import bpy
import bgl
import blf
import time

# information for the add-ons window
bl_addon_info = {
    'name': '3D View:Screencast Key Status Tool',
    'author': 'Paulo Gomes',
    'version': (0,4),
    'blender': (2, 5, 4),
    'location': 'View3D > Spacebar > Search for "Screencast Key Status Tool"',
    'description': 'Display keys pressed in the 3d-view, useful for screencasts.',
    'warning': '',
    'wiki_url': '',
    'tracker_url': '',
    'category': '3D View'}

def draw_callback_px(self, context):
    # draw text in the 3d-view
    blf.size(0, 20, 72)
    final = 0

    # only display key-presses of last 2 seconds
    for i in range(len(self.key)):
        if time.time()-self.time[i] < 2:
            blf.position(0, 15, 50+20*i, 0)
            blf.draw(0, self.key[i])
            final = i
        else:
            break

    # get rid of statuses that aren't displayed anymore
    self.key = self.key[:final+1]
    self.time = self.time[:final+1]

class ScreencastKeysStatus(bpy.types.Operator):
    '''Draw keys pressed in 3DView'''
    bl_idname = 'view3d.screencast_keys'
    bl_label = 'Screencast Key Status Tool'

    def modal(self, context, event):
        context.area.tag_redraw()

        # keys that shouldn't show up in the 3d-view
        ignore_keys = ['LEFT_SHIFT', 'RIGHT_SHIFT', 'LEFT_ALT',
        'RIGHT_ALT', 'LEFT_CTRL', 'RIGHT_CTRL', 'TIMER', 'MOUSEMOVE',
        'MIDDLEMOUSE','LEFTMOUSE', 'RIGHTMOUSE', 'WHEELDOWNMOUSE',
        'WHEELUPMOUSE']

        if event.value == 'PRESS':
            # add key-press to display-list
            sc_keys = []

            if event.shift:
                sc_keys.append('Shift ')

            if event.alt:
                sc_keys.append('Alt ')

            if event.ctrl:
                sc_keys.append('Ctrl ')

            if event.type not in ignore_keys:
                sc_keys.append(event.type)

                self.key.insert(0, '+ '.join(map(str, sc_keys)))
                self.time.insert(0, time.time())

        if event.type == ('F7'):
            # stop script
            context.region.callback_remove(self._handle)
            return {'CANCELLED'}

        return {'PASS_THROUGH'}

    def invoke(self, context, event):
        if context.area.type == 'VIEW_3D':
            # start script
            context.window_manager.add_modal_handler(self)

            self._handle = context.region.callback_add(draw_callback_px, (self, context), 'POST_PIXEL')
            self.key = []
            self.time = []

            return {'RUNNING_MODAL'}

        else:
            # operator not invoked from within the 3d-view
            self.report({'WARNING'}, 'View3D not found, cannot run operator')
            return {'CANCELLED'}

def register():
    pass

def unregister():
    pass

if __name__ == '__main__':
    register()