libui: Add a basic Label component

libui/CMakeLists.txt

@@ -16,6 +16,7 @@ set(SOURCES
     src/Alignment.cpp
     src/Container.cpp
     src/Button.cpp
+    src/Label.cpp
 )
 
 add_library(ui ${SOURCES})

libui/include/ui/Label.h

@@ -0,0 +1,41 @@
+/**
+ * @file Label.h
+ * @author apio (cloudapio.eu)
+ * @brief A simple one-line text widget.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <ui/Alignment.h>
+#include <ui/Font.h>
+#include <ui/Widget.h>
+
+namespace ui
+{
+    /**
+     * @brief Displays one line of text.
+     *
+     * This component does not handle newlines.
+     */
+    class Label final : public Widget
+    {
+      public:
+        Label(StringView text, VerticalAlignment valign = VerticalAlignment::Center,
+              HorizontalAlignment halign = HorizontalAlignment::Center, SharedPtr<Font> font = Font::default_font());
+
+        void set_text(StringView text)
+        {
+            m_text = text;
+        }
+
+        Result<void> draw(Canvas& canvas) override;
+
+      private:
+        StringView m_text;
+        VerticalAlignment m_valign;
+        HorizontalAlignment m_halign;
+        SharedPtr<Font> m_font;
+    };
+}

libui/src/Label.cpp

@@ -0,0 +1,36 @@
+/**
+ * @file Label.cpp
+ * @author apio (cloudapio.eu)
+ * @brief A simple one-line text widget.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <luna/Utf8.h>
+#include <ui/Label.h>
+
+namespace ui
+{
+    Label::Label(StringView text, VerticalAlignment valign, HorizontalAlignment halign, SharedPtr<Font> font)
+        : m_text(text), m_valign(valign), m_halign(halign), m_font(font)
+    {
+    }
+
+    Result<void> Label::draw(Canvas& canvas)
+    {
+        ui::Rect contained;
+        contained.pos = { 0, 0 };
+        contained.width = static_cast<int>(m_text.length() * m_font->width());
+        contained.height = m_font->height();
+        auto subcanvas =
+            canvas.subcanvas(ui::align({ 0, 0, m_rect.width, m_rect.height }, contained, m_valign, m_halign));
+
+        Utf8StringDecoder decoder(m_text.chars());
+        wchar_t buf[4096];
+        TRY(decoder.decode(buf, sizeof(buf)));
+
+        m_font->render(buf, ui::BLACK, subcanvas);
+        return {};
+    }
+}