Correct wxHTML IMG ALIGN=CENTER placement

Capture the current text metrics when parsing image cells and use them to
position ALIGN=CENTER images relative to the surrounding text center and
not to the total cell height.

Add a parser regression test for the image and adjacent word vertical
centers.

Fixes #2976.

Closes #26669.

src/html/m_image.cpp

@@ -3,6 +3,7 @@
 // Purpose:     wxHtml module for displaying images
 // Author:      Vaclav Slavik
 // Copyright:   (c) 1999 Vaclav Slavik, Joel Lucsy
+//              (c) 2026 wxWidgets development team
 // Licence:     wxWindows licence
 /////////////////////////////////////////////////////////////////////////////
 
@@ -291,6 +292,7 @@ public:
                     int w = wxDefaultCoord, bool wpercent = false,
                     int h = wxDefaultCoord, bool hpresent = false,
                     double scale = 1.0, int align = wxHTML_ALIGN_BOTTOM,
+                    int textHeight = 0, int textDescent = 0,
                     const wxString& mapname = wxEmptyString);
     virtual ~wxHtmlImageCell();
     void Draw(wxDC& dc, int x, int y, int view_y1, int view_y2,
@@ -318,6 +320,7 @@ public:
 private:
     wxBitmap           *m_bitmap;
     int                 m_align;
+    int                 m_textHeight, m_textDescent;
     int                 m_bmpW, m_bmpH;
     bool                m_bmpWpercent:1;
     bool                m_bmpHpresent:1;
@@ -364,6 +367,7 @@ wxHtmlImageCell::wxHtmlImageCell(const wxHtmlTag& tag,
                                  wxHtmlWindowInterface *windowIface,
                                  wxFSFile *input, double scaleHDPI,
                                  int w, bool wpercent, int h, bool hpresent, double scale, int align,
+                                 int textHeight, int textDescent,
                                  const wxString& mapname) : wxHtmlCell(tag)
     , m_mapName(mapname)
 {
@@ -374,6 +378,8 @@ wxHtmlImageCell::wxHtmlImageCell(const wxHtmlTag& tag,
     m_bmpW   = w;
     m_bmpH   = h;
     m_align  = align;
+    m_textHeight = textHeight;
+    m_textDescent = textDescent;
     m_bmpWpercent = wpercent;
     m_bmpHpresent = hpresent;
     m_imageMap = nullptr;
@@ -564,7 +570,9 @@ void wxHtmlImageCell::Layout(int w)
             m_Descent = m_Height;
             break;
         case wxHTML_ALIGN_CENTER :
-            m_Descent = m_Height / 2;
+            // Center the image vertically with respect to the text and not the
+            // total cell height.
+            m_Descent = (m_Height - m_textHeight) / 2 + m_textDescent;
             break;
         case wxHTML_ALIGN_BOTTOM :
         default :
@@ -748,12 +756,15 @@ TAG_HANDLER_BEGIN(IMG, "IMG,MAP,AREA")
                         mn = mn.Mid( 1 );
                     }
                 }
+
+                m_WParser->CreateCurrentFont();
+                const wxFontMetrics fm = m_WParser->GetDC()->GetFontMetrics();
                 wxHtmlImageCell *cel = new wxHtmlImageCell(
                                           tag,
                                           m_WParser->GetWindowInterface(),
                                           str, scaleHDPI, w, wpercent, h, hpresent,
                                           m_WParser->GetPixelScale(),
-                                          al, mn);
+                                          al, fm.height, fm.descent, mn);
                 m_WParser->ApplyStateToCell(cel);
                 m_WParser->StopCollapsingSpaces();
                 cel->SetAlt(tag.GetParam(wxT("alt")));

tests/html/htmlparser.cpp

@@ -4,6 +4,7 @@
 // Author:      Vadim Zeitlin
 // Created:     2011-01-13
 // Copyright:   (c) 2011 Vadim Zeitlin <vadim@wxwidgets.org>
+//              (c) 2026 wxWidgets development team
 ///////////////////////////////////////////////////////////////////////////////
 
 // ----------------------------------------------------------------------------
@@ -17,6 +18,7 @@
 
 #ifndef WX_PRECOMP
     #include "wx/dcmemory.h"
+    #include "wx/log.h"
 #endif // WX_PRECOMP
 
 #include "wx/html/winpars.h"
@@ -42,6 +44,36 @@ TEST_CASE("wxHtmlParser::ParseInvalid", "[html][parser][error]")
     delete p.Parse("<!---");
 }
 
+TEST_CASE("wxHtmlParser::ImageAlignCenter", "[html][parser]")
+{
+    wxBitmap bmp(200, 200);
+    wxMemoryDC dc(bmp);
+
+    wxHtmlWinParser p;
+    p.SetDC(&dc);
+
+    wxLogNull noLog;
+    std::unique_ptr<wxHtmlContainerCell> const cells(
+        static_cast<wxHtmlContainerCell*>(p.Parse(
+            R"(<img id="img" width="100" height="100" align="center" src="dummy"/>Text)"
+        ))
+    );
+
+    REQUIRE( cells );
+    cells->Layout(200);
+
+    const wxString id("img");
+    const wxHtmlCell* const image = cells->Find(wxHTML_COND_ISANCHOR, &id);
+    REQUIRE( image );
+
+    const wxHtmlCell* const word = image->GetNext();
+    REQUIRE( word );
+    REQUIRE_FALSE( word->IsFormattingCell() );
+
+    CHECK( word->GetPosY() + word->GetHeight() / 2 ==
+           image->GetPosY() + image->GetHeight() / 2 );
+}
+
 TEST_CASE("wxHtmlCell::Detach", "[html][cell]")
 {
     wxMemoryDC dc;