refactor(font): return TextMesh from Font::vertices to include bounding box

Replace the plain vertex vector with a TextMesh struct that carries width, height, and min coordinates. Update Label to compute and store these values immediately on text change (removing lazy dirty update). Fix Button's width/height to factor in scale and use concrete widget types for background and foreground.

src/ui/label.cpp

@@ -7,7 +7,7 @@ Label::Label(const std::string& id) : Widget(id) {}
 Label::Label() {}
 Label& Label::set_text(std::string_view text) {
     m_text.text = text;
-    m_dirty = true;
+    update_vertices();
     return *this;
 }
 
@@ -18,25 +18,30 @@ Label& Label::set_color(Color color) {
 
 void Label::update(float dt) { on_update(dt); }
 
-void Label::on_update(float dt) {
-    (void)dt;
-    if (m_dirty) {
-        update_vertices();
-        m_dirty = false;
-    }
-}
+void Label::on_update(float dt) { (void)dt; }
 
 void Label::render(Renderer& renderer) { on_render(renderer); }
 
 void Label::on_render(Renderer& renderer) { renderer.render_lable(*this); }
 
 void Label::update_vertices() {
-    m_data.m_vertices = Font::vertices(m_text.text);
+    auto textmesh = Font::vertices(m_text.text);
+    m_data.m_vertices = std::move(textmesh.vertices);
+
+    m_offset_x = textmesh.min_x;
+    m_offset_y = textmesh.min_y;
+    m_width = textmesh.width;
+    m_height = textmesh.height;
+
     m_data.update_sum();
     m_data.upload();
 }
 
 const UIVertexData& Label::data() const { return m_data; }
 const TextStyle& Label::text_style() const { return m_text; }
+float Label::width() const { return m_width; }
+float Label::height() const { return m_height; }
+float Label::offset_x() const { return m_offset_x; }
+float Label::offset_y() const { return m_offset_y; }
 
 } // namespace Cubed