Configure font fallback
Overview
Define ordered font fallbacks for characters missing from the preferred font. Rules can target Unicode ranges and list several fonts in order, helping multilingual presentations render with a suitable glyph source. Make those fonts available to the library before rendering.
Usage example (C#)
Install Aspose.Slides for .NET before running this standalone example. Use a Greek character outside the base Microsoft Himalaya font’s character coverage. Install Arial and Microsoft Himalaya before running. The rule assigns Arial to the Greek Unicode range for rendering; fallback rules are render-time configuration.
using System;
using Aspose.Slides;
using Aspose.Slides.Export;
using var presentation = new Presentation();
var shape = presentation.Slides[0].Shapes.AddAutoShape(ShapeType.Rectangle, 40, 40, 500, 140);
shape.AddTextFrame("Sample slide");
shape.TextFrame.Text = "α";
shape.TextFrame.Paragraphs[0].Portions[0].PortionFormat.LatinFont = new FontData("Microsoft Himalaya");
shape.TextFrame.Paragraphs[0].Portions[0].PortionFormat.FontHeight = 72;
var rules = new FontFallBackRulesCollection();
rules.Add(new FontFallBackRule(0x0370, 0x03FF, "Arial"));
presentation.FontsManager.FontFallBackRulesCollection = rules;
using var image = presentation.Slides[0].GetImage(1f, 1f);
image.Save("fallback.png", Aspose.Slides.ImageFormat.Png);
presentation.Save("source.pptx", SaveFormat.Pptx);
FAQ
Does fallback order matter?
Yes. The library tries the configured font sequence for the character range. Put the preferred fallback first.
How is missing-glyph fallback different from font substitution?
Substitution replaces an unavailable font family. Missing-glyph fallback supplies a font for characters the selected font cannot display.
Can I assign fallback rules to a specific Unicode range?
Yes. Define the start and end Unicode code points and the fallback font or ordered font list for that range.
Guides
Related feature: Load fonts from a folder.