Add Event Listener only one time?

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#1

Is there a way to make sure that a listener is added to a uno object only once?

For instance I have class that represents a cell. When the cell is created I want to add a listener to the cell.

class MyCellClass:
    def __init__(self, cell_name: str):
        # other code ...
        # how to only add if there is not already a MyCellModifyListener attached?
        modify_listener = MyCellModifyListener()
        self._cell.component.addModifyListener(modify_listener)

First Instance

my_first_cell = MyCellClass("A2")
# now my_first_cell "A2" has a listener attached

Later I may want to create another instance of cell on “A2”.

my_second_cell = MyCellClass("A2")
# now my_second_cell "A2" has a listener attached. Not preferred!

At this point there would be two cell modify listeners. I would like to ensure there is only one.
Is there a way to do this?

#2 
class MyCellClass:
    def __init__(self, cell_name: str):
        # other code ...
        # how to only add if there is not already a MyCellModifyListener attached?
        modify_listener = MyCellModifyListener()
        self._cell.component.removeModifyListener(modify_listener)
        self._cell.component.addModifyListener(modify_listener)
#3

This not working for the scenario I am trying to solve.

class CellCustomPropListener(unohelper.Base, XModifyListener):
    def __init__(self) -> None:
        XModifyListener.__init__(self)

    def modified(self, event: EventObject) -> None:
        try:
            _ = event.Source.AbsoluteName  # type: ignore
            log.debug(f"CellCustomPropListener: modified: {event.Source.AbsoluteName}")
        except RuntimeException:
            # cell is deleted
            log.debug("CellCustomPropListener: modified: Cell is deleted")

Then I am running something like:

def main():
    # other code ...
    cell = sheet["B2"]
    cell.value = 10
    print()
    cell2 = sheet["B2"]
    cell2.value = 12
    print()
    cell3 = sheet["B2"]
    cell3.value = 14
    print()

Outputs

30/05/2024 16:50:11 - DEBUG - CellCustomPropListener: modified: $Sheet1.$B$2

30/05/2024 16:50:11 - DEBUG - CellCustomPropListener: modified: $Sheet1.$B$2
30/05/2024 16:50:11 - DEBUG - CellCustomPropListener: modified: $Sheet1.$B$2

30/05/2024 16:50:11 - DEBUG - CellCustomPropListener: modified: $Sheet1.$B$2
30/05/2024 16:50:11 - DEBUG - CellCustomPropListener: modified: $Sheet1.$B$2
30/05/2024 16:50:11 - DEBUG - CellCustomPropListener: modified: $Sheet1.$B$2

In Cell class

class Cell:
    def __init__(self):
        # other code ...
        modify_listener = CellCustomPropListener()
        self.component.removeModifyListener(modify_listener)
        self.component.addModifyListener(modify_listener)
#4

Not sure if I’m missing something, but wouldn’t keeping track i.e. a map of cell addresses and ranges listeners where added to and allowing only unique entries be the solution?

#5

That most likely is possible, but also kinda defeats the purpose listeners. My inquiry to to figure out I there is another way to discover if a listener has been added via the API.


I can see that mapping and tracking between lets say cell adddress or cell.AbsoluteName as a possible solution. But this has drawbacks. The biggest I can think of right now is What if a cell were to be moved, Now its cell address and AbsoluteName are changed and the map is invalid. Preferable a solution that did not require any tracking at all. Is there any know way to query a uno object for its listeners?

#6

True, with the cell moving around that’s not feasible unless you track every move. Still, I don’t see why calling removeModifyListener() before addModifyListener() with one single instance listener object is not an option. But no, a SheetCell object (or any supporting css::util::XModifyListener) can’t be queried for its listeners.

#7

Hmm… maybe if the CellCustomPropListener class were a singleton this may work. I will have to give this a try later. The cell that listener is attached to is not passed directly to the listener so I suspect a singleton will work.

#8

Well I gave it a shot. Exact same results.

Singleton Instance.

class CellCustomPropListener(unohelper.Base, XModifyListener):
    _instance = None

    def __new__(cls, *args, **kwargs):
        if cls._instance is None:
            cls._instance = super().__new__(cls)
            cls._instance._is_init = False
        return cls._instance

    def __init__(self) -> None:
        if self._is_init:
            return
        XModifyListener.__init__(self)
        self._is_init = True

    def modified(self, event: EventObject) -> None:
        try:
            _ = event.Source.AbsoluteName  # type: ignore
            log.debug(f"CellCustomPropListener: modified: {event.Source.AbsoluteName}")
        except RuntimeException:
            # cell is deleted
            log.debug("CellCustomPropListener: modified: Cell is deleted")

On Cell Class:

Class Cell:
    def __init__(self):
        # other code ...
        self.component.removeModifyListener(CellCustomPropListener())
        self.component.addModifyListener(CellCustomPropListener())

Test ONE:

def main():

    loader = Lo.load_office(connector=Lo.ConnectPipe(), opt=Options(log_level=logging.DEBUG))
    doc = CalcDoc.create_doc(loader=loader, visible=True)
    try:
        sheet = doc.sheets[0]
        cell = sheet["B2"]
        cell.value = 10
        print()
        cell2 = sheet["B2"]
        cell2.value = 12
        print()
        cell3 = sheet["B2"]
        cell3.value = 14
        print()
    finally:
        doc.close()
        Lo.close_office()

Test Two: Use only one cell var.

def main():

    loader = Lo.load_office(connector=Lo.ConnectPipe(), opt=Options(log_level=logging.DEBUG))
    doc = CalcDoc.create_doc(loader=loader, visible=True)
    try:
        sheet = doc.sheets[0]
        cell = sheet["B2"]
        cell.value = 10
        print()
        cell = sheet["B2"]
        cell.value = 12
        print()
        cell = sheet["B2"]
        cell.value = 14
        print()
    finally:
        doc.close()
        Lo.close_office()

Same output for both test.

31/05/2024 11:15:29 - DEBUG - CellCustomPropListener: modified: $Sheet1.$B$2

31/05/2024 11:15:29 - DEBUG - CellCustomPropListener: modified: $Sheet1.$B$2
31/05/2024 11:15:29 - DEBUG - CellCustomPropListener: modified: $Sheet1.$B$2

31/05/2024 11:15:29 - DEBUG - CellCustomPropListener: modified: $Sheet1.$B$2
31/05/2024 11:15:29 - DEBUG - CellCustomPropListener: modified: $Sheet1.$B$2
31/05/2024 11:15:29 - DEBUG - CellCustomPropListener: modified: $Sheet1.$B$2
#16

Oh! So you create a new instance of the listener every time, and try to remove that new, never existed before, instance from the pre-existed listeners list, then try to add yet another instance?

#17

Not exactly the CellCustomPropListener() is a Singleton class, so it is always the same instance.

1 Like
#9

Hallo
Maybe something like:

import uno, unohelper
from com.sun.star.util import XModifyListener

global INSTANCES
INSTANCES = set()

class Observe(unohelper.Base, XModifyListener):
    
    def __init__(self, cell_range=None):
        unique = cell_range.AbsoluteName
        if unique in INSTANCES:
            return
        INSTANCES.add( unique )
        self.cell_range = cell_range
        XModifyListener.__init__(self)
        self.cell_range.addModifyListener(self)
        self._current = unique
        
    def modified(self, event):
        self.cell_range = event.Source
        if self._current != self.cell_range.AbsoluteName:
            INSTANCES.remove(self._current)
            INSTANCES.add(self.cell_range.AbsoluteName)
            self._current = self.cell_range.AbsoluteName
        # the following pattern prevents endless loops meanwhile modifying
        # the cell itself
        # … stolen from
        # https://forum.openoffice.org/en/forum/viewtopic.php?p=175732#p175732    
        event.Source.removeModifyListener(self)
        _string = event.Source.String 
        if _string.islower():
            _string = _string.upper()
        else:
            _string = _string.lower()
        event.Source.String = _string
        event.Source.addModifyListener(self)
        print(event.Source.AbsoluteName, flush=True)
            
    def disposing(self):
        pass

…addModifyListener is called in the __init__ so you have only:

def main():
    doc = XSCRIPTCONTEXT.getDocument()
    cell = doc.Sheets[0]['A10']
    Observe( cell )
    # do something and try again and again

with thanks to @Villeroy … from this really old topic

#10

Don’t you think that this pattern would fail a soon as the involved cells tracked in INSTANCE have there AbsolutName changed such as when a new row or column are inserted?

#11

try and test yourself!

#12

did i really write that code?

#13

Not the whole but essential parts inside the modified-method !

#14

This mostly working. Except cause error when terminating. See the bottom here.

from __future__ import annotations
from typing import Any, cast, TYPE_CHECKING
import uno
import unohelper
from com.sun.star.util import XModifyListener
from com.sun.star.uno import RuntimeException

from ooodev.io.log import logging as log

if TYPE_CHECKING:
    from com.sun.star.lang import EventObject


class CellCustomPropListener(unohelper.Base, XModifyListener):
    _instances = {}

    def __new__(cls, cell_range: Any):
        unique = cell_range.AbsoluteName
        if unique not in cls._instances:
            inst = super().__new__(cls)
            inst._is_init = False
            cls._instances[unique] = inst
        return cls._instances[unique]

    def __init__(self, cell_range: Any) -> None:
        if self._is_init:
            return
        self._cell_range = cell_range
        XModifyListener.__init__(self)
        self._cell_range.addModifyListener(self)
        self._current = cell_range.AbsoluteName
        self._is_init = True

    def modified(self, event: EventObject) -> None:
        try:
            src = cast(Any, event.Source)
            self._cell_range = event.Source
            if self._current != self._cell_range.AbsoluteName:  # type: ignore
                self.__class__._instances.pop(self._current)
                self.__class__._instances[self._cell_range.AbsoluteName] = self  # type: ignore
                self._current = self._cell_range.AbsoluteName  # type: ignore
            src.removeModifyListener(self)
            # the following pattern prevents endless loops meanwhile modifying
            # the cell itself
            # … stolen from
            # https://forum.openoffice.org/en/forum/viewtopic.php?p=175732#p175732
            # update cell if needed here
            log.debug(f"CellCustomPropListener: modified: {src.AbsoluteName}")
            src.addModifyListener(self)

        except RuntimeException:
            # cell is deleted
            log.debug("CellCustomPropListener: modified: Cell is deleted")
            try:
                log.debug("CellCustomPropListener: modified: Attempting to clean up")
                if self._current and self._current in self.__class__._instances:
                    self.__class__._instances.pop(self._current)
                    log.debug(f"CellCustomPropListener: modified: Cleaned up {self._current}")
                    self._current = ""
            except Exception as e:
                log.error(f"CellCustomPropListener: modified: {e}")

    def disposing(self):
        if self._current in self.__class__._instances:
            self.__class__._instances.pop(self._current)

    @classmethod
    def clear(cls):
        cls._instances.clear()
        log.debug("CellCustomPropListener: clear: Cleared all instances")

Python runner

from __future__ import annotations
import logging
import uno

from ooodev.calc import CalcDoc
from ooodev.loader import Lo
from ooodev.loader.inst.options import Options
from ooodev.calc.cell.cell_custom_prop_listener import CellCustomPropListener

def main():

    loader = Lo.load_office(connector=Lo.ConnectPipe(), opt=Options(log_level=logging.DEBUG))
    doc = CalcDoc.create_doc(loader=loader, visible=True)
    try:
        sheet = doc.sheets[0]
        sheet2 = doc.sheets.insert_sheet("Sheet2")
        cell1 = sheet["B2"]
        CellCustomPropListener(cell1.component)
        cell1.value = 10
        print()
        cell2 = sheet["B2"]
        CellCustomPropListener(cell2.component)
        cell2.value = 12

        print()
        cell_c4 = sheet["C4"]
        CellCustomPropListener(cell_c4.component)
        cell_c4.value = 12

        print()
        cell3 = sheet["B2"]
        CellCustomPropListener(cell3.component)
        cell3.value = 14
        print()
        cell_c4.value = "Done"
        print()

        cell = sheet2["A1"]
        CellCustomPropListener(cell.component)
        cell.value = 10

        cell = sheet2["B1"]
        CellCustomPropListener(cell.component)
        cell.value = 12

        cell_b3 = sheet2["B3"]
        CellCustomPropListener(cell_b3.component)
        cell_b3.value = 12
        CellCustomPropListener.clear()

    finally:
        doc.close()
        Lo.close_office()

if __name__ == "__main__":
    main()

Log output

31/05/2024 15:21:12 - DEBUG - CellCustomPropListener: modified: $Sheet1.$B$2

31/05/2024 15:21:12 - DEBUG - CellCustomPropListener: modified: $Sheet1.$B$2

31/05/2024 15:21:12 - DEBUG - CellCustomPropListener: modified: $Sheet1.$C$4

31/05/2024 15:21:12 - DEBUG - CellCustomPropListener: modified: $Sheet1.$B$2

31/05/2024 15:21:12 - DEBUG - CellCustomPropListener: modified: $Sheet1.$C$4

31/05/2024 15:21:12 - DEBUG - CellCustomPropListener: modified: $Sheet2.$A$1
31/05/2024 15:21:12 - DEBUG - CellCustomPropListener: modified: $Sheet2.$B$1
31/05/2024 15:22:08 - DEBUG - CellCustomPropListener: modified: $Sheet2.$B$3
31/05/2024 15:22:08 - DEBUG - CellCustomPropListener: clear: Cleared all instances

Error output.

double free or corruption (out)
Unspecified Application Error


Fatal exception: Signal 6
Stack:
/usr/lib/libreoffice/program/libuno_sal.so.3(+0x41be2)[0x78f108a18be2]
/usr/lib/libreoffice/program/libuno_sal.so.3(+0x41d9a)[0x78f108a18d9a]
...
/lib/x86_64-linux-gnu/libc.so.6(+0x94ac3)[0x78f103094ac3]
/lib/x86_64-linux-gnu/libc.so.6(+0x126850)[0x78f103126850]
Leaking python objects bridged to UNO for reason pyuno runtime is not initialized, (the pyuno.bootstrap needs to be called before using any uno classes) at ./pyuno/source/module/pyuno_runtime.cxx:358
Leaking python objects bridged to UNO for reason pyuno runtime is not initialized, (the pyuno.bootstrap needs to be called before using any uno classes) at ./pyuno/source/module/pyuno_runtime.cxx:358
Traceback (most recent call last):
  File "/home/paul/.pyenv/versions/3.10.5/lib/python3.10/runpy.py", line 196, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/home/paul/.pyenv/versions/3.10.5/lib/python3.10/runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "/home/paul/.vscode/extensions/ms-python.debugpy-2024.6.0-linux-x64/bundled/libs/debugpy/adapter/../../debugpy/launcher/../../debugpy/__main__.py", line 39, in <module>
    cli.main()
  File "/home/paul/.vscode/extensions/ms-python.debugpy-2024.6.0-linux-x64/bundled/libs/debugpy/adapter/../../debugpy/launcher/../../debugpy/../debugpy/server/cli.py", line 430, in main
    run()
  File "/home/paul/.vscode/extensions/ms-python.debugpy-2024.6.0-linux-x64/bundled/libs/debugpy/adapter/../../debugpy/launcher/../../debugpy/../debugpy/server/cli.py", line 284, in run_file
    runpy.run_path(target, run_name="__main__")
  File "/home/paul/.vscode/extensions/ms-python.debugpy-2024.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_runpy.py", line 321, in run_path
    return _run_module_code(code, init_globals, run_name,
  File "/home/paul/.vscode/extensions/ms-python.debugpy-2024.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_runpy.py", line 135, in _run_module_code
    _run_code(code, mod_globals, init_globals,
  File "/home/paul/.vscode/extensions/ms-python.debugpy-2024.6.0-linux-x64/bundled/libs/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_runpy.py", line 124, in _run_code
    exec(code, run_globals)
  File "/home/paul/Documents/Projects/Python/LibreOffice/ooouno-dev-tools/tmp/calc_prop_listen.py", line 65, in <module>
    main()
  File "/home/paul/Documents/Projects/Python/LibreOffice/ooouno-dev-tools/tmp/calc_prop_listen.py", line 60, in main
    doc.close()
  File "/home/paul/Documents/Projects/Python/LibreOffice/ooouno-dev-tools/ooodev/utils/partial/doc_io_partial.py", line 89, in close
    result = self.__lo_inst.close(closable, deliver_ownership)
  File "/home/paul/Documents/Projects/Python/LibreOffice/ooouno-dev-tools/ooodev/loader/inst/lo_inst.py", line 1379, in close
    closeable.close(cargs.event_data)

I am getting errors when LibreOffice is terminating. I suspect all the listeners need to be released from the cells before closing.

#15

I managed to get rid of errors except if a cell is deleted.

CellCustomPropListener.clear() must be called before the document is closed.


If I try and clean up deleted cell event.Source.removeModifyListener(self) I get error.
and closing has the same error as posted above. If I don’t cleanup I still get the same error when closing. Do you have any improvements for this? I think the listener is not being released from the deleted cell.

from __future__ import annotations
from typing import Any, cast, TYPE_CHECKING
import contextlib
import uno
import unohelper
from com.sun.star.util import XModifyListener
from com.sun.star.uno import RuntimeException

from ooodev.io.log import logging as log

if TYPE_CHECKING:
    from com.sun.star.lang import EventObject


class CellCustomPropListener(unohelper.Base, XModifyListener):
    _instances = {}

    def __new__(cls, cell_range: Any):
        unique = cell_range.AbsoluteName
        if unique not in cls._instances:
            inst = super().__new__(cls)
            inst._is_init = False
            cls._instances[unique] = inst
        return cls._instances[unique]

    def __init__(self, cell_range: Any) -> None:
        if self._is_init:
            return
        self._cell_range = cell_range
        XModifyListener.__init__(self)
        self._cell_range.addModifyListener(self)
        self._current = cell_range.AbsoluteName
        self._is_init = True

    def modified(self, event: EventObject) -> None:
        try:
            src = cast(Any, event.Source)
            self._cell_range = src
            if self._current != self._cell_range.AbsoluteName:  # type: ignore
                inst = self.__class__._instances.pop(self._current)
                inst.removeModifyListener(self)
                inst = None
                self.__class__._instances[self._cell_range.AbsoluteName] = self  # type: ignore
                self._current = self._cell_range.AbsoluteName  # type: ignore
            src.removeModifyListener(self)
            # the following pattern prevents endless loops meanwhile modifying
            # the cell itself
            # … stolen from
            # https://forum.openoffice.org/en/forum/viewtopic.php?p=175732#p175732
            # update cell if needed here
            log.debug(f"CellCustomPropListener: modified: {src.AbsoluteName}")
            src.addModifyListener(self)

        except RuntimeException:
            # cell is deleted
            log.debug("CellCustomPropListener: modified: Cell is deleted")
            try:
                log.debug("CellCustomPropListener: modified: Attempting to clean up")
                if self._current and self._current in self.__class__._instances:
                    self.__class__._instances.pop(self._current)
                    log.debug(f"CellCustomPropListener: modified: Cleaning up {self._current}")
                    event.Source.removeModifyListener(self)
                    log.debug(f"CellCustomPropListener: modified: Cleaned up {self._current}")
                    self._current = ""
            except Exception as e:
                log.error(f"CellCustomPropListener: modified: {e}")

    def disposing(self):
        if self._current in self.__class__._instances:
            self.__class__._instances.pop(self._current)

    @classmethod
    def clear(cls):
        for inst in cls._instances.values():
            with contextlib.suppress(Exception):
                inst._cell_range.removeModifyListener(inst)
        cls._instances.clear()
        log.debug("CellCustomPropListener: clear: Cleared all instances")

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