widget: delete whole words with key modifier

Delete entire words with key modifier, ie "ctrl + delete".

Signed-off-by: Jack Mordaunt <jackmordaunt@gmail.com>

widget/editor_test.go

@@ -92,6 +92,7 @@ const (
 	moveEnd
 	moveCoord
 	moveWord
+	deleteWord
 	moveLast // Mark end; never generated.
 )
 
@@ -143,6 +144,8 @@ func TestEditorCaretConsistency(t *testing.T) {
 				e.moveCoord(image.Pt(int(x), int(y)))
 			case moveWord:
 				e.moveWord(int(distance))
+			case deleteWord:
+				e.deleteWord(int(distance))
 			default:
 				return false
 			}
@@ -203,6 +206,58 @@ func TestEditorMoveWord(t *testing.T) {
 		}
 	}
 }
+
+func TestEditorDeleteWord(t *testing.T) {
+	type Test struct {
+		Text   string
+		Start  int
+		Delete int
+
+		Want   int
+		Result string
+	}
+	tests := []Test{
+		{"", 0, 0, 0, ""},
+		{"", 0, -1, 0, ""},
+		{"", 0, 1, 0, ""},
+		{"hello", 0, -1, 0, "hello"},
+		{"hello", 0, 1, 0, ""},
+		{"hello world", 3, 1, 3, "hel world"},
+		{"hello world", 3, -1, 0, "lo world"},
+		{"hello world", 8, -1, 6, "hello rld"},
+		{"hello world", 8, 1, 8, "hello wo"},
+		{"hello    world", 3, 1, 3, "hel    world"},
+		{"hello    world", 3, 2, 3, "helworld"},
+		{"hello    world", 8, 1, 8, "hello   "},
+		{"hello    world", 8, -1, 5, "hello world"},
+		{"hello brave new world", 0, 3, 0, " new world"},
+	}
+	setup := func(t string) *Editor {
+		e := new(Editor)
+		gtx := layout.Context{
+			Ops:         new(op.Ops),
+			Constraints: layout.Exact(image.Pt(100, 100)),
+		}
+		cache := text.NewCache(gofont.Collection())
+		fontSize := unit.Px(10)
+		font := text.Font{}
+		e.SetText(t)
+		e.Layout(gtx, cache, font, fontSize)
+		return e
+	}
+	for ii, tt := range tests {
+		e := setup(tt.Text)
+		e.Move(tt.Start)
+		e.deleteWord(tt.Delete)
+		if e.rr.caret != tt.Want {
+			t.Fatalf("[%d] deleteWord: bad caret position: got %d, want %d", ii, e.rr.caret, tt.Want)
+		}
+		if e.Text() != tt.Result {
+			t.Fatalf("[%d] deleteWord: invalid result: got %q, want %q", ii, e.Text(), tt.Result)
+		}
+	}
+}
+
 func TestEditorNoLayout(t *testing.T) {
 	var e Editor
 	e.SetText("hi!\n")