From 8a09b93e4a13ba6cd3031f6503ca592893db593e Mon Sep 17 00:00:00 2001
From: Andy Williams <andy@andy.xyz>
Date: Thu, 13 May 2021 17:33:40 +0100
Subject: [PATCH] Fix issue with line resize

Fixes #2208
---
 canvas/line.go      |  9 ++++++---
 canvas/line_test.go | 19 +++++++++++++++++++
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/canvas/line.go b/canvas/line.go
index 66a59f7306..85960b417e 100644
--- a/canvas/line.go
+++ b/canvas/line.go
@@ -45,9 +45,12 @@ func (l *Line) Position() fyne.Position {
 
 // Move the line object to a new position, relative to its parent / canvas
 func (l *Line) Move(pos fyne.Position) {
-	size := l.Size()
-	l.Position1 = pos
-	l.Position2 = fyne.NewPos(l.Position1.X+size.Width, l.Position1.Y+size.Height)
+	oldPos := l.Position()
+	deltaX := pos.X - oldPos.X
+	deltaY := pos.Y - oldPos.Y
+
+	l.Position1 = l.Position1.Add(fyne.NewPos(deltaX, deltaY))
+	l.Position2 = l.Position2.Add(fyne.NewPos(deltaX, deltaY))
 }
 
 // MinSize for a Line simply returns Size{1, 1} as there is no
diff --git a/canvas/line_test.go b/canvas/line_test.go
index 1aae0783e2..064a5bf826 100644
--- a/canvas/line_test.go
+++ b/canvas/line_test.go
@@ -18,6 +18,25 @@ func TestLine_MinSize(t *testing.T) {
 	assert.True(t, min.Height > 0)
 }
 
+func TestLine_Move(t *testing.T) {
+	line := canvas.NewLine(color.Black)
+
+	line.Resize(fyne.NewSize(10, 10))
+	assert.Equal(t, fyne.NewPos(0, 0), line.Position1)
+	assert.Equal(t, fyne.NewPos(10, 10), line.Position2)
+
+	line.Move(fyne.NewPos(5, 5))
+	assert.Equal(t, fyne.NewPos(5, 5), line.Position1)
+	assert.Equal(t, fyne.NewPos(15, 15), line.Position2)
+
+	// rotate
+	line.Position1 = fyne.NewPos(0, 10)
+	line.Position2 = fyne.NewPos(10, 0)
+	line.Move(fyne.NewPos(10, 10))
+	assert.Equal(t, fyne.NewPos(10, 20), line.Position1)
+	assert.Equal(t, fyne.NewPos(20, 10), line.Position2)
+}
+
 func TestLine_Resize(t *testing.T) {
 	line := canvas.NewLine(color.Black)