defines a QuickTerminalSize type, for use with the quick-terminal-siz…

…e config

It's not yet a full implementation, but it's a start

WIP of #2384

src/config/Config.zig

@@ -1270,6 +1270,10 @@ keybind: Keybinds = .{},
 /// by the operating system.
 @"quick-terminal-screen": QuickTerminalScreen = .main,
 
+/// TODO: DOCS
+/// https://github.com/ghostty-org/ghostty/issues/2384#issuecomment-2401129283
+@"quick-terminal-size": QuickTerminalSize = .{ .value = 0.25, .mode = QuickTerminalSizeMode.percentage },
+
 /// Whether to enable shell integration auto-injection or not. Shell integration
 /// greatly enhances the terminal experience by enabling a number of features:
 ///
@@ -4832,3 +4836,103 @@ test "test entryFormatter" {
     try p.formatEntry(formatterpkg.entryFormatter("a", buf.writer()));
     try std.testing.expectEqualStrings("a = 584y 49w 23h 34m 33s 709ms 551µs 615ns\n", buf.items);
 }
+
+/// Initial implementation, only using 1 dimension for now
+/// Per https://github.com/ghostty-org/ghostty/issues/2384, we may eventually
+/// support 2 dimensions
+pub const QuickTerminalSizeMode = enum {
+    pixels,
+    percentage,
+};
+
+pub const QuickTerminalSize = struct {
+    const Self = @This();
+
+    value: f64 = 0,
+    mode: QuickTerminalSizeMode = QuickTerminalSizeMode.percentage,
+
+    pub fn clone(self: Self, _: Allocator) !Self {
+        return self;
+    }
+
+    pub fn equal(self: Self, other: Self) bool {
+        return std.meta.eql(self, other);
+    }
+
+    pub fn parseCLI(input_: ?[]const u8) !QuickTerminalSize {
+        const input = input_ orelse return error.ValueRequired;
+
+        // strip the whitespace and see what we're left with
+        const whitespace = " \t";
+        var trimmedInput = std.mem.trim(u8, input, whitespace);
+
+        // 0 chars: trivially invalid
+        // 1 char:  invalid because there's no room for both a number and a unit
+        if (trimmedInput.len <= 1) {
+            return error.InvalidValue;
+        }
+
+        var mode: QuickTerminalSizeMode = undefined;
+
+        if (trimmedInput[trimmedInput.len - 1] == '%') {
+            mode = QuickTerminalSizeMode.percentage;
+            trimmedInput = trimmedInput[0..(trimmedInput.len - 1)];
+        } else if (trimmedInput.len >= 2 and std.mem.endsWith(u8, trimmedInput, "px")) {
+            mode = QuickTerminalSizeMode.pixels;
+            trimmedInput = trimmedInput[0..(trimmedInput.len - 2)];
+        } else {
+            return error.InvalidValue;
+        }
+
+        var value = std.fmt.parseFloat(
+            f64,
+            trimmedInput,
+        ) catch return error.InvalidValue;
+
+        if (mode == QuickTerminalSizeMode.percentage) {
+            value = value / 100;
+        }
+
+        return .{ .value = value, .mode = mode };
+    }
+
+    pub fn formatEntry(self: Self, formatter: anytype) !void {
+        // placeholder for now
+        _ = self;
+        _ = formatter;
+    }
+
+    // Reminder for myself: zig build test -Dtest-filter=QuickTerminalSize
+    test "parse QuickTerminalSize" {
+        const testing = std.testing;
+
+        {
+            const v = try QuickTerminalSize.parseCLI("25%");
+            try testing.expectEqual(QuickTerminalSize{
+                .value = 0.25,
+                .mode = QuickTerminalSizeMode.percentage,
+            }, v);
+        }
+
+        {
+            const v = try QuickTerminalSize.parseCLI("    42%    ");
+            try testing.expectEqual(QuickTerminalSize{
+                .value = 0.42,
+                .mode = QuickTerminalSizeMode.percentage,
+            }, v);
+        }
+
+        {
+            const v = try QuickTerminalSize.parseCLI("42px");
+            try testing.expectEqual(QuickTerminalSize{
+                .value = 42,
+                .mode = QuickTerminalSizeMode.pixels,
+            }, v);
+        }
+
+        try testing.expectError(error.ValueRequired, QuickTerminalSize.parseCLI(null));
+        try testing.expectError(error.InvalidValue, QuickTerminalSize.parseCLI(""));
+        try testing.expectError(error.InvalidValue, QuickTerminalSize.parseCLI("    "));
+        try testing.expectError(error.InvalidValue, QuickTerminalSize.parseCLI("a"));
+    }
+};