Friday, 18 May 2012

Solution for web pages with white spaces failing in Internet Explorer 9 (IE9)

If you have a webpage with white spaces/new line character between the ending of one html tag and beginning of another, then chances are there that it may not display or work properly in Internet Explorer 9. I checked the  html code generated for Internet Explorer 8(where it works!) and Internet Explorer 9. There is no difference. Then what has gone wrong?

Issue : 
  • Internet Explorer 9 is conforming to HTML 5 specifications. Accordingly HTML parsing has been changed in IE 9. One change that affects almost every page is how whitespace parsed. While IE8 removes or collapses whitespace, IE9 persists all whitespace into the DOM at parse-time. Refer to the following link for more details : 
  • HTML 5 logo
  • So, if you have java script code which accesses the nodes in DOM ignoring the white spaces previously, then you are bound to be in big  trouble. In IE9, all the white spaces/new lines in DOM are treated as nodes. So, when you traverse using APIs like firstChild may not reference to the element you might have intended.

Solutions :

  1. If you want to traverse elements (ignoring the white spaces) only then use Element Traversal APIs - calling functions such as nextElementSibling to ensure that you don’t reference a stray newline character or white space by mistake.
  2. On the other hand, make sure that your code is backward compatible with previous browser versions by adding check for the same while traversing the elements in DOM
  3. Removing the white spaces - this is a tedious job, as you would be doing the work of the browser done previously. But here you don't need to have the check for Internet Explorer browser versions. 

Tuesday, 15 May 2012

How to avoid GetSaveFileNameW failing in IE9 in Windows7?

GetSaveFileNameW is a Windows API. It creates a Save dialog box that lets the user specify the drive, directory, and name of a file to save. I had a ActiveX  plugin which was using this function to get the name of the file user is saving. It was working fine in IE8 in Windows XP but it started failing in IE9 on Windows 7. It did not create a dialog box and returned error!

CommDlgExtendedError : When inquired through CommDlgExtendedError about the reason for failure of GetSaveFileNameW, it said error code : 0xFFFF

Internet Explorer 9 logo
Explanation for error code 0xFFFF(CDERR_DIALOGFAILURE) - The dialog box could not be created. The common dialog box function's call to the DialogBox function failed. For example, this error occurs if the common dialog box call specifies an invalid window handle.

Debugging : Internet literature provided little help. Then, I checked whether this function - GetSaveFileNameW - worked fine for a standalone application. It did and then tried with the same set of parameters in ActiveX plugin. But it did not work for ActiveX plugin 

Reason for failure : Later I found that IE9 was not fully supporting the ATL version I was using. GetSaveFileNameW was failing because of the flag OFN_EXPLORER. How?

Solution : OPENFILENAMEW structure is filled before passing as a parameter to GetSaveFileNameW. Here, we set the flag OFN_EXPLORER in the Flags attribute of OPENFILENAMEW structure. If the OFN_EXPLORER flag is set, the system uses the specified template to create a dialog box that is a child of the default Explorer-style dialog box. If the OFN_EXPLORER flag is not set, the system uses the template to create an old-style dialog box that replaces the default dialog box. I was setting the flag - OFN_EXPLORER. I now reset the OPENFILENAMEW and it works!!!

Monday, 26 December 2011

Workaround for old Firefox Plugins crashing on Windows 7

I had an old plugin which was working fine in Windows XP. When I moved to Windows 7, this plugin kept crashing whenever opened. After a while, I was able to find a workaround for making this plugin work.
Windows 7

The answer lies in DEP (Data Execution Prevention). This feature was enabled in my Windows 7 machine. After I disable this feature I was able to run my plugin in Firefox. Here is how you can disable DEP in Windows 7.

1. Go to command prompt
2. Execute the command bcdedit /set nx AlwaysOff
3. Reboot the machine (rebooting is required for the above setting to reflect)

Ideally with DEP enabled, if you want to run your plugin, you have to build the plugin with the latest version of Windows SDK.

Friday, 17 June 2011

How to make your old plugins work with Firefox 4?

I had a old plugin, which was working fine with Firefox 3.6. When I upgraded to Firefox 4.0.1, it suddenly stopped working. Firefox was listing it in the list of plugins installed and pointing to the right dll to load. Googling for this issue did not help. Also, tried replicating the registry entries similar to the ones in the machine which had Firefox 3.6 installed. No, it also did not work out.

From Process Explorer, came to know that Firefox 4.0.1 was not at all loading the dll. Then I looked into the Firefox logs to see what exactly is going on with this plugin dll.
[ Use the following commands to get the Firefox browser logs in file c:\plugins.log.
C:\> set NSPR_LOG_MODULES=all:5
C:\> set NSPR_LOG_FILE=c:\plugins.log
C:\> cd C:\Program Files\Mozilla Firefox
C:\> firefox.exe ]

To my surprise, Firefox was actually loading the plugin dll. But immediately it was unloading it. Then I put debug logs in all the plugin implemented APIs, to see what was going wrong. Finally found out that in NPP_Initialize(), I was calling NS_GetServiceManager(), an XPCOM API to get a reference to the XPCOM service manager. It was failing to get the reference and NPP_Initialize() was returning NPERR_GENERIC_ERROR to the browser. Cause of the issue is thus found out. Looking for solutions in Google again, I hit on the code project link, which explained two ways of getting the reference for XPCOM service manager. One, I was using in my plugin using the XPCOM API, NS_GetServiceManager(). The other one used the XPCOM API NS_InitXPCOM2(). Tried this one. Wow, it worked!

You can surely try this solution, if you are looking for solutions as to why your old plugin is not working in Firefox 4.0.1. See you then. Happy debugging!


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