Fix wxCheckBox and wxRadioButton accessibility in wxMSW dark mode

Previously these controls acted like generic buttons when they were
owner-drawn which was, in particular, always the case when using dark
mode, because the built-in implementation doesn't do anything useful for
owner-drawn buttons.

Implement IAccessible support for them ourselves in order to make it
work in this case too.

Closes #26184.

Closes #26187.

include/wx/msw/checkbox.h

@@ -58,6 +58,10 @@ public:
     // implementation only from now on
     virtual WXDWORD MSWGetStyle(long flags, WXDWORD *exstyle = nullptr) const override;
 
+#if wxUSE_ACCESSIBILITY
+    virtual wxAccessible* CreateAccessible() override;
+#endif
+
 protected:
     virtual wxSize DoGetBestClientSize() const override;
 

include/wx/msw/ownerdrawnbutton.h

@@ -125,6 +125,8 @@ public:
         return MSWDrawButton(item) || Base::MSWOnDraw(item);
     }
 
+    using wxMSWOwnerDrawnButtonBase::MSWIsOwnerDrawn;
+
 protected:
     bool IsOwnerDrawn() const { return MSWIsOwnerDrawn(); }
 };

include/wx/msw/private/accessible.h

@@ -0,0 +1,91 @@
+///////////////////////////////////////////////////////////////////////////////
+// Name:        wx/msw/private/accessible.h
+// Purpose:     Accessible helpers for wxMSW owner-drawn controls
+// Author:      Quin Gillespie
+// Created:     2026-02-13
+// Copyright:   (c) 2026 Quin Gillespie
+// Licence:     wxWindows licence
+///////////////////////////////////////////////////////////////////////////////
+
+#ifndef _WX_PRIVATE_ACCESSIBLE_H_
+#define _WX_PRIVATE_ACCESSIBLE_H_
+
+#include "wx/access.h"
+
+#if wxUSE_ACCESSIBILITY
+
+// When controls such as wxCheckBox and wxRadioButton are switched to
+// owner-drawn mode (e.g. to support custom foreground colours in dark mode),
+// Windows replaces the native button style with BS_OWNERDRAW. The standard
+// IAccessible implementation that Windows provides via
+// CreateStdAccessibleObject() inspects the window style to determine the
+// control role, so it reports owner-drawn controls as generic buttons.
+//
+// This base class provides the correct role (specified as the template
+// parameter) and state (via virtual MSWGetCheckedState() function) for
+// owner-drawn controls.
+//
+// Note that it only takes effect when the control is actually owner-drawn;
+// otherwise it returns wxACC_NOT_IMPLEMENTED to fall back to the standard
+// Windows accessible.
+template <class TControl, wxAccRole Role>
+class wxOwnerDrawnAccessible : public wxWindowAccessible
+{
+public:
+    explicit wxOwnerDrawnAccessible(TControl* win)
+        : wxWindowAccessible(win)
+    {
+    }
+
+    virtual wxAccStatus GetRole(int childId, wxAccRole* role) override
+    {
+        if ( childId != wxACC_SELF )
+            return wxACC_NOT_IMPLEMENTED;
+
+        TControl* const ctrl = wxStaticCast(GetWindow(), TControl);
+        wxCHECK(ctrl, wxACC_FAIL);
+
+        if ( !ctrl->MSWIsOwnerDrawn() )
+            return wxACC_NOT_IMPLEMENTED;
+
+        *role = Role;
+
+        return wxACC_OK;
+    }
+
+    virtual wxAccStatus GetState(int childId, long* state) override
+    {
+        if ( childId != wxACC_SELF )
+            return wxACC_NOT_IMPLEMENTED;
+
+        TControl* const ctrl = wxStaticCast(GetWindow(), TControl);
+        wxCHECK(ctrl, wxACC_FAIL);
+
+        if ( !ctrl->MSWIsOwnerDrawn() )
+            return wxACC_NOT_IMPLEMENTED;
+
+        long st = 0;
+        if ( !ctrl->IsEnabled() )
+            st |= wxACC_STATE_SYSTEM_UNAVAILABLE;
+        if ( !ctrl->IsShown() )
+            st |= wxACC_STATE_SYSTEM_INVISIBLE;
+        if ( ctrl->IsFocusable() )
+            st |= wxACC_STATE_SYSTEM_FOCUSABLE;
+        if ( ctrl->HasFocus() )
+            st |= wxACC_STATE_SYSTEM_FOCUSED;
+
+        st |= MSWGetCheckedState(ctrl);
+
+        *state = st;
+        return wxACC_OK;
+    }
+
+protected:
+    // Return checked state flags (e.g. wxACC_STATE_SYSTEM_CHECKED) for the
+    // current state of the control.
+    virtual long MSWGetCheckedState(TControl* ctrl) const = 0;
+};
+
+#endif // wxUSE_ACCESSIBILITY
+
+#endif // _WX_PRIVATE_ACCESSIBLE_H_

include/wx/msw/radiobut.h

@@ -53,6 +53,10 @@ public:
 
     virtual WXDWORD MSWGetStyle(long style, WXDWORD *exstyle) const override;
 
+#if wxUSE_ACCESSIBILITY
+    virtual wxAccessible* CreateAccessible() override;
+#endif
+
 protected:
     virtual wxBorder GetDefaultBorder() const override { return wxBORDER_NONE; }
     virtual wxSize DoGetBestSize() const override;

src/msw/checkbox.cpp

@@ -34,6 +34,10 @@
 #include "wx/private/window.h"
 #include "wx/msw/missing.h"
 
+#if wxUSE_ACCESSIBILITY
+    #include "wx/msw/private/accessible.h"
+#endif
+
 // ============================================================================
 // implementation
 // ============================================================================
@@ -277,4 +281,52 @@ void wxCheckBox::MSWDrawButtonBitmap(wxDC& dc, const wxRect& rect, int flags)
     wxRendererNative::Get().DrawCheckBox(this, dc, rect, flags);
 }
 
+#if wxUSE_ACCESSIBILITY
+
+namespace
+{
+
+// When the checkbox is owner-drawn (e.g. in dark mode), the native BS_CHECKBOX
+// style is replaced with BS_OWNERDRAW, causing the standard Windows accessible
+// object to report the control as a generic button. This custom accessible
+// ensures the correct role and checked state are always reported.
+class wxCheckBoxAccessible
+    : public wxOwnerDrawnAccessible<wxCheckBox, wxROLE_SYSTEM_CHECKBUTTON>
+{
+public:
+    explicit wxCheckBoxAccessible(wxCheckBox* win)
+        : wxOwnerDrawnAccessible(win)
+    {
+    }
+
+protected:
+    long MSWGetCheckedState(wxCheckBox* cb) const override
+    {
+        switch ( cb->Get3StateValue() )
+        {
+            case wxCHK_CHECKED:
+                return wxACC_STATE_SYSTEM_CHECKED;
+
+            case wxCHK_UNDETERMINED:
+                return wxACC_STATE_SYSTEM_MIXED;
+
+            case wxCHK_UNCHECKED:
+                return 0;
+        }
+
+        wxFAIL_MSG( wxT("unexpected Get3StateValue() return value") );
+
+        return 0;
+    }
+};
+
+} // anonymous namespace
+
+wxAccessible* wxCheckBox::CreateAccessible()
+{
+    return new wxCheckBoxAccessible(this);
+}
+
+#endif // wxUSE_ACCESSIBILITY
+
 #endif // wxUSE_CHECKBOX

src/msw/radiobut.cpp

@@ -33,6 +33,10 @@
 #include "wx/renderer.h"
 #include "wx/msw/uxtheme.h"
 
+#if wxUSE_ACCESSIBILITY
+    #include "wx/msw/private/accessible.h"
+#endif
+
 // ============================================================================
 // wxRadioButton implementation
 // ============================================================================
@@ -347,4 +351,39 @@ void wxRadioButton::MSWDrawButtonBitmap(wxDC& dc, const wxRect& rect, int flags)
     wxRendererNative::Get().DrawRadioBitmap(this, dc, rect, flags);
 }
 
+#if wxUSE_ACCESSIBILITY
+
+namespace
+{
+
+// When the radio button is owner-drawn (e.g. in dark mode), the native
+// BS_RADIOBUTTON style is replaced with BS_OWNERDRAW, causing the standard
+// Windows accessible object to report the control as a generic button. This
+// custom accessible ensures the correct role and checked state are always
+// reported.
+class wxRadioButtonAccessible :
+    public wxOwnerDrawnAccessible<wxRadioButton, wxROLE_SYSTEM_RADIOBUTTON>
+{
+public:
+    explicit wxRadioButtonAccessible(wxRadioButton* win)
+        : wxOwnerDrawnAccessible(win)
+    {
+    }
+
+protected:
+    long MSWGetCheckedState(wxRadioButton* rb) const override
+    {
+        return rb->GetValue() ? wxACC_STATE_SYSTEM_CHECKED : 0;
+    }
+};
+
+} // anonymous namespace
+
+wxAccessible* wxRadioButton::CreateAccessible()
+{
+    return new wxRadioButtonAccessible(this);
+}
+
+#endif // wxUSE_ACCESSIBILITY
+
 #endif // wxUSE_RADIOBTN