Start UI core layout value tests

src/ui_core/layout_value.h

@@ -0,0 +1,24 @@
+#pragma once
+
+#include "foundation/result.h"
+
+#include <cstdint>
+#include <string_view>
+
+namespace pp::ui {
+
+enum class LayoutLengthKind : std::uint8_t {
+    auto_value,
+    pixels,
+    percent,
+};
+
+struct LayoutLength {
+    LayoutLengthKind kind = LayoutLengthKind::auto_value;
+    std::uint32_t value = 0;
+};
+
+[[nodiscard]] pp::foundation::Result<LayoutLength> parse_layout_length(std::string_view text) noexcept;
+[[nodiscard]] const char* layout_length_kind_name(LayoutLengthKind kind) noexcept;
+
+}