Windowless Silverlight (and Flash?) Application in Firefox: Messages about Invalid Mouse Positions

Question

When I create a windowless Silverlight application and run it on Firefox, the wrong mouse positions are reported. There is a vertical offset between the actual position of the mouse and what the application responds to.

I also noted this Flash question because my research shows that this problem also occurs when using Flash (see links below).

Playback:

Step 1. Create a new Silverlight application.

Step 2: Inside the MainApp.xaml grid, add the following:

<HyperlinkButton NavigateUri="http://google.com" VerticalAlignment="Center" HorizontalAlignment="Center">GOOGLE</HyperlinkButton>

Step 3: In SilverApplicationXTestPage.aspx (in a web project), add the following parameter to the Silverlight object:

<param name="windowless" value="true" />

Now run the silverlight application. When you hover a link, it is not underlined. Now slowly move the mouse up to a certain offset above the link that it will be highlighted.

This problem does not occur if you do one of the following:

• Switch Firefox to full screen mode (it seems that the top panel is causing the bias, so when it is not visible, there is no bias).
• Do not use Silverlight in windowless mode.
• Use any other browser.

I am using Silverlight 4 on Firefox 8.0 on Windows 7.

This seems like an old issue that affects not only Silverlight, but also Flash.

In my research, I came across the following suggested workarounds, without which I worked for me:

• Do not use overflow in css.
• Use css to set the 1px html field.
• Do not use iframes (but the playback steps described above do not use iframes).

As I mentioned, none of the above workarounds work.

Here are some links to mentions of this problem or similar:

http://forums.silverlight.net/t/161640.aspx/1/10

https://bugzilla.mozilla.org/show_bug.cgi?id=362193

http://forums.silverlight.net/t/94583.aspx/2/10#

https://bugzilla.mozilla.org/show_bug.cgi?id=536429

Does anyone know how to overcome this? Any workaround? I'm desperate!

Answer 1

I found this: http://support.mozilla.org/en-US/questions/795168 .

"Enabling plugin-container.exe in about: config (dom.ipc.plugins.enabled) fixes the mouse problem, but then the Silverlight plug-in pop-ups (like webcam / microphone resolution) freeze the browser."

I did not see a pop-up issue (copy permissions) after a configuration change.

Running this full screen mode also helped before I changed the configuration.

This requires the user to change browser settings, which is not ideal.

This is similar to this question: Silverlight - poor mouse position when embedding in html page when Firefox zooms in