Windows 8 Release Preview Build 8400 Available for OEMs and TAP; Metro Apps Background Tasks Explained; Viewsonic Teases Windows 8 Multi-touch Display;

Windows 8 Release Preview Build number 8400 (8400.0.WINMAIN_WIN8RC.120518-1423), weighing in at 2.43GB is now avilable for download to those part of the OEM or TAP program on Microsoft Connect, WinUnleaked reports. The rest of public will have to wait until the official release slated for June first week.Windows 8 Release Preview [x86 - ENG]File name: […]

Windows 8 Release Preview Build 8400 available for download on Microsoft Connect to OEMs and TAP

Windows 8 Release Preview Build number 8400 (8400.0.WINMAIN_WIN8RC.120518-1423), weighing in at 2.43GB is now avilable for download to those part of the OEM or TAP program on Microsoft Connect, WinUnleaked reports.

The rest of public will have to wait until the official release slated for June first week.

Windows 8 Release Preview [x86 - ENG]

File name: 8400.0.WINMAIN_WIN8RC.120518-1423_X86FRE_CLIENT_EN-US-HRC_CCSA_X86FRE_EN-US_DV5.ISO
Size: 2.43GB
CRC32: 70B0ACEA
MD5: 7285DA50A07E33BC3B5A20E48AFAF375
SHA-1: 8BED436F0959E7120A44BF7C29FF0AA962BDEFC9

In other Windows 8 news,

Engadget is reporting that it has received an invite from Viewsonic, who is teasing the media with what it is calling its "Touch and Connect" product line up, including a 22-inch "smart business tablet monitor," powered by what appears to be Android 4.0 Ice Cream Sandwich -- to be unveiled during the Computex trade show in Taipei.

The giant touch-enabled device will be joined by a Windows 8 multi-touch display, new cloud computing solutions, high-end laser projectors and some interactive electronic billboards.

ViewSonic teases 22-inch Android ICS tablet

Viewsonic will also be showing off what it is calling a 22-inch "smart business tablet monitor" that, at least according to the invite picture, is running on Android 4.0 (Ice Cream Sandwich).

Viewsonic will also be showing off some non-PC and mobile OS products at Computex, including some interactive billboards. All in all, it sounds like an very interesting line-up.

Also, In its latest post, Hari Pulapaka, Program Manager, Windows, talk about background tasks and how Windows 8 metro app can run code in the background even when it is suspended.

Pulapaka describe two common scenarios with example code that show you how to run "own Metro app code in the background", "downloading POP email every 15 minutes with a lock screen capable app" and how any app can do work in the background when the device is on AC power.

"Background task triggers are designed for varied scenarios and applications, and so have different requirements and resource management constraints. The apps that always need to stay up to date need to be on the lock screen, this is limited to 7 apps. You don't have to use background tasks if you simply want to keep your app fresh with content. You can always use live tiles or scheduled notifications as we explained in the post Create a great tile experience," Pulapaka explains.

You can build more advanced VOIP, instant messaging or push email apps using other background task triggers such as Control Channel or Push Notification.

"In contrast, if you want to do opportunistic work, any app can use the maintenance trigger which runs on AC or certain system triggers. To use these triggers the app doesn't need to be on the lock screen. Apps on the lock screen have more relaxed resource management constraints because they need to run more frequently (that's why we limit the number and put the user in control!)" he said.

In the download POP mail every 15 minutes example, he says, "Because an app uses background tasks to always stay up-to-date even when the user isn't using their Windows 8 device, the way a user controls what apps can use these background tasks is by granting them permission to appear on the lock screen. Because the lock screen is designed to provide users info about their apps without the need for them to unlock their Windows 8 device."

Windows 8 Metro Style Apps Background Taks: download POP mail every 15 minutes on lock screen

"This relationship is a two-way street: your app can use these types of background tasks only if it is on the lock screen and, likewise, your app can appear on the lock screen only if it requests to use these types of background tasks. Because a relatively small number of apps can be placed on the lock screen, it is important for your app to provide a good lock screen experience. If it doesn't, users will likely remove it to make room for something else."

"Examples of apps include: a mail app that shows a count of unread email messages, a calendar app that shows upcoming appointments in the detailed status slot, or a messaging app that shows how many messages a user has missed," explain Pulapaka.

To add your app to the lock screen , it needs to specify the lock screen notifications type available in the Application UI tab of the manifest.

"Each app on the lock screen receives 2 seconds of CPU time every 15 minutes, which can be used by all of the background tasks of the app. At the end of 15 minutes, each app on the lock screen receives another 2 seconds of CPU time for use by its background tasks. Any unused CPU time in the 15-minute interval is lost and the app can't accumulate it," he said.

"Each app not on the lock screen receives 1 second of CPU time every 2 hours. If the app uses all of its available CPU time, its background tasks are suspended until the app's CPU quota is replenished at the next generation for CPU quota updates."

Windows 8 Metro Style apps Background task manifest declarations

Adding Metro Style App to a lock screen: Background task manifest declarations