widget: report SubmitEvents for IME newlines in submit mode

Before this change, an IME text edit would always have its newlines
replaced with spaces. However, for Editors where Submit is enabled
we want newlines to result in SubmitEvents.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

widget/editor_test.go

@@ -1067,6 +1067,35 @@ func TestEditor_Filter(t *testing.T) {
 	}
 }
 
+func TestEditor_Submit(t *testing.T) {
+	e := new(Editor)
+	e.Submit = true
+
+	gtx := layout.Context{
+		Ops:         new(op.Ops),
+		Constraints: layout.Exact(image.Pt(100, 100)),
+		Queue: newQueue(
+			key.EditEvent{Range: key.Range{Start: 0, End: 0}, Text: "ab1\n"},
+		),
+	}
+	cache := text.NewCache(gofont.Collection())
+	fontSize := unit.Sp(10)
+	font := text.Font{}
+	e.Layout(gtx, cache, font, fontSize, nil)
+
+	if got, want := e.Text(), "ab1"; got != want {
+		t.Errorf("editor failed to filter newline")
+	}
+	got := e.Events()
+	want := []EditorEvent{
+		ChangeEvent{},
+		SubmitEvent{Text: e.Text()},
+	}
+	if !reflect.DeepEqual(want, got) {
+		t.Errorf("editor failed to register submit")
+	}
+}
+
 func textWidth(e *Editor, lineNum, colStart, colEnd int) float32 {
 	var w fixed.Int26_6
 	glyphs := e.lines[lineNum].Layout.Glyphs