From c8e0b811275b3c8d4e9f8674e5412a1b7b8d2326 Mon Sep 17 00:00:00 2001
From: Kyosuke Fujimoto <kyoro.f@gmail.com>
Date: Sun, 29 Nov 2020 09:26:31 +0900
Subject: [PATCH 1/2] Add test cases of split container divider drag

---
 widget/splitcontainer_test.go | 58 +++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/widget/splitcontainer_test.go b/widget/splitcontainer_test.go
index 31f47eb7a7..bb847c69f9 100644
--- a/widget/splitcontainer_test.go
+++ b/widget/splitcontainer_test.go
@@ -280,6 +280,64 @@ func TestSplitContainer_divider_drag(t *testing.T) {
 	})
 }
 
+func TestSplitContainer_divider_drag_StartOffsetLessThanMinSize(t *testing.T) {
+	size := fyne.NewSize(30, 30)
+	objA := canvas.NewRectangle(color.NRGBA{0, 0, 0, 0})
+	objA.SetMinSize(size)
+	objB := canvas.NewRectangle(color.NRGBA{0, 0, 0, 0})
+	objB.SetMinSize(size)
+	t.Run("Horizontal", func(t *testing.T) {
+		split := NewHSplitContainer(objA, objB)
+		split.Resize(fyne.NewSize(100, 100))
+		divider := newDivider(split)
+		t.Run("Leading", func(t *testing.T) {
+			split.SetOffset(0.1)
+
+			divider.Dragged(&fyne.DragEvent{
+				DraggedX: 10,
+			})
+			divider.DragEnd()
+
+			assert.Equal(t, 0.4, split.Offset)
+		})
+		t.Run("Trailing", func(t *testing.T) {
+			split.SetOffset(0.9)
+
+			divider.Dragged(&fyne.DragEvent{
+				DraggedX: -10,
+			})
+			divider.DragEnd()
+
+			assert.Equal(t, 0.6, split.Offset)
+		})
+	})
+	t.Run("Vertical", func(t *testing.T) {
+		split := NewVSplitContainer(objA, objB)
+		split.Resize(fyne.NewSize(100, 100))
+		divider := newDivider(split)
+		t.Run("Leading", func(t *testing.T) {
+			split.SetOffset(0.1)
+
+			divider.Dragged(&fyne.DragEvent{
+				DraggedY: 10,
+			})
+			divider.DragEnd()
+
+			assert.Equal(t, 0.4, split.Offset)
+		})
+		t.Run("Trailing", func(t *testing.T) {
+			split.SetOffset(0.9)
+
+			divider.Dragged(&fyne.DragEvent{
+				DraggedY: -10,
+			})
+			divider.DragEnd()
+
+			assert.Equal(t, 0.6, split.Offset)
+		})
+	})
+}
+
 func TestSplitContainer_divider_hover(t *testing.T) {
 	t.Run("Horizontal", func(t *testing.T) {
 		divider := newDivider(&SplitContainer{Horizontal: true})

From 9d830a16859b7abb6bed5488b23a5e33a626a366 Mon Sep 17 00:00:00 2001
From: Kyosuke Fujimoto <kyoro.f@gmail.com>
Date: Sun, 29 Nov 2020 09:29:06 +0900
Subject: [PATCH 2/2] Fix when dragging divider of split container

---
 widget/splitcontainer.go | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/widget/splitcontainer.go b/widget/splitcontainer.go
index 82c1cd95c7..8a97b1c922 100644
--- a/widget/splitcontainer.go
+++ b/widget/splitcontainer.go
@@ -222,8 +222,20 @@ func (d *divider) DragEnd() {
 func (d *divider) Dragged(event *fyne.DragEvent) {
 	offset := d.split.Offset
 	if d.split.Horizontal {
+		if leadingRatio := float64(d.split.Leading.Size().Width) / float64(d.split.Size().Width); offset < leadingRatio {
+			offset = leadingRatio
+		}
+		if trailingRatio := 1. - (float64(d.split.Trailing.Size().Width) / float64(d.split.Size().Width)); offset > trailingRatio {
+			offset = trailingRatio
+		}
 		offset += float64(event.DraggedX) / float64(d.split.Size().Width)
 	} else {
+		if leadingRatio := float64(d.split.Leading.Size().Height) / float64(d.split.Size().Height); offset < leadingRatio {
+			offset = leadingRatio
+		}
+		if trailingRatio := 1. - (float64(d.split.Trailing.Size().Height) / float64(d.split.Size().Height)); offset > trailingRatio {
+			offset = trailingRatio
+		}
 		offset += float64(event.DraggedY) / float64(d.split.Size().Height)
 	}
 	d.split.SetOffset(offset)