[Gambas-user] To fast do..loops for process management!

[Demosthenes Koptsis]

On Sun, Nov 30, 2008 at 11:27 PM, Benoit Minisini
<gambas at ...1...> wrote:
> On jeudi 27 novembre 2008, Demosthenes Koptsis wrote:
>> Hi dear list,
>>
>> I write a front-end for mpg123 mp3 console player in gambas2 but i
>> came face to face with a bug and i need your help!
>> i dont know if the bug is due to gambas or my writing code or mpg123
>> player's.
>>
>> The story is like this....
>>
>> '### I have two public vars
>>
>> PUBLIC hProcess AS Process 'varProcess is a Process variable for SHELL
>> command PUBLIC iNrPlayingSong AS Integer 'public var to hold the nr of
>> playing song
>>
>> '### i execute a command to play mp3 songs
>>
>> .....
>>     'format sting command
>>     sCommand = "mpg123 -vC@ " & sPlaylistFile 'play in verbose mode
>> (v), interactive (C), and load a playlist (@)
>>     'execute command
>>     hProcess = SHELL sCommand FOR INPUT OUTPUT
>> .....
>>
>>
>> '### previous track sub
>> PUBLIC SUB btnPreviousTrack_Click()
>>
>>     IF NOT IsNull(hProcess) THEN
>>       IF hProcess.State = 1 THEN PRINT #hProcess, "d"  'mpg123 recieve
>> a keyboard "d" to go previous track
>>     ENDIF
>>
>> END
>>
>>
>> '### next track sub
>> PUBLIC SUB btnNextTrack_Click()
>>
>>   IF NOT IsNull(hProcess) THEN
>>     IF hProcess.State = 1 THEN PRINT #hProcess, "f"   'mpg123 recieve
>> a keyboard "f" to go next track
>>   ENDIF
>>
>> END
>>
>> '### NOTE, the previous SUBs are the same. They differ only to letters
>> "f" and "d"
>>
>>
>> '#### A wait sub for the system, see next!
>> PUBLIC SUB WaitSystem()
>>
>>   'wait the system
>>   FMain.Mouse = 3
>>   WAIT 0.05
>>   FMain.Mouse = 0
>>
>> END
>>
>>
>>
>> '########### So far with no bug, the code is working
>>
>>
>>
>> '### i write a sub if user click in playlist a list item = a mp3 track
>>
>> PUBLIC SUB lvwPlayList_DblClick()
>>
>>   DIM iCounter AS Integer = iNrPlayingSong 'var get current playing
>> song and also act as counter. iNrPlayingSong get its value from SUB
>> Process_Read()
>>
>>   IF NOT IsNull(lvwPlayList.Key) THEN
>>
>> '### This do..loop part working fine
>>       'if user click an item with key greater than number of playing song
>>     IF (lvwPlayList.key + 1) > iCounter THEN 'go next track
>>        DO
>>           IF iCounter = (lvwPlayList.key + 1) THEN BREAK
>>           'PRINT "Go next track"
>>           btnNextTrack_Click()
>>           INC iCounter
>>        LOOP
>>     ENDIF
>>
>>       'if user click an item with key smaller than number of playing song
>>     IF (lvwPlayList.key + 1) < iCounter THEN 'go previous track
>>        DO
>>           IF iCounter = (lvwPlayList.key + 1) THEN BREAK
>>           'PRINT "Go previous track"
>>           btnPreviousTrack_Click()
>>
>>         ' ### Now the strange bug
>>           '!FIXEME!
>> ###########################################################################
>>######### WaitSystem() '***!!!!!***---> ### [ -- i need to force a wait
>> system sub to working correctly --- ]
>>           'Probably there is a bug.
>>         'the hProcess does not recieve the btnPreviousTrack_Click() command
>> as recieves btnNextTrack_Click()
>>
>>           'The same code in btnNextTrack_Click() works fine.
>>           'Sorry for the annoying bug.
>>           '!FIXEME!
>> ###########################################################################
>>#########
>>
>>           DEC iCounter
>>
>>        LOOP
>>     ENDIF
>>
>>   ENDIF
>>
>> END
>>
>> '####################
>>
>> To test this bug make a long playlist with up to 200 mp3s.
>>
>> if you check the two subs btnNextTrack_Click() and
>> btnPreviousTrack_Click() are the same.
>> If you check the two DO..LOOPs parts are the same, they only change in
>> btnNextTrack_Click() and btnPreviousTrack_Click().
>> In first case the btnNextTrack_Click() works.
>> In second case i need to force a wait to application to work the
>> btnPreviousTrack_Click().
>>
>> I test to PRINT the vars which they be read from Sub Read_Process and
>> they are ok. Vars iNrPlayingSong, iCounter are OK.
>> My conclusion is that hProcess cannot recieve so quickly the previous
>> command from gambas2.
>> So the questions now!
>> Is this a bug of mpg123 player or a bug of gambas in process management?
>>
>>
>> I attach my project if you want to look its strange bug.
>>
>> --
>>
>> Γεια χαρα σε όλους!!!
>>
>> Regards,
>>
>> Demosthenes Koptsis
>
> I don't really see any bug, but I can be wrong as your code is not very clear.
>
> What I can tell you is that there is no guarantee that you will get the answer
> of a command sent to mpg123 immediately, so the song number stored in your
> public variable is not necessarily accurate.

I checked the var which holds the number of playing song by PRINT it
and is correct.

>
> Next, the event loop is only run if no code is run, or if you call the WAIT
> instruction.

That means, i cant get results from a running process with
Process_Read when i run code in a do...loop?

If this is true i cant run simultaneously processes and loop code!

>And the Process_Read function is called only by the event loop!
>
> Regards,
>
> --
> Benoit Minisini
>
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-- 

Γεια χαρα σε όλους!!!

Regards,

Demosthenes Koptsis