No.
Firstly, the opening is far too long for a cannon door. You don't need to expose anywhere that length of the barrel to fire.
Secondly, if the cannon is placed there, the muzzle flash would almost certainly dazzle the pilot when it is fired. Half the canopy would be scorched and covered with soot after every shot.
Thirdly, if placed there, the vibrations and cuccussive forces released when the gun fires will do all sorts of bad things to the pilot and delicate instruments in the cockpit and will probably result in structural integrity issues developing with the canopy in the long term.
Lastly, when those doors open to expose whatever is inside, they will obstruct part of the pilots view to that side. Not a great idea during a dogfight.
i do not completly agree, the position of the gun has to do more with the needed space for avionics and radar in front of the cockpit and the refuelling probe optimal position just right or left of the canopy.
The F-18 and F-5 use guns in front of the canopy, there is no problems of soot or scorched canopies or dazzled pilots, niether problems with their radars or avionics.
That opening most likely is for the refuelling probe because that is the best position for the pilot while refuelling.
Most jets position the guns on wing like f-15, MiG-29, on the engine nacelle like MiG-31, Rafale or just behind the nose radome usually on a ventral position like F-4, MiG-23 rather than the unusual above the radome like the F-18 or F-5 because avionics and radar are usually located on the fore fuselage just inmediately infront and behind the cockpit
If you look at this F-86 you will find it has its guns pretty close to the canopy[video=youtube;FFk9JAvVxcA]http://www.youtube.com/watch?v=FFk9JAvVxcA&feature=related[/video]
