Feature: hscroll_indicator (#753)

This is the symetrical of `vscroll_indicator`.

Requested by @ibrahimnasson.

Fixed:https://github.com/ArthurSonzogni/FTXUI/issues/752

src/ftxui/dom/color.cpp

@@ -12,7 +12,7 @@
 
 namespace ftxui {
 
-  namespace {
+namespace {
 class BgColor : public NodeDecorator {
  public:
   BgColor(Element child, Color color)

src/ftxui/dom/dbox.cpp

@@ -13,7 +13,7 @@
 
 namespace ftxui {
 
-  namespace {
+namespace {
 class DBox : public Node {
  public:
   explicit DBox(Elements children) : Node(std::move(children)) {}

src/ftxui/dom/frame.cpp

@@ -37,7 +37,6 @@ class Select : public Node {
   }
 };
 
-
 class Focus : public Select {
  public:
   using Select::Select;
@@ -143,7 +142,6 @@ class FocusCursor : public Focus {
   Screen::Cursor::Shape shape_;
 };
 
-
 }  // namespace
 
 /// @brief Set the `child` to be the one selected among its siblings.

src/ftxui/dom/gauge.cpp

@@ -159,7 +159,7 @@ class Gauge : public Node {
   Direction direction_;
 };
 
-}  // namespace ftxui
+}  // namespace
 
 /// @brief Draw a high definition progress bar progressing in specified
 /// direction.

src/ftxui/dom/scroll_indicator.cpp

@@ -7,7 +7,7 @@
 #include <utility>    // for move
 #include <vector>     // for __alloc_traits<>::value_type
 
-#include "ftxui/dom/elements.hpp"        // for Element, vscroll_indicator
+#include "ftxui/dom/elements.hpp"  // for Element, vscroll_indicator, hscroll_indicator
 #include "ftxui/dom/node.hpp"            // for Node, Elements
 #include "ftxui/dom/node_decorator.hpp"  // for NodeDecorator
 #include "ftxui/dom/requirement.hpp"     // for Requirement
@@ -16,7 +16,7 @@
 
 namespace ftxui {
 
-/// @brief Add a filter that will invert the foreground and the background
+/// @brief Display a vertical scrollbar to the right.
 /// colors.
 /// @ingroup dom
 Element vscroll_indicator(Element child) {
@@ -72,4 +72,61 @@ Element vscroll_indicator(Element child) {
   return std::make_shared<Impl>(std::move(child));
 }
 
+/// @brief Display an horizontal scrollbar to the bottom.
+/// colors.
+/// @ingroup dom
+Element hscroll_indicator(Element child) {
+  class Impl : public NodeDecorator {
+    using NodeDecorator::NodeDecorator;
+
+    void ComputeRequirement() override {
+      NodeDecorator::ComputeRequirement();
+      requirement_ = children_[0]->requirement();
+      requirement_.min_y++;
+    }
+
+    void SetBox(Box box) override {
+      box_ = box;
+      box.y_max--;
+      children_[0]->SetBox(box);
+    }
+
+    void Render(Screen& screen) final {
+      NodeDecorator::Render(screen);
+
+      const Box& stencil = screen.stencil;
+
+      const int size_inner = box_.x_max - box_.x_min;
+      if (size_inner <= 0) {
+        return;
+      }
+      const int size_outter = stencil.x_max - stencil.x_min + 1;
+      if (size_outter >= size_inner) {
+        return;
+      }
+
+      int size = 2 * size_outter * size_outter / size_inner;
+      size = std::max(size, 1);
+
+      const int start_x =
+          2 * stencil.x_min +  //
+          2 * (stencil.x_min - box_.x_min) * size_outter / size_inner;
+
+      const int y = stencil.y_max;
+      for (int x = stencil.x_min; x <= stencil.x_max; ++x) {
+        const int x_left = 2 * x + 0;
+        const int x_right = 2 * x + 1;
+        const bool left = (start_x <= x_left) && (x_left <= start_x + size);
+        const bool right = (start_x <= x_right) && (x_right <= start_x + size);
+
+        const char* c =
+            left ? (right ? "─" : "╴") : (right ? "╶" : " ");  // NOLINT
+        screen.PixelAt(x, y) = Pixel();
+        screen.PixelAt(x, y).character = c;
+      }
+    }
+  };
+  return std::make_shared<Impl>(std::move(child));
+}
+
 }  // namespace ftxui

src/ftxui/dom/scroll_indicator_test.cpp

@@ -26,6 +26,18 @@ Element MakeVerticalList(int focused_index, int n) {
   return vbox(std::move(list)) | vscroll_indicator | frame | border;
 }
 
+Element MakeHorizontalList(int focused_index, int n) {
+  Elements list;
+  for (int i = 0; i < n; ++i) {
+    auto element = text(std::to_string(i));
+    if (i == focused_index) {
+      element |= focus;
+    }
+    list.push_back(element);
+  }
+  return hbox(std::move(list)) | hscroll_indicator | frame | border;
+}
+
 std::string PrintVerticalList(int focused_index, int n) {
   auto element = MakeVerticalList(focused_index, n);
   Screen screen(6, 6);
@@ -33,9 +45,16 @@ std::string PrintVerticalList(int focused_index, int n) {
   return screen.ToString();
 }
 
+std::string PrintHorizontalList(int focused_index, int n) {
+  auto element = MakeHorizontalList(focused_index, n);
+  Screen screen(6, 4);
+  Render(screen, element);
+  return screen.ToString();
+}
+
 }  // namespace
 
-TEST(ScrollIndicator, Basic) {
+TEST(ScrollIndicator, BasicVertical) {
   EXPECT_EQ(PrintVerticalList(0, 10),
             "╭────╮\r\n"
             "│0  ┃│\r\n"
@@ -108,6 +127,56 @@ TEST(ScrollIndicator, Basic) {
             "╰────╯");
 }
 
+TEST(ScrollIndicator, BasicHorizontal) {
+  EXPECT_EQ(PrintHorizontalList(0, 10),
+            "╭────╮\r\n"
+            "│0123│\r\n"
+            "│──  │\r\n"
+            "╰────╯");
+
+  EXPECT_EQ(PrintHorizontalList(1, 10),
+            "╭────╮\r\n"
+            "│0123│\r\n"
+            "│──  │\r\n"
+            "╰────╯");
+
+  EXPECT_EQ(PrintHorizontalList(2, 10),
+            "╭────╮\r\n"
+            "│1234│\r\n"
+            "│──  │\r\n"
+            "╰────╯");
+  EXPECT_EQ(PrintHorizontalList(3, 10),
+            "╭────╮\r\n"
+            "│2345│\r\n"
+            "│╶─╴ │\r\n"
+            "╰────╯");
+  EXPECT_EQ(PrintHorizontalList(4, 10),
+            "╭────╮\r\n"
+            "│3456│\r\n"
+            "│ ── │\r\n"
+            "╰────╯");
+  EXPECT_EQ(PrintHorizontalList(5, 10),
+            "╭────╮\r\n"
+            "│4567│\r\n"
+            "│ ╶─╴│\r\n"
+            "╰────╯");
+  EXPECT_EQ(PrintHorizontalList(6, 10),
+            "╭────╮\r\n"
+            "│5678│\r\n"
+            "│  ──│\r\n"
+            "╰────╯");
+  EXPECT_EQ(PrintHorizontalList(7, 10),
+            "╭────╮\r\n"
+            "│6789│\r\n"
+            "│  ──│\r\n"
+            "╰────╯");
+  EXPECT_EQ(PrintHorizontalList(8, 10),
+            "╭────╮\r\n"
+            "│6789│\r\n"
+            "│  ──│\r\n"
+            "╰────╯");
+}
+
 namespace {
 
 Element MakeHorizontalFlexboxList(int n) {

src/ftxui/dom/size.cpp

@@ -79,7 +79,7 @@ class Size : public Node {
   Constraint constraint_;
   int value_;
 };
-} // namespace
+}  // namespace
 
 /// @brief Apply a constraint on the size of an element.
 /// @param direction Whether the WIDTH of the HEIGHT of the element must be

src/ftxui/dom/table.cpp

@@ -47,7 +47,6 @@ Table::Table() {
   Initialize({});
 }
 
-
 /// @brief Create a table from a vector of vector of string.
 /// @param input The input data.
 /// @ingroup dom