diff --git a/kernel/trunk/const.inc b/kernel/trunk/const.inc
index e3b60e4a63..b21151c39f 100644
--- a/kernel/trunk/const.inc
+++ b/kernel/trunk/const.inc
@@ -1,6 +1,6 @@
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;                                                              ;;
-;; Copyright (C) KolibriOS team 2004-2017. All rights reserved. ;;
+;; Copyright (C) KolibriOS team 2004-2021. All rights reserved. ;;
 ;; Distributed under terms of the GNU General Public License    ;;
 ;;                                                              ;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -505,7 +505,7 @@ struct  APPDATA
         wait_param      dd ?            ;+100  +++
         tls_base        dd ?            ;+104
                         dd ?            ;+108
-        event_filter    dd ?            ;+112
+                        dd ?            ;+112
         draw_bgr_x      dd ?            ;+116
         draw_bgr_y      dd ?            ;+120
                         dd ?            ;+124
@@ -516,7 +516,7 @@ struct  APPDATA
         saved_box       BOX             ;+144
         ipc_start       dd ?            ;+160
         ipc_size        dd ?            ;+164
-        event_mask      dd ?            ;+168
+        event_mask      dd ?            ;+168 ; mask which accumulates occurred events
         debugger_slot   dd ?            ;+172
         terminate_protection dd ?       ;+176
         keyboard_mode   db ?            ;+180
@@ -538,7 +538,7 @@ APP_OBJ_OFFSET  = 48
 APP_EV_OFFSET   = 40
 
 struct  TASKDATA
-        event_mask      dd ?
+        event_mask      dd ? ; mask which stores event types allowed for task
         pid             dd ?
                         dw ?
         state           db ?
@@ -590,6 +590,7 @@ ends
 
 label WDATA.fl_wstyle byte at WDATA.cl_workarea + 3
 
+assert sizeof.WDATA = 32
 
 struct  SYS_VARS
         bpp             dd ?
diff --git a/kernel/trunk/core/sys32.inc b/kernel/trunk/core/sys32.inc
index fc59323c34..6622926f2d 100644
--- a/kernel/trunk/core/sys32.inc
+++ b/kernel/trunk/core/sys32.inc
@@ -1,6 +1,6 @@
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;                                                              ;;
-;; Copyright (C) KolibriOS team 2004-2020. All rights reserved. ;;
+;; Copyright (C) KolibriOS team 2004-2021. All rights reserved. ;;
 ;;  Distributed under terms of the GNU General Public License.  ;;
 ;;                                                              ;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -554,7 +554,7 @@ destroy_thread:
 
         pusha   ; save window coordinates for window restoring
         cld
-        shl     esi, 5
+        shl     esi, BSF sizeof.WDATA
         add     esi, window_data
         mov     eax, [esi+WDATA.box.left]
         mov     [draw_limits.left], eax
@@ -566,16 +566,12 @@ destroy_thread:
         mov     [draw_limits.bottom], eax
 
         xor     eax, eax
-        mov     [esi+WDATA.box.left], eax
-        mov     [esi+WDATA.box.width], eax
-        mov     [esi+WDATA.box.top], eax
-        mov     [esi+WDATA.box.height], eax
-        mov     [esi+WDATA.cl_workarea], eax
-        mov     [esi+WDATA.cl_titlebar], eax
-        mov     [esi+WDATA.cl_frames], eax
-        mov     dword [esi+WDATA.z_modif], eax; clear all flags: z_modif, wstate, redraw, wdrawn
+        mov     edi, esi
+        mov     ecx, sizeof.WDATA/4
+        rep stosd
+
         lea     edi, [esi-window_data+draw_data]
-        mov     ecx, 32/4
+        mov     ecx, sizeof.WDATA/4
         rep stosd
         popa
 
diff --git a/kernel/trunk/core/taskman.inc b/kernel/trunk/core/taskman.inc
index b981fcb636..b7e397fb22 100644
--- a/kernel/trunk/core/taskman.inc
+++ b/kernel/trunk/core/taskman.inc
@@ -1,6 +1,6 @@
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;                                                              ;;
-;; Copyright (C) KolibriOS team 2004-2016. All rights reserved. ;;
+;; Copyright (C) KolibriOS team 2004-2021. All rights reserved. ;;
 ;;  Distributed under terms of the GNU General Public License.  ;;
 ;;                                                              ;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -484,9 +484,9 @@ pid_to_slot:
         push    ebx
         push    ecx
         mov     ebx, [TASK_COUNT]
-        shl     ebx, 5 ; ebx *= 32 (32 is size of TASKDATA struct)
+        shl     ebx, BSF sizeof.TASKDATA ; multiply by size 
         ; add 2*32 cause:
-        ; 0x80003000 - 0x80003020 isnt a task actually
+        ; [TASK_TABLE; TASK_TABLE + 32) isnt a task actually
         ; skip first process in the task table
         mov     ecx, 2*32
 
@@ -509,7 +509,7 @@ pid_to_slot:
         ret
 
 .pid_found:
-        shr     ecx, 5
+        shr     ecx, BSF sizeof.TASKDATA ; divide by size
         mov     eax, ecx ;convert offset to index of slot
         pop     ecx
         pop     ebx
diff --git a/kernel/trunk/kernel.asm b/kernel/trunk/kernel.asm
index 04aa13c1d7..628025d361 100644
--- a/kernel/trunk/kernel.asm
+++ b/kernel/trunk/kernel.asm
@@ -1,6 +1,6 @@
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;
-;; Copyright (C) KolibriOS team 2004-2020. All rights reserved.
+;; Copyright (C) KolibriOS team 2004-2021. All rights reserved.
 ;; PROGRAMMING:
 ;; Ivan Poddubny
 ;; Marat Zakiyanov (Mario79)
@@ -30,6 +30,12 @@
 ;; turbanoff
 ;; Asper
 ;; art_zh
+;; dunkaist
+;; Coldy
+;; rgimad
+;; Boppan
+;; Doczom
+;; and others
 ;;
 ;; Data in this file was originally part of MenuetOS project which is
 ;; distributed under the terms of GNU GPL. It is modified and redistributed as
@@ -4045,9 +4051,6 @@ align 4
 set_app_param:
         mov     edi, [TASK_BASE]
         mov     eax, ebx
-        btr     eax, 3                           ; move MOUSE_FILTRATION
-        mov     ebx, [current_slot]              ; bit into event_filter
-        setc    byte [ebx+APPDATA.event_filter]
         xchg    eax, [edi + TASKDATA.event_mask] ; set new event mask
         mov     [esp+32], eax                    ; return old mask value
         ret