1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
|
///////////////////////////////////////////////////////////////////////////////
// Name: interface/wx/eventfilter.h
// Purpose: wxEventFilter class documentation
// Author: Vadim Zeitlin
// Created: 2011-11-21
// Copyright: (c) 2011 Vadim Zeitlin <vadim@wxwidgets.org>
// Licence: wxWindows licence
///////////////////////////////////////////////////////////////////////////////
/**
A global event filter for pre-processing all the events generated in the
program.
This is a very simple class which just provides FilterEvent() virtual
method to be called by wxEvtHandler before starting process of any event.
Thus, inheriting from this class and overriding FilterEvent() allows to
capture and possibly handle or ignore all the events happening in the
program. Of course, having event filters adds additional overhead to every
event processing and so should not be used lightly and your FilterEvent()
code should try to return as quickly as possible, especially for the events
it is not interested in.
An example of using this class:
@code
// This class allows to determine the last time the user has worked with
// this application:
class LastActivityTimeDetector : public wxEventFilter
{
public:
LastActivityTimeDetector()
{
wxEvtHandler::AddFilter(this);
m_last = wxDateTime::Now();
}
virtual ~LastActivityTimeDetector()
{
wxEvtHandler::RemoveFilter(this);
}
virtual int FilterEvent(wxEvent& event)
{
// Update the last user activity
const wxEventType t = event.GetEventType();
if ( t == wxEVT_KEY_DOWN || t == wxEVT_MOTION ||
t == wxEVT_LEFT_DOWN ||
t == wxEVT_RIGHT_DOWN ||
t == wxEVT_MIDDLE_DOWN )
{
m_last = wxDateTime::Now();
}
// Continue processing the event normally as well.
return Event_Skip;
}
// This function could be called periodically from some timer to
// do something (e.g. hide sensitive data or log out from remote
// server) if the user has been inactive for some time period.
bool IsInactiveFor(const wxTimeSpan& diff) const
{
return wxDateTime::Now() - diff > m_last;
}
private:
wxDateTime m_last;
};
@endcode
Notice that wxApp derives from wxEventFilter and is registered as an event
filter during its creation so you may also override FilterEvent() method in
your wxApp-derived class and, in fact, this is often the most convenient
way to do it. However creating a new class deriving directly from
wxEventFilter allows to isolate the event filtering code in its own
separate class and also to have several independent filters, if necessary.
@category{events}
@since 2.9.3
*/
class wxEventFilter
{
public:
/// Possible return values for FilterEvent().
enum
{
/// Process event as usual.
Event_Skip = -1,
/// Don't process the event normally at all.
Event_Ignore = 0,
/// Event was already handled, don't process it normally.
Event_Processed = 1
};
/**
Default constructor.
Constructor does not register this filter using
wxEvtHandler::AddFilter(), it's your responsibility to do it when
necessary.
Notice that the objects of this class can't be copied.
*/
wxEventFilter();
/**
Destructor.
You must call wxEvtHandler::RemoveFilter() before destroying this
object (possibly from the derived class destructor), failure to do this
is indicated by an assert unless assertions are disabled.
*/
virtual ~wxEventFilter();
/**
Override this method to implement event pre-processing.
This method allows to filter all the events processed by the program,
so you should try to return quickly from it to avoid slowing down the
program to a crawl.
Although the return type of this method is @c int, this is only due to
backwards compatibility concerns and the actual return value must be
one of the @c Event_XXX constants defined above:
- Event_Skip to continue processing the event normally (this should
be used in most cases).
- Event_Ignore to not process this event at all (this can be used
to suppress some events).
- Event_Processed to not process this event normally but indicate
that it was already processed by the event filter and so no default
processing should take place neither (this should only be used if
the filter really did process the event).
*/
virtual int FilterEvent(wxEvent& event) = 0;
};
|
