add Element.Hover

resolve #151

element.go

@@ -45,8 +45,8 @@ func (el *Element) ScrollIntoViewE() error {
 	return proto.DOMScrollIntoViewIfNeeded{ObjectID: el.ObjectID}.Call(el)
 }
 
-// ClickE will press then release the button just like a human.
-func (el *Element) ClickE(button proto.InputMouseButton) error {
+// HoverE the mouse over the center of the element.
+func (el *Element) HoverE() error {
 	err := el.WaitVisibleE()
 	if err != nil {
 		return err
@@ -57,12 +57,22 @@ func (el *Element) ClickE(button proto.InputMouseButton) error {
 		return err
 	}
 
-	box, err := el.boxCenter()
+	box, err := el.BoxE()
 	if err != nil {
 		return err
 	}
 
-	err = el.page.Mouse.MoveE(box.X, box.Y, 1)
+	err = el.page.Mouse.MoveE(box.CenterX(), box.CenterY(), 1)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// ClickE will press then release the button just like a human.
+func (el *Element) ClickE(button proto.InputMouseButton) error {
+	err := el.HoverE()
 	if err != nil {
 		return err
 	}
@@ -82,7 +92,7 @@ func (el *Element) ClickE(button proto.InputMouseButton) error {
 
 // ClickableE checks if the element is behind another element, such as when invisible or covered by a modal.
 func (el *Element) ClickableE() (bool, error) {
-	box, err := el.boxCenter()
+	box, err := el.BoxE()
 	if err != nil {
 		return false, err
 	}
@@ -93,8 +103,8 @@ func (el *Element) ClickableE() (bool, error) {
 	}
 
 	elAtPoint, err := el.page.ElementFromPointE(
-		int64(box.X)+scroll.Value.Get("x").Int(),
-		int64(box.Y)+scroll.Value.Get("y").Int(),
+		int64(box.CenterX())+scroll.Value.Get("x").Int(),
+		int64(box.CenterY())+scroll.Value.Get("y").Int(),
 	)
 	if err != nil {
 		return false, err
@@ -112,18 +122,6 @@ func (el *Element) ClickableE() (bool, error) {
 	return false, nil
 }
 
-func (el *Element) boxCenter() (*proto.DOMRect, error) {
-	box, err := el.BoxE()
-	if err != nil {
-		return nil, err
-	}
-
-	x := box.X + box.Width/2
-	y := box.Y + box.Height/2
-
-	return &proto.DOMRect{X: x, Y: y}, nil
-}
-
 // BoxE returns the size of an element and its position relative to the main frame.
 func (el *Element) BoxE() (*proto.DOMRect, error) {
 	res, err := proto.DOMGetBoxModel{ObjectID: el.ObjectID}.Call(el)

element_test.go

@@ -80,6 +80,14 @@ func (s *S) TestNotClickable() {
 	})
 }
 
+func (s *S) TestHover() {
+	p := s.page.Navigate(srcFile("fixtures/click.html"))
+	el := p.Element("button")
+	el.Eval(`this.onmouseenter = () => this.dataset['a'] = 1`)
+	el.Hover()
+	s.Equal("1", el.Eval(`this.dataset['a']`).String())
+}
+
 func (s *S) TestElementContext() {
 	p := s.page.Navigate(srcFile("fixtures/click.html"))
 	el := p.Element("button").Timeout(time.Minute).CancelTimeout()

lib/proto/utils.go

@@ -202,3 +202,13 @@ func (box *DOMBoxModel) Rect() *DOMRect {
 		Height: box.Content[7] - box.Content[1],
 	}
 }
+
+// CenterX of the rectangle
+func (rect *DOMRect) CenterX() float64 {
+	return rect.X + rect.Width/2
+}
+
+// CenterY of the rectangle
+func (rect *DOMRect) CenterY() float64 {
+	return rect.Y + rect.Height/2
+}

lib/proto/utils_test.go

@@ -131,6 +131,9 @@ func TestRect(t *testing.T) {
 	b := &proto.DOMBoxModel{Content: proto.DOMQuad{
 		336, 382, 361, 382, 361, 421, 336, 412,
 	}}
+	rect := b.Rect()
+	assert.Equal(t, proto.DOMRect{X: 336, Y: 382, Width: 25, Height: 30}, *rect)
 
-	assert.Equal(t, proto.DOMRect{X: 336, Y: 382, Width: 25, Height: 30}, *b.Rect())
+	assert.Equal(t, 348.5, rect.CenterX())
+	assert.Equal(t, 397.0, rect.CenterY())
 }

page.go

@@ -638,6 +638,7 @@ func (p *Page) initJS(force bool) error {
 	return nil
 }
 
+// We use this function to make sure every frame(page, iframe) will only have one IsolatedWorld.
 func (p *Page) getExecutionID(force bool) (proto.RuntimeExecutionContextID, error) {
 	if !p.IsIframe() {
 		return 0, nil

sugar.go

@@ -498,6 +498,12 @@ func (el *Element) ScrollIntoView() *Element {
 	return el
 }
 
+// Hover the mouse over the center of the element.
+func (el *Element) Hover() *Element {
+	kit.E(el.HoverE())
+	return el
+}
+
 // Click the element
 func (el *Element) Click() *Element {
 	kit.E(el.ClickE(proto.InputMouseButtonLeft))