Test case for #166

This test reproduces the symptoms of the crash in #166.

Next step is to make it not crash any more.

.gitignore

@@ -1,3 +1,4 @@
 /moar
 /moar.exe
 /releases/moar-*
+/m/__debug_bin*

m/scrollPosition_test.go

@@ -0,0 +1,40 @@
+package m
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/walles/moar/twin"
+	"gotest.tools/v3/assert"
+)
+
+func TestCanonicalize1000(t *testing.T) {
+	pager := Pager{}
+	pager.screen = twin.NewFakeScreen(100, 100)
+	pager.reader = NewReaderFromText("test", strings.Repeat("a\n", 2000))
+	pager.ShowStatusBar = true
+	pager.ShowLineNumbers = true
+	pager.scrollPosition = newScrollPosition("TestCanonicalize1000")
+
+	scrollPosition := scrollPosition{
+		internalDontTouch: scrollPositionInternal{
+			lineNumberOneBased: 1000,
+			deltaScreenLines:   0,
+			name:               "Fake scroll position",
+			canonicalizing:     false,
+			canonical: scrollPositionCanonical{
+				width:              0,
+				height:             0,
+				showLineNumbers:    false,
+				showStatusBar:      false,
+				wrapLongLines:      false,
+				lineNumberOneBased: 0,
+				deltaScreenLines:   0,
+			},
+		},
+	}
+
+	lineNumberOneBased := scrollPosition.lineNumberOneBased(&pager)
+
+	assert.Equal(t, lineNumberOneBased, 1)
+}