Fix GTK-CRITICAL when SetBitmap() is called after Append() on a wxMenuItem (PR #26771)

ykne

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Aug 1, 2026, 8:58:42 PM (3 days ago) Aug 1

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Bug

wxMenu::GtkAppend() (src/gtk/menu.cpp) decides whether to build a
GtkImageMenuItem or a plain GtkMenuItem based on
mitem->GetBitmap().IsOk() at Append() time:

case wxITEM_NORMAL:
    if (mitem->GetBitmap().IsOk())
        menuItem = gtk_image_menu_item_new_with_label("");
    else
    {
        const char* stockid = wxGetStockGtkID(mitem->GetId());
        if (stockid)
            menuItem = gtk_image_menu_item_new_from_stock(stockid, nullptr);
        else
            menuItem = gtk_menu_item_new_with_label(""); // <-- plain item
    }

But wxMenu::Append() returns the new wxMenuItem* precisely to
support the common idiom:

menu->Append(id, label)->SetBitmap(bmp);

Here SetBitmap() runs after Append() already built the
underlying GTK widget. For any non-stock id, that widget ends up
being a plain GtkMenuItem. Later, whenever the menu is actually
shown (wxWindowGTK::DoPopupMenu() → wxMenu::SetupBitmaps() →
wxMenuItem::SetupBitmaps()), wx calls:

gtk_image_menu_item_set_image(GTK_IMAGE_MENU_ITEM(m_menuItem), image);

on that plain GtkMenuItem, which trips the GTK_IS_IMAGE_MENU_ITEM
assertion:

Gtk-CRITICAL **: gtk_image_menu_item_set_image: assertion 'GTK_IS_IMAGE_MENU_ITEM (image_menu_item)' failed

and the bitmap is silently never attached.

Repro

Minimal standalone repro (not included in this PR, happy to attach if
useful):

wxMenu menu;
menu.Append(wxID_HIGHEST + 1000, "Test Item")->SetBitmap(wxBitmap(16, 16));
PopupMenu(&menu, wxPoint(20, 20));

Confirmed present on both the 3.2 branch and master, built from
source (not just the Fedora-packaged wx), with --with-gtk=3 and
system third-party libs.

Fix

Always build a GtkImageMenuItem for wxITEM_NORMAL (unless a stock
GTK id already provides one via gtk_image_menu_item_new_from_stock).
An empty GtkImageMenuItem behaves identically to a plain
GtkMenuItem, so this is a no-op for items that never get a bitmap,
and fixes the assertion (and the missing icon) for items that get
SetBitmap() called after Append().

Verified: rebuilt both 3.2 and master from source with the fix
applied, reran the repro above — no assertion, clean stderr.

A separate PR with the same fix against the 3.2 branch will follow
if useful; let me know your preference on which branch should take
this first.

🤖 Generated with Claude Code

You can view, comment on, or merge this pull request online at:

https://github.com/wxWidgets/wxWidgets/pull/26771

Commit Summary

5c1c3e4 Always create a GtkImageMenuItem for wxITEM_NORMAL items in wxGTK

File Changes

(1 file)

M src/gtk/menu.cpp (12)

Patch Links:

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VZ

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Aug 2, 2026, 1:23:18 PM (2 days ago) Aug 2

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vadz left a comment (wxWidgets/wxWidgets#26771)

Thanks, I agree that using SetBitmap() should work, of course, but OTOH it seems a bit wrong to unconditionally create image menu items when many (most?) of them are not going to use images. I think replacing the existing item with an image item in SetBitmap(), if necessary, should work too, but I'm not sure if it's worth it.

I believe that the really correct thing to do would be stop using GtkImageMenuItem entirely and always create a box ourselves and then pack whatever we need into it, just as the documentation for this class suggests. But this would require many more changes...

@paulcor Do you have any thoughts about this?

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paulcor

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Aug 2, 2026, 1:43:48 PM (2 days ago) Aug 2

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paulcor left a comment (wxWidgets/wxWidgets#26771)

This is fine.

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paulcor

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Aug 2, 2026, 1:43:57 PM (2 days ago) Aug 2

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Merged #26771 into master.

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