From 30a85c4c5ba96882336adc7af12da50b900b0836 Mon Sep 17 00:00:00 2001
From: Arthur Sonzogni <sonzogniarthur@gmail.com>
Date: Mon, 17 May 2021 00:44:37 +0200
Subject: [PATCH] Clear terminal on resize. (#99)

---
 include/ftxui/screen/screen.hpp            |  2 +-
 src/ftxui/component/screen_interactive.cpp | 15 +++++++++------
 src/ftxui/screen/screen.cpp                | 16 ++++++++++++----
 3 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/include/ftxui/screen/screen.hpp b/include/ftxui/screen/screen.hpp
index 0c75202..91cbce9 100644
--- a/include/ftxui/screen/screen.hpp
+++ b/include/ftxui/screen/screen.hpp
@@ -63,7 +63,7 @@ class Screen {
   int dimy() { return dimy_; }
 
   // Move the terminal cursor n-lines up with n = dimy().
-  std::string ResetPosition();
+  std::string ResetPosition(bool clear = false);
 
   // Fill with space.
   void Clear();
diff --git a/src/ftxui/component/screen_interactive.cpp b/src/ftxui/component/screen_interactive.cpp
index 786f40a..0b45c6e 100644
--- a/src/ftxui/component/screen_interactive.cpp
+++ b/src/ftxui/component/screen_interactive.cpp
@@ -382,11 +382,6 @@ void ScreenInteractive::Loop(Component component) {
   // The main loop.
   while (!quit_) {
     if (!event_receiver_->HasPending()) {
-      std::cout << reset_cursor_position << ResetPosition();
-      static int i = -2;
-      if (i % 10 == 0)
-        std::cout << DeviceStatusReport(DSRMode::kCursor);
-      ++i;
       Draw(component);
       std::cout << ToString() << set_cursor_position;
       Flush();
@@ -442,8 +437,11 @@ void ScreenInteractive::Draw(Component component) {
       break;
   }
 
+  bool resized = (dimx != dimx_) || (dimy != dimy_);
+  std::cout << reset_cursor_position << ResetPosition(/*clear=*/resized);
+
   // Resize the screen if needed.
-  if (dimx != dimx_ || dimy != dimy_) {
+  if (resized) {
     dimx_ = dimx;
     dimy_ = dimy;
     pixels_ = std::vector<std::vector<Pixel>>(dimy, std::vector<Pixel>(dimx));
@@ -451,6 +449,11 @@ void ScreenInteractive::Draw(Component component) {
     cursor_.y = dimy_ - 1;
   }
 
+  static int i = -2;
+  if (i % 10 == 0)
+    std::cout << DeviceStatusReport(DSRMode::kCursor);
+  ++i;
+
   Render(*this, document);
 
   // Set cursor position for user using tools to insert CJK characters.
diff --git a/src/ftxui/screen/screen.cpp b/src/ftxui/screen/screen.cpp
index 110fd6b..8e51444 100644
--- a/src/ftxui/screen/screen.cpp
+++ b/src/ftxui/screen/screen.cpp
@@ -36,6 +36,7 @@ static const wchar_t* INVERTED_RESET = L"\x1B[27m";
 
 static const char* MOVE_LEFT = "\r";
 static const char* MOVE_UP = "\x1B[1A";
+static const char* CLEAR_LINE = "\x1B[2K";
 
 bool In(const Box& stencil, int x, int y) {
   return stencil.x_min <= x && x <= stencil.x_max &&  //
@@ -219,11 +220,18 @@ Pixel& Screen::PixelAt(int x, int y) {
 ///
 /// @return The string to print in order to reset the cursor position to the
 ///         beginning.
-std::string Screen::ResetPosition() {
+std::string Screen::ResetPosition(bool clear) {
   std::stringstream ss;
-  ss << MOVE_LEFT;
-  for (int y = 1; y < dimy_; ++y) {
-    ss << MOVE_UP;
+  if (clear) {
+    ss << MOVE_LEFT << CLEAR_LINE;
+    for (int y = 1; y < dimy_; ++y) {
+      ss << MOVE_UP << CLEAR_LINE;
+    }
+  } else {
+    ss << MOVE_LEFT;
+    for (int y = 1; y < dimy_; ++y) {
+      ss << MOVE_UP;
+    }
   }
   return ss.str();
 }