Support inherited attributes in wxPropertyGrid XRC handler

Allow specifying recurse="1" to inherit the attribute, as this is much
nicer than having to specify it for all the children.

Also add support for this to wxPropertyGridPopulator, which is used by
the XRC handler.

docs/doxygen/overviews/xrc_format.h

@@ -1865,6 +1865,11 @@ to use it.
 @row3col{choices, @ref overview_xrcformat_type_string,
     Space-separated string containing the possible choices for the properties
     using them, e.g. wxFlagsProperty or wxEnumProperty.}
+@row3col{attribute, @ref overview_xrcformat_type_string,
+    Value for the property attribute with the name specified by the `name`
+    attribute of this element. Additional `recurse` attribute is supported and,
+    if specified with the value of `1`, results in the attribute being set for
+    this property and all its children recursively.}
 @endTable
 
 These elements define individual rows of @ref xrc_wxpropertygrid or @ref

include/wx/propgrid/propgrid.h

@@ -2157,7 +2157,8 @@ public:
     // Empty string mean autodetect.
     bool AddAttribute( const wxString& name,
                        const wxString& type,
-                       const wxString& value );
+                       const wxString& value,
+                       wxPGPropertyValuesFlags flags = wxPGPropertyValuesFlags::DontRecurse );
 
     // Called once in AddChildren.
     virtual void DoScanForChildren() = 0;
@@ -2197,6 +2198,9 @@ protected:
     // Tree-hierarchy of added properties (that can have children).
     std::vector<wxPGProperty*> m_propHierarchy;
 
+    // Recursively set attributes.
+    std::unordered_map<wxString, wxVariant> m_inheritedAttributes;
+
     // Hashmap for string-id to wxPGChoicesData mapping.
     std::unordered_map<wxString, wxPGChoicesData*> m_dictIdChoices;
 };

interface/wx/propgrid/propgrid.h

@@ -1534,10 +1534,16 @@ public:
 
         @param value
             Attribute value.
+
+        @param flags
+            Flags used when setting the attribute. Currently only
+            wxPGPropertyValuesFlags::Recurse is used here. This parameter is
+            only available since wxWidgets 3.3.0.
     */
     bool AddAttribute( const wxString& name,
                        const wxString& type,
-                       const wxString& value );
+                       const wxString& value,
+                       wxPGPropertyValuesFlags flags = wxPGPropertyValuesFlags::DontRecurse );
 
     /**
         Called once in AddChildren.

src/propgrid/propgrid.cpp

@@ -6416,9 +6416,22 @@ wxPGProperty* wxPropertyGridPopulator::Add( const wxString& propClass,
 
 void wxPropertyGridPopulator::AddChildren( wxPGProperty* property )
 {
+    // Preserve inherited attributes to be able to restore them later:
+    // attributes recursively set for the children of this property shouldn't
+    // be inherited by its siblings.
+    const auto inheritedAttributesOrig = m_inheritedAttributes;
+
+    // Apply inherited attributes to the property.
+    for ( const auto& it : m_inheritedAttributes )
+    {
+        property->SetAttribute(it.first, it.second);
+    }
+
     m_propHierarchy.push_back(property);
     DoScanForChildren();
     m_propHierarchy.pop_back();
+
+    m_inheritedAttributes = std::move(inheritedAttributesOrig);
 }
 
 // -----------------------------------------------------------------------
@@ -6540,7 +6553,8 @@ bool wxPropertyGridPopulator::ToLongPCT( const wxString& s, long* pval, long max
 
 bool wxPropertyGridPopulator::AddAttribute( const wxString& name,
                                             const wxString& type,
-                                            const wxString& value )
+                                            const wxString& value,
+                                            wxPGPropertyValuesFlags flags )
 {
     if ( m_propHierarchy.empty() )
         return false;
@@ -6589,6 +6603,11 @@ bool wxPropertyGridPopulator::AddAttribute( const wxString& name,
         }
     }
 
+    if ( !!(flags & wxPGPropertyValuesFlags::Recurse) )
+    {
+        m_inheritedAttributes[name] = variant;
+    }
+
     p->SetAttribute( name, variant );
 
     return true;

src/xrc/xh_propgrid.cpp

@@ -175,8 +175,12 @@ wxObject *wxPropertyGridXmlHandler::DoCreateResource()
         wxString s1 = node->GetAttribute("name");
         if ( s1.length() )
         {
+            wxPGPropertyValuesFlags flags = node->GetAttribute("recurse") == "1"
+                ? wxPGPropertyValuesFlags::Recurse
+                : wxPGPropertyValuesFlags::DontRecurse;
+
             m_populator->AddAttribute( s1, node->GetAttribute("type"),
-                                       node->GetNodeContent() );
+                                       node->GetNodeContent(), flags );
         }
     }
     else if( m_class == wxT("wxPropertyGrid"))