From 6bb2d4ed7c3d498f999d6ac0c042336da1c11b18 Mon Sep 17 00:00:00 2001
From: cztomczak <cztomczak@users.noreply.github.com>
Date: Mon, 20 Aug 2018 12:13:43 +0200
Subject: [PATCH] Add javascript_erors.py and ondomready.py snippets (#403)

---
 docs/Tutorial.md                         |  3 +-
 examples/README-examples.md              | 41 +++++++++-------
 examples/snippets/javascript_bindings.py |  3 +-
 examples/snippets/javascript_errors.py   | 61 ++++++++++++++++++++++++
 examples/snippets/ondomready.py          | 50 +++++++++++++++++++
 src/cef_v59..v66_changes.txt             |  2 +
 6 files changed, 140 insertions(+), 20 deletions(-)
 create mode 100644 examples/snippets/javascript_errors.py
 create mode 100644 examples/snippets/ondomready.py

diff --git a/docs/Tutorial.md b/docs/Tutorial.md
index c6c0fcf7..ea32cb42 100644
--- a/docs/Tutorial.md
+++ b/docs/Tutorial.md
@@ -9,7 +9,8 @@ basics. This tutorial will discuss the three featured examples:
 [hello_world.py](../examples/hello_world.py),
 [tutorial.py](../examples/tutorial.py)
 and [screenshot.py](../examples/screenshot.py). There are many
-more examples that you can find in the [README-examples.md](../examples/README-examples.md)
+more examples that you can find in the
+[README-examples.md](../examples/README-examples.md)
 file, but these examples are out of scope for this tutorial.
 
 
diff --git a/examples/README-examples.md b/examples/README-examples.md
index 0f0ef9a4..4ef36045 100644
--- a/examples/README-examples.md
+++ b/examples/README-examples.md
@@ -4,8 +4,8 @@ Table of contents:
 * [Hello World!](#hello-world)
 * [Supported examples](#supported-examples)
   * [Featured](#featured)
-  * [GUI frameworks](#gui-frameworks)
   * [Snippets](#snippets)
+  * [GUI frameworks](#gui-frameworks)
   * [Build executable with PyInstaller](#build-executable-with-pyinstaller)
   * [Unit tests](#unit-tests)
 * [Other examples](#other-examples)
@@ -42,8 +42,31 @@ workarounds.
   discussed in great details in Tutorial in the [Off-screen rendering](../docs/Tutorial.md#off-screen-rendering)
   section.
 
+
+### Snippets
+
+See small code snippets that show various CEF features in the
+[examples/snippets/](snippets/) directory:
+
+- [javascript_bindings.py](snippets/javascript_bindings.py) - Communicate
+    between Python and Javascript asynchronously using
+    inter-process messaging with the use of Javascript Bindings.
+- [javascript_errors.py](snippets/javascript_errors.py) - Two ways for
+    intercepting Javascript errors.
+- [mouse_clicks.py](snippets/mouse_clicks.py) - Perform mouse clicks
+    and mouse movements programmatically.
+- [network_cookies.py](snippets/network_cookies.py) - Implement
+    interfaces to block or allow cookies over network requests.
+- [onbeforeclose.py](snippets/onbeforeclose.py) - Implement interface
+    to execute custom code before browser window closes.
+- [ondomready.py](snippets/ondomready.py) - Execute custom Python code
+    on a web page as soon as DOM is ready.
+
+
 ### GUI frameworks
 
+Examples of embedding CEF browser using various GUI frameworks:
+
 - [gtk2.py](gtk2.py): example for [PyGTK](http://www.pygtk.org/)
   library (GTK 2)
 - [gtk3.py](gtk3.py): example for [PyGObject / PyGI](https://wiki.gnome.org/Projects/PyGObject)
@@ -64,22 +87,6 @@ workarounds.
   toolkit. This example implements High DPI support on Windows.
 
 
-### Snippets
-
-See small code snippets that test various features in the
-[examples/snippets/](snippets/) directory:
-
-- [javascript_bindings.py](snippets/javascript_bindings.py) - Communicate
-    between Python and Javascript asynchronously using
-    inter-process messaging with the use of Javascript Bindings.
-- [mouse_clicks.py](snippets/mouse_clicks.py) - Perform mouse clicks
-    and mouse movements programmatically.
-- [network_cookies.py](snippets/network_cookies.py) - Implement
-    interfaces to block or allow cookies over network requests.
-- [onbeforeclose.py](snippets/onbeforeclose.py) - Implement interface
-    to execute custom code before browser window closes.
-
-
 ### Build executable with PyInstaller
 
 - [PyInstaller example](pyinstaller/README-pyinstaller.md):
diff --git a/examples/snippets/javascript_bindings.py b/examples/snippets/javascript_bindings.py
index 7c7dccc5..63135463 100644
--- a/examples/snippets/javascript_bindings.py
+++ b/examples/snippets/javascript_bindings.py
@@ -17,7 +17,6 @@
     </style>
     <script>
     function print(msg) {
-        console.log(msg+" [JS]");
         document.getElementById("console").innerHTML += msg+"<br>";
     }
     function js_function(value) {
@@ -41,7 +40,7 @@
 def main():
     cef.Initialize()
     browser = cef.CreateBrowserSync(url=cef.GetDataUrl(g_htmlcode),
-                                    window_title="OnBeforeClose")
+                                    window_title="Javascript Bindings")
     browser.SetClientHandler(LifespanHandler())
     bindings = cef.JavascriptBindings()
     bindings.SetFunction("py_function", py_function)
diff --git a/examples/snippets/javascript_errors.py b/examples/snippets/javascript_errors.py
new file mode 100644
index 00000000..c33ef8d7
--- /dev/null
+++ b/examples/snippets/javascript_errors.py
@@ -0,0 +1,61 @@
+"""
+Two ways for intercepting Javascript errors:
+1. window.onerror event in Javascript
+2. DisplayHandler.OnConsoleMessage in Python
+"""
+
+from cefpython3 import cefpython as cef
+
+g_htmlcode = """
+<!doctype html>
+<html>
+<head>
+    <style>
+    body, html {
+        font-family: Arial;
+        font-size: 11pt;
+    }
+    </style>
+    <script>
+    function print(msg) {
+        document.getElementById("console").innerHTML += msg+"<br>";
+    }
+    window.onerror = function(message, source, lineno, colno, error) {
+        print("[JS:window.onerror] "+error+" (line "+lineno+")");
+        // Return false so that default event handler is fired and
+        // OnConsoleMessage can also intercept this error.
+        return false;
+    };
+    window.onload = function() {
+        forceError();
+    };
+    </script>
+</head>
+<body>
+    <h1>Javascript Errors</h1>
+    <div id=console></div>
+</body>
+</html>
+"""
+
+
+def main():
+    cef.Initialize()
+    browser = cef.CreateBrowserSync(url=cef.GetDataUrl(g_htmlcode),
+                                    window_title="Javascript Errors")
+    browser.SetClientHandler(DisplayHandler())
+    cef.MessageLoop()
+    cef.Shutdown()
+
+
+class DisplayHandler(object):
+    def OnConsoleMessage(self, browser, message, line, **_):
+        if "error" in message.lower() or "uncaught" in message.lower():
+            logmsg = "[Py:OnConsoleMessage] {message} (line {line})" \
+                     .format(message=message, line=line)
+            print(logmsg)
+            browser.ExecuteFunction("print", logmsg)
+
+
+if __name__ == '__main__':
+    main()
diff --git a/examples/snippets/ondomready.py b/examples/snippets/ondomready.py
new file mode 100644
index 00000000..caeacc02
--- /dev/null
+++ b/examples/snippets/ondomready.py
@@ -0,0 +1,50 @@
+"""
+Execute custom Python code on a web page as soon as DOM is ready.
+Implements a custom "_OnDomReady" event in the LifespanHandler object.
+"""
+
+from cefpython3 import cefpython as cef
+
+
+def main():
+    cef.Initialize()
+    browser = cef.CreateBrowserSync(url="https://www.google.com/",
+                                    window_title="_OnDomReady event")
+    lifespan_handler = LifespanHandler(browser)
+    browser.SetClientHandler(lifespan_handler)
+    bindings = cef.JavascriptBindings()
+    bindings.SetFunction("LifespanHandler_OnDomReady",
+                         lifespan_handler["_OnDomReady"])
+    browser.SetJavascriptBindings(bindings)
+    cef.MessageLoop()
+    del lifespan_handler
+    del browser
+    cef.Shutdown()
+
+
+class LifespanHandler(object):
+    def __init__(self, browser):
+        self.browser = browser
+
+    def __getitem__(self, key):
+        return getattr(self, key)
+
+    def OnLoadStart(self, browser, **_):
+        browser.ExecuteJavascript("""
+            if (document.readyState === "complete") {
+                LifespanHandler_OnDomReady();
+            } else {
+                document.addEventListener("DOMContentLoaded", function() {
+                    LifespanHandler_OnDomReady();
+                });
+            }
+        """)
+
+    def _OnDomReady(self):
+        print("DOM is ready!")
+        self.browser.ExecuteFunction("alert",
+                                     "Message from Python: DOM is ready!")
+
+
+if __name__ == '__main__':
+    main()
diff --git a/src/cef_v59..v66_changes.txt b/src/cef_v59..v66_changes.txt
index f78800d3..1024bdaf 100644
--- a/src/cef_v59..v66_changes.txt
+++ b/src/cef_v59..v66_changes.txt
@@ -83,6 +83,8 @@ NEW FEATURES
     + network_cookies.py
     + mouse_clicks.py
     + javascript_bindings.py
+    + javascript_errors.py
+    + ondomready.py
 + cef.GetDataUrl
 
 internal/cef_types.h