Added AdvanceWidth to VerticalShapedGlyph

Author: swmal

src/EPPlus.Fonts.OpenType.Tests/Subsetting/VerticalSubsettingTests.cs

@@ -1,4 +1,4 @@
-/*************************************************************************************************
+ /*************************************************************************************************
   Required Notice: Copyright (C) EPPlus Software AB. 
   This software is licensed under PolyForm Noncommercial License 1.0.0 
   and may only be used for noncommercial purposes 

src/EPPlus.Fonts.OpenType.Tests/TextShaping/VerticalTextShapingTests.cs

@@ -296,5 +296,73 @@ public void ShapeLightVertical_SurrogatePair_ProducesOneEntryWithCharCountTwo()
         }
 
         #endregion
+
+        #region Centering tests
+
+        [TestMethod]
+        public void ShapeVertical_CjkText_GlyphsHavePositiveAdvanceWidth()
+        {
+            // Arrange
+            var font = OpenTypeFonts.GetFontDataOpen(FontFolders, "BIZ UDGothic", FontSubFamily.Regular, true);
+            var shaper = new TextShaper(font);
+
+            // Act
+            var result = shaper.ShapeVertical("日本語");
+
+            // Assert - AdvanceWidth is required for horizontal centering in vertical text columns
+            foreach (var glyph in result.Glyphs)
+            {
+                Assert.IsTrue(glyph.AdvanceWidth > 0,
+                    $"Glyph {glyph.GlyphId} has AdvanceWidth {glyph.AdvanceWidth}, expected > 0");
+            }
+        }
+
+        [TestMethod]
+        public void ShapeVertical_AdvanceWidthMatchesHmtxAdvanceWidth()
+        {
+            // Arrange - AdvanceWidth on VerticalShapedGlyph must equal hmtx advanceWidth
+            // since centering calculations depend on this value being accurate
+            var font = OpenTypeFonts.GetFontDataOpen(FontFolders, "BIZ UDGothic", FontSubFamily.Regular, true);
+            var shaper = new TextShaper(font);
+
+            // Act
+            var result = shaper.ShapeVertical("日本");
+
+            // Assert
+            foreach (var glyph in result.Glyphs)
+            {
+                var expectedAdvanceWidth = font.HmtxTable.GetAdvanceWidth(glyph.GlyphId);
+                Assert.AreEqual(expectedAdvanceWidth, glyph.AdvanceWidth,
+                    $"Glyph {glyph.GlyphId}: AdvanceWidth {glyph.AdvanceWidth} " +
+                    $"does not match hmtx advanceWidth {expectedAdvanceWidth}");
+            }
+        }
+
+        [TestMethod]
+        public void ShapeVertical_FontWithoutVmtx_AdvanceWidthMatchesHmtxAdvanceWidth()
+        {
+            // Arrange - Roboto has no vmtx table, both YAdvance and AdvanceWidth
+            // should fall back to hmtx and be equal to each other
+            var font = OpenTypeFonts.GetFontDataOpen(FontFolders, "Roboto", FontSubFamily.Regular, true);
+            var shaper = new TextShaper(font);
+            Assert.IsNull(font.VmtxTable, "Roboto should not have a vmtx table");
+
+            // Act
+            var result = shaper.ShapeVertical("ABC");
+
+            // Assert
+            foreach (var glyph in result.Glyphs)
+            {
+                var expectedAdvanceWidth = font.HmtxTable.GetAdvanceWidth(glyph.GlyphId);
+                Assert.AreEqual(expectedAdvanceWidth, glyph.AdvanceWidth,
+                    $"Glyph {glyph.GlyphId}: AdvanceWidth {glyph.AdvanceWidth} " +
+                    $"does not match hmtx advanceWidth {expectedAdvanceWidth}");
+                Assert.AreEqual(glyph.YAdvance, glyph.AdvanceWidth,
+                    $"Glyph {glyph.GlyphId}: YAdvance and AdvanceWidth should be equal " +
+                    $"when falling back to hmtx (YAdvance={glyph.YAdvance}, AdvanceWidth={glyph.AdvanceWidth})");
+            }
+        }
+
+        #endregion
     }
 }

src/EPPlus.Fonts.OpenType/TextShaping/TextShaper.Vertical.cs

@@ -110,11 +110,14 @@ private List<VerticalShapedGlyph> MapToVerticalGlyphs(string text)
                 ushort advanceHeight;
                 short topSideBearing;
                 GetVerticalMetrics(font, glyphId, out advanceHeight, out topSideBearing);
+                // Fetch horizontal advance width for centering
+                ushort advanceWidth = font.HmtxTable.GetAdvanceWidth(glyphId);
 
                 glyphs.Add(new VerticalShapedGlyph(
                     glyphId,
                     advanceHeight,
                     topSideBearing,
+                    advanceWidth,
                     (ushort)i,
                     (byte)charCount,
                     fontId

src/EPPlus.Interfaces/Drawing/Text/VerticalShapedGlyph.cs

@@ -43,6 +43,14 @@ public class VerticalShapedGlyph
         /// </summary>
         public short TopSideBearing;
 
+        /// <summary>
+        /// Horizontal advance width in font design units.
+        /// Sourced from the 'hmtx' table.
+        /// Used by the renderer to center the glyph horizontally in a vertical text column:
+        /// xOffset = (columnWidth - AdvanceWidth) / 2
+        /// </summary>
+        public ushort AdvanceWidth;
+
         /// <summary>
         /// Index of the original character that produced this glyph.
         /// Used to map shaped glyphs back to character positions.
@@ -75,12 +83,13 @@ public VerticalShapedGlyph()
         /// <summary>
         /// Creates a new vertical shaped glyph with all fields specified.
         /// </summary>
-        public VerticalShapedGlyph(ushort glyphId, ushort yAdvance, short topSideBearing,
+        public VerticalShapedGlyph(ushort glyphId, ushort yAdvance, short topSideBearing, ushort advanceWidth,
                                    ushort clusterIndex, byte charCount, byte fontId = 0)
         {
             GlyphId = glyphId;
             YAdvance = yAdvance;
             TopSideBearing = topSideBearing;
+            AdvanceWidth = advanceWidth;
             ClusterIndex = clusterIndex;
             CharCount = charCount;
             FontId = fontId;