I am quite new to windows 8 phone and I don't know all the life cycle methods and when what is called.
My problem is the following: I have a page that loads some data from the disk and when the user exits the program ( or suspends ) the data should be saved. As far as I can tell Page doesn't have an OnSuspending method only someOnNavigatingFrom, but those are not called when you just exit the program. So I read that I should use the OnSuspending in my App.xaml.cs, but this class doesn't have this data and also shouldn't have it, maybe only for OnSuspending. But I don't know how to get the data from my page in the OnSuspending method.
The OnSuspending event is quite fragile and you cannot expect it to run and save the state for a long time. But it depends on how long it would take for you to save. It doesn't even get triggered when you hit the home key while closing the app. If you really want an easy way. Just register a background task. While your app is in the background, the state can be saved and when you open the app again things are in place.
There are certain constraints With Background task as well, you cant do heavy lifting etc...here's a link you could use.
https://msdn.microsoft.com/en-us/library/windows/apps/xaml/hh977056.aspx
Implement an observer pattern (i.e. pub/sub) for your view-models to subscribe to in the event that your app is being suspended.
Your app handles the suspended event. As a result, publish a message for your view-models to respond to within your app's method handler for the suspended event.
You can use an EventAggregator or MessageBus (that I wrote).
Related
I am writing a gtkmm3 application and I need to create and show new GUI elements from a non-GUI thread. Specifically, I am trying to add a tab to a notebook.
I create the notebook in the gui thread like so:
Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.examples.base");
if(!Glib::thread_supported()) Glib::thread_init();
Gtk::Window window;
notebook = new Gtk::Notebook();
window.add(*notebook);
notebook -> show();
Worker bee;
bee.start();
return app->run(window);
and the I create and add a new tab like so:
Gtk::Label label("label");
Gtk::Label child("child");
notebook -> append_page(child, label);
notebook -> show_all();
If I insert the tab creation code before notebook->show() it works fine. But if I put the tab creation code into its own worker thread, the new tab never shows.
I'm guessing that the failure has to do with the fact that the new tab is created on the worker thread and that violates gtkmm's GUI stuff on the GUI thread convention.
The trouble is that the worker thread is responsible for creating new tabs, and I don't know how many tabs to create at compile time.
In APIs like Swing, and gtk+ there are mechanisms to handle this case. In Swing there is an invokeLater method that allows me to pass a lambda to the GUI thread for invokation, and gtk+ uses gdk_threads_enter/leave to ensure that only one thread is playing the GUI at once.
What is gtkmm's answer to this issue?
In general you should just avoid ever using GTK+ (or gtkmm) UI API from anything but the main thread. It's not meant to work.
You need to let the main thread respond when the other thread says that it should, instead of actually doing the UI work in the other thread. People like to use Glib::Dispatcher for this with gtkmm: https://developer.gnome.org/gtkmm-tutorial/stable/sec-using-glib-dispatcher.html.en .
But also think hard about whether you really need another thread at all. It might be fine to do the work in an idle handler: https://developer.gnome.org/gtkmm-tutorial/stable/sec-idle-functions.html.en
I am working on an LOB (side-loading) app and I need to log events, crashes to ETW (Event Viewer logs). I see that most suggest writing own file IO wrapper.
With Windows 8.1, we have new logging capabilities in "Windows.Foundation.Diagnostics" which has classes for "LoggingChannel" and "LoggingSession". But the code sample for them still write to the isolated local storage as files:
http://code.msdn.microsoft.com/windowsapps/LoggingSession-Sample-ccd52336
Also, earlier than 8.1, we have "EventSource" and "EventListener" and as per a sample project (http://code.msdn.microsoft.com/windowsapps/Logging-Sample-for-Windows-0b9dffd7/sourcecode?fileId=67472&pathId=1214683397), it also writes to the sample isolated storage as files.
So, my questions are:
Can we utilize new "Windows.Foundation.Diagnostics" classes to write to ETW?
Are ("LoggingChannel" and "LoggingSession") equivalent to ("EventSource" and "EventListener") ultimately?
Will I still have to write C++ component for writing to ETW?
Forum of Microsoft just gave this answer:
It is not designed with such thing in mind.
I also tried using PInvoke for consuming EventRegister, EventWrite C++ functions. The code runs but I have no idea where find the log. The EventRegister only takes GUID as input and I don't know if it can be mapped to EventViewer application.
Short answer to the questions:
Windows.Foundation.Diagnostics.LoggingChannel writes events to ETW. However, it does not give you complete control over the event in the way that EventRegister/EventWrite do.
LoggingChannel is somewhat equivalent to .NET's EventSource. However, LoggingChannel always writes events to ETW, while EventSource can write to ETW but also has capabilities to bypass ETW. LoggingSession is similar in concept to EventListener, except that LoggingSession always receives events from ETW, while EventListener only works with EventSource (bypassing ETW). Note that you can use both LoggingChannel and EventSource in Windows Store apps.
You will have to write C++ code to use ETW if you need more capabilities than LoggingChannel or EventSource provides.
A few other comments based on things you mentioned:
Event Viewer shows data from the Event Log. The Event Log is not the same as ETW. Event Viewer records data from various sources, and ETW is one of the sources that Event Viewer supports. However, Event Viewer does not record all ETW events -- there are billions of ETW events every hour, and it would fill your hard disk if all of them were recorded. To send an ETW event to Event Viewer, you first have to make your event follow certain rules, and then you have to update the Event Viewer settings to watch for your specific event.
Event Log is designed to record events that are of interest to system administrators and system analysis tools. Because of this design, Microsoft requires administrator privileges to change the Event Log configuration. In order to have your events show up in Event Log, you need to have administrator privileges to change Event Log settings to make Event Log listen to your app's ETW events.
LoggingChannel does not support the necessary settings to make your ETW event look the way Event Log expects, so LoggingChannel cannot be used to write to the Event Log.
If you use EventRegister and EventWrite, you can write events in the format that Event Log expects, but you would still need to have administrator privileges to change Event Log settings to accept your events.
Note that EventRegister and EventWrite (and LoggingChannel) are for sending data to ETW. You can send anything you want to ETW, but by default ETW will just ignore it and throw it all away. ETW is the system for routing events from the provider to anybody who is interested in the event. If nobody is interested in the event, it gets thrown away by default.
LoggingChannel writes events out to ETW, but ETW will just drop them unless there is a session to record them. From within your app, you can record the events using LoggingSession. From outside your app, you can record the events using a tool such as xperf or tracelog.
You can use Windows.Foundation.Diagnostics.LoggingChannel from Windows 8.1 to write ETW events with some limitations. In particular: all events from all apps will always use the same provider GUID (4bd2826e-54a1-4ba9-bf63-92b73ea1ac4a), there is no way to access the keyword, channel, task, or opcode features of ETW, and you can only write very simple events. The Windows 8.1 LoggingChannel API is mainly focused on providing a simple string-based logging facility.
Windows 10 adds a bunch of new features, removing many of the limitations. You can use a different provider GUID (so it is easier to record just the events from your app), you can set keywords, tasks, and opcodes, and you can write strongly-typed events (i.e. events with strongly-typed field values instead of just a flat string). The Windows 10 LoggingChannel API allows you to use LoggingChannel for fairly advanced ETW scenarios, though it still works for simple logging.
I have a plugin which has a content stream pushed to it from an external service which I then draw into a PluginWindowlessWin.
I maintain a reference to the PluginWindowlessWin object so that I can call Invalidate() when new content arrives. However, in certain circumstances (e.g., plugin object removed from the page), the PluginWindowlessWin object is deleted without notifying my plugin. Thus, I end up calling Invalidate() on a bad pointer and crashing.
How can I continue to notify the browser of updates so it will continue to send refresh events - through Invalidate() calls or otherwise - without relying on objects that may be silently deleted?
When using a windowless plugin, you can't draw except when the browser requests it. Sounds like you have that part. You can ask the browser to request a draw by calling InvalidateWindow on the PluginWindowlessWin.
Once AttachedEvent is called on your plugin, PluginWindowlessWin will be available; you can even save the reference if you want. However, you need to release it when DetachedEvent is called.
My Facebook app is a flash game. I want the game swf to save its latest state to the server when the window unloads. Since I embed the swf with swfobject, I use its embed handler to add a onbeforeunload listener to window:
function embedHandler(event)
{
shell=event.ref;
window.onbeforeunload=function(event)
{
shell.message("save", null);
//delay the unloading a bit so flash has time to contact server
var now = new Date().getTime();
var later=now+50;
while (now < later)
{
now = new Date().getTime();
}
}
}
Here's the problem. This works every time when the swf is loaded directly from the app (a rails app). It never works when the swf is loaded from Amazon.
All the cross-domain issues are worked out between the swf and the app--the rails app accepts calls from Amazon swf, and the Amazon swf loads data from the rails app.
ExternalInterface also works for both outgoing and ingoing calls. But I suspect this is nonetheless a browser security issue, since the inward-going ExternalInterface call only fails when:
it is called from inside the window.onbeforeunload handler
the swf originates from Amazon.
What is the problem? How does one unobtrusively save game state when the game is from a CDN and the save is triggered by onbeforeunload in Javascript? Or is there a better way to accomplish this same thing?
Testing in Firefox.
ExternalInterface also works for both outgoing and ingoing calls. But
I suspect this is nonetheless a browser security issue, since the
inward-going ExternalInterface call only fails when:
it is called from inside the window.onbeforeunload handler
the swf originates from Amazon.
From the sounds of it you worked out all the security issues.
It is more likely a lack of understanding on your part on what is going on behind the scene when onbeforeunload is triggered.
This is a function that will not wait for your "game.swf" to finish the call back via ExternalInterface.This is why you added a stalling mechanism to delay that process. However, I will assume here that this works from the rails app because that is a local server and you are not subject to the lag monster.
Now you might be thinking well I put in a delay it should work. Well that delay is on 50 milliseconds. Try increasing to to 5000(5 seconds) and you should see it start to work on the cdn.
The saving of data should be controlled via the flash app and not triggered by an outside source.
In the game itself you should have milestones that should trigger a save event.
In closing I do want to add that is by far the worst method you could use to save information up to a server. onbeforeunload is unreliable and is subject to cross browser issues let alone putting a lag loop in the JavaScript is just a bad idea and in the end just annoy your users to the point that they won't return.
We want to create a Windows desktop version of our weather widget
There are 2 special things about the widget.
It consumes a lot of processor time
while active - it displays an
animated picture (Flash without GPU acceleration, unfortunately).
It updates the weather from our
server (frequent server requests from all widget users).
When the user does not look at the widget there is no need for animation and weather loading.
So I have an idea of putting my widget to sleep when it is not visible and hense not used.
Is it possible to detect whether the widget is used or not.
Speaking precisely I need to know whether the widget is covered by other windows?
I mostly interested in Vista/7 gadgets engine, however I also would like to know if this problem is solved in these widget engines
Yahoo widgets
Google desktop
Hope to find some desktop widget guru here.
Pasha
If you InvalidateRect and don't get a subsequent WM_PAINT message, than your window is hidden. You can call UpdateWindow after InvalidateRect to force the WM_PAINT message to happen (or not happen) right away.
So you could do something like this
request server data (and cancel request timer if any)
when data arrives InvalidateRect
when WM_PAINT message arrives, draw the data and set a timer for next request
when timer arrives, goto 1
When you stop getting WM_PAINT messages, you stop re-setting your timer, and you therefor stop requesting updates from the server. When the WM_PAINT message happens (because you are no longer covered). You start requesting data again.