Fix automerge in tables. (#333)

CHANGELOG.md

@@ -17,6 +17,9 @@ Element gaugeUp(float ratio);
 Element gaugeDown(float ratio);
 Element gaugeDirection(float ratio, GaugeDirection);
 ```
+- Add the `automerge` decorator. This makes separator characters to be merged
+  with others nearby.
+- Fix the `Table` rendering function, to allow automerging characters.
 
 #### Component
 - Support SIGTSTP. (ctrl+z).

CMakeLists.txt

@@ -44,6 +44,7 @@ add_library(dom
   include/ftxui/dom/node.hpp
   include/ftxui/dom/requirement.hpp
   include/ftxui/dom/take_any_args.hpp
+  src/ftxui/dom/automerge.cpp
   src/ftxui/dom/blink.cpp
   src/ftxui/dom/bold.cpp
   src/ftxui/dom/border.cpp

include/ftxui/dom/elements.hpp

@@ -81,6 +81,7 @@ Element color(Color, Element);
 Element bgcolor(Color, Element);
 Decorator focusPosition(int x, int y);
 Decorator focusPositionRelative(float x, float y);
+Element automerge(Element);
 
 // --- Layout is
 // Horizontal, Vertical or stacked set of elements.

src/ftxui/component/dropdown.cpp

@@ -17,8 +17,8 @@ Component Dropdown(ConstStringListRef entries, int* selected) {
     Impl(ConstStringListRef entries, int* selected)
         : entries_(std::move(entries)), selected_(selected) {
       CheckboxOption option;
-      option.style_checked = "↓│";
-      option.style_unchecked = "→│";
+      option.style_checked = "↓ ";
+      option.style_unchecked = "→ ";
       checkbox_ = Checkbox(&title_, &show_, option),
       radiobox_ = Radiobox(entries_, selected_);
 

src/ftxui/dom/automerge.cpp

@@ -0,0 +1,36 @@
+#include <memory>   // for make_shared
+#include <utility>  // for move
+
+#include "ftxui/dom/elements.hpp"        // for Element, automerge
+#include "ftxui/dom/node.hpp"            // for Node
+#include "ftxui/dom/node_decorator.hpp"  // for NodeDecorator
+#include "ftxui/screen/box.hpp"          // for Box
+#include "ftxui/screen/screen.hpp"       // for Pixel, Screen
+
+namespace ftxui {
+
+/// @brief Enable character to be automatically merged with others nearby.
+/// @ingroup dom
+Element automerge(Element child) {
+  class Impl : public NodeDecorator {
+   public:
+    using NodeDecorator::NodeDecorator;
+
+    void Render(Screen& screen) override {
+      for (int y = box_.y_min; y <= box_.y_max; ++y) {
+        for (int x = box_.x_min; x <= box_.x_max; ++x) {
+          screen.PixelAt(x, y).automerge = true;
+        }
+      }
+      Node::Render(screen);
+    }
+  };
+
+  return std::make_shared<Impl>(std::move(child));
+}
+
+}  // namespace ftxui
+
+// 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.

src/ftxui/dom/table.cpp

@@ -250,10 +250,10 @@ void TableSelection::Border(BorderStyle style) {
   BorderTop(style);
   BorderBottom(style);
 
-  table_->elements_[y_min_][x_min_] = text(charset[style][0]);
-  table_->elements_[y_min_][x_max_] = text(charset[style][1]);
-  table_->elements_[y_max_][x_min_] = text(charset[style][2]);
-  table_->elements_[y_max_][x_max_] = text(charset[style][3]);
+  table_->elements_[y_min_][x_min_] = text(charset[style][0]) | automerge;
+  table_->elements_[y_min_][x_max_] = text(charset[style][1]) | automerge;
+  table_->elements_[y_max_][x_min_] = text(charset[style][2]) | automerge;
+  table_->elements_[y_max_][x_max_] = text(charset[style][3]) | automerge;
 }
 
 void TableSelection::Separator(BorderStyle style) {
@@ -261,8 +261,8 @@ void TableSelection::Separator(BorderStyle style) {
     for (int x = x_min_ + 1; x <= x_max_ - 1; ++x) {
       if (y % 2 == 0 || x % 2 == 0) {
         Element& e = table_->elements_[y][x];
-        e = (y % 2) ? separatorCharacter(charset[style][5])
-                    : separatorCharacter(charset[style][4]);
+        e = (y % 2) ? separatorCharacter(charset[style][5]) | automerge
+                    : separatorCharacter(charset[style][4]) | automerge;
       }
     }
   }
@@ -272,7 +272,8 @@ void TableSelection::SeparatorVertical(BorderStyle style) {
   for (int y = y_min_ + 1; y <= y_max_ - 1; ++y) {
     for (int x = x_min_ + 1; x <= x_max_ - 1; ++x) {
       if (x % 2 == 0) {
-        table_->elements_[y][x] = separatorCharacter(charset[style][5]);
+        table_->elements_[y][x] =
+            separatorCharacter(charset[style][5]) | automerge;
       }
     }
   }
@@ -282,30 +283,39 @@ void TableSelection::SeparatorHorizontal(BorderStyle style) {
   for (int y = y_min_ + 1; y <= y_max_ - 1; ++y) {
     for (int x = x_min_ + 1; x <= x_max_ - 1; ++x) {
       if (y % 2 == 0) {
-        table_->elements_[y][x] = separatorCharacter(charset[style][4]);
+        table_->elements_[y][x] =
+            separatorCharacter(charset[style][4]) | automerge;
       }
     }
   }
 }
 
 void TableSelection::BorderLeft(BorderStyle style) {
-  for (int y = y_min_; y <= y_max_; y++)
-    table_->elements_[y][x_min_] = separatorCharacter(charset[style][5]);
+  for (int y = y_min_; y <= y_max_; y++) {
+    table_->elements_[y][x_min_] =
+        separatorCharacter(charset[style][5]) | automerge;
+  }
 }
 
 void TableSelection::BorderRight(BorderStyle style) {
-  for (int y = y_min_; y <= y_max_; y++)
-    table_->elements_[y][x_max_] = separatorCharacter(charset[style][5]);
+  for (int y = y_min_; y <= y_max_; y++) {
+    table_->elements_[y][x_max_] =
+        separatorCharacter(charset[style][5]) | automerge;
+  }
 }
 
 void TableSelection::BorderTop(BorderStyle style) {
-  for (int x = x_min_; x <= x_max_; x++)
-    table_->elements_[y_min_][x] = separatorCharacter(charset[style][4]);
+  for (int x = x_min_; x <= x_max_; x++) {
+    table_->elements_[y_min_][x] =
+        separatorCharacter(charset[style][4]) | automerge;
+  }
 }
 
 void TableSelection::BorderBottom(BorderStyle style) {
-  for (int x = x_min_; x <= x_max_; x++)
-    table_->elements_[y_max_][x] = separatorCharacter(charset[style][4]);
+  for (int x = x_min_; x <= x_max_; x++) {
+    table_->elements_[y_max_][x] =
+        separatorCharacter(charset[style][4]) | automerge;
+  }
 }
 
 }  // namespace ftxui