Anurag Bhatnagar's Blog

Taking on a task in the Mouse Lock implementation

Now that I am getting a handle on the code (limited to the MouseLockable class) and encouraged by the progress made by Diogo and Raymond in implementing some of the tasks required for the Mouse Lock implementation, I decided to jump right in as well.

One of the requirements as per the specs is that the mouse cursor not be displayed while the mouse lock is on. So clearly, this method will be called from within the lock() method which we’ve got a start on. Next idea that immediately comes to mind is to somehow use the code that implements the CSS property of ‘cursor:none’ to achieve the same goal within the window that has mouse lock enabled.

Some of my colleagues have also started on the same road and I thought I would join in and discover with them.

The first breakthrough was to stumble upon this: Bug 346690. It is the bug that implements the Cursor:None property of CSS3 in firefox. Going through the discussion in the comments of that thread gave me various clues like ‘OnHideCursor()’ method and where some of the code relating to this implementation was saved. For windows, it is found in the file: mozilla-central/widget/src/windows/nsWindow.cpp.

I found an interesting part of the code in this file here:

case eCursor_none:
      newCursor = ::LoadCursor(nsToolkit::mDllInstance, MAKEINTRESOURCE(IDC_NONE));
      break;

It seems to be the code where the properties for the cursor are set in c++. So the next step is to study it further, discuss on irc and use mxr and dxr to find more clues as to how the CSS3 cursor none property was implemented.