Allow users to chose how the buffers are padded

src/client.cc

@@ -166,7 +166,7 @@ void Client::redraw_ifn()
 
     const bool needs_redraw = window.needs_redraw(context());
     if (needs_redraw)
-        ui.draw(window.update_display_buffer(context()), get_face("Default"));
+        ui.draw(window.update_display_buffer(context()), get_face("Default"), get_face("BufferPadding"));
 
     DisplayLine mode_line = generate_mode_line();
     if (needs_redraw or

src/face_registry.cc

@@ -121,6 +121,7 @@ FaceRegistry::FaceRegistry()
         { "StatusCursor", Face{ Color::Black, Color::Cyan } },
         { "Prompt", Face{ Color::Yellow, Color::Default } },
         { "MatchingChar", Face{ Color::Default, Color::Default, Attribute::Bold } },
+        { "BufferPadding", Face{ Color::Blue, Color::Default, Attribute::Bold } },
       }
 {}
 

src/main.cc

@@ -251,7 +251,9 @@ void register_options()
                        "    ncurses_set_title             bool\n"
                        "    ncurses_enable_mouse          bool\n"
                        "    ncurses_wheel_up_button       int\n"
-                       "    ncurses_wheel_down_button     int\n",
+                       "    ncurses_wheel_down_button     int\n"
+                       "    ncurses_buffer_padding_str           str\n"
+                       "    ncurses_buffer_padding_type          fill|single|off\n",
                        UserInterface::Options{});
     reg.declare_option("modelinefmt", "format string used to generate the modeline",
                        "%val{bufname} %val{cursor_line}:%val{cursor_char_column} "_str);
@@ -292,7 +294,7 @@ std::unique_ptr<UserInterface> create_local_ui(bool dummy_ui)
         void info_show(StringView, StringView, CharCoord, Face, InfoStyle) override {}
         void info_hide() override {}
 
-        void draw(const DisplayBuffer&, const Face&) override {}
+        void draw(const DisplayBuffer&, const Face&, const Face&) override {}
         void draw_status(const DisplayLine&, const DisplayLine&, const Face&) override {}
         CharCoord dimensions() override { return {24,80}; }
         bool is_key_available() override { return false; }

src/ncurses_ui.cc

@@ -7,6 +7,7 @@
 #include "keys.hh"
 #include "register_manager.hh"
 #include "utf8_iterator.hh"
+#include "face_registry.hh"
 
 #include <algorithm>
 
@@ -341,8 +342,11 @@ void NCursesUI::draw_line(NCursesWin* window, const DisplayLine& line,
     }
 }
 
+static const DisplayLine empty_line = String(" ");
+
 void NCursesUI::draw(const DisplayBuffer& display_buffer,
-                     const Face& default_face)
+                     const Face& default_face,
+                     const Face& padding_face)
 {
     wbkgdset(m_window, COLOR_PAIR(get_color_pair(default_face)));
 
@@ -357,12 +361,18 @@ void NCursesUI::draw(const DisplayBuffer& display_buffer,
         ++line_index;
     }
 
-    set_face(m_window, { Color::Blue, Color::Default }, default_face);
+    set_face(m_window, { Color::Blue, Color::Default }, padding_face);
+
+    const DisplayLine padding_line = m_buffer_padding_str;
+    const DisplayLine* padding_line_ptr = m_buffer_padding_type != BufferPaddingType::None ?
+                                            &padding_line : &empty_line;
     while (line_index < m_dimensions.line + (m_status_on_top ? 1 : 0))
     {
         wmove(m_window, (int)line_index++, 0);
         wclrtoeol(m_window);
-        waddch(m_window, '~');
+        draw_line(m_window, *padding_line_ptr, 0, m_dimensions.column, padding_face);
+        if (m_buffer_padding_type == BufferPaddingType::Single)
+            padding_line_ptr = &empty_line;
     }
 
     m_dirty = true;
@@ -981,6 +991,20 @@ void NCursesUI::set_ui_options(const Options& options)
         m_wheel_down_button = wheel_down_it != options.end() ?
             str_to_int_ifp(wheel_down_it->value).value_or(5) : 5;
     }
+
+    {
+        auto padding_str_it = options.find("ncurses_buffer_padding_str");
+        m_buffer_padding_str = padding_str_it == options.end() or !padding_str_it->value.length() ?
+                                "~" : padding_str_it->value;
+
+        auto padding_type_it = options.find("ncurses_buffer_padding_type");
+        if (padding_type_it == options.end() or padding_type_it->value == "fill")
+            m_buffer_padding_type = BufferPaddingType::Fill;
+        else if (padding_type_it->value == "single")
+            m_buffer_padding_type = BufferPaddingType::Single;
+        else
+            m_buffer_padding_type = BufferPaddingType::None;
+    }
 }
 
 }

src/ncurses_ui.hh

@@ -13,6 +13,8 @@ namespace Kakoune
 
 struct NCursesWin;
 
+enum BufferPaddingType { None, Single, Fill };
+
 class NCursesUI : public UserInterface
 {
 public:
@@ -23,7 +25,8 @@ public:
     NCursesUI& operator=(const NCursesUI&) = delete;
 
     void draw(const DisplayBuffer& display_buffer,
-              const Face& default_face) override;
+              const Face& default_face,
+              const Face& padding_face) override;
 
     void draw_status(const DisplayLine& status_line,
                      const DisplayLine& mode_line,
@@ -121,6 +124,9 @@ private:
     int m_wheel_up_button = 4;
     int m_wheel_down_button = 5;
 
+    String		  	  m_buffer_padding_str = "~";
+    BufferPaddingType m_buffer_padding_type = BufferPaddingType::None;
+
     bool m_set_title = true;
 
     bool m_dirty = false;

src/remote.cc

@@ -249,7 +249,8 @@ public:
     void info_hide() override;
 
     void draw(const DisplayBuffer& display_buffer,
-              const Face& default_face) override;
+              const Face& default_face,
+              const Face& padding_face) override;
 
     void draw_status(const DisplayLine& status_line,
                      const DisplayLine& mode_line,
@@ -334,12 +335,14 @@ void RemoteUI::info_hide()
 }
 
 void RemoteUI::draw(const DisplayBuffer& display_buffer,
-                    const Face& default_face)
+                    const Face& default_face,
+                    const Face& padding_face)
 {
     Message msg(m_socket_watcher.fd());
     msg.write(RemoteUIMsg::Draw);
     msg.write(display_buffer);
     msg.write(default_face);
+    msg.write(padding_face);
 }
 
 void RemoteUI::draw_status(const DisplayLine& status_line,
@@ -504,7 +507,8 @@ void RemoteClient::process_next_message()
     {
         auto display_buffer = read<DisplayBuffer>(socket);
         auto default_face = read<Face>(socket);
-        m_ui->draw(display_buffer, default_face);
+        auto padding_face = read<Face>(socket);
+        m_ui->draw(display_buffer, default_face, padding_face);
         break;
     }
     case RemoteUIMsg::DrawStatus:

src/user_interface.hh

@@ -53,7 +53,8 @@ public:
     virtual void info_hide() = 0;
 
     virtual void draw(const DisplayBuffer& display_buffer,
-                      const Face& default_face) = 0;
+                      const Face& default_face,
+                      const Face& padding_face) = 0;
 
     virtual void draw_status(const DisplayLine& status_line,
                              const DisplayLine& mode_line,