config: add background-opacity and float parsing for config

src/cli_args.zig

@@ -144,6 +144,11 @@ fn parseIntoField(
                     0,
                 ),
 
+                f64 => try std.fmt.parseFloat(
+                    f64,
+                    value orelse return error.ValueRequired,
+                ),
+
                 else => unreachable,
             };
 
@@ -298,6 +303,20 @@ test "parseIntoField: unsigned numbers" {
     try testing.expectEqual(@as(u8, 1), data.u8);
 }
 
+test "parseIntoField: floats" {
+    const testing = std.testing;
+    var arena = ArenaAllocator.init(testing.allocator);
+    defer arena.deinit();
+    const alloc = arena.allocator();
+
+    var data: struct {
+        f64: f64,
+    } = undefined;
+
+    try parseIntoField(@TypeOf(data), alloc, &data, "f64", "1");
+    try testing.expectEqual(@as(f64, 1.0), data.f64);
+}
+
 test "parseIntoField: optional field" {
     const testing = std.testing;
     var arena = ArenaAllocator.init(testing.allocator);

src/config.zig

@@ -63,6 +63,10 @@ pub const Config = struct {
     /// The color of the cursor. If this is not set, a default will be chosen.
     @"cursor-color": ?Color = null,
 
+    /// The opacity level (opposite of transparency) of the background.
+    /// A value of 1 is fully opaque and a value of 0 is fully transparent.
+    @"background-opacity": f64 = 1.0,
+
     /// The command to run, usually a shell. If this is not an absolute path,
     /// it'll be looked up in the PATH. If this is not set, a default will
     /// be looked up from your system. The rules for the default lookup are:
@@ -754,6 +758,7 @@ pub const Config = struct {
         switch (@typeInfo(T)) {
             inline .Bool,
             .Int,
+            .Float,
             => return src,
 
             .Optional => |info| return try cloneValue(
@@ -879,6 +884,7 @@ fn equal(comptime T: type, old: T, new: T) bool {
 
         inline .Bool,
         .Int,
+        .Float,
         .Enum,
         => return old == new,