add support for notepad.allocateIndicator function about pythonscript

[alankilborn]

Note that the Notepad++ code for allocating indicators will NOT store a -1 in the calling argument upon failure as the corresponding marker allocation code will.

Preliminary documentation for the API is here: notepad-plus-plus/npp-usermanual#542

[alankilborn]

Here's some test code exercising the call in Notepad++:

# -*- coding: utf-8 -*-
from __future__ import print_function

from Npp import *
from ctypes import ( addressof, WinDLL )
from ctypes.wintypes import ( HWND, UINT, WPARAM, LPARAM, DWORD )

LRESULT = LPARAM

user32 = WinDLL('user32')

SendMessageW = user32.SendMessageW
SendMessageW.restype = LRESULT
SendMessageW.argtypes = [ HWND, UINT, WPARAM, LPARAM ]

WM_USER = 0x400
NPPMSG = (WM_USER + 1000)

def notepad_allocateIndicator_RAW(num_indicators_to_alloc):
    NPPM_ALLOCATEINDICATOR = (NPPMSG + 113)
    lowest_allocated_indicator_id = DWORD()  # not sure DWORD is the correct thing to use here...
    __ = SendMessageW(notepad.hwnd, NPPM_ALLOCATEINDICATOR, num_indicators_to_alloc, addressof(lowest_allocated_indicator_id))
    return None if __ == 0 else lowest_allocated_indicator_id

num_indicators_needed = 3
start_indicator_id = notepad_allocateIndicator_RAW(num_indicators_needed)
if start_indicator_id is None:
    print('could not allocate enough indicator(s) to fulfill request')
else:
    start_indicator_id = start_indicator_id.value  # c_ulong to int
    print('allocated indicator ids:', list(range(start_indicator_id, start_indicator_id + num_indicators_needed)))

[alankilborn]

Thanks @chcg Christian!