use enum for underline styles

src/renderer/Metal.zig

@@ -911,7 +911,7 @@ pub fn updateCell(
         });
     }
 
-    if (cell.attrs.underline) {
+    if (cell.attrs.underline != .none) {
         self.cells.appendAssumeCapacity(.{
             .mode = .underline,
             .grid_pos = .{ @intToFloat(f32, x), @intToFloat(f32, y) },

src/renderer/OpenGL.zig

@@ -928,7 +928,7 @@ pub fn updateCell(
         var i: usize = 0;
         if (colors.bg != null) i += 1;
         if (!cell.empty()) i += 1;
-        if (cell.attrs.underline) i += 1;
+        if (cell.attrs.underline != .none) i += 1;
         if (cell.attrs.strikethrough) i += 1;
         break :needed i;
     };
@@ -1002,7 +1002,7 @@ pub fn updateCell(
         });
     }
 
-    if (cell.attrs.underline) {
+    if (cell.attrs.underline != .none) {
         self.cells.appendAssumeCapacity(.{
             .mode = .underline,
             .grid_col = @intCast(u16, x),

src/terminal/Screen.zig

@@ -56,6 +56,7 @@ const Allocator = std.mem.Allocator;
 
 const utf8proc = @import("utf8proc");
 const trace = @import("tracy").trace;
+const sgr = @import("sgr.zig");
 const color = @import("color.zig");
 const point = @import("point.zig");
 const CircBuf = @import("circ_buf.zig").CircBuf;
@@ -167,10 +168,10 @@ pub const Cell = struct {
         bold: bool = false,
         italic: bool = false,
         faint: bool = false,
-        underline: bool = false,
         blink: bool = false,
         inverse: bool = false,
         strikethrough: bool = false,
+        underline: sgr.Attribute.Underline = .none,
 
         /// True if this is a wide character. This char takes up
         /// two cells. The following cell ALWAYS is a space.
@@ -241,7 +242,7 @@ pub const Cell = struct {
     }
 
     test {
-        //log.warn("CELL={} {}", .{ @sizeOf(Cell), @alignOf(Cell) });
+        //log.warn("CELL={} bits={} {}", .{ @sizeOf(Cell), @bitSizeOf(Cell), @alignOf(Cell) });
         try std.testing.expectEqual(12, @sizeOf(Cell));
     }
 };

src/terminal/Terminal.zig

@@ -379,12 +379,12 @@ pub fn setAttribute(self: *Terminal, attr: sgr.Attribute) !void {
             self.screen.cursor.pen.attrs.faint = true;
         },
 
-        .underline => {
+        .underline => |v| {
-            self.screen.cursor.pen.attrs.underline = true;
+            self.screen.cursor.pen.attrs.underline = v;
         },
 
         .reset_underline => {
-            self.screen.cursor.pen.attrs.underline = false;
+            self.screen.cursor.pen.attrs.underline = .none;
         },
 
         .blink => {

src/terminal/sgr.zig

@@ -31,7 +31,7 @@ pub const Attribute = union(enum) {
     faint: void,
 
     /// Underline the text
-    underline: void,
+    underline: Underline,
     reset_underline: void,
 
     /// Blink the text
@@ -75,6 +75,15 @@ pub const Attribute = union(enum) {
         g: u8,
         b: u8,
     };
+
+    pub const Underline = enum(u3) {
+        none = 0,
+        single = 1,
+        double = 2,
+        curly = 3,
+        dotted = 4,
+        dashed = 5,
+    };
 };
 
 /// Parser parses the attributes from a list of SGR parameters.
@@ -107,7 +116,7 @@ pub const Parser = struct {
 
             3 => return Attribute{ .italic = {} },
 
-            4 => return Attribute{ .underline = {} },
+            4 => return Attribute{ .underline = .single },
 
             5 => return Attribute{ .blink = {} },