Add hflow.

examples/dom/hflow.cpp

@@ -0,0 +1,51 @@
+#include "ftxui/screen/screen.hpp"
+#include "ftxui/screen/string.hpp"
+#include "ftxui/dom/elements.hpp"
+#include <iostream>
+
+int main(int argc, const char *argv[])
+{
+  using namespace ftxui;
+  auto make_box = [](size_t dimx, size_t dimy) {
+    std::wstring title = to_wstring(dimx) + L"x" + to_wstring(dimy);
+    return
+      window(
+        text(title) | hcenter | bold,
+        text(L"content") | hcenter | dim
+      ) | size(WIDTH, EQUAL, dimx)
+        | size(HEIGHT, EQUAL, dimy)
+        ;
+  };
+
+  auto document =
+    hflow(
+      make_box(7,7),
+      make_box(7,5),
+      make_box(5,7),
+      make_box(10,4),
+      make_box(10,4),
+      make_box(10,4),
+      make_box(10,4),
+      make_box(11,4),
+      make_box(11,4),
+      make_box(11,4),
+      make_box(11,4),
+      make_box(12,4),
+      make_box(12,5),
+      make_box(12,4),
+      make_box(13,4),
+      make_box(13,3),
+      make_box(13,3),
+      make_box(10,3)
+    ) | size(WIDTH, GREATER_THAN, 20)
+      | border
+      | size(HEIGHT, GREATER_THAN, 30)
+      | size(WIDTH, LESS_THAN, 50)
+      ;
+
+  auto screen = Screen::TerminalOutput(document);
+  Render(screen, document.get());
+  std::cout << screen.ToString() << std::endl;
+
+  return 0;
+}