ConVar - equivalent to RegisterConVarChanges

[joshtrav]

I have been browsing the wiki, as well as the source on convars.

https://github.com/Source-Python-Dev-Team/Source.Python/blob/master/src/core/modules/cvars/cvars_wrap_python.cpp
http://wiki.sourcepython.com/pages/cvars

I haven't found anything that would resemble a way to hook a convar change, is there a current wrapper for an equivalent? If not, would it be feasible as a feature request?

[satoon101]

If you don't need to stop the change from happening, you could always just add the NOTIFY flag to the ConVar and listen to the event server_cvar.

Outside of that, we do have an experimental branch currently that will allow you to hook exposed methods of a class.
https://github.com/Source-Python-Dev-Team/Source.Python/tree/exposed_function_hooks

Here is an example of its usage:
https://github.com/Source-Python-Dev-Team/Source.Python/commit/408e95b0e0cc3ab25a5551eb46169709ece35d8a#commitcomment-11510933

[joshtrav]

Thanks for the info. I think the first option will work just fine. I assume I could then just set the bDontBroadcast value to True in the server_cvar event?

[satoon101]

To set the bDontBroadcast, you will have to hook fire_game_event. Basic event calling does not have that implemented. We do plan on having a PreEvent decorator at some point, probably once the experimental branch is finalized. Currently, you have to do it more like:

Syntax: Select all

from core import PLATFORM
from events import GameEvent
from events.manager import GameEventManager
from memory import Convention
from memory import DataType
from memory import get_object_pointer
from memory import make_object
from memory.hooks import PreHook

FIRE_EVENT_FUNC = get_object_pointer(
    GameEventManager).make_virtual_function(
    7 if PLATFORM == 'windows' else 8,
    Convention.THISCALL,
    (DataType.POINTER, DataType.POINTER, DataType.BOOL),
    DataType.VOID
)

@PreHook(FIRE_EVENT_FUNC)
def pre_fire_event(arguments):
    game_event = make_object(GameEvent, arguments[1])
    if game_event.get_name() == 'server_cvar':
        arguments[2] = True

Though, hopefully fairly soon, you will just be able to do something more like:

Syntax: Select all

from events.hooks import PreEvent


@PreEvent
def server_cvar(game_event):
    # Block the broadcasting of the event to clients
    return False

[stonedegg]

Though, hopefully fairly soon, you will just be able to do something more like:

[python]from events.hooks import PreEvent


@PreEvent
def server_cvar(game_event):
# Block the broadcasting of the event to clients
return False[/python]

Yes please!!

[Ayuto]

I would like to take this chance to show another feature of SP, which is already available since a long time. Though, we have improved this feature a few weeks ago.

You can create functions, which have an address in memory, so you can pass them to any function you want. This means that you can create C++ functions with any calling convention on the fly!

Syntax: Select all

# This example has been made for Windows (CS:S)
import memory

from memory import DataType
from memory import Convention
from memory import Callback

from cvars import cvar

from _cvars import _IConVar

# Get the cvar pointer
cvar_ptr = memory.get_object_pointer(cvar)

# virtual void ICvar::InstallGlobalChangeCallback(FnChangeCallback_t callback) = 0;
InstallGlobalChangeCallback = cvar_ptr.make_virtual_function(
    18,
    Convention.THISCALL,
    [DataType.POINTER, DataType.POINTER],
    DataType.VOID
)

# virtual void ICvar::RemoveGlobalChangeCallback(FnChangeCallback_t callback) = 0;
RemoveGlobalChangeCallback = cvar_ptr.make_virtual_function(
    19,
    Convention.THISCALL,
    [DataType.POINTER, DataType.POINTER],
    DataType.VOID
)

# Create a function in memory, which can be treated just like a function
# pointer. Awesome, eh? :P
# typedef void ( *FnChangeCallback_t )( IConVar *var, const char *pOldValue, float flOldValue );
@Callback(
    Convention.CDECL,
    [DataType.POINTER, DataType.STRING, DataType.FLOAT],
    DataType.VOID)
def on_cvar_changed(args):
    """Called whenever a ConVar changes."""
    convar = memory.make_object(_IConVar, args[0])
    old_str_value = args[1]
    old_float_value = args[2]
    print(convar.get_name(), 'has changed')

def load():
    # Install the callback
    InstallGlobalChangeCallback(cvar_ptr, on_cvar_changed)

def unload():
    # Remove the callback
    RemoveGlobalChangeCallback(cvar_ptr, on_cvar_changed)

[joshtrav]

Though, hopefully fairly soon, you will just be able to do something more like:

Syntax: Select all

from events.hooks import PreEvent


@PreEvent
def server_cvar(game_event):
    # Block the broadcasting of the event to clients
    return False

This will be very nice, and thanks for the current way as well!

I would like to take this chance to show another feature of SP, which is already available since a long time. Though, we have improved this feature a few weeks ago.

You can create functions, which have an address in memory, so you can pass them to any function you want. This means that you can create C++ functions with any calling convention on the fly!

Syntax: Select all

# This example has been made for Windows (CS:S)
import memory

from memory import DataType
from memory import Convention
from memory import Callback

from cvars import cvar

from _cvars import _IConVar

# Get the cvar pointer
cvar_ptr = memory.get_object_pointer(cvar)

# virtual void ICvar::InstallGlobalChangeCallback(FnChangeCallback_t callback) = 0;
InstallGlobalChangeCallback = cvar_ptr.make_virtual_function(
    18,
    Convention.THISCALL,
    [DataType.POINTER, DataType.POINTER],
    DataType.VOID
)

# virtual void ICvar::RemoveGlobalChangeCallback(FnChangeCallback_t callback) = 0;
RemoveGlobalChangeCallback = cvar_ptr.make_virtual_function(
    19,
    Convention.THISCALL,
    [DataType.POINTER, DataType.POINTER],
    DataType.VOID
)

# Create a function in memory, which can be treated just like a function
# pointer. Awesome, eh? :P
# typedef void ( *FnChangeCallback_t )( IConVar *var, const char *pOldValue, float flOldValue );
@Callback(
    Convention.CDECL,
    [DataType.POINTER, DataType.STRING, DataType.FLOAT],
    DataType.VOID)
def on_cvar_changed(args):
    """Called whenever a ConVar changes."""
    convar = memory.make_object(_IConVar, args[0])
    old_str_value = args[1]
    old_float_value = args[2]
    print(convar.get_name(), 'has changed')

def load():
    # Install the callback
    InstallGlobalChangeCallback(cvar_ptr, on_cvar_changed)

def unload():
    # Remove the callback
    RemoveGlobalChangeCallback(cvar_ptr, on_cvar_changed)

This seems very involved and powerful, is there a substantial amount of info on the wiki in regards to this that I missed?

[Ayuto]

We haven't added that to the wiki yet. But here is the source code: https://github.com/Source-Python-Dev-Team/Source.Python/blob/master/addons/source-python/packages/source-python/memory/__init__.py#L77

I can add that to the wiki today.

[joshtrav]

Ayuto, would you still need to hook the GameEventManager to stop the broadcast using the method you posted?

[Ayuto]

The callback gets called everytime a ConVar changes and it doesn't need the NOTIFY flag. But yes, if it has this flag, you would need to hook FireEvent.