5 files changed, 63 insertions, 42 deletions

diff --git a/README.md b/README.md
index bad64fc..c4227a2 100644
--- a/README.md
+++ b/README.md
@@ -441,7 +441,7 @@ test "Display width" {
 }
 ```
 
-This has a build option, `"cjk"`, which will consider [ambiguous characters](https://www.unicode.org/reports/tr11/tr11-6.html) as double-width.
+This module has build options.  The first is `cjk`, which will consider [ambiguous characters](https://www.unicode.org/reports/tr11/tr11-6.html) as double-width.
 
 To choose this option, add it to the dependency like so:
 
@@ -451,6 +451,8 @@ const zg = b.dependency("zg", .{
 });
 ```
 
+The other options are `c0_width` and `c1_width`.  The standard behavior is to treat C0 and C1 control codes as zero-width, except for delete and backspace, which are -1 (the logic ensures that a `strWidth` is always at least 0).  If printing control codes with replacement characters, it's necessary to assign these a width, hence the options.  When provided these values must fit in an `i4`, this allows for C1s to be printed as `\u{80}` if desired.
+
 ## Scripts
 
 Unicode categorizes code points by the Script in which they belong. A Script
diff --git a/build.zig b/build.zig
index 4c4a35a..ce362ea 100644
--- a/build.zig
+++ b/build.zig
@@ -16,10 +16,24 @@ pub fn build(b: *std.Build) void {
     const gbp_gen_out = run_gbp_gen_exe.addOutputFileArg("gbp.bin.z");
 
     // Display width
-    const cjk = b.option(bool, "cjk", "Ambiguouse code points are wide (display width: 2).") orelse false;
+    const cjk = b.option(bool, "cjk", "Ambiguous code points are wide (display width: 2).") orelse false;
     const options = b.addOptions();
     options.addOption(bool, "cjk", cjk);
 
+    // Visible Controls
+    const c0_width = b.option(
+        i4,
+        "c0_width",
+        "C0 controls have this width (default: 0, <BS> <Del> default -1)",
+    );
+    options.addOption(?i4, "c0_width", c0_width);
+    const c1_width = b.option(
+        i4,
+        "c1_width",
+        "C1 controls have this width (default: 0)",
+    );
+    options.addOption(?i4, "c1_width", c1_width);
+
     const dwp_gen_exe = b.addExecutable(.{
         .name = "dwp",
         .root_source_file = b.path("codegen/dwp.zig"),
@@ -210,6 +224,7 @@ pub fn build(b: *std.Build) void {
     display_width.addImport("code_point", code_point);
     display_width.addImport("grapheme", grapheme);
     display_width.addImport("DisplayWidthData", width_data);
+    display_width.addOptions("options", options); // For testing
 
     // Normalization
     const ccc_data = b.createModule(.{
diff --git a/codegen/dwp.zig b/codegen/dwp.zig
index c581eb6..5e5bf6a 100644
--- a/codegen/dwp.zig
+++ b/codegen/dwp.zig
@@ -4,7 +4,7 @@ const builtin = @import("builtin");
 const options = @import("options");
 
 const block_size = 256;
-const Block = [block_size]i3;
+const Block = [block_size]i4;
 
 const BlockMap = std.HashMap(
     Block,
@@ -17,7 +17,7 @@ const BlockMap = std.HashMap(
         }
 
         pub fn eql(_: @This(), a: Block, b: Block) bool {
-            return std.mem.eql(i3, &a, &b);
+            return std.mem.eql(i4, &a, &b);
         }
     },
     std.hash_map.default_max_load_percentage,
@@ -28,7 +28,7 @@ pub fn main() !void {
     defer arena.deinit();
     const allocator = arena.allocator();
 
-    var flat_map = std.AutoHashMap(u21, i3).init(allocator);
+    var flat_map = std.AutoHashMap(u21, i4).init(allocator);
     defer flat_map.deinit();
 
     var line_buf: [4096]u8 = undefined;
@@ -147,10 +147,10 @@ pub fn main() !void {
     var stage1 = std.ArrayList(u16).init(allocator);
     defer stage1.deinit();
 
-    var stage2 = std.ArrayList(i3).init(allocator);
+    var stage2 = std.ArrayList(i4).init(allocator);
     defer stage2.deinit();
 
-    var block: Block = [_]i3{0} ** block_size;
+    var block: Block = [_]i4{0} ** block_size;
     var block_len: u16 = 0;
 
     for (0..0x110000) |i| {
@@ -163,8 +163,8 @@ pub fn main() !void {
             0x2e3b => width = 3,
 
             // C0/C1 control codes
-            0...0x20,
-            0x80...0xa0,
+            0...0x20 => width = if (options.c0_width) |c0| c0 else 0,
+            0x80...0x9f => width = if (options.c1_width) |c1| c1 else 0,
 
             // Line separator
             0x2028,
@@ -204,7 +204,7 @@ pub fn main() !void {
         if (cp == 0xad) width = 1;
 
         // Backspace and delete
-        if (cp == 0x8 or cp == 0x7f) width = -1;
+        if (cp == 0x8 or cp == 0x7f) width = if (options.c0_width) |c0| c0 else -1;
 
         // Process block
         block[block_len] = width;
diff --git a/src/DisplayWidth.zig b/src/DisplayWidth.zig
index 621b8c1..04e6b0c 100644
--- a/src/DisplayWidth.zig
+++ b/src/DisplayWidth.zig
@@ -1,5 +1,6 @@
 const std = @import("std");
 const builtin = @import("builtin");
+const options = @import("options");
 const ArrayList = std.ArrayList;
 const mem = std.mem;
 const simd = std.simd;
@@ -60,6 +61,7 @@ test "strWidth" {
     const data = try DisplayWidthData.init(testing.allocator);
     defer data.deinit();
     const self = Self{ .data = &data };
+    const c0 = options.c0_width orelse 0;
 
     try testing.expectEqual(@as(usize, 5), self.strWidth("Hello\r\n"));
     try testing.expectEqual(@as(usize, 1), self.strWidth("\u{0065}\u{0301}"));
@@ -74,19 +76,21 @@ test "strWidth" {
     try testing.expectEqual(@as(usize, 1), self.strWidth("\u{2764}")); // Default text presentation
     try testing.expectEqual(@as(usize, 1), self.strWidth("\u{2764}\u{FE0E}")); // Default text presentation with VS15 selector
     try testing.expectEqual(@as(usize, 2), self.strWidth("\u{2764}\u{FE0F}")); // Default text presentation with VS16 selector
-    try testing.expectEqual(@as(usize, 0), self.strWidth("A\x08")); // Backspace
-    try testing.expectEqual(@as(usize, 0), self.strWidth("\x7FA")); // DEL
-    try testing.expectEqual(@as(usize, 0), self.strWidth("\x7FA\x08\x08")); // never less than o
+    const expect_bs: usize = if (c0 == 0) 0 else 1 + c0;
+    try testing.expectEqual(expect_bs, self.strWidth("A\x08")); // Backspace
+    try testing.expectEqual(expect_bs, self.strWidth("\x7FA")); // DEL
+    const expect_long_del: usize = if (c0 == 0) 0 else 1 + (c0 * 3);
+    try testing.expectEqual(expect_long_del, self.strWidth("\x7FA\x08\x08")); // never less than 0
 
     // wcwidth Python lib tests. See: https://github.com/jquast/wcwidth/blob/master/tests/test_core.py
     const empty = "";
     try testing.expectEqual(@as(usize, 0), self.strWidth(empty));
     const with_null = "hello\x00world";
-    try testing.expectEqual(@as(usize, 10), self.strWidth(with_null));
+    try testing.expectEqual(@as(usize, 10 + c0), self.strWidth(with_null));
     const hello_jp = "コンニチハ, セカイ!";
     try testing.expectEqual(@as(usize, 19), self.strWidth(hello_jp));
     const control = "\x1b[0m";
-    try testing.expectEqual(@as(usize, 3), self.strWidth(control));
+    try testing.expectEqual(@as(usize, 3 + c0), self.strWidth(control));
     const balinese = "\u{1B13}\u{1B28}\u{1B2E}\u{1B44}";
     try testing.expectEqual(@as(usize, 3), self.strWidth(balinese));
 
diff --git a/src/WidthData.zig b/src/WidthData.zig
index 1b7fb2e..d77879e 100644
--- a/src/WidthData.zig
+++ b/src/WidthData.zig
@@ -9,7 +9,7 @@ const GraphemeData = @import("GraphemeData");
 allocator: mem.Allocator,
 g_data: GraphemeData,
 s1: []u16 = undefined,
-s2: []i3 = undefined,
+s2: []i4 = undefined,
 
 const Self = @This();
 
@@ -34,7 +34,7 @@ pub fn init(allocator: mem.Allocator) mem.Allocator.Error!Self {
     for (0..stage_1_len) |i| self.s1[i] = reader.readInt(u16, endian) catch unreachable;
 
     const stage_2_len: u16 = reader.readInt(u16, endian) catch unreachable;
-    self.s2 = try allocator.alloc(i3, stage_2_len);
+    self.s2 = try allocator.alloc(i4, stage_2_len);
     errdefer allocator.free(self.s2);
     for (0..stage_2_len) |i| self.s2[i] = @intCast(reader.readInt(i8, endian) catch unreachable);
 
@@ -52,33 +52,33 @@ pub fn deinit(self: *const Self) void {
 /// 3, where BACKSPACE and DELETE return -1 and 3-em-dash returns 3. C0/C1
 /// control codes return 0. If `cjk` is true, ambiguous code points return 2,
 /// otherwise they return 1.
-pub fn codePointWidth(self: Self, cp: u21) i3 {
+pub fn codePointWidth(self: Self, cp: u21) i4 {
     return self.s2[self.s1[cp >> 8] + (cp & 0xff)];
 }
 
 test "codePointWidth" {
-    try testing.expectEqual(@as(i3, 0), codePointWidth(0x0000)); // null
-    try testing.expectEqual(@as(i3, -1), codePointWidth(0x8)); // \b
-    try testing.expectEqual(@as(i3, -1), codePointWidth(0x7f)); // DEL
-    try testing.expectEqual(@as(i3, 0), codePointWidth(0x0005)); // Cf
-    try testing.expectEqual(@as(i3, 0), codePointWidth(0x0007)); // \a BEL
-    try testing.expectEqual(@as(i3, 0), codePointWidth(0x000A)); // \n LF
-    try testing.expectEqual(@as(i3, 0), codePointWidth(0x000B)); // \v VT
-    try testing.expectEqual(@as(i3, 0), codePointWidth(0x000C)); // \f FF
-    try testing.expectEqual(@as(i3, 0), codePointWidth(0x000D)); // \r CR
-    try testing.expectEqual(@as(i3, 0), codePointWidth(0x000E)); // SQ
-    try testing.expectEqual(@as(i3, 0), codePointWidth(0x000F)); // SI
-
-    try testing.expectEqual(@as(i3, 0), codePointWidth(0x070F)); // Cf
-    try testing.expectEqual(@as(i3, 1), codePointWidth(0x0603)); // Cf Arabic
-
-    try testing.expectEqual(@as(i3, 1), codePointWidth(0x00AD)); // soft-hyphen
-    try testing.expectEqual(@as(i3, 2), codePointWidth(0x2E3A)); // two-em dash
-    try testing.expectEqual(@as(i3, 3), codePointWidth(0x2E3B)); // three-em dash
-
-    try testing.expectEqual(@as(i3, 1), codePointWidth(0x00BD)); // ambiguous halfwidth
-
-    try testing.expectEqual(@as(i3, 1), codePointWidth('é'));
-    try testing.expectEqual(@as(i3, 2), codePointWidth('😊'));
-    try testing.expectEqual(@as(i3, 2), codePointWidth('统'));
+    try testing.expectEqual(@as(i4, 0), codePointWidth(0x0000)); // null
+    try testing.expectEqual(@as(i4, -1), codePointWidth(0x8)); // \b
+    try testing.expectEqual(@as(i4, -1), codePointWidth(0x7f)); // DEL
+    try testing.expectEqual(@as(i4, 0), codePointWidth(0x0005)); // Cf
+    try testing.expectEqual(@as(i4, 0), codePointWidth(0x0007)); // \a BEL
+    try testing.expectEqual(@as(i4, 0), codePointWidth(0x000A)); // \n LF
+    try testing.expectEqual(@as(i4, 0), codePointWidth(0x000B)); // \v VT
+    try testing.expectEqual(@as(i4, 0), codePointWidth(0x000C)); // \f FF
+    try testing.expectEqual(@as(i4, 0), codePointWidth(0x000D)); // \r CR
+    try testing.expectEqual(@as(i4, 0), codePointWidth(0x000E)); // SQ
+    try testing.expectEqual(@as(i4, 0), codePointWidth(0x000F)); // SI
+
+    try testing.expectEqual(@as(i4, 0), codePointWidth(0x070F)); // Cf
+    try testing.expectEqual(@as(i4, 1), codePointWidth(0x0603)); // Cf Arabic
+
+    try testing.expectEqual(@as(i4, 1), codePointWidth(0x00AD)); // soft-hyphen
+    try testing.expectEqual(@as(i4, 2), codePointWidth(0x2E3A)); // two-em dash
+    try testing.expectEqual(@as(i4, 3), codePointWidth(0x2E3B)); // three-em dash
+
+    try testing.expectEqual(@as(i4, 1), codePointWidth(0x00BD)); // ambiguous halfwidth
+
+    try testing.expectEqual(@as(i4, 1), codePointWidth('é'));
+    try testing.expectEqual(@as(i4, 2), codePointWidth('😊'));
+    try testing.expectEqual(@as(i4, 2), codePointWidth('统'));
 }