Feature: Windows. (#690)

Into ftxui/component/, add:
```
Container::Stacked(...)
Window(...);
```

Together, they can be used to display draggable/resizable windows.

Bug:https://github.com/ArthurSonzogni/FTXUI/issues/682

* Fix typo.

CMakeLists.txt

@@ -132,6 +132,7 @@ add_library(component
   src/ftxui/component/terminal_input_parser.cpp
   src/ftxui/component/terminal_input_parser.hpp
   src/ftxui/component/util.cpp
+  src/ftxui/component/window.cpp
 )
 
 target_link_libraries(dom

examples/component/CMakeLists.txt

@@ -43,4 +43,5 @@ example(tab_horizontal)
 example(tab_vertical)
 example(textarea)
 example(toggle)
+example(window)
 example(with_restored_io)

examples/component/window.cpp

@@ -0,0 +1,86 @@
+#include <ftxui/component/component.hpp>
+#include <ftxui/component/screen_interactive.hpp>
+
+using namespace ftxui;
+
+Component DummyWindowContent() {
+  class Impl : public ComponentBase {
+   private:
+    bool checked[3] = {false, false, false};
+    float slider = 50;
+
+   public:
+    Impl() {
+      Add(Container::Vertical({
+          Checkbox("Check me", &checked[0]),
+          Checkbox("Check me", &checked[1]),
+          Checkbox("Check me", &checked[2]),
+          Slider("Slider", &slider, 0.f, 100.f),
+      }));
+    }
+  };
+  return Make<Impl>();
+}
+
+int main() {
+
+  int window_1_left = 20;
+  int window_1_top = 10;
+  int window_1_width = 40;
+  int window_1_height = 20;
+
+  auto window_1 = Window({
+      .inner = DummyWindowContent(),
+      .title = "First window",
+      .left = &window_1_left,
+      .top = &window_1_top,
+      .width = &window_1_width,
+      .height = &window_1_height,
+  });
+
+  auto window_2 = Window({
+      .inner = DummyWindowContent(),
+      .title = "My window",
+      .left = 40,
+      .top = 20,
+  });
+
+  auto window_3 = Window({
+      .inner = DummyWindowContent(),
+      .title = "My window",
+      .left = 60,
+      .top = 30,
+  });
+
+  auto window_4 = Window({
+      .inner = DummyWindowContent(),
+  });
+
+  auto window_5 = Window({});
+
+  auto window_container = Container::Stacked({
+      window_1,
+      window_2,
+      window_3,
+      window_4,
+      window_5,
+  });
+
+  auto display_win_1 = Renderer([&] {
+    return text("window_1: " +  //
+                std::to_string(window_1_width) + "x" +
+                std::to_string(window_1_height) + " + " +
+                std::to_string(window_1_left) + "," +
+                std::to_string(window_1_top));
+  });
+
+  auto layout = Container::Vertical({
+      display_win_1,
+      window_container,
+  });
+
+  auto screen = ScreenInteractive::Fullscreen();
+  screen.Loop(layout);
+
+  return EXIT_SUCCESS;
+}

examples/dom/CMakeLists.txt

@@ -35,4 +35,3 @@ example(style_underlined_double)
 example(table)
 example(vbox_hbox)
 example(vflow)
-example(window)

examples/dom/window.cpp

@@ -1,34 +0,0 @@
-#include <stdlib.h>                // for EXIT_SUCCESS
-#include <ftxui/dom/elements.hpp>  // for operator|=, Element, bgcolor, color, graph, border
-#include <ftxui/screen/screen.hpp>  // for Fixed, Screen
-#include <vector>                   // for vector
-
-#include "ftxui/dom/node.hpp"      // for Render
-#include "ftxui/screen/color.hpp"  // for Color, Color::DarkBlue, Color::Red, ftxui
-
-int main() {
-  using namespace ftxui;
-  Element document = graph([](int x, int y) {
-    std::vector<int> result(x, 0);
-    for (int i{0}; i < x; ++i) {
-      result[i] = ((3 * i) / 2) % y;
-    }
-    return result;
-  });
-
-  document |= color(Color::Red);
-  document |= bgcolor(Color::DarkBlue);
-  document |= border;
-
-  const int width = 80;
-  const int height = 10;
-  auto screen =
-      Screen::Create(Dimension::Fixed(width), Dimension::Fixed(height));
-  Render(screen, document);
-  screen.Print();
-  return EXIT_SUCCESS;
-}
-
-// Copyright 2020 Arthur Sonzogni. All rights reserved.
-// Use of this source code is governed by the MIT license that can be found in
-// the LICENSE file.

include/ftxui/component/component.hpp

@@ -40,6 +40,7 @@ Component Vertical(Components children, int* selector);
 Component Horizontal(Components children);
 Component Horizontal(Components children, int* selector);
 Component Tab(Components children, int* selector);
+Component Stacked(Components children);
 }  // namespace Container
 
 Component Button(ButtonOption options);
@@ -131,6 +132,8 @@ ComponentDecorator Hoverable(std::function<void()> on_enter,
                              std::function<void()> on_leave);
 ComponentDecorator Hoverable(std::function<void(bool)> on_change);
 
+Component Window(WindowOptions option);
+
 }  // namespace ftxui
 
 #endif /* end of include guard: FTXUI_COMPONENT_HPP */

include/ftxui/component/component_options.hpp

@@ -226,6 +226,39 @@ struct SliderOption {
   Color color_inactive = Color::GrayDark;
 };
 
+// Parameter pack used by `WindowOptions::render`.
+struct WindowRenderState {
+  Element inner;             /// < The element wrapped inside this window.
+  const std::string& title;  /// < The title of the window.
+  bool active = false;       /// < Whether the window is the active one.
+  bool drag = false;         /// < Whether the window is being dragged.
+  bool resize = false;       /// < Whether the window is being resized.
+  bool hover_left = false;   /// < Whether the resizeable left side is hovered.
+  bool hover_right = false;  /// < Whether the resizeable right side is hovered.
+  bool hover_top = false;    /// < Whether the resizeable top side is hovered.
+  bool hover_down = false;   /// < Whether the resizeable down side is hovered.
+};
+
+// @brief Option for the `Window` component.
+// @ingroup component
+struct WindowOptions {
+  Component inner;            /// < The component wrapped by this window.
+  ConstStringRef title = "";  /// < The title displayed by this window.
+
+  Ref<int> left = 0;     /// < The left side position of the window.
+  Ref<int> top = 0;      /// < The top side position of the window.
+  Ref<int> width = 20;   /// < The width of the window.
+  Ref<int> height = 10;  /// < The height of the window.
+
+  Ref<bool> resize_left = true;   /// < Can the left side be resized?
+  Ref<bool> resize_right = true;  /// < Can the right side be resized?
+  Ref<bool> resize_top = true;    /// < Can the top side be resized?
+  Ref<bool> resize_down = true;   /// < Can the down side be resized?
+
+  /// An optional function to customize how the window looks like:
+  std::function<Element(const WindowRenderState&)> render;
+};
+
 }  // namespace ftxui
 
 #endif /* end of include guard: FTXUI_COMPONENT_COMPONENT_OPTIONS_HPP */

src/ftxui/component/container.cpp

@@ -235,6 +235,62 @@ class TabContainer : public ContainerBase {
   }
 };
 
+class StackedContainer : public ContainerBase{
+ public:
+  StackedContainer(Components children)
+      : ContainerBase(std::move(children), nullptr) {}
+
+ private:
+  Element Render() final {
+    Elements elements;
+    for (auto& child : children_) {
+      elements.push_back(child->Render());
+    }
+    // Reverse the order of the elements.
+    std::reverse(elements.begin(), elements.end());
+    return dbox(std::move(elements));
+  }
+
+  bool Focusable() const final {
+    for (auto& child : children_) {
+      if (child->Focusable()) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  Component ActiveChild() final {
+    if (children_.size() == 0)
+      return nullptr;
+    return children_[0];
+  }
+
+  void SetActiveChild(ComponentBase* child) final {
+    if (children_.size() == 0) {
+      return;
+    }
+
+    // Find `child` and put it at the beginning without change the order of the
+    // other children.
+    auto it = std::find_if(children_.begin(), children_.end(),
+                           [child](const Component& c) { return c.get() == child; });
+    if (it == children_.end()) {
+      return;
+    }
+    std::rotate(children_.begin(), it, it + 1);
+  }
+
+  bool OnEvent(Event event) final {
+    for (auto& child : children_) {
+      if (child->OnEvent(event)) {
+        return true;
+      }
+    }
+    return false;
+  }
+};
+
 namespace Container {
 
 /// @brief A list of components, drawn one by one vertically and navigated
@@ -345,6 +401,33 @@ Component Tab(Components children, int* selector) {
   return std::make_shared<TabContainer>(std::move(children), selector);
 }
 
+/// @brief A list of components to be stacked on top of each other.
+/// Events are propagated to the first component, then the second if not
+/// handled, etc.
+/// The components are drawn in the reverse order they are given.
+/// When a component take focus, it is put at the front, without changing the
+/// relative order of the other elements.
+///
+/// This should be used with the `Window` component. 
+///
+/// @param children The list of components.
+/// @ingroup component
+/// @see Window
+///
+/// ### Example
+///
+/// ```cpp
+/// auto container = Container::Stacked({
+///   children_1,
+///   children_2,
+///   children_3,
+///   children_4,
+/// });
+/// ```
+Component Stacked(Components children) {
+  return std::make_shared<StackedContainer>(std::move(children));
+}
+
 }  // namespace Container
 
 }  // namespace ftxui

src/ftxui/component/slider.cpp

@@ -135,24 +135,12 @@ class SliderBase : public ComponentBase {
   }
 
   bool OnMouseEvent(Event event) {
-    if (captured_mouse_ && event.mouse().motion == Mouse::Released) {
-      captured_mouse_ = nullptr;
-      return true;
-    }
-
-    if (gauge_box_.Contain(event.mouse().x, event.mouse().y) &&
-        CaptureMouse(event)) {
-      TakeFocus();
-    }
-
-    if (event.mouse().button == Mouse::Left &&
-        event.mouse().motion == Mouse::Pressed &&
-        gauge_box_.Contain(event.mouse().x, event.mouse().y) &&
-        !captured_mouse_) {
-      captured_mouse_ = CaptureMouse(event);
-    }
-
     if (captured_mouse_) {
+      if (event.mouse().motion == Mouse::Released) {
+        captured_mouse_ = nullptr;
+        return true;
+      }
+
       switch (options_.direction) {
         case Direction::Right: {
           value_() = min_() + (event.mouse().x - gauge_box_.x_min) *
@@ -182,6 +170,23 @@ class SliderBase : public ComponentBase {
       value_() = std::max(min_(), std::min(max_(), value_()));
       return true;
     }
+
+    if (event.mouse().button != Mouse::Left ||
+        event.mouse().motion != Mouse::Pressed) {
+      return false;
+    }
+
+    if (!gauge_box_.Contain(event.mouse().x, event.mouse().y)) {
+      return false;
+    }
+
+    captured_mouse_ = CaptureMouse(event);
+
+    if (captured_mouse_) {
+      TakeFocus();
+      return true;
+    }
+
     return false;
   }
 
@@ -214,7 +219,9 @@ class SliderWithLabel : public ComponentBase {
       return false;
     }
 
-    if (!box_.Contain(event.mouse().x, event.mouse().y)) {
+    mouse_hover_ = box_.Contain(event.mouse().x, event.mouse().y);
+
+    if (!mouse_hover_) {
       return false;
     }
 
@@ -222,13 +229,13 @@ class SliderWithLabel : public ComponentBase {
       return false;
     }
 
-    TakeFocus();
     return true;
   }
 
   Element Render() override {
     auto focus_management = Focused() ? focus : Active() ? select : nothing;
-    auto gauge_color = Focused() ? color(Color::White) : color(Color::GrayDark);
+    auto gauge_color = (Focused() || mouse_hover_) ? color(Color::White)
+                                                   : color(Color::GrayDark);
     return hbox({
                text(label_()) | dim | vcenter,
                hbox({
@@ -242,6 +249,7 @@ class SliderWithLabel : public ComponentBase {
 
   ConstStringRef label_;
   Box box_;
+  bool mouse_hover_ = false;
 };
 
 /// @brief An horizontal slider.

src/ftxui/component/slider_test.cpp

@@ -53,8 +53,9 @@ TEST(SliderTest, Right) {
   });
   Screen screen(11, 1);
   Render(screen, slider->Render());
+  EXPECT_EQ(value, 50);
   EXPECT_TRUE(slider->OnEvent(MousePressed(3, 0)));
-  EXPECT_EQ(value, 30);
+  EXPECT_EQ(value, 50);
   EXPECT_TRUE(slider->OnEvent(MousePressed(9, 0)));
   EXPECT_EQ(value, 90);
   EXPECT_TRUE(slider->OnEvent(MousePressed(9, 2)));
@@ -76,8 +77,9 @@ TEST(SliderTest, Left) {
   });
   Screen screen(11, 1);
   Render(screen, slider->Render());
+  EXPECT_EQ(value, 50);
   EXPECT_TRUE(slider->OnEvent(MousePressed(3, 0)));
-  EXPECT_EQ(value, 70);
+  EXPECT_EQ(value, 50);
   EXPECT_TRUE(slider->OnEvent(MousePressed(9, 0)));
   EXPECT_EQ(value, 10);
   EXPECT_TRUE(slider->OnEvent(MousePressed(9, 2)));
@@ -99,8 +101,9 @@ TEST(SliderTest, Down) {
   });
   Screen screen(1, 11);
   Render(screen, slider->Render());
+  EXPECT_EQ(value, 50);
   EXPECT_TRUE(slider->OnEvent(MousePressed(0, 3)));
-  EXPECT_EQ(value, 30);
+  EXPECT_EQ(value, 50);
   EXPECT_TRUE(slider->OnEvent(MousePressed(0, 9)));
   EXPECT_EQ(value, 90);
   EXPECT_TRUE(slider->OnEvent(MousePressed(2, 9)));
@@ -122,8 +125,9 @@ TEST(SliderTest, Up) {
   });
   Screen screen(1, 11);
   Render(screen, slider->Render());
+  EXPECT_EQ(value, 50);
   EXPECT_TRUE(slider->OnEvent(MousePressed(0, 3)));
-  EXPECT_EQ(value, 70);
+  EXPECT_EQ(value, 50);
   EXPECT_TRUE(slider->OnEvent(MousePressed(0, 9)));
   EXPECT_EQ(value, 10);
   EXPECT_TRUE(slider->OnEvent(MousePressed(2, 9)));

src/ftxui/component/window.cpp

@@ -0,0 +1,306 @@
+#define NOMINMAX
+#include <algorithm>
+#include <ftxui/component/component.hpp>
+#include <ftxui/component/component_base.hpp>
+#include <ftxui/component/screen_interactive.hpp>  // for ScreenInteractive
+#include "ftxui/dom/node_decorator.hpp"            // for NodeDecorator
+
+namespace ftxui {
+
+namespace {
+
+Decorator PositionAndSize(int left, int top, int width, int height) {
+  return [=](Element element) {
+    element |= size(WIDTH, EQUAL, width);
+    element |= size(HEIGHT, EQUAL, height);
+
+    auto padding_left = emptyElement() | size(WIDTH, EQUAL, left);
+    auto padding_top = emptyElement() | size(HEIGHT, EQUAL, top);
+
+    return vbox({
+        padding_top,
+        hbox({
+            padding_left,
+            element,
+        }),
+    });
+  };
+}
+
+class ResizeDecorator : public NodeDecorator {
+ public:
+  ResizeDecorator(Element child,
+                  bool resize_left,
+                  bool resize_right,
+                  bool resize_top,
+                  bool resize_down,
+                  Color color)
+      : NodeDecorator(std::move(child)),
+        color_(color),
+        resize_left_(resize_left),
+        resize_right_(resize_right),
+        resize_top_(resize_top),
+        resize_down_(resize_down) {}
+
+  void Render(Screen& screen) override {
+    NodeDecorator::Render(screen);
+
+    if (resize_left_) {
+      for (int y = box_.y_min; y <= box_.y_max; ++y) {
+        auto& cell = screen.PixelAt(box_.x_min, y);
+        cell.foreground_color = color_;
+        cell.automerge = false;
+      }
+    }
+    if (resize_right_) {
+      for (int y = box_.y_min; y <= box_.y_max; ++y) {
+        auto& cell = screen.PixelAt(box_.x_max, y);
+        cell.foreground_color = color_;
+        cell.automerge = false;
+      }
+    }
+    if (resize_top_) {
+      for (int x = box_.x_min; x <= box_.x_max; ++x) {
+        auto& cell = screen.PixelAt(x, box_.y_min);
+        cell.foreground_color = color_;
+        cell.automerge = false;
+      }
+    }
+    if (resize_down_) {
+      for (int x = box_.x_min; x <= box_.x_max; ++x) {
+        auto& cell = screen.PixelAt(x, box_.y_max);
+        cell.foreground_color = color_;
+        cell.automerge = false;
+      }
+    }
+  }
+
+  Color color_;
+  const bool resize_left_;
+  const bool resize_right_;
+  const bool resize_top_;
+  const bool resize_down_;
+};
+
+Element DefaultRenderState(const WindowRenderState& state) {
+  Element element = state.inner;
+  if (state.active) {
+    element |= dim;
+  }
+
+  element = window(text(state.title), element);
+  element |= clear_under;
+
+
+  Color color = Color::Red;
+
+  element = std::make_shared<ResizeDecorator>(  //
+      element,                                  //
+      state.hover_left,                         //
+      state.hover_right,                        //
+      state.hover_top,                          //
+      state.hover_down,                         //
+      color                                     //
+  );
+
+  return element;
+}
+
+class WindowImpl : public ComponentBase, public WindowOptions {
+ public:
+  WindowImpl(WindowOptions option) : WindowOptions(std::move(option)) {
+    if (!inner) {
+      inner = Make<ComponentBase>();
+    }
+    Add(inner);
+  }
+
+ private:
+  Element Render() final {
+    auto element = ComponentBase::Render();
+
+    bool captureable =
+        captured_mouse_ || ScreenInteractive::Active()->CaptureMouse();
+
+    const WindowRenderState state = {
+        element,
+        title(),
+        Active(),
+        drag_,
+        resize_left_ || resize_right_ || resize_down_ || resize_top_,
+        (resize_left_hover_ || resize_left_) && captureable,
+        (resize_right_hover_ || resize_right_) && captureable,
+        (resize_top_hover_ || resize_top_) && captureable,
+        (resize_down_hover_ || resize_down_) && captureable,
+    };
+
+    element = render ? render(state) : DefaultRenderState(state);
+
+    // Position and record the drawn area of the window.
+    element |= reflect(box_window_);
+    element |= PositionAndSize(left(), top(), width(), height());
+    element |= reflect(box_);
+
+    return element;
+  }
+
+  bool OnEvent(Event event) final {
+    if (ComponentBase::OnEvent(event)) {
+      return true;
+    }
+
+    if (!event.is_mouse()) {
+      return false;
+    }
+
+    mouse_hover_ = box_window_.Contain(event.mouse().x, event.mouse().y);
+
+    resize_down_hover_ = false;
+    resize_top_hover_ = false;
+    resize_left_hover_ = false;
+    resize_right_hover_ = false;
+
+    if (mouse_hover_) {
+      resize_left_hover_ = event.mouse().x == left() + box_.x_min;
+      resize_right_hover_ =
+          event.mouse().x == left() + width() - 1 + box_.x_min;
+      resize_top_hover_ = event.mouse().y == top() + box_.y_min;
+      resize_down_hover_ = event.mouse().y == top() + height() - 1 + box_.y_min;
+
+      // Apply the component options:
+      resize_top_hover_ &= resize_top();
+      resize_left_hover_ &= resize_left();
+      resize_down_hover_ &= resize_down();
+      resize_right_hover_ &= resize_right();
+    }
+
+    if (captured_mouse_) {
+      if (event.mouse().motion == Mouse::Released) {
+        captured_mouse_ = nullptr;
+        return true;
+      }
+
+      if (resize_left_) {
+        width() = left() + width() - event.mouse().x + box_.x_min;
+        left() = event.mouse().x - box_.x_min;
+      }
+
+      if (resize_right_) {
+        width() = event.mouse().x - resize_start_x - box_.x_min;
+      }
+
+      if (resize_top_) {
+        height() = top() + height() - event.mouse().y + box_.y_min;
+        top() = event.mouse().y - box_.y_min;
+      }
+
+      if (resize_down_) {
+        height() = event.mouse().y - resize_start_y - box_.y_min;
+      }
+
+      if (drag_) {
+        left() = event.mouse().x - drag_start_x - box_.x_min;
+        top() = event.mouse().y - drag_start_y - box_.y_min;
+      }
+
+      // Clamp the window size.
+      width() = std::max<int>(width(), title().size() + 2);
+      height() = std::max<int>(height(), 2);
+
+      return true;
+    }
+
+    resize_left_ = false;
+    resize_right_ = false;
+    resize_top_ = false;
+    resize_down_ = false;
+
+    if (!mouse_hover_) {
+      return false;
+    }
+
+    if (!CaptureMouse(event)) {
+      return true;
+    }
+
+    if (event.mouse().button != Mouse::Left ||
+        event.mouse().motion != Mouse::Pressed) {
+      return true;
+    }
+
+    TakeFocus();
+
+    captured_mouse_ = CaptureMouse(event);
+    if (!captured_mouse_) {
+      return true;
+    }
+
+    resize_left_ = resize_left_hover_;
+    resize_right_ = resize_right_hover_;
+    resize_top_ = resize_top_hover_;
+    resize_down_ = resize_down_hover_;
+
+    resize_start_x = event.mouse().x - width() - box_.x_min;
+    resize_start_y = event.mouse().y - height() - box_.y_min;
+    drag_start_x = event.mouse().x - left() - box_.x_min;
+    drag_start_y = event.mouse().y - top() - box_.y_min;
+
+    // Drag only if we are not resizeing a border yet:
+    drag_ = !resize_right_ && !resize_down_ && !resize_top_ && !resize_left_;
+    return true;
+  }
+
+  Box box_;
+  Box box_window_;
+
+  CapturedMouse captured_mouse_;
+  int drag_start_x = 0;
+  int drag_start_y = 0;
+  int resize_start_x = 0;
+  int resize_start_y = 0;
+
+  bool mouse_hover_ = false;
+  bool drag_ = false;
+  bool resize_top_ = false;
+  bool resize_left_ = false;
+  bool resize_down_ = false;
+  bool resize_right_ = false;
+
+  bool resize_top_hover_ = false;
+  bool resize_left_hover_ = false;
+  bool resize_down_hover_ = false;
+  bool resize_right_hover_ = false;
+};
+
+}  // namespace
+
+/// @brief A draggeable / resizeable window. To use multiple of them, they must
+/// be stacked using `Container::Stacked({...})` component;
+///
+/// @param option A struct holding every parameters.
+/// @ingroup component
+/// @see Window
+///
+/// ### Example
+///
+/// ```cpp
+/// auto window_1= Window({
+///     .inner = DummyWindowContent(),
+///     .title = "First window",
+/// });
+///
+/// auto window_2= Window({
+///     .inner = DummyWindowContent(),
+///     .title = "Second window",
+/// });
+///
+/// auto container = Container::Stacked({
+///   window_1,
+///   window_2,
+/// });
+/// ```
+Component Window(WindowOptions option) {
+  return Make<WindowImpl>(std::move(option));
+}
+
+};  // namespace ftxui