Updating dependencies

README.md

@@ -1,102 +1,18 @@
 # About chromedp [![Build Status][1]][2] [![Coverage Status][3]][4]
 
-Package chromedp is a faster, simpler way to drive browsers in Go using the
+Package chromedp is a faster, simpler way to drive browsers supporting the
-[Chrome Debugging Protocol][5] (for Chrome, Edge, Safari, etc) without external
+[Chrome DevTools Protocol][5] in Go using the without external dependencies
-dependencies (ie, Selenium, PhantomJS, etc).
+(ie, Selenium, PhantomJS, etc).
-
-**NOTE:** chromedp's API is currently unstable, and may change at a moments
-notice. There are likely extremely bad bugs lurking in this code. **CAVEAT USER**.
 
 ## Installing
 
-Install in the usual way:
+Install in the usual Go way:
 
 ```sh
 go get -u github.com/chromedp/chromedp
 ```
 
-## Using
+## Examples
-
-Below is a simple Google search performed using chromedp (taken from
-[examples/simple][6]):
-
-This example shows logic for a simple search for a known website, clicking on
-the right link, and then taking a screenshot of a specific element on the
-loaded page and saving that to a local file on disk.
-
-```go
-// Command simple is a chromedp example demonstrating how to do a simple google
-// search.
-package main
-
-import (
-	"context"
-	"fmt"
-	"io/ioutil"
-	"log"
-	"time"
-
-	"github.com/chromedp/cdproto/cdp"
-	"github.com/chromedp/chromedp"
-)
-
-func main() {
-	var err error
-
-	// create context
-	ctxt, cancel := context.WithCancel(context.Background())
-	defer cancel()
-
-	// create chrome instance
-	c, err := chromedp.New(ctxt, chromedp.WithLog(log.Printf))
-	if err != nil {
-		log.Fatal(err)
-	}
-
-	// run task list
-	var site, res string
-	err = c.Run(ctxt, googleSearch("site:brank.as", "Home", &site, &res))
-	if err != nil {
-		log.Fatal(err)
-	}
-
-	// shutdown chrome
-	err = c.Shutdown(ctxt)
-	if err != nil {
-		log.Fatal(err)
-	}
-
-	// wait for chrome to finish
-	err = c.Wait()
-	if err != nil {
-		log.Fatal(err)
-	}
-
-	log.Printf("saved screenshot from search result listing `%s` (%s)", res, site)
-}
-
-func googleSearch(q, text string, site, res *string) chromedp.Tasks {
-	var buf []byte
-	sel := fmt.Sprintf(`//a[text()[contains(., '%s')]]`, text)
-	return chromedp.Tasks{
-		chromedp.Navigate(`https://www.google.com`),
-		chromedp.WaitVisible(`#hplogo`, chromedp.ByID),
-		chromedp.SendKeys(`#lst-ib`, q+"\n", chromedp.ByID),
-		chromedp.WaitVisible(`#res`, chromedp.ByID),
-		chromedp.Text(sel, res),
-		chromedp.Click(sel),
-		chromedp.WaitNotVisible(`.preloader-content`, chromedp.ByQuery),
-		chromedp.WaitVisible(`a[href*="twitter"]`, chromedp.ByQuery),
-		chromedp.Location(site),
-		chromedp.ScrollIntoView(`.banner-section.third-section`, chromedp.ByQuery),
-		chromedp.Sleep(2 * time.Second), // wait for animation to finish
-		chromedp.Screenshot(`.banner-section.third-section`, &buf, chromedp.ByQuery),
-		chromedp.ActionFunc(func(context.Context, cdp.Executor) error {
-			return ioutil.WriteFile("screenshot.png", buf, 0644)
-		}),
-	}
-}
-```
 
 Please see the [examples][6] project for more examples. Please refer to the
 [GoDoc API listing][7] for a summary of the API and Actions.
@@ -104,11 +20,11 @@ Please see the [examples][6] project for more examples. Please refer to the
 ## Resources
 
 * [chromedp: A New Way to Drive the Web][8] - GopherCon SG 2017 talk
-* [Chrome DevTools Protocol][5] - Chrome Debugging Protocol Domain documentation
+* [Chrome DevTools Protocol][5] - Chrome DevTools Protocol Domain documentation
 * [chromedp examples][6] - various `chromedp` examples
 * [`github.com/chromedp/cdproto`][9] - GoDoc listing for the CDP domains used by `chromedp`
 * [`github.com/chromedp/cdproto-gen`][10] - tool used to generate `cdproto`
-* [`github.com/chromedp/chromedp-proxy`][11] - a simple CDP proxy for logging/debugging CDP clients and browser instances
+* [`github.com/chromedp/chromedp-proxy`][11] - a simple CDP proxy for logging CDP clients and browsers
 
 ## TODO
 

chromedp.go

@@ -1,9 +1,9 @@
-// Package chromedp is a high level Chrome Debugging Protocol domain manager
+// Package chromedp is a high level Chrome DevTools Protocol client that
-// that simplifies driving web browsers (Chrome, Safari, Edge, Android Web
+// simplifies driving browsers for scraping, unit testing, or profiling web
-// Views, and others) for scraping, unit testing, or profiling web pages.
+// pages using the CDP.
 //
-// chromedp requires no third-party dependencies (ie, Selenium), implementing
+// chromedp requires no third-party dependencies, implementing the async Chrome
-// the async Chrome Debugging Protocol natively.
+// DevTools Protocol entirely in Go.
 package chromedp
 
 import (
@@ -35,8 +35,9 @@ const (
 	DefaultPoolEndPort = 10000
 )
 
-// CDP contains information for managing a Chrome process runner, low level
+// CDP is the high-level Chrome DevTools Protocol browser manager, handling the
-// JSON and websocket client, and associated network, page, and DOM handling.
+// browser process runner, WebSocket clients, associated targets, and network,
+// page, and DOM events.
 type CDP struct {
 	// r is the chrome runner.
 	r *runner.Runner
@@ -90,7 +91,7 @@ func New(ctxt context.Context, opts ...Option) (*CDP, error) {
 
 	// watch handlers
 	if c.watch == nil {
-		c.watch = c.r.WatchPageTargets(ctxt)
+		c.watch = c.r.Client().WatchPageTargets(ctxt)
 	}
 
 	go func() {
@@ -339,7 +340,7 @@ func (c *CDP) Run(ctxt context.Context, a Action) error {
 	return a.Do(ctxt, cur)
 }
 
-// Option is a Chrome Debugging Protocol option.
+// Option is a Chrome DevTools Protocol option.
 type Option func(*CDP) error
 
 // WithRunner is a CDP option to specify the underlying Chrome runner to

client/chrome.go

@@ -4,7 +4,7 @@ import "fmt"
 
 //go:generate easyjson -omit_empty -output_filename easyjson.go chrome.go
 
-// Chrome holds connection information for a Chrome, Edge, or Safari target.
+// Chrome holds connection information for a Chrome target.
 //
 //easyjson:json
 type Chrome struct {
@@ -20,7 +20,7 @@ type Chrome struct {
 
 // String satisfies the stringer interface.
 func (c Chrome) String() string {
-	return fmt.Sprintf("%s (`%s`)", c.ID, c.Title)
+	return fmt.Sprintf("[%s]: %q", c.ID, c.Title)
 }
 
 // GetID returns the target ID.
@@ -33,6 +33,12 @@ func (c *Chrome) GetType() TargetType {
 	return c.Type
 }
 
+// GetDevtoolsURL returns the devtools frontend target URL, satisfying the
+// domains.Target interface.
+func (c *Chrome) GetDevtoolsURL() string {
+	return c.DevtoolsURL
+}
+
 // GetWebsocketURL provides the websocket URL for the target, satisfying the
 // domains.Target interface.
 func (c *Chrome) GetWebsocketURL() string {

client/client.go

@@ -1,5 +1,4 @@
-// Package client provides the low level Chrome Debugging Protocol JSON types
+// Package client provides the low level Chrome DevTools Protocol client.
-// and related funcs.
 package client
 
 //go:generate go run gen.go
@@ -45,15 +44,16 @@ const (
 	ErrUnsupportedProtocolVersion Error = "unsupported protocol version"
 )
 
-// Target is the common interface for a Chrome Debugging Protocol target.
+// Target is the common interface for a Chrome DevTools Protocol target.
 type Target interface {
 	String() string
 	GetID() string
 	GetType() TargetType
+	GetDevtoolsURL() string
 	GetWebsocketURL() string
 }
 
-// Client is a Chrome Debugging Protocol client.
+// Client is a Chrome DevTools Protocol client.
 type Client struct {
 	url     string
 	check   time.Duration
@@ -63,7 +63,7 @@ type Client struct {
 	rw       sync.RWMutex
 }
 
-// New creates a new Chrome Debugging Protocol client.
+// New creates a new Chrome DevTools Protocol client.
 func New(opts ...Option) *Client {
 	c := &Client{
 		url:     DefaultEndpoint,
@@ -120,8 +120,7 @@ func (c *Client) ListTargets(ctxt context.Context) ([]Target, error) {
 	var err error
 
 	var l []json.RawMessage
-	err = c.doReq(ctxt, "list", &l)
+	if err = c.doReq(ctxt, "list", &l); err != nil {
-	if err != nil {
 		return nil, err
 	}
 
@@ -200,8 +199,7 @@ func (c *Client) newTarget(ctxt context.Context, buf []byte) (Target, error) {
 	case "chrome", "chromium", "microsoft edge", "safari", "":
 		x := new(Chrome)
 		if buf != nil {
-			err = easyjson.Unmarshal(buf, x)
+			if err = easyjson.Unmarshal(buf, x); err != nil {
-			if err != nil {
 				return nil, err
 			}
 		}
@@ -226,8 +224,7 @@ func (c *Client) NewPageTargetWithURL(ctxt context.Context, urlstr string) (Targ
 		u += "?" + urlstr
 	}
 
-	err = c.doReq(ctxt, u, t)
+	if err = c.doReq(ctxt, u, t); err != nil {
-	if err != nil {
 		return nil, err
 	}
 
@@ -251,23 +248,15 @@ func (c *Client) CloseTarget(ctxt context.Context, t Target) error {
 
 // VersionInfo returns information about the remote debugging protocol.
 func (c *Client) VersionInfo(ctxt context.Context) (map[string]string, error) {
-	var err error
+	v := make(map[string]string)
-
+	if err := c.doReq(ctxt, "version", &v); err != nil {
-	v := map[string]string{}
-	err = c.doReq(ctxt, "version", &v)
-	if err != nil {
 		return nil, err
 	}
-
 	return v, nil
 }
 
 // WatchPageTargets watches for new page targets.
 func (c *Client) WatchPageTargets(ctxt context.Context) <-chan Target {
-	if ctxt == nil {
-		ctxt = context.Background()
-	}
-
 	ch := make(chan Target)
 	go func() {
 		defer close(ch)
@@ -311,10 +300,11 @@ func (c *Client) WatchPageTargets(ctxt context.Context) <-chan Target {
 	return ch
 }
 
-// Option is a Chrome Debugging Protocol client option.
+// Option is a Chrome DevTools Protocol client option.
 type Option func(*Client)
 
-// URL is a client option to specify the remote Chrome instance to connect to.
+// URL is a client option to specify the remote Chrome DevTools Protocol
+// instance to connect to.
 func URL(urlstr string) Option {
 	return func(c *Client) {
 		// since chrome 66+, dev tools requires the host name to be either an

client/gen.go

@@ -26,17 +26,26 @@ const (
 
 var (
 	flagOut = flag.String("out", "targettype.go", "out file")
-
-	typeAsStringRE = regexp.MustCompile(`type_as_string\s+==\s+"([^"]+)"`)
 )
 
 func main() {
 	flag.Parse()
 
+	if err := run(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+var typeAsStringRE = regexp.MustCompile(`type_as_string\s+==\s+"([^"]+)"`)
+
+// run executes the generator.
+func run() error {
+	var err error
+
 	// grab source
 	buf, err := grab(devtoolsHTTPClientCc)
 	if err != nil {
-		log.Fatal(err)
+		return err
 	}
 
 	// find names
@@ -55,15 +64,11 @@ func main() {
 		decodeVals += fmt.Sprintf("case %s:\n*tt=%s\n", name, name)
 	}
 
-	err = ioutil.WriteFile(*flagOut, []byte(fmt.Sprintf(targetTypeSrc, constVals, decodeVals)), 0644)
+	if err = ioutil.WriteFile(*flagOut, []byte(fmt.Sprintf(targetTypeSrc, constVals, decodeVals)), 0644); err != nil {
-	if err != nil {
+		return err
-		log.Fatal(err)
 	}
 
-	err = exec.Command("gofmt", "-w", "-s", *flagOut).Run()
+	return exec.Command("gofmt", "-w", "-s", *flagOut).Run()
-	if err != nil {
-		log.Fatal(err)
-	}
 }
 
 // grab retrieves a file from the chromium source code.
@@ -93,7 +98,6 @@ const (
 // Code generated by gen.go. DO NOT EDIT.
 
 import (
-	// "errors"
 	easyjson "github.com/mailru/easyjson"
 	jlexer "github.com/mailru/easyjson/jlexer"
 	jwriter "github.com/mailru/easyjson/jwriter"
@@ -129,7 +133,6 @@ func (tt *TargetType) UnmarshalEasyJSON(in *jlexer.Lexer) {
 %s
 
 	default:
-		// in.AddError(errors.New("unknown TargetType"))
 		*tt = z
 	}
 }

client/targettype.go

@@ -3,7 +3,6 @@ package client
 // Code generated by gen.go. DO NOT EDIT.
 
 import (
-	// "errors"
 	easyjson "github.com/mailru/easyjson"
 	jlexer "github.com/mailru/easyjson/jlexer"
 	jwriter "github.com/mailru/easyjson/jwriter"
@@ -70,7 +69,6 @@ func (tt *TargetType) UnmarshalEasyJSON(in *jlexer.Lexer) {
 		*tt = Worker
 
 	default:
-		// in.AddError(errors.New("unknown TargetType"))
 		*tt = z
 	}
 }

client/transport.go

@@ -6,7 +6,7 @@ import (
 	"github.com/gorilla/websocket"
 )
 
-const (
+var (
 	// DefaultReadBufferSize is the default maximum read buffer size.
 	DefaultReadBufferSize = 25 * 1024 * 1024
 
@@ -14,7 +14,7 @@ const (
 	DefaultWriteBufferSize = 10 * 1024 * 1024
 )
 
-// Transport is the common interface to send/receive messages.
+// Transport is the common interface to send/receive messages to a target.
 type Transport interface {
 	Read() ([]byte, error)
 	Write([]byte) error
@@ -43,7 +43,7 @@ func (c *Conn) Write(buf []byte) error {
 // Dial dials the specified target's websocket URL.
 //
 // Note: uses gorilla/websocket.
-func Dial(t Target, opts ...DialOption) (Transport, error) {
+func Dial(urlstr string, opts ...DialOption) (Transport, error) {
 	d := &websocket.Dialer{
 		ReadBufferSize:  DefaultReadBufferSize,
 		WriteBufferSize: DefaultWriteBufferSize,
@@ -55,7 +55,7 @@ func Dial(t Target, opts ...DialOption) (Transport, error) {
 	}
 
 	// connect
-	conn, _, err := d.Dial(t.GetWebsocketURL(), nil)
+	conn, _, err := d.Dial(urlstr, nil)
 	if err != nil {
 		return nil, err
 	}
@@ -65,5 +65,3 @@ func Dial(t Target, opts ...DialOption) (Transport, error) {
 
 // DialOption is a dial option.
 type DialOption func(*websocket.Dialer)
-
-// TODO: add dial options ...

go.mod

@@ -1,10 +1,10 @@
 module github.com/chromedp/chromedp
 
 require (
-	github.com/chromedp/cdproto v0.0.0-20180703215205-c125a34ea3b3
+	github.com/chromedp/cdproto v0.0.0-20180713053126-e314dc107013
 	github.com/disintegration/imaging v1.4.2
 	github.com/gorilla/websocket v1.2.0
 	github.com/knq/sysutil v0.0.0-20180306023629-0218e141a794
 	github.com/mailru/easyjson v0.0.0-20180606163543-3fdea8d05856
-	golang.org/x/image v0.0.0-20180628062038-cc896f830ced
+	golang.org/x/image v0.0.0-20180708004352-c73c2afc3b81
 )

go.sum

@@ -1,9 +1,19 @@
 github.com/chromedp/cdproto v0.0.0-20180522032958-55db67b53f25/go.mod h1:C2GPAraqdt1KfZU7aSmx1XUgarNq/3JmxevQkmCjOVs=
+github.com/chromedp/cdproto v0.0.0-20180703215205-c125a34ea3b3 h1:4b4LwyHW4sf6zXZqWsKMYoICFLWGhaqwpEHlnQMN5SE=
 github.com/chromedp/cdproto v0.0.0-20180703215205-c125a34ea3b3/go.mod h1:C2GPAraqdt1KfZU7aSmx1XUgarNq/3JmxevQkmCjOVs=
+github.com/chromedp/cdproto v0.0.0-20180713053126-e314dc107013 h1:8nmuTwCseJcww39MvVHI59223+PxSzn6g3cl8ChF0/4=
+github.com/chromedp/cdproto v0.0.0-20180713053126-e314dc107013/go.mod h1:C2GPAraqdt1KfZU7aSmx1XUgarNq/3JmxevQkmCjOVs=
+github.com/disintegration/imaging v1.4.2 h1:BSVxoYQ2NfLdvIGCDD8GHgBV5K0FCEsc0d/6FxQII3I=
 github.com/disintegration/imaging v1.4.2/go.mod h1:9B/deIUIrliYkyMTuXJd6OUFLcrZ2tf+3Qlwnaf/CjU=
+github.com/gorilla/websocket v1.2.0 h1:VJtLvh6VQym50czpZzx07z/kw9EgAxI3x1ZB8taTMQQ=
 github.com/gorilla/websocket v1.2.0/go.mod h1:E7qHFY5m1UJ88s3WnNqhKjPHQ0heANvMoAMk2YaljkQ=
+github.com/knq/sysutil v0.0.0-20180306023629-0218e141a794 h1:hgWKTlyruPI7k8W+0FmTMLf+8d2KPxyzTxsfDDQhNp8=
 github.com/knq/sysutil v0.0.0-20180306023629-0218e141a794/go.mod h1:BjPj+aVjl9FW/cCGiF3nGh5v+9Gd3VCgBQbod/GlMaQ=
 github.com/mailru/easyjson v0.0.0-20180323154445-8b799c424f57/go.mod h1:C1wdFJiN94OJF2b5HbByQZoLdCWB1Yqtg26g4irojpc=
+github.com/mailru/easyjson v0.0.0-20180606163543-3fdea8d05856 h1:hOnidOuIWNsFRPcxxStGeN3NNm4n4+w6KJ9cVJIh70o=
 github.com/mailru/easyjson v0.0.0-20180606163543-3fdea8d05856/go.mod h1:C1wdFJiN94OJF2b5HbByQZoLdCWB1Yqtg26g4irojpc=
 golang.org/x/image v0.0.0-20180403161127-f315e4403028/go.mod h1:ux5Hcp/YLpHSI86hEcLt0YII63i6oz57MZXIpbrjZUs=
+golang.org/x/image v0.0.0-20180628062038-cc896f830ced h1:2QsAEqOy4Mp+V4HL2Wr1iBNpZWaL72EvTO4oj5bmr5w=
 golang.org/x/image v0.0.0-20180628062038-cc896f830ced/go.mod h1:ux5Hcp/YLpHSI86hEcLt0YII63i6oz57MZXIpbrjZUs=
+golang.org/x/image v0.0.0-20180708004352-c73c2afc3b81 h1:00VmoueYNlNz/aHIilyyQz/MHSqGoWJzpFv/HW8xpzI=
+golang.org/x/image v0.0.0-20180708004352-c73c2afc3b81/go.mod h1:ux5Hcp/YLpHSI86hEcLt0YII63i6oz57MZXIpbrjZUs=

handler.go

@@ -24,7 +24,7 @@ import (
 	"github.com/chromedp/chromedp/client"
 )
 
-// TargetHandler manages a Chrome Debugging Protocol target.
+// TargetHandler manages a Chrome DevTools Protocol target.
 type TargetHandler struct {
 	conn client.Transport
 
@@ -64,7 +64,7 @@ type TargetHandler struct {
 
 // NewTargetHandler creates a new handler for the specified client target.
 func NewTargetHandler(t client.Target, logf, debugf, errf func(string, ...interface{})) (*TargetHandler, error) {
-	conn, err := client.Dial(t)
+	conn, err := client.Dial(t.GetWebsocketURL())
 	if err != nil {
 		return nil, err
 	}

kb/kb.go

@@ -5,6 +5,7 @@ package kb
 //go:generate go run gen.go -out keys.go -pkg kb
 
 import (
+	"runtime"
 	"unicode"
 
 	"github.com/chromedp/cdproto/input"
@@ -97,6 +98,9 @@ func Encode(r rune) []*input.DispatchKeyEventParams {
 		NativeVirtualKeyCode:  v.Native,
 		WindowsVirtualKeyCode: v.Windows,
 	}
+	if runtime.GOOS == "darwin" {
+		keyDown.NativeVirtualKeyCode = 0
+	}
 	if v.Shift {
 		keyDown.Modifiers |= input.ModifierShift
 	}

pool.go

@@ -74,7 +74,11 @@ func (p *Pool) Allocate(ctxt context.Context, opts ...runner.CommandLineOption)
 
 	// create runner
 	r.r, err = runner.New(append([]runner.CommandLineOption{
-		runner.HeadlessPathPort("", r.port),
+		runner.ExecPath(runner.LookChromeNames("headless_shell")),
+		runner.RemoteDebuggingPort(r.port),
+		runner.NoDefaultBrowserCheck,
+		runner.NoFirstRun,
+		runner.Headless,
 	}, opts...)...)
 	if err != nil {
 		defer r.Release()

runner/path_darwin.go

@@ -3,10 +3,11 @@
 package runner
 
 const (
-	// DefaultChromePath is the default path to the Chrome application.
+	// DefaultChromePath is the default path to use for Chrome if the
+	// executable is not in $PATH.
 	DefaultChromePath = `/Applications/Google Chrome.app/Contents/MacOS/Google Chrome`
 )
 
-func findChromePath() string {
+// DefaultChromeNames are the default Chrome executable names to look for in
-	return DefaultChromePath
+// $PATH.
-}
+var DefaultChromeNames []string

runner/path_unix.go

@@ -2,30 +2,18 @@
 
 package runner
 
-import "os/exec"
-
 const (
-	// DefaultChromePath is the default path to the google-chrome executable if
+	// DefaultChromePath is the default path to use for Chrome if the
-	// a variant cannot be found on $PATH.
+	// executable is not in $PATH.
 	DefaultChromePath = "/usr/bin/google-chrome"
 )
 
-// chromeNames are the Chrome executable names to search for in the path.
+// DefaultChromeNames are the default Chrome executable names to look for in
-var chromeNames = []string{
+// $PATH.
+var DefaultChromeNames = []string{
 	"google-chrome",
 	"chromium-browser",
 	"chromium",
 	"google-chrome-beta",
 	"google-chrome-unstable",
 }
-
-func findChromePath() string {
-	for _, p := range chromeNames {
-		path, err := exec.LookPath(p)
-		if err == nil {
-			return path
-		}
-	}
-
-	return DefaultChromePath
-}

runner/path_windows.go

@@ -2,32 +2,12 @@
 
 package runner
 
-import "os/exec"
-
 const (
-	// DefaultChromePath is the default path to use for Google Chrome if the
+	// DefaultChromePath is the default path to use for Chrome if the
 	// executable is not in %PATH%.
 	DefaultChromePath = `C:\Program Files (x86)\Google\Chrome\Application\chrome.exe`
-
-	// DefaultEdgeDiagnosticsAdapterPath is the default path to use for the
-	// Microsoft Edge Diagnostics Adapter if the executable is not in %PATH%.
-	DefaultEdgeDiagnosticsAdapterPath = `c:\Edge\EdgeDiagnosticsAdapter\x64\EdgeDiagnosticsAdapter.exe`
 )
 
-func findChromePath() string {
+// DefaultChromeNames are the default Chrome executable names to look for in
-	path, err := exec.LookPath(`chrome.exe`)
+// %PATH%.
-	if err == nil {
+var DefaultChromeNames = []string{`chrome.exe`}
-		return path
-	}
-
-	return DefaultChromePath
-}
-
-func findEdgePath() string {
-	path, err := exec.LookPath(`EdgeDiagnosticsAdapter.exe`)
-	if err == nil {
-		return path
-	}
-
-	return DefaultEdgeDiagnosticsAdapterPath
-}

runner/runner.go

@@ -3,10 +3,8 @@ package runner
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"io/ioutil"
-	"net/url"
 	"os"
 	"os/exec"
 	"regexp"
@@ -22,6 +20,35 @@ const (
 	DefaultUserDataDirPrefix = "chromedp-runner.%d."
 )
 
+// Error is a runner error.
+type Error string
+
+// Error satisfies the error interface.
+func (err Error) Error() string {
+	return string(err)
+}
+
+// Error values.
+const (
+	// ErrAlreadyStarted is the already started error.
+	ErrAlreadyStarted Error = "already started"
+
+	// ErrAlreadyWaiting is the already waiting error.
+	ErrAlreadyWaiting Error = "already waiting"
+
+	// ErrInvalidURLs is the invalid url-opts error.
+	ErrInvalidURLOpts Error = "invalid url-opts"
+
+	// ErrInvalidCmdOpts is the invalid cmd-opts error.
+	ErrInvalidCmdOpts Error = "invalid cmd-opts"
+
+	// ErrInvalidProcessOpts is the invalid process-opts error.
+	ErrInvalidProcessOpts Error = "invalid process-opts"
+
+	// ErrInvalidExecPath is the invalid exec-path error.
+	ErrInvalidExecPath Error = "invalid exec-path"
+)
+
 // Runner holds information about a running Chrome process.
 type Runner struct {
 	opts    map[string]interface{}
@@ -34,19 +61,18 @@ type Runner struct {
 func New(opts ...CommandLineOption) (*Runner, error) {
 	var err error
 
-	cliOpts := map[string]interface{}{}
+	cliOpts := make(map[string]interface{})
 
 	// apply opts
 	for _, o := range opts {
-		err = o(cliOpts)
+		if err = o(cliOpts); err != nil {
-		if err != nil {
 			return nil, err
 		}
 	}
 
 	// set default Chrome options if exec-path not provided
 	if _, ok := cliOpts["exec-path"]; !ok {
-		cliOpts["exec-path"] = findChromePath()
+		cliOpts["exec-path"] = LookChromeNames()
 		for k, v := range map[string]interface{}{
 			"no-first-run":             true,
 			"no-default-browser-check": true,
@@ -61,8 +87,7 @@ func New(opts ...CommandLineOption) (*Runner, error) {
 	// add KillProcessGroup and ForceKill if no other cmd opts provided
 	if _, ok := cliOpts["cmd-opts"]; !ok {
 		for _, o := range []CommandLineOption{KillProcessGroup, ForceKill} {
-			err = o(cliOpts)
+			if err = o(cliOpts); err != nil {
-			if err != nil {
 				return nil, err
 			}
 		}
@@ -79,9 +104,9 @@ var cliOptRE = regexp.MustCompile(`^[a-z0-9\-]+$`)
 // buildOpts generates the command line options for Chrome.
 func (r *Runner) buildOpts() []string {
 	var opts []string
+	var urls []string
 
-	// process options
+	// process opts
-	var urlstr string
 	for k, v := range r.opts {
 		if !cliOptRE.MatchString(k) || v == nil {
 			continue
@@ -91,8 +116,8 @@ func (r *Runner) buildOpts() []string {
 		case "exec-path", "cmd-opts", "process-opts":
 			continue
 
-		case "start-url":
+		case "url-opts":
-			urlstr = v.(string)
+			urls = v.([]string)
 
 		default:
 			switch z := v.(type) {
@@ -110,16 +135,16 @@ func (r *Runner) buildOpts() []string {
 		}
 	}
 
-	if urlstr == "" {
+	if urls == nil {
-		urlstr = "about:blank"
+		urls = append(urls, "about:blank")
 	}
 
-	return append(opts, urlstr)
+	return append(opts, urls...)
 }
 
 // Start starts a Chrome process using the specified context. The Chrome
 // process can be terminated by closing the passed context.
-func (r *Runner) Start(ctxt context.Context) error {
+func (r *Runner) Start(ctxt context.Context, opts ...string) error {
 	var err error
 	var ok bool
 
@@ -128,12 +153,7 @@ func (r *Runner) Start(ctxt context.Context) error {
 	r.rw.RUnlock()
 
 	if cmd != nil {
-		return errors.New("already started")
+		return ErrAlreadyStarted
-	}
-
-	// setup context
-	if ctxt == nil {
-		ctxt = context.Background()
 	}
 
 	// set user data dir, if not provided
@@ -147,36 +167,41 @@ func (r *Runner) Start(ctxt context.Context) error {
 		}
 	}
 
-	// ensure exec-path set
+	// get exec path
-	execPath, ok := r.opts["exec-path"]
+	var execPath string
+	if p, ok := r.opts["exec-path"]; ok {
+		execPath, ok = p.(string)
 		if !ok {
-		return errors.New("exec-path command line option not set, or chrome executable not found in $PATH")
+			return ErrInvalidExecPath
+		}
+	}
+
+	// ensure execPath is valid
+	if execPath == "" {
+		return ErrInvalidExecPath
 	}
 
 	// create cmd
-	r.cmd = exec.CommandContext(ctxt, execPath.(string), r.buildOpts()...)
+	r.cmd = exec.CommandContext(ctxt, execPath, append(r.buildOpts(), opts...)...)
 
 	// apply cmd opts
 	if cmdOpts, ok := r.opts["cmd-opts"]; ok {
 		for _, co := range cmdOpts.([]func(*exec.Cmd) error) {
-			err = co(r.cmd)
+			if err = co(r.cmd); err != nil {
-			if err != nil {
 				return err
 			}
 		}
 	}
 
 	// start process
-	err = r.cmd.Start()
+	if err = r.cmd.Start(); err != nil {
-	if err != nil {
 		return err
 	}
 
 	// apply process opts
 	if processOpts, ok := r.opts["process-opts"]; ok {
 		for _, po := range processOpts.([]func(*os.Process) error) {
-			err = po(r.cmd.Process)
+			if err = po(r.cmd.Process); err != nil {
-			if err != nil {
 				// TODO: do something better here, as we want to kill
 				// the child process, do cleanup, etc.
 				panic(err)
@@ -235,7 +260,7 @@ func (r *Runner) Wait() error {
 	r.rw.RUnlock()
 
 	if waiting {
-		return errors.New("already waiting")
+		return ErrAlreadyWaiting
 	}
 
 	r.rw.Lock()
@@ -272,7 +297,7 @@ func (r *Runner) Port() int {
 	return p
 }
 
-// Client returns a Chrome Debugging Protocol client for the running Chrome
+// Client returns a Chrome DevTools Protocol client for the running Chrome
 // process.
 func (r *Runner) Client(opts ...client.Option) *client.Client {
 	return client.New(append(opts,
@@ -280,12 +305,6 @@ func (r *Runner) Client(opts ...client.Option) *client.Client {
 	)...)
 }
 
-// WatchPageTargets returns a channel that will receive new page targets as
-// they are created.
-func (r *Runner) WatchPageTargets(ctxt context.Context, opts ...client.Option) <-chan client.Target {
-	return r.Client(opts...).WatchPageTargets(ctxt)
-}
-
 // Run starts a new Chrome process runner, using the provided context and
 // command line options.
 func Run(ctxt context.Context, opts ...CommandLineOption) (*Runner, error) {
@@ -298,20 +317,19 @@ func Run(ctxt context.Context, opts ...CommandLineOption) (*Runner, error) {
 	}
 
 	// start
-	err = r.Start(ctxt)
+	if err = r.Start(ctxt); err != nil {
-	if err != nil {
 		return nil, err
 	}
 
 	return r, nil
 }
 
-// CommandLineOption is a Chrome command line option.
+// CommandLineOption is a runner command line option.
 //
 // see: http://peter.sh/experiments/chromium-command-line-switches/
 type CommandLineOption func(map[string]interface{}) error
 
-// Flag is a generic Chrome command line option to pass a name=value flag to
+// Flag is a generic command line option to pass a name=value flag to
 // Chrome.
 func Flag(name string, value interface{}) CommandLineOption {
 	return func(m map[string]interface{}) error {
@@ -335,33 +353,12 @@ func Path(path string) CommandLineOption {
 	}
 }
 
-// HeadlessPathPort is the Chrome command line option to set the default
+// ExecPath is a command line option to set the exec path.
-// settings for running the headless_shell executable. If path is empty, then
-// an attempt will be made to find headless_shell on the path.
-func HeadlessPathPort(path string, port int) CommandLineOption {
-	if path == "" {
-		path, _ = exec.LookPath("headless_shell")
-	}
-
-	return func(m map[string]interface{}) error {
-		m["exec-path"] = path
-		m["remote-debugging-port"] = port
-		m["headless"] = true
-		return nil
-	}
-}
-
-// ExecPath is a Chrome command line option to set the exec path.
 func ExecPath(path string) CommandLineOption {
 	return Flag("exec-path", path)
 }
 
-// Port is the Chrome command line option to set the remote debugging port.
+// UserDataDir is the command line option to set the user data dir.
-func Port(port int) CommandLineOption {
-	return Flag("remote-debugging-port", port)
-}
-
-// UserDataDir is the Chrome command line option to set the user data dir.
 //
 // Note: set this option to manually set the profile directory used by Chrome.
 // When this is not set, then a default path will be created in the /tmp
@@ -370,27 +367,17 @@ func UserDataDir(dir string) CommandLineOption {
 	return Flag("user-data-dir", dir)
 }
 
-// StartURL is the Chrome command line option to set the initial URL.
+// ProxyServer is the command line option to set the outbound proxy server.
-func StartURL(urlstr string) CommandLineOption {
+func ProxyServer(proxy string) CommandLineOption {
-	return Flag("start-url", urlstr)
-}
-
-// Proxy is the Chrome command line option to set the outbound proxy.
-func Proxy(proxy string) CommandLineOption {
 	return Flag("proxy-server", proxy)
 }
 
-// ProxyPacURL is the Chrome command line option to set the URL of a proxy PAC file.
+// WindowSize is the command line option to set the initial window size.
-func ProxyPacURL(pacURL url.URL) CommandLineOption {
-	return Flag("proxy-pac-url", pacURL.String())
-}
-
-// WindowSize is the Chrome command line option to set the initial window size.
 func WindowSize(width, height int) CommandLineOption {
 	return Flag("window-size", fmt.Sprintf("%d,%d", width, height))
 }
 
-// UserAgent is the Chrome command line option to set the default User-Agent
+// UserAgent is the command line option to set the default User-Agent
 // header.
 func UserAgent(userAgent string) CommandLineOption {
 	return Flag("user-agent", userAgent)
@@ -413,45 +400,83 @@ func NoDefaultBrowserCheck(m map[string]interface{}) error {
 	return Flag("no-default-browser-check", true)(m)
 }
 
-// DisableGPU is the Chrome command line option to disable the GPU process.
+// RemoteDebuggingPort is the command line option to set the remote
+// debugging port.
+func RemoteDebuggingPort(port int) CommandLineOption {
+	return Flag("remote-debugging-port", port)
+}
+
+// Headless is the command line option to run in headless mode.
+func Headless(m map[string]interface{}) error {
+	return Flag("headless", true)(m)
+}
+
+// DisableGPU is the command line option to disable the GPU process.
 func DisableGPU(m map[string]interface{}) error {
 	return Flag("disable-gpu", true)(m)
 }
 
-// CmdOpt is a Chrome command line option to modify the underlying exec.Cmd
+// URL is the command line option to add a URL to open on process start.
-// prior to invocation.
+//
+// Note: this can be specified multiple times, and each URL will be opened in a
+// new tab.
+func URL(urlstr string) CommandLineOption {
+	return func(m map[string]interface{}) error {
+		var urls []string
+		if u, ok := m["url-opts"]; ok {
+			urls, ok = u.([]string)
+			if !ok {
+				return ErrInvalidURLOpts
+			}
+		}
+		m["url-opts"] = append(urls, urlstr)
+		return nil
+	}
+}
+
+// CmdOpt is a command line option to modify the underlying exec.Cmd
+// prior to the call to exec.Cmd.Start in Run.
 func CmdOpt(o func(*exec.Cmd) error) CommandLineOption {
 	return func(m map[string]interface{}) error {
 		var opts []func(*exec.Cmd) error
-
 		if e, ok := m["cmd-opts"]; ok {
 			opts, ok = e.([]func(*exec.Cmd) error)
 			if !ok {
-				return errors.New("cmd-opts is in invalid state")
+				return ErrInvalidCmdOpts
 			}
 		}
-
 		m["cmd-opts"] = append(opts, o)
-
 		return nil
 	}
 }
 
-// ProcessOpt is a Chrome command line option to modify the child os.Process
+// ProcessOpt is a command line option to modify the child os.Process
-// after started exec.Cmd.Start.
+// after the call to exec.Cmd.Start in Run.
 func ProcessOpt(o func(*os.Process) error) CommandLineOption {
 	return func(m map[string]interface{}) error {
 		var opts []func(*os.Process) error
-
 		if e, ok := m["process-opts"]; ok {
 			opts, ok = e.([]func(*os.Process) error)
 			if !ok {
-				return errors.New("process-opts is in invalid state")
+				return ErrInvalidProcessOpts
 			}
 		}
-
 		m["process-opts"] = append(opts, o)
-
 		return nil
 	}
 }
+
+// LookChromeNames looks for the platform's DefaultChromeNames and any
+// additional names using exec.LookPath, returning the first encountered
+// location or the platform's DefaultChromePath if no names are found on the
+// path.
+func LookChromeNames(additional ...string) string {
+	for _, p := range append(additional, DefaultChromeNames...) {
+		path, err := exec.LookPath(p)
+		if err == nil {
+			return path
+		}
+	}
+
+	return DefaultChromePath
+}