在仅支持ECMA3的Photoshop中检测文本层notdef字符的可行性问询

Great question! First, let me clear up a misconception I had earlier — those strange replacement symbols you see (like �) aren't actually mojibake (garbled text). JosefZ corrected me on this: they're .notdef glyphs, which Photoshop displays when the selected font doesn't have a glyph for the character you're trying to render.

To answer your core question: Yes, you can detect .notdef characters in a text layer even with Photoshop's ECMA3-only scripting limitations, though it requires some creative workarounds since direct glyph access isn't built into the scripting API here.

Let me start with the test script I used to validate this behavior:

var theLayer = activeDocument.activeLayer;
if (theLayer.kind == "LayerKind.TEXT") {
  // theLayer.textItem.font = "ArialMT"; // Fails to render Japanese characters
  theLayer.textItem.font = "Meiryo"; // Renders correctly
  theLayer.textItem.contents = "グウェンステファニー";
}

Test Results: #

• When using the Meiryo font (which supports Japanese characters), the text displays exactly as intended: グウェンステファニー
• Switching to Arial (which lacks Japanese glyphs), Photoshop replaces missing characters with .notdef glyphs, showing up as: ���������
  Note: The � characters here are just a stand-in for the actual .notdef symbols you'd see in Photoshop

Practical Detection Methods for ECMA3 #

Since ECMA3 doesn't include modern string utilities or direct glyph mapping tools, here are two reliable workarounds:

• Cross-font comparison: Render the same text content using a font that supports all characters in your string (like a comprehensive Unicode font) and the target font. If the visual output differs (or you check for bounding box inconsistencies), it indicates .notdef glyphs are present.
• Character code validation: For specific character ranges you're working with, temporarily switch the text layer to a font that supports those characters. If the layer's appearance changes, the original font was using .notdef for some characters.

Neither method is a perfect one-liner, but they're effective given the ECMA3 constraints in Photoshop.

内容的提问来源于stack exchange，提问作者Ghoul Fool