position of last bracket.