Sending Data

The power state of the user's computer and the amount of storage your gadget requires can have a significant impact on the user's experience. Consider both the power state and typical storage needs when designing your device.

Device Updates

You have control over how often your gadget sends updated information to a device. However, no updates are possible when the computer is asleep. When the computer is asleep, offline gadgets operate by reading cached information stored on the device. However, online-only gadgets work only when the computer is awake. Some devices can wake the computer from sleep when the user wants to use an online-only gadget.

Two additional options affect the process of device updates:

Updating gadgets from the device. On some devices, users can choose Update Gadgets on the context menu of the device to update gadgets with information from the computer cache. If this option is chosen when the computer is asleep, the user is prompted to wake up the computer to perform the update. The Update Gadgets option is not available on the context menu when the device cannot wake the computer, such as when the computer is shut down.

The following screen shot shows the Update Gadgets option, which can appear on the context menu on a Windows SideShow-compatible device that is running the .NET Micro Framework when the user presses the MENU button on the home page.

Waking the computer automatically. When a user turns on the Automatic Wake feature, Windows Vista wakes the computer from sleep at a user-specified frequency so that gadgets can get updated information from the Internet or a local network and send that information to connected devices.

The following screen shot shows the Automatic wake page in Windows SideShow in Control Panel.

Gadgets should not rely exclusively on the Automatic Wake feature to update devices, for the following reasons:

• Automatic Wake is off by default. Users must opt in manually to make this update mechanism available to gadgets.

• Automatic Wake works only when the computer is asleep, not when it is shut down.

• Some computers cannot wake up while they are hibernating.

• Automatic updates can run only when the user is logged in.

• The computer returns to sleep a few minutes after Automatic Wake is invoked, regardless of whether updating is successful.

• When the computer wakes, only the devices that are connected at that time will be updated.

• The computer manufacturer can disable Automatic Wake.

• System administrators can disable Automatic Wake using Group Policy.

• The gadget must be running when the system wakes. For more information about this, see "Use the gadget manager" in Working with a Gadget.

Limit Device Resource Usage

Users are likely to have multiple gadgets turned on for their devices. Gadgets share device resources, including a very limited amount of storage space. Gadget data is truncated based on the number of gadgets turned on for a device.

If users believe that your gadget is consuming too much storage, they may choose to turn off your gadget to free up resources for their other gadgets.

You can avoid over-consuming device resources in three ways:

• Limit the amount of data your gadget sends.

• Send images that are appropriately sized for the target device. Ensure that your gadget doesn't try to send high-resolution color images to devices that have small monochrome bitmap displays. For more information, see Device Capabilities.

• Provide settings for your gadget that allow users to change the information that is sent to devices.