wxTextCtrl per class handler overrides per-instance handler

Question

wxWidgets 3.0.2, MSVC 2013.

The essence of this question is: how does one override the default file drop handler on a wxTextCtrl? There's a default handler that the superclass installs that I need to override.

I am trying to make a wxWidgets text area that accepts a file drop event. I couldn't find a per class event for file drops in the documentation so I fell back to copying the sample code, which manually Connects a handler in the constructor. Here's my class definition.

struct BitsTextCtrl : public wxTextCtrl {
    AsmFrame *m_frame;

    BitsTextCtrl(AsmFrame *frame, wxPanel *parent);
    void onMouseEvent(wxMouseEvent& evt) { evt.Skip(); /* for now */ }
    void onDropFiles(wxDropFilesEvent &evt); // my target to setup in the constructor

    wxDECLARE_EVENT_TABLE();
};

The implementation looks like the following. The constructor sets up the file drop handler for this instance (much like the samples).

BitsTextCtrl::BitsTextCtrl(AsmFrame *frame, wxPanel *parent)
    : wxTextCtrl(parent,
        wxID_ANY, wxT(""),
        wxDefaultPosition, wxSize(DFT_W/2,3*DFT_H/4),
        wxTE_RICH2 | wxTE_MULTILINE | wxTE_DONTWRAP | wxTE_PROCESS_TAB | wxHSCROLL)
{
    SetFont(wxFont(12, wxTELETYPE, wxNORMAL, wxNORMAL));
    SetBackgroundColour(wxColor(0xffeeeeeeUL));
    DragAcceptFiles(true);
    Connect(
        wxEVT_DROP_FILES,
        wxDropFilesEventHandler(BitsTextCtrl::onDropFiles),
        NULL, this);
}

void BitsTextCtrl::onDropFiles(wxDropFilesEvent &evt) {
    if (evt.GetNumberOfFiles() == 1) {
       wxString* dropped = evt.GetFiles();
       SetValue(FormatBits(ReadBinary(dropped->c_str())));        
    }
    evt.Skip();
}

wxBEGIN_EVENT_TABLE(BitsTextCtrl, wxTextCtrl)
    EVT_MOUSE_EVENTS(BitsTextCtrl::onMouseEvent)
    // NOTE: no entry for EVT_DROP_FILES
wxEND_EVENT_TABLE()

My handler gets called correctly and all is well, but then the default per-class handler in wxTextAreaBase (parent to wxTextArea clobbers my input). Specifically, this is wired up to wxTextCtrl::OnDropFiles (note casing difference "On" vs "on") appears to be a default handler that just assumes input is text (which it's not in my case).

Digging through the wxWidgets event handling code I found the following.

// from wxWidgets/...event.cpp (with my annotations in [..])
bool wxEvtHandler::TryHereOnly(wxEvent& event)
{
    // If the event handler is disabled it doesn't process any events
    if ( !GetEvtHandlerEnabled() )
        return false;

    // Handle per-instance dynamic event tables first
    [This is the path the calls my handler: does the right thing]
    if ( m_dynamicEvents && SearchDynamicEventTable(event) )
        return true;

    // Then static per-class event tables
    [This is the default per-class handler than clobbers my hard work]
    if ( GetEventHashTable().HandleEvent(event, this) )
        return true;
    ....

How do I disable the per-class event? Or perhaps override it instead? The docs don't list an event table entry for file drops.

UPDATE: Okay so there is an per class entry (just not listed in the documentation). EVT_MOUSE_EVENTS(BitsTextCtrl::onMouseEvent) can replace the Connect call in the constructor, but now I just have two copies of the event handler being called. Same problem.

score 0 · Accepted Answer · answered Mar 11 '16 at 05:48

0

The solution was to avoid calling wxEvent::Skip in the event handler. I misunderstood this method. Skip() means "don't conusme call the next handler". Not calling skip tells wxWindows that we are done with the event.

answered Mar 11 '16 at 05:48

Tim

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wxTextCtrl per class handler overrides per-instance handler

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