Natural panning to older versions of Blender

space_view3d_pan_naturally.py

bl_info = {
    'name': 'Pan naturally',
    'author': '',
    'version': (0, 0, 1),
    'blender': (2, 6, 0),
    'location': '3d view > Alt + LMB-drag',
    'description': 'Pan view naturally for older Blender versions.',
    'wiki_url': '',
    'tracker_url': '',
    'category': '3D View'}

import bpy
import pprint
from mathutils import *
from math import *

class PanNaturally(bpy.types.Operator):
    '''Pan naturally.'''
    bl_idname = "view3d.pan_naturally"
    bl_label = "Pan naturally"
    
    horizontal_distance=0
    vertical_distance=0
    mouse_last_pos=Vector((0,0))
    
    def execute(self, context):
        region_3d = context.space_data.region_3d
        
        xa=Vector((1,0,0))
        ya=Vector((0,1,0))
        
        xa.rotate(region_3d.view_rotation)
        ya.rotate(region_3d.view_rotation)

        region_3d.view_location = region_3d.view_location + self.horizontal_distance * xa + self.vertical_distance * ya

        return {'FINISHED'}
    
    def modal(self, context, event):
        region_3d = context.space_data.region_3d
        
        if event.type == 'TRACKPADPAN':
            
            self.report({'INFO'}, str(event.mouse_x))

            #find the yaw and pitch angles from the mouse position variation
            mouse_pos=Vector((event.mouse_region_x,event.mouse_region_y))
            self.horizontal_distance=-(mouse_pos.x-self.mouse_last_pos.x)/500.0*region_3d.view_distance
            self.vertical_distance=-(mouse_pos.y-self.mouse_last_pos.y)/500.0*region_3d.view_distance
            self.execute(context)
            self.mouse_last_pos=Vector((event.mouse_region_x,event.mouse_region_y))
        
        elif event.type in {'MOUSEMOVE', 'LEFTMOUSE', 'MIDDLEMOUSE', 'RIGHTMOUSE', 'ESC'}:
            return {'FINISHED'}
        
        return {'RUNNING_MODAL'}
    
    def invoke(self, context, event):
        
        if context.space_data.type == 'VIEW_3D':
            region_3d = context.space_data.region_3d
            self.mouse_last_pos=Vector((event.mouse_region_x,event.mouse_region_y))
                        
            context.window_manager.modal_handler_add(self)
            
            if region_3d.view_perspective == 'CAMERA':
                region_3d.view_perspective = 'PERSP'
            
            return {'RUNNING_MODAL'}
        
        else:
            return {'CANCELLED'}


def register():
    bpy.utils.register_class(PanNaturally)
    
    wm = bpy.context.window_manager
    km = wm.keyconfigs.addon.keymaps.new(name="3D View", space_type='VIEW_3D')
    #kmi = km.keymap_items.new('view3d.pan_naturally', 'EVT_TWEAK_L', 'ANY', shift=False, ctrl=False, alt=False)
    kmi = km.keymap_items.new('view3d.pan_naturally', 'TRACKPADPAN', 'ANY')

def unregister():
    bpy.utils.unregister_class(PanNaturally)
    
    wm = bpy.context.window_manager
    km = wm.keyconfigs.addon.keymaps['3D View']
    for kmi in km.keymap_items:
        if kmi.idname == 'view3d.pan_naturally':
            km.keymap_items.remove(kmi)

if __name__ == "__main__":
    register()