Fix creating under GTK when the parent is already shown

In this case GTKHandleRealized() was called before everything was
initialized and nothing worked.

Work around this by postponing showing the window until the end of
Create().

src/common/webview_chromium.cpp

@@ -99,6 +99,9 @@ struct ImplData
 #ifdef __WXGTK__
     // Due to delayed creation of the browser in wxGTK we need to remember the
     // URL passed to Create() as we can't use it there directly.
+    //
+    // We also use this as a flag: it will be non-empty if the browser needs to
+    // be created.
     wxString m_initialURL;
 #endif // __WXGTK__
 
@@ -407,6 +410,26 @@ bool wxWebViewChromium::Create(wxWindow* parent,
         return false;
 
     style |= wxHSCROLL | wxVSCROLL;
+
+    // Hide the window while creating it, so that its GTKHandleRealized() is
+    // not called immediately, but only later, once we show it when exiting
+    // this function.
+    class DelayedShow
+    {
+    public:
+        explicit DelayedShow(wxWindow& self) : self_{self}
+        {
+            self_.wxWindowBase::Hide();
+        }
+
+        ~DelayedShow()
+        {
+            self_.Show();
+        }
+
+    private:
+        wxWindowBase& self_;
+    } delayedShow{*this};
 #endif
 
     if ( !wxControl::Create(parent, id, pos, size, style,
@@ -460,7 +483,7 @@ bool wxWebViewChromium::Create(wxWindow* parent,
     // Under wxGTK we need to wait until the window becomes realized in order
     // to get the X11 window handle, so postpone calling DoCreateBrowser()
     // until GTKHandleRealized().
-    m_implData->m_initialURL = url;
+    m_implData->m_initialURL = url.empty() ? wxString(" ") : url;
 #else
     // Under the other platforms we can call it immediately.
     if ( !DoCreateBrowser(url) )
@@ -478,9 +501,17 @@ bool wxWebViewChromium::Create(wxWindow* parent,
 
 void wxWebViewChromium::GTKHandleRealized()
 {
+    auto& initialURL = m_implData->m_initialURL;
+
+    if ( initialURL.empty() )
+        return;
+
     // Unfortunately there is nothing we can do here if it fails, so just
     // ignore the return value.
-    DoCreateBrowser(m_implData->m_initialURL);
+    DoCreateBrowser(initialURL);
+
+    // Ensure we don't call it any more.
+    initialURL.clear();
 }
 
 #endif // __WXGTK__
@@ -551,6 +582,7 @@ bool wxWebViewChromium::DoCreateBrowser(const wxString& url)
         return false;
     }
 
+    wxLogTrace(TRACE_CEF, "Browser created");
     return true;
 }