cmd/gogio: add clicks to the e2e tests

The test app now responds to mouse clicks; clicking on one of the four
sections of the app flips it to red color until clicked again.

Add a Click method to the TestDriver interface, and implement it in both
of the current drivers. Unfortunately, I failed at implementing it in
X11 with the xdg library, after a few wasted hours. Instead, start
relying on more external tools which are simple to use and not heavy to
install.

Signed-off-by: Daniel Martí <mvdan@mvdan.cc>

cmd/gogio/js_test.go

@@ -15,6 +15,7 @@ import (
 	"os/exec"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/chromedp/cdproto/runtime"
 	"github.com/chromedp/chromedp"
@@ -118,6 +119,8 @@ func (d *JSTestDriver) Start(t_ *testing.T, path string, width, height int) (cle
 	); err != nil {
 		d.t.Fatal(err)
 	}
+	// TODO(mvdan): synchronize with the app instead
+	time.Sleep(200 * time.Millisecond)
 
 	return cleanups
 }
@@ -136,6 +139,16 @@ func (d *JSTestDriver) Screenshot() image.Image {
 	return img
 }
 
+func (d *JSTestDriver) Click(x, y int) {
+	if err := chromedp.Run(d.ctx,
+		chromedp.MouseClickXY(float64(x), float64(y)),
+	); err != nil {
+		d.t.Fatal(err)
+	}
+	// TODO(mvdan): synchronize with the app instead
+	time.Sleep(200 * time.Millisecond)
+}
+
 func TestJS(t *testing.T) {
 	t.Parallel()