Selection Screen hangs/stuck when returning, maybe because of char1024 field

Hi,

In my selection-screen program, I use method CL_GUI_FRONTEND_SERVICES=>FILE_OPEN_DIALOG. It opens a pop-up screen to select a desired file, and puts the value into the parameter P_FILENM (char1024). After I select the file and close the pop-up screen, It takes about 2-3 seconds for the selection-screen parameter to refresh itself with the filename inside P_FILENM text-box. After execution, the program displays the file's contents in an SALV table. When I go back to the selection-screen using method GO_SALV_TABLE->CLOSE_SCREEN, it takes another 3-4 seconds during which the screen hangs, I can see the empty screen with the execution button but no parameters, and only then they appear and the screen becomes available.

My question is: why are those delays happening? Maybe it is related to the char1024 field? How can I prevent them from delaying the program's operation?

Thank you!

--------------------------------------------

SELECTION-SCREEN BEGIN OF LINE.

PARAMETER p_filenm TYPE zfilename. " Filename Upload textbox - ZFILENAME is based on CHAR1024

SELECTION-SCREEN END OF LINE.

--------------------------------------------

AT SELECTION-SCREEN ON VALUE-REQUEST FOR p_filenm.

PERFORM file_open_dialog CHANGING gv_file_name.

p_filenm = gv_file_name.

START-OF-SELECTION.

" get data

......

PERFORM setup_salv CHANGING gt_data[]

go_salv_table

go_salv_events

go_salv_events_handler

go_salv_display

go_salv_sorts

go_salv_columns

go_salv_column

go_salv_functions.

go_salv_table->display( ).

go_salv_table->close_screen( ).

--------------------------------------------

FORM file_open_dialog CHANGING ev_file_name TYPE zfilename.

DATA: lt_file_tab TYPE filetable,

ls_file LIKE LINE OF lt_file_tab[].

gv_report_title = text-001. " Choose a file

" Opening the File Selection dialog:

CALL METHOD cl_gui_frontend_services=>file_open_dialog

EXPORTING

window_title = gv_report_title

* DEFAULT_EXTENSION =

* DEFAULT_FILENAME =

file_filter = gc_filetypes_filter

* WITH_ENCODING =

* INITIAL_DIRECTORY =

* MULTISELECTION =

CHANGING

file_table = lt_file_tab[]

rc = gv_rc

* USER_ACTION =

* FILE_ENCODING =

EXCEPTIONS

file_open_dialog_failed = 1

cntl_error = 2

error_no_gui = 3

not_supported_by_gui = 4

OTHERS = 5.

IF sy-subrc <> 0.

MESSAGE ID sy-msgid TYPE sy-msgty NUMBER sy-msgno

WITH sy-msgv1 sy-msgv2 sy-msgv3 sy-msgv4.

ENDIF.

" Getting the selected file:

READ TABLE lt_file_tab[]

INTO ls_file INDEX 1.

" Setting the selected file as the parameter:

ev_file_name = ls_file-filename.

ENDFORM.