I want to avoid word-wrapping in grid cell and instead have a tool-tip so each row is on a single line. How can I add a tooltip to a cell when the content it's not fully visible?
There is no direct way for this. You need to determine the size of the text in some method and than your GridCellRenderer needs to setup the qtip attribute if needed (http://www.sencha.com/examples/explorer.html#basicgrid)