Introduce xflex and yflex.

examples/component/homescreen.cpp

@@ -363,7 +363,7 @@ class Tab : public Component {
     return vbox({
         text(L"FTXUI Demo") | bold | hcenter,
         tab_selection.Render() | hcenter,
-        container.Render(),
+        container.Render() | flex,
     });
   }
 };

include/ftxui/dom/elements.hpp

@@ -61,11 +61,20 @@ Element hflow(Elements);
 // -- Flexibility ---
 // Define how to share the remaining space when not all of it is used inside a
 // container.
-Element flex(Element);         // Expand/Minimize if possible/needed.
-Element flex_grow(Element);    // Expand element if possible.
-Element flex_shrink(Element);  // Minimize element if needed.
-Element notflex(Element);      // Reset the flex attribute.
-Element filler();              // A blank expandable element.
+Element flex(Element);          // Expand/Minimize if possible/needed.
+Element flex_grow(Element);     // Expand element if possible.
+Element flex_shrink(Element);   // Minimize element if needed.
+
+Element xflex(Element);         // Expand/Minimize if possible/needed.
+Element xflex_grow(Element);    // Expand element if possible.
+Element xflex_shrink(Element);  // Minimize element if needed.
+
+Element yflex(Element);         // Expand/Minimize if possible/needed.
+Element yflex_grow(Element);    // Expand element if possible.
+Element yflex_shrink(Element);  // Minimize element if needed.
+
+Element notflex(Element);       // Reset the flex attribute.
+Element filler();               // A blank expandable element.
 
 // -- Size override;
 enum Direction { WIDTH, HEIGHT };

src/ftxui/dom/composite_decorator.cpp

@@ -8,11 +8,11 @@
 namespace ftxui {
 
 Element hcenter(Element child) {
-  return hbox(filler(), std::move(child), filler()) | flex_grow;
+  return hbox(filler(), std::move(child), filler()) | xflex_grow;
 }
 
 Element vcenter(Element child) {
-  return vbox(filler(), std::move(child), filler()) | flex_grow;
+  return vbox(filler(), std::move(child), filler()) | yflex_grow;
 }
 
 Element center(Element child) {

src/ftxui/dom/flex.cpp

@@ -14,11 +14,27 @@ void function_flex_grow(Requirement& r) {
   r.flex_grow_y = 1;
 }
 
+void function_xflex_grow(Requirement& r) {
+  r.flex_grow_x = 1;
+}
+
+void function_yflex_grow(Requirement& r) {
+  r.flex_grow_y = 1;
+}
+
 void function_flex_shrink(Requirement& r) {
   r.flex_shrink_x = 1;
   r.flex_shrink_y = 1;
 }
 
+void function_xflex_shrink(Requirement& r) {
+  r.flex_shrink_x = 1;
+}
+
+void function_yflex_shrink(Requirement& r) {
+  r.flex_shrink_y = 1;
+}
+
 void function_flex(Requirement& r) {
   r.flex_grow_x = 1;
   r.flex_grow_y = 1;
@@ -26,6 +42,16 @@ void function_flex(Requirement& r) {
   r.flex_shrink_y = 1;
 }
 
+void function_xflex(Requirement& r) {
+  r.flex_grow_x = 1;
+  r.flex_shrink_x = 1;
+}
+
+void function_yflex(Requirement& r) {
+  r.flex_grow_y = 1;
+  r.flex_shrink_y = 1;
+}
+
 void function_not_flex(Requirement& r) {
   r.flex_grow_x = 0;
   r.flex_grow_y = 0;
@@ -65,14 +91,38 @@ Element flex(Element child) {
   return std::make_shared<Flex>(function_flex, std::move(child));
 }
 
+Element xflex(Element child) {
+  return std::make_shared<Flex>(function_xflex, std::move(child));
+}
+
+Element yflex(Element child) {
+  return std::make_shared<Flex>(function_yflex, std::move(child));
+}
+
 Element flex_grow(Element child) {
   return std::make_shared<Flex>(function_flex_grow, std::move(child));
 }
 
+Element xflex_grow(Element child) {
+  return std::make_shared<Flex>(function_xflex_grow, std::move(child));
+}
+
+Element yflex_grow(Element child) {
+  return std::make_shared<Flex>(function_yflex_grow, std::move(child));
+}
+
 Element flex_shrink(Element child) {
   return std::make_shared<Flex>(function_flex_shrink, std::move(child));
 }
 
+Element xflex_shrink(Element child) {
+  return std::make_shared<Flex>(function_xflex_shrink, std::move(child));
+}
+
+Element yflex_shrink(Element child) {
+  return std::make_shared<Flex>(function_yflex_shrink, std::move(child));
+}
+
 Element notflex(Element child) {
   return std::make_shared<Flex>(function_not_flex, std::move(child));
 }