From 81e086788d2ed3a4d5fd525cc3750f1a1ffc9a67 Mon Sep 17 00:00:00 2001
From: Arthur Sonzogni <sonzogniarthur@gmail.com>
Date: Mon, 13 Jun 2022 21:49:36 +0200
Subject: [PATCH] Avoid making new allocation to clear the screen. (#420)

Previously, a new 2D vector was allocated for every new frame. This
caused a lot of temporary allocation to be made.

This patch modify "Screen::Clear" so that it do make a new allocation,
but clear the existing one instead.

Bug:https://github.com/ArthurSonzogni/FTXUI/issues/290#issuecomment-1153327251
---
 src/ftxui/screen/screen.cpp | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/ftxui/screen/screen.cpp b/src/ftxui/screen/screen.cpp
index c3d95559..130d88f1 100644
--- a/src/ftxui/screen/screen.cpp
+++ b/src/ftxui/screen/screen.cpp
@@ -487,8 +487,11 @@ std::string Screen::ResetPosition(bool clear) const {
 
 /// @brief Clear all the pixel from the screen.
 void Screen::Clear() {
-  pixels_ = std::vector<std::vector<Pixel>>(dimy_,
-                                            std::vector<Pixel>(dimx_, Pixel()));
+  for (auto& line : pixels_) {
+    for (auto& cell : line) {
+      cell = Pixel();
+    }
+  }
   cursor_.x = dimx_ - 1;
   cursor_.y = dimy_ - 1;
 }