phoenix_title Window IDs Overview

Various controls and other parts of wxPython need an ID. Sometimes the ID may be directly provided by the user or have a predefined value, such as wx.ID_OPEN. Often, however, the value of the ID is unimportant and is created automatically by calling wx.Window.NewControlId or by passing wx.ID_ANY as the ID of an object.

There are two ways to generate an ID. One way is to start at a negative number, and for each new ID, return the next smallest number. This is fine for systems that can use the full range of negative numbers for IDs, as this provides more than enough IDs and it would take a very very long time to run out and wrap around. However, some systems cannot use the full range of the ID value. Windows, for example, can only use 16 bit IDs, and only has about 32000 possible automatic IDs that can be generated by wx.Window.NewControlId. If the program runs long enough, depending on the program itself, using this first method would cause the IDs to wrap around into the positive ID range and cause possible clashes with any directly specified ID values.

The other way is to keep track of the IDs returned by wx.Window.NewControlId and don’t return them again until the ID is completely free and not being used by any other objects. This will make sure that the ID values do not clash with one another. This is accomplished by keeping a reference count for each of the IDs that can possibly be returned by wx.Window.NewControlId. Other IDs are not reference counted.