Fix nested markup conversion to NSAttributedString

wxMarkupToAttrStringBase implementation of markup parsing failed to
correctly apply nested attributes: in e.g. <i><b>foo</b></i>, only the
outer attribute was in effect.

This was due to applying - and overwriting - attributes to a span in
OnAttrEnd(), which is called first for the inner span, and then for the
outer one, overwriting all inner changes.

Instead, apply the currently effective attributes to text in OnText(),
similarly to how wxMarkupParserRenderOutput does it. As a side effect,
this also eliminates the need to apply default font to the entire range
first.

Closes #25864.

include/wx/osx/cocoa/private/markuptoattr.h

@@ -37,12 +37,6 @@ protected:
 
         [m_attrString beginEditing];
 
-        // First thing we do is change the default string font: as mentioned in
-        // Apple documentation, attributed strings use "Helvetica 12" font by
-        // default which is different from the system "Lucida Grande" font. So
-        // we need to explicitly change the font for the entire string.
-        ApplyFont(font, NSMakeRange(0, [m_attrString length]));
-
         // Now translate the markup tags to corresponding attributes.
         wxMarkupParser parser(*this);
         parser.Parse(markup);
@@ -56,27 +50,6 @@ protected:
             [m_attrString release];
     }
 
-    void ApplyFont(const wxFont& font, const NSRange& range)
-    {
-        [m_attrString addAttribute:NSFontAttributeName
-                      value:font.OSXGetNSFont()
-                      range:range];
-
-        if ( font.GetStrikethrough() )
-        {
-            [m_attrString addAttribute:NSStrikethroughStyleAttributeName
-                                 value:@(NSUnderlineStyleSingle)
-                                 range:range];
-        }
-
-        if ( font.GetUnderlined() )
-        {
-            [m_attrString addAttribute:NSUnderlineStyleAttributeName
-                                 value:@(NSUnderlineStyleSingle)
-                                 range:range];
-        }
-    }
-
     // prepare text chunk for display, e.g. strip mnemonics from it
     virtual wxString PrepareText(const wxString& text) = 0;
 
@@ -89,43 +62,35 @@ public:
         return m_attrString;
     }
 
-
     // Implement base class pure virtual methods to process markup tags.
     virtual void OnText(const wxString& text) override
     {
-        m_pos += PrepareText(text).length();
+        const Attr& attr = GetAttr();
+
+        NSMutableDictionary *dict = [NSMutableDictionary dictionary];
+
+        dict[NSFontAttributeName] = attr.effectiveFont.OSXGetNSFont();
+        if ( attr.effectiveFont.GetStrikethrough() )
+            dict[NSStrikethroughStyleAttributeName] = @(NSUnderlineStyleSingle);
+        if ( attr.effectiveFont.GetUnderlined() )
+            dict[NSUnderlineStyleAttributeName] = @(NSUnderlineStyleSingle);
+
+        if ( attr.effectiveForeground.IsOk() )
+            dict[NSForegroundColorAttributeName] = attr.effectiveForeground.OSXGetWXColor();
+
+        if ( attr.effectiveBackground.IsOk() )
+            dict[NSBackgroundColorAttributeName] = attr.effectiveBackground.OSXGetWXColor();
+
+        const unsigned len = PrepareText(text).length();
+
+        [m_attrString addAttributes:dict range:NSMakeRange(m_pos, len)];
+
+        m_pos += len;
     }
 
-    virtual void OnAttrStart(const Attr& WXUNUSED(attr)) override
-    {
-        // Just remember the starting position of the range, we can't really
-        // set the attribute until we find the end of it.
-        m_rangeStarts.push(m_pos);
-    }
+    virtual void OnAttrStart(const Attr& WXUNUSED(attr)) override {}
 
-    virtual void OnAttrEnd(const Attr& attr) override
-    {
-        unsigned start = m_rangeStarts.top();
-        m_rangeStarts.pop();
-
-        const NSRange range = NSMakeRange(start, m_pos - start);
-
-        ApplyFont(attr.font, range);
-
-        if ( attr.foreground.IsOk() )
-        {
-            [m_attrString addAttribute:NSForegroundColorAttributeName
-                          value:attr.foreground.OSXGetWXColor()
-                          range:range];
-        }
-
-        if ( attr.background.IsOk() )
-        {
-            [m_attrString addAttribute:NSBackgroundColorAttributeName
-                          value:attr.background.OSXGetWXColor()
-                          range:range];
-        }
-    }
+    virtual void OnAttrEnd(const Attr& WXUNUSED(attr)) override {}
 
 private:
     // The attributed string we're building.
@@ -133,9 +98,6 @@ private:
 
     // The current position in the output string.
     unsigned m_pos;
-
-    // The positions of starting ranges.
-    wxStack<unsigned> m_rangeStarts;
 };