From 0279bed8c4a3718802aa8e56ebcff84a9173332e Mon Sep 17 00:00:00 2001
From: ArthurSonzogni <sonzogniarthur@gmail.com>
Date: Thu, 11 Apr 2024 23:07:09 +0200
Subject: [PATCH] Add Box::IsEmpty()

---
 CHANGELOG.md                 | 3 +++
 include/ftxui/screen/box.hpp | 2 +-
 src/ftxui/dom/canvas.cpp     | 3 ++-
 src/ftxui/screen/box.cpp     | 7 +++----
 4 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6a976af7..b441a05e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -29,6 +29,9 @@ current (development)
   reflecting the current scroll position. Proposed by @ibrahimnasson in
   [issue 752](https://github.com/ArthurSonzogni/FTXUI/issues/752)
 
+### Screen
+- Feature: Add `Box::IsEmpty()`.
+
 ### Build
 - Support for cmake's "unity/jumbo" builds. Fixed by @ClausKlein.
 
diff --git a/include/ftxui/screen/box.hpp b/include/ftxui/screen/box.hpp
index 32e08fff..9fc27921 100644
--- a/include/ftxui/screen/box.hpp
+++ b/include/ftxui/screen/box.hpp
@@ -15,7 +15,7 @@ struct Box {
   static auto Intersection(Box a, Box b) -> Box;
   static auto Union(Box a, Box b) -> Box;
   bool Contain(int x, int y) const;
-  int Area() const noexcept;
+  bool IsEmpty();
   bool operator==(const Box& other) const;
   bool operator!=(const Box& other) const;
 };
diff --git a/src/ftxui/dom/canvas.cpp b/src/ftxui/dom/canvas.cpp
index c441e6da..854c8c6c 100644
--- a/src/ftxui/dom/canvas.cpp
+++ b/src/ftxui/dom/canvas.cpp
@@ -850,8 +850,9 @@ void Canvas::DrawImage(int x,
     y = 0;
   }
 
-  if (crop.Area() == 0)
+  if (crop.IsEmpty()) {
     return;
+  }
 
   const auto xend = x + crop.x_max - crop.x_min;
   const auto yend = y + crop.y_max - crop.y_min;
diff --git a/src/ftxui/screen/box.cpp b/src/ftxui/screen/box.cpp
index e3eba85b..0210153b 100644
--- a/src/ftxui/screen/box.cpp
+++ b/src/ftxui/screen/box.cpp
@@ -39,11 +39,10 @@ bool Box::Contain(int x, int y) const {
          y_max >= y;
 }
 
-/// @return the are of the box
+/// @return whether the box is empty.
 /// @ingroup screen
-int Box::Area() const noexcept {
-  const auto area = (x_max - x_min) * (y_max - y_min);
-  return area < 0 ? 0 : area;
+bool Box::IsEmpty() {
+  return x_min > x_max || y_min > y_max;
 }
 
 /// @return whether |other| is the same as |this|