Select a drawing tool and start an operation
The m_current_tool should not be null, but this function would need to execute to correct the issue. Otherwise, the value would be 'stuck' at null. So, this function treats m_current_tool equal to null as a valid precondition.
| name | 
                 The name of the tool to select  | 
            
| x | 
                 The x coordinate to start the tool operation  | 
            
| y | 
                 The y coordinate to start the tool operation  |