[litwindow-users] Re: wxListCtrl and library status

[Hajo K. <mai...@ha...>]

yrs90 wrote:

 > I have left the existing interface the same, making minimal modifications
 > and additions to handle multi-columns. I am not yet comfortable with how
 > much of the interface can/should be modified.
 >
 >
I have no idea either. We'll just have to wait and see.

 > flawed.  I thought it would be nice to pass an aggregate to a 
function, say
 > SetColumns(), and have the columns created from the struct elements.

Take a look at wxTextCtrl. It accepts an accessor as a parameter, much 
like you are planning to do with SetColumns. As for the internal names I 
would suggest a new properties: ColumnTitles, perhaps even a combination 
of title-member variable name. Example:
ListCtrl.ColumnTitles:="m_id=ID, m_name=Name" where the string consists 
of membername=columnheader pairs separated by a ,

 > I made enough progress that my ListCtrl without distinct columns is being
 > populated. This was a straightforward modeled after wxListBox.  When 
I tried
 > to extend it to include columns I encountered two problems.  First, I 
tried
 > to add two functions, SetColumns and GetColumns.
 >
 > Class wxListCtrlAdapter {
 > ...
 > void SetColumns(const accessor &newValue);
 > const accessor &GetColumns() const;
 > ...
 > }
 >
 > BEGIN_ADAPTER_NO_COPY(wxListCtrlAdapter)
 > PROP_I(lwListAdapterBase)
 > PROP_GetSet(accessor, Columns)
 > END_ADAPTER()
 >
 > However, when I create a rule:
 >
 > RULE("m_IPListWindow.Columns", make_expr<accessor>("m_targetlist"))
 >
 > I get an error thrown stating that the "GetAccessor couldn't find a 
variable
 > ' m_IPListWindow.Columns'"
 >
 >
Yes, you overlooked one important point. You have created a data adapter 
for the wxListCtrlAdapter, but I guess that you haven't created a data 
adapter for wxListCtrl itself. I call the concept behind this a 
'co-object'. Essentially you are trying to extend wxListCtrl, but 
without modifying the wxListCtrl sources. So I introduced a 
wxSomethingAdapter class that contains the extensions. The following 
code binds this adapter class to the original class:

BEGIN_ADAPTER_NO_COPY(wxListCtrl)
   PROP_CO(wxListCtrlAdapter)
   PROP_I(wxControl)
END_ADAPTER()

It is almost as if you are adding a new superclass wxListCtrlAdapter to 
wxListCtrl. While the C++ inheritance looks like this:

class wxListCtrl:public wxControl

the data adapter inheritance is this:
class wxListCtrl:public wxListCtrlAdapter, public wxControl

In other words, when a wxListCtrl object is accessed through a data 
adapter, it 'inherites' not only wxControl properties but also 
wxListCtrlAdapter properties.

Have a look at base_objects.cpp and how this is done with the 
wxListBoxAdapter.

In order to make this work, the co-object mechanism needs a way to 
create the co-object and attach it to the original object. This is done 
through template overloading, which tells the mechanism to call 'new 
wxListCtrlAdapter' the first time the PROP_CO(wxListCtrlAdapter) is 
seen. The pointer to this object must then be stored someplace. I 
currently attach the new adapter object as a handler to the original 
wxWidgets object and destroy the object when the wxEVT_DESTROY_WINDOW 
event comes my way.

Just take a close look at the connection between 
BEGIN_ADAPTER_NO_COPY(wxListBox) and 
BEGIN_ADAPTER_NO_COPY(wxListBoxAdapter). The template overloading 
function is somewere there.

 > My second problem, is one related to my original design.  I am not 
sure how
 > to initialize the columns if I don't have an instance of the aggregate to
 > pass.  Perhaps, though, there is a better way to pass the column 
names and
 > associations between the columns and the aggregate contents.  Any
 > suggestions on this front?
 >
 >
You could create the ColumnHeader property I described above if you want 
to create the columns before you actually pass in a container. But keep 
in mind that the columns of the control might change over time. So I'd 
create them only after I actually have a container and change them 
everytime the element type of the container changes.

Regards, and thanks for your work. It is very appreciated.

Hajo