From 9360ffff499d78aa94bf20514972a18ea980b5f3 Mon Sep 17 00:00:00 2001
From: Jakub Sobon <jakub.sobon@elohim.sk>
Date: Sun, 27 Dec 2020 02:53:08 -0500
Subject: [PATCH] Bugfix: avoid crash on terminal rezise with tcell.

---
 CHANGELOG.md             |  5 +++++
 private/canvas/canvas.go | 21 +++++++--------------
 2 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index aedbf0f..729e75e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -28,6 +28,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   func (*BarChart) Mouse(m *terminalapi.Mouse, meta *widgetapi.EventMeta) error { ... }
   ```
 
+### Fixed
+
+- `termdash` no longer crashes when `tcell` is used and the terminal window
+  downsizes while content is being drawn.
+
 ### Added
 
 #### Infrastructure changes
diff --git a/private/canvas/canvas.go b/private/canvas/canvas.go
index 65a1e69..9682d98 100644
--- a/private/canvas/canvas.go
+++ b/private/canvas/canvas.go
@@ -195,21 +195,14 @@ func (c *Canvas) copyTo(offset image.Point, dstSetCell setCellFunc) error {
 }
 
 // Apply applies the canvas to the corresponding area of the terminal.
-// Guarantees to stay within limits of the area the canvas was created with.
 func (c *Canvas) Apply(t terminalapi.Terminal) error {
-	termArea, err := area.FromSize(t.Size())
-	if err != nil {
-		return err
-	}
-
-	bufArea, err := area.FromSize(c.buffer.Size())
-	if err != nil {
-		return err
-	}
-
-	if !bufArea.In(termArea) {
-		return fmt.Errorf("the canvas area %+v doesn't fit onto the terminal %+v", bufArea, termArea)
-	}
+	// Note - the size of the terminal might have changed since we started
+	// drawing, since terminal windows are inherently racy (the user can resize
+	// them at any time).
+	//
+	// This is ok, since the underlying terminal layer will just ignore cells
+	// that are out of bounds and termdash will redraw again once it receives
+	// the resize event. Regression for #281.
 
 	// The image.Point{0, 0} of this canvas isn't always exactly at
 	// image.Point{0, 0} on the terminal.