Generate wxEVT_ENTER_WINDOW in icon part of wxSearchCtrl in wxGTK

Mouse motion events happening over GtkEntry icons are consumed by this
class "event" callback, which simply returns GDK_EVENT_STOP for them if
the icon is insensitive (which is the case for GtkSearchEntry) and so
our "enter-notify-event" callback is never called.

Fix this by handling "event" signal ourselves and generating
wxEVT_ENTER_WINDOW from it if necessary.

Doing this required adding a global pointer to the window currently
under mouse, which is also used for generating wxEVT_LEAVE_WINDOW if
necessary.

See #24245.

include/wx/gtk/private/event.h

@@ -88,6 +88,12 @@ template<typename T> void InitMouseEvent(wxWindowGTK *win,
     event.SetTimestamp( gdk_event->time );
 }
 
+// Update the window currently known to be under the mouse pointer.
+//
+// Returns true if it was updated, false if this window was already known to
+// contain the mouse pointer.
+bool SetWindowUnderMouse(wxWindowGTK* win);
+
 } // namespace wxGTKImpl
 
 #endif // _GTK_PRIVATE_EVENT_H_

src/gtk/srchctrl.cpp

@@ -20,6 +20,7 @@
 
 #include "wx/utils.h"
 #include "wx/gtk/private.h"
+#include "wx/gtk/private/event.h"
 #include "wx/gtk/private/gtk3-compat.h"
 
 
@@ -93,6 +94,28 @@ wx_gtk_icon_press(GtkEntry* WXUNUSED(entry),
     }
 }
 
+static gboolean
+wx_gtk_entry_event(GtkEntry* WXUNUSED(entry),
+                   GdkEvent* event,
+                   wxSearchCtrl* ctrl)
+{
+    if ( event->type == GDK_MOTION_NOTIFY )
+    {
+        // GtkEntry "event" signal handler ignores motion events happening over
+        // inactive icons, but we want to notify the window about the mouse
+        // entering it when they happen.
+        if ( wxGTKImpl::SetWindowUnderMouse(ctrl) )
+        {
+            wxMouseEvent mouseEvent(wxEVT_ENTER_WINDOW);
+            wxGTKImpl::InitMouseEvent(ctrl, mouseEvent, (GdkEventMotion*)event);
+
+            ctrl->GTKProcessEvent(mouseEvent);
+        }
+    }
+
+    return FALSE;
+}
+
 }
 
 // ============================================================================
@@ -209,6 +232,8 @@ void wxSearchCtrl::GTKCreateSearchEntryWidget()
     }
 
     g_signal_connect(m_entry, "icon-press", G_CALLBACK(wx_gtk_icon_press), this);
+
+    g_signal_connect(m_entry, "event", G_CALLBACK(wx_gtk_entry_event), this);
 }
 
 GtkEditable *wxSearchCtrl::GetEditable() const

src/gtk/window.cpp

@@ -234,6 +234,23 @@ static wxWindowGTK *gs_deferredFocusOut = nullptr;
 GdkEvent    *g_lastMouseEvent = nullptr;
 int          g_lastButtonNumber = 0;
 
+static wxWindowGTK* g_windowUnderMouse = nullptr;
+
+namespace wxGTKImpl
+{
+
+bool SetWindowUnderMouse(wxWindowGTK* win)
+{
+    if ( g_windowUnderMouse == win )
+        return false;
+
+    g_windowUnderMouse = win;
+
+    return true;
+}
+
+} // namespace wxGTKImpl
+
 #ifdef wxHAS_XKB
 namespace
 {
@@ -2251,6 +2268,26 @@ gtk_window_enter_callback( GtkWidget* widget,
         return FALSE;
     }
 
+    if ( g_windowUnderMouse == win )
+    {
+        // This can happen if the enter event was generated from another
+        // callback, as is the case for wxSearchCtrl, for example.
+        wxLogTrace(TRACE_MOUSE, "Reentering window %s", wxDumpWindow(win));
+        return FALSE;
+    }
+
+    if ( g_windowUnderMouse )
+    {
+        // We must not have got the leave event for the previous window, so
+        // generate it now -- better late than never.
+        wxMouseEvent event( wxEVT_LEAVE_WINDOW );
+        InitMouseEvent(g_windowUnderMouse, event, gdk_event);
+
+        (void)g_windowUnderMouse->GTKProcessEvent(event);
+    }
+
+    g_windowUnderMouse = win;
+
     wxMouseEvent event( wxEVT_ENTER_WINDOW );
     InitMouseEvent(win, event, gdk_event);
 
@@ -2285,6 +2322,9 @@ gtk_window_leave_callback( GtkWidget* widget,
         return FALSE;
     }
 
+    if ( win == g_windowUnderMouse )
+        g_windowUnderMouse = nullptr;
+
     wxMouseEvent event( wxEVT_LEAVE_WINDOW );
     InitMouseEvent(win, event, gdk_event);
 
@@ -2914,6 +2954,9 @@ wxWindowGTK::~wxWindowGTK()
     if ( g_captureWindow == this )
         g_captureWindow = nullptr;
 
+    if ( g_windowUnderMouse == this )
+        g_windowUnderMouse = nullptr;
+
     if (m_wxwindow)
     {
         GTKDisconnect(m_wxwindow);