Implement GetSizeFromTextSize() for wxSpinCtrl.

Implement it for the native MSW and GTK versions and the generic one used in
the other ports and also for wxSpinCtrlDouble under MSW.

Also test this function in the spin page of the widgets sample.

Closes #14840.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72995 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/spinctrl.cpp

@@ -337,10 +337,39 @@ GdkWindow *wxSpinCtrlGTKBase::GTKGetWindow(wxArrayGdkWindows& windows) const
 
 wxSize wxSpinCtrlGTKBase::DoGetBestSize() const
 {
-    wxSize ret( wxControl::DoGetBestSize() );
-    wxSize best(95, ret.y); // FIXME: 95?
-    CacheBestSize(best);
-    return best;
+    return DoGetSizeFromTextSize(95); // TODO: 95 is completely arbitrary
+}
+
+wxSize wxSpinCtrlGTKBase::DoGetSizeFromTextSize(int xlen, int ylen) const
+{
+    wxASSERT_MSG( m_widget, wxS("GetSizeFromTextSize called before creation") );
+
+    // Set an as small as possible size for the control, so preferred sizes
+    // return "natural" sizes, not taking into account the previous ones (which
+    // seems to be GTK+3 behaviour)
+    gtk_widget_set_size_request(m_widget, 0, 0);
+
+    // Both Gtk+2 and Gtk+3 use current value/range to measure control's width.
+    // So, we can't ask Gtk+ for its width. Instead, we used hardcoded values.
+
+    // Returned height is OK
+    wxSize totalS = GTKGetPreferredSize(m_widget);
+
+#if GTK_CHECK_VERSION(3,4,0)
+    // two buttons in horizontal
+    totalS.x = 46 + 15; // margins included
+#else
+    // two small buttons in vertical
+    totalS.x = GetFont().GetPixelSize().y + 13; // margins included
+#endif
+
+    wxSize tsize(xlen + totalS.x, totalS.y);
+
+    // Check if the user requested a non-standard height.
+    if ( ylen > 0 )
+        tsize.IncBy(0, ylen - GetCharHeight());
+
+    return tsize;
 }
 
 // static