diff --git a/include/ftxui/dom/requirement.hpp b/include/ftxui/dom/requirement.hpp
index 701959c..84d4419 100644
--- a/include/ftxui/dom/requirement.hpp
+++ b/include/ftxui/dom/requirement.hpp
@@ -11,23 +11,20 @@ namespace ftxui {
 
 struct Requirement {
   // The required size to fully draw the element.
-  struct {
-    int x = 0;
-    int y = 0;
-  } min;
+  int min_x = 0;
+  int min_y = 0;
 
   // How much flexibility is given to the component.
-  struct {
-    int x = 0;
-    int y = 0;
-  } flex;
+  int flex_x = 0;
+  int flex_y = 0;
 
-  // Frame.
+  // Focus management to support the frame/focus/select element.
   enum Selection {
     NORMAL = 0,
     SELECTED = 1,
     FOCUSED = 2,
-  } selection = NORMAL;
+  };
+  Selection selection = NORMAL;
   Box selected_box;
 };
 
diff --git a/src/ftxui/component/screen_interactive.cpp b/src/ftxui/component/screen_interactive.cpp
index 5f4a6e4..5c1971c 100644
--- a/src/ftxui/component/screen_interactive.cpp
+++ b/src/ftxui/component/screen_interactive.cpp
@@ -300,7 +300,7 @@ void ScreenInteractive::Draw(Component* component) {
     case Dimension::TerminalOutput:
       document->ComputeRequirement();
       dimx = Terminal::Size().dimx;
-      dimy = document->requirement().min.y;
+      dimy = document->requirement().min_y;
       break;
     case Dimension::Fullscreen:
       dimx = Terminal::Size().dimx;
@@ -309,8 +309,8 @@ void ScreenInteractive::Draw(Component* component) {
     case Dimension::FitComponent:
       auto terminal = Terminal::Size();
       document->ComputeRequirement();
-      dimx = std::min(document->requirement().min.x, terminal.dimx);
-      dimy = std::min(document->requirement().min.y, terminal.dimy);
+      dimx = std::min(document->requirement().min_x, terminal.dimx);
+      dimy = std::min(document->requirement().min_y, terminal.dimy);
       break;
   }
 
diff --git a/src/ftxui/dom/border.cpp b/src/ftxui/dom/border.cpp
index 173da77..20a1b33 100644
--- a/src/ftxui/dom/border.cpp
+++ b/src/ftxui/dom/border.cpp
@@ -27,11 +27,11 @@ class Border : public Node {
   void ComputeRequirement() override {
     Node::ComputeRequirement();
     requirement_ = children[0]->requirement();
-    requirement_.min.x += 2;
-    requirement_.min.y += 2;
+    requirement_.min_x += 2;
+    requirement_.min_y += 2;
     if (children.size() == 2) {
-      requirement_.min.x =
-          std::max(requirement_.min.x, children[1]->requirement().min.x + 2);
+      requirement_.min_x =
+          std::max(requirement_.min_x, children[1]->requirement().min_x + 2);
     }
     requirement_.selected_box.x_min++;
     requirement_.selected_box.x_max++;
diff --git a/src/ftxui/dom/dbox.cpp b/src/ftxui/dom/dbox.cpp
index 8dfda72..4a1f91b 100644
--- a/src/ftxui/dom/dbox.cpp
+++ b/src/ftxui/dom/dbox.cpp
@@ -15,16 +15,16 @@ class DBox : public Node {
   ~DBox() {}
 
   void ComputeRequirement() override {
-    requirement_.min.x = 0;
-    requirement_.min.y = 0;
-    requirement_.flex.x = 1;
-    requirement_.flex.y = 0;
+    requirement_.min_x = 0;
+    requirement_.min_y = 0;
+    requirement_.flex_x = 1;
+    requirement_.flex_y = 0;
     for (auto& child : children) {
       child->ComputeRequirement();
-      requirement_.min.x =
-          std::max(requirement_.min.x, child->requirement().min.x);
-      requirement_.min.y =
-          std::max(requirement_.min.y, child->requirement().min.y);
+      requirement_.min_x =
+          std::max(requirement_.min_x, child->requirement().min_x);
+      requirement_.min_y =
+          std::max(requirement_.min_y, child->requirement().min_y);
 
       if (requirement_.selection < child->requirement().selection) {
         requirement_.selection = child->requirement().selection;
diff --git a/src/ftxui/dom/flex.cpp b/src/ftxui/dom/flex.cpp
index 22910b0..10d6bed 100644
--- a/src/ftxui/dom/flex.cpp
+++ b/src/ftxui/dom/flex.cpp
@@ -13,14 +13,14 @@ class Flex : public Node {
   Flex(Element child) : Node(unpack(std::move(child))) {}
   ~Flex() override {}
   void ComputeRequirement() override {
-    requirement_.min.x = 0;
-    requirement_.min.y = 0;
+    requirement_.min_x = 0;
+    requirement_.min_y = 0;
     if (!children.empty()) {
       children[0]->ComputeRequirement();
       requirement_ = children[0]->requirement();
     }
-    requirement_.flex.x = 1;
-    requirement_.flex.y = 1;
+    requirement_.flex_x = 1;
+    requirement_.flex_y = 1;
   }
 
   void SetBox(Box box) override {
@@ -36,14 +36,14 @@ class NotFlex : public Flex {
   NotFlex(Element child) : Flex(std::move(child)) {}
   ~NotFlex() override {}
   void ComputeRequirement() override {
-    requirement_.min.x = 0;
-    requirement_.min.y = 0;
+    requirement_.min_x = 0;
+    requirement_.min_y = 0;
     if (!children.empty()) {
       children[0]->ComputeRequirement();
       requirement_ = children[0]->requirement();
     }
-    requirement_.flex.x = 0;
-    requirement_.flex.y = 0;
+    requirement_.flex_x = 0;
+    requirement_.flex_y = 0;
   }
 };
 
diff --git a/src/ftxui/dom/frame.cpp b/src/ftxui/dom/frame.cpp
index d2dbde7..e0dceaa 100644
--- a/src/ftxui/dom/frame.cpp
+++ b/src/ftxui/dom/frame.cpp
@@ -23,8 +23,8 @@ class Select : public Node {
     auto& selected_box = requirement_.selected_box;
     selected_box.x_min = 0;
     selected_box.y_min = 0;
-    selected_box.x_max = requirement_.min.x;
-    selected_box.y_max = requirement_.min.y;
+    selected_box.x_max = requirement_.min_x;
+    selected_box.y_max = requirement_.min_y;
     requirement_.selection = Requirement::SELECTED;
   };
 
@@ -76,8 +76,8 @@ class Frame : public Node {
     int external_dimx = box.x_max - box.x_min;
     int external_dimy = box.y_max - box.y_min;
 
-    int internal_dimx = std::max(requirement_.min.x, external_dimx);
-    int internal_dimy = std::max(requirement_.min.y, external_dimy);
+    int internal_dimx = std::max(requirement_.min_x, external_dimx);
+    int internal_dimy = std::max(requirement_.min_y, external_dimy);
 
     auto& selected_box = requirement_.selected_box;
     int focused_dimx = selected_box.x_max - selected_box.x_min;
@@ -96,13 +96,13 @@ class Frame : public Node {
 
     // int dx = box.x_max - box.x_min;
     // int dy = box.y_max - box.y_min;
-    // int cdx = std::min(children[0].requirement().min.x
+    // int cdx = std::min(children[0].requirement().min_x
 
     // Box children_box;
     // children_box.x_min =
-    // if (box.x_max - box.x_min >= children[0].requirement().min.x && //
+    // if (box.x_max - box.x_min >= children[0].requirement().min_x && //
 
-    // box.y_max - box.y_min >= children[0].requirement().min.y) {
+    // box.y_max - box.y_min >= children[0].requirement().min_y) {
     // children_[0]->SetBox(box);
     // dx = 0;
     // dy = 0;
diff --git a/src/ftxui/dom/gauge.cpp b/src/ftxui/dom/gauge.cpp
index b16edf2..f7c174b 100644
--- a/src/ftxui/dom/gauge.cpp
+++ b/src/ftxui/dom/gauge.cpp
@@ -15,8 +15,8 @@ class Gauge : public Node {
   ~Gauge() override {}
 
   void ComputeRequirement() override {
-    requirement_.flex.x = 1;
-    requirement_.min.y = 1;
+    requirement_.flex_x = 1;
+    requirement_.min_y = 1;
   }
 
   void Render(Screen& screen) override {
diff --git a/src/ftxui/dom/graph.cpp b/src/ftxui/dom/graph.cpp
index b8035e6..81ff081 100644
--- a/src/ftxui/dom/graph.cpp
+++ b/src/ftxui/dom/graph.cpp
@@ -14,10 +14,10 @@ class Graph : public Node {
   ~Graph() override {}
 
   void ComputeRequirement() override {
-    requirement_.flex.x = 1;
-    requirement_.flex.y = 1;
-    requirement_.min.x = 1;
-    requirement_.min.y = 1;
+    requirement_.flex_x = 1;
+    requirement_.flex_y = 1;
+    requirement_.min_x = 1;
+    requirement_.min_y = 1;
   }
 
   void Render(Screen& screen) override {
diff --git a/src/ftxui/dom/hbox.cpp b/src/ftxui/dom/hbox.cpp
index 6004e8a..9b702ed 100644
--- a/src/ftxui/dom/hbox.cpp
+++ b/src/ftxui/dom/hbox.cpp
@@ -15,21 +15,21 @@ class HBox : public Node {
   ~HBox() {}
 
   void ComputeRequirement() override {
-    requirement_.min.x = 0;
-    requirement_.min.y = 0;
-    requirement_.flex.x = 1;
-    requirement_.flex.y = 0;
+    requirement_.min_x = 0;
+    requirement_.min_y = 0;
+    requirement_.flex_x = 1;
+    requirement_.flex_y = 0;
     for (auto& child : children) {
       child->ComputeRequirement();
       if (requirement_.selection < child->requirement().selection) {
         requirement_.selection = child->requirement().selection;
         requirement_.selected_box = child->requirement().selected_box;
-        requirement_.selected_box.x_min += requirement_.min.x;
-        requirement_.selected_box.x_max += requirement_.min.x;
+        requirement_.selected_box.x_min += requirement_.min_x;
+        requirement_.selected_box.x_max += requirement_.min_x;
       }
-      requirement_.min.x += child->requirement().min.x;
-      requirement_.min.y =
-          std::max(requirement_.min.y, child->requirement().min.y);
+      requirement_.min_x += child->requirement().min_x;
+      requirement_.min_y =
+          std::max(requirement_.min_y, child->requirement().min_y);
     }
   }
 
@@ -38,10 +38,10 @@ class HBox : public Node {
 
     int flex_sum = 0;
     for (auto& child : children)
-      flex_sum += child->requirement().flex.x;
+      flex_sum += child->requirement().flex_x;
 
     int space = box.x_max - box.x_min + 1;
-    int extra_space = space - requirement_.min.x;
+    int extra_space = space - requirement_.min_x;
 
     int remaining_flex = flex_sum;
     int remaining_extra_space = extra_space;
@@ -51,13 +51,13 @@ class HBox : public Node {
       Box child_box = box;
       child_box.x_min = x;
 
-      child_box.x_max = x + child->requirement().min.x - 1;
+      child_box.x_max = x + child->requirement().min_x - 1;
 
-      if (child->requirement().flex.x) {
-        int added_space = remaining_extra_space * child->requirement().flex.x /
+      if (child->requirement().flex_x) {
+        int added_space = remaining_extra_space * child->requirement().flex_x /
                           remaining_flex;
         remaining_extra_space -= added_space;
-        remaining_flex -= child->requirement().flex.x;
+        remaining_flex -= child->requirement().flex_x;
         child_box.x_max += added_space;
       }
       child_box.x_max = std::min(child_box.x_max, box.x_max);
diff --git a/src/ftxui/dom/hflow.cpp b/src/ftxui/dom/hflow.cpp
index 94987ef..fb0d3ca 100644
--- a/src/ftxui/dom/hflow.cpp
+++ b/src/ftxui/dom/hflow.cpp
@@ -15,10 +15,10 @@ class HFlow : public Node {
   ~HFlow() {}
 
   void ComputeRequirement() override {
-    requirement_.min.x = 0;
-    requirement_.min.y = 0;
-    requirement_.flex.x = 1;
-    requirement_.flex.y = 1;
+    requirement_.min_x = 0;
+    requirement_.min_y = 0;
+    requirement_.flex_x = 1;
+    requirement_.flex_y = 1;
     for (auto& child : children)
       child->ComputeRequirement();
   }
@@ -35,25 +35,25 @@ class HFlow : public Node {
       Requirement requirement = child->requirement();
 
       // Does it fit the end of the row?
-      if (x + requirement.min.x > box.x_max) {
+      if (x + requirement.min_x > box.x_max) {
         // No? Use the next row.
         x = box.x_min;
         y = y_next;
       }
 
       // Does the current row big enough to contain the element?
-      if (y + requirement.min.y > box.y_max + 1)
+      if (y + requirement.min_y > box.y_max + 1)
         break;  // No? Ignore the element.
 
       Box children_box;
       children_box.x_min = x;
-      children_box.x_max = x + requirement.min.x - 1;
+      children_box.x_max = x + requirement.min_x - 1;
       children_box.y_min = y;
-      children_box.y_max = y + requirement.min.y - 1;
+      children_box.y_max = y + requirement.min_y - 1;
       child->SetBox(children_box);
 
-      x = x + requirement.min.x;
-      y_next = std::max(y_next, y + requirement.min.y);
+      x = x + requirement.min_x;
+      y_next = std::max(y_next, y + requirement.min_y);
     }
   }
 };
diff --git a/src/ftxui/dom/separator.cpp b/src/ftxui/dom/separator.cpp
index cc9286a..4ae2a7a 100644
--- a/src/ftxui/dom/separator.cpp
+++ b/src/ftxui/dom/separator.cpp
@@ -13,8 +13,8 @@ class Separator : public Node {
   Separator() {}
   ~Separator() override {}
   void ComputeRequirement() override {
-    requirement_.min.x = 1;
-    requirement_.min.y = 1;
+    requirement_.min_x = 1;
+    requirement_.min_y = 1;
   }
 
   void Render(Screen& screen) override {
diff --git a/src/ftxui/dom/size.cpp b/src/ftxui/dom/size.cpp
index d6fa767..1a59ca0 100644
--- a/src/ftxui/dom/size.cpp
+++ b/src/ftxui/dom/size.cpp
@@ -23,7 +23,7 @@ class Size : public Node {
     Node::ComputeRequirement();
     requirement_ = children[0]->requirement();
 
-    auto& value = direction_ == WIDTH ? requirement_.min.x : requirement_.min.y;
+    auto& value = direction_ == WIDTH ? requirement_.min_x : requirement_.min_y;
 
     switch (constraint_) {
       case LESS_THAN:
@@ -38,9 +38,9 @@ class Size : public Node {
     }
 
     if (direction_ == WIDTH)
-      requirement_.flex.x = 0;
+      requirement_.flex_x = 0;
     else
-      requirement_.flex.y = 0;
+      requirement_.flex_y = 0;
   }
 
   void SetBox(Box box) override {
diff --git a/src/ftxui/dom/text.cpp b/src/ftxui/dom/text.cpp
index ba81010..ec38a24 100644
--- a/src/ftxui/dom/text.cpp
+++ b/src/ftxui/dom/text.cpp
@@ -15,8 +15,8 @@ class Text : public Node {
   ~Text() {}
 
   void ComputeRequirement() override {
-    requirement_.min.x = wstring_width(text_);
-    requirement_.min.y = 1;
+    requirement_.min_x = wstring_width(text_);
+    requirement_.min_y = 1;
   }
 
   void Render(Screen& screen) override {
diff --git a/src/ftxui/dom/vbox.cpp b/src/ftxui/dom/vbox.cpp
index a7ec7ef..8f67189 100644
--- a/src/ftxui/dom/vbox.cpp
+++ b/src/ftxui/dom/vbox.cpp
@@ -16,21 +16,21 @@ class VBox : public Node {
   ~VBox() {}
 
   void ComputeRequirement() {
-    requirement_.min.x = 0;
-    requirement_.min.y = 0;
-    requirement_.flex.x = 0;
-    requirement_.flex.y = 1;
+    requirement_.min_x = 0;
+    requirement_.min_y = 0;
+    requirement_.flex_x = 0;
+    requirement_.flex_y = 1;
     for (auto& child : children) {
       child->ComputeRequirement();
       if (requirement_.selection < child->requirement().selection) {
         requirement_.selection = child->requirement().selection;
         requirement_.selected_box = child->requirement().selected_box;
-        requirement_.selected_box.y_min += requirement_.min.y;
-        requirement_.selected_box.y_max += requirement_.min.y;
+        requirement_.selected_box.y_min += requirement_.min_y;
+        requirement_.selected_box.y_max += requirement_.min_y;
       }
-      requirement_.min.y += child->requirement().min.y;
-      requirement_.min.x =
-          std::max(requirement_.min.x, child->requirement().min.x);
+      requirement_.min_y += child->requirement().min_y;
+      requirement_.min_x =
+          std::max(requirement_.min_x, child->requirement().min_x);
     }
   }
 
@@ -39,10 +39,10 @@ class VBox : public Node {
 
     int flex_sum = 0;
     for (auto& child : children)
-      flex_sum += child->requirement().flex.y;
+      flex_sum += child->requirement().flex_y;
 
     int space = box.y_max - box.y_min + 1;
-    int extra_space = space - requirement_.min.y;
+    int extra_space = space - requirement_.min_y;
 
     int remaining_flex = flex_sum;
     int remaining_extra_space = extra_space;
@@ -52,13 +52,13 @@ class VBox : public Node {
       Box child_box = box;
       child_box.y_min = y;
 
-      child_box.y_max = y + child->requirement().min.y - 1;
+      child_box.y_max = y + child->requirement().min_y - 1;
 
-      if (child->requirement().flex.y) {
-        int added_space = remaining_extra_space * child->requirement().flex.y /
+      if (child->requirement().flex_y) {
+        int added_space = remaining_extra_space * child->requirement().flex_y /
                           remaining_flex;
         remaining_extra_space -= added_space;
-        remaining_flex -= child->requirement().flex.y;
+        remaining_flex -= child->requirement().flex_y;
         child_box.y_max += added_space;
       }
       child_box.y_max = std::min(child_box.y_max, box.y_max);
diff --git a/src/ftxui/screen/screen.cpp b/src/ftxui/screen/screen.cpp
index a310524..9dd14c2 100644
--- a/src/ftxui/screen/screen.cpp
+++ b/src/ftxui/screen/screen.cpp
@@ -55,8 +55,8 @@ Dimension Dimension::Fixed(int v) {
 Dimension Dimension::Fit(std::shared_ptr<Node>& e) {
   e->ComputeRequirement();
   Terminal::Dimensions size = Terminal::Size();
-  return Dimension{std::min(e->requirement().min.x, size.dimx),
-                   std::min(e->requirement().min.y, size.dimy)};
+  return Dimension{std::min(e->requirement().min_x, size.dimx),
+                   std::min(e->requirement().min_y, size.dimy)};
 }
 
 Dimension Dimension::Full() {