commit b7166203b09e06389a9cfdfa586436b169e8106f
author Daniel McNab <36049421+DJMcNab@users.noreply.github.com> Mon Jun 24 16:15:28 2024 +0100
committer GitHub <noreply@github.com> Mon Jun 24 15:15:28 2024 +0000
tree 96a07c336909959f25f26c91160684f179dbd872
parent 886604b20376089ba2921b14b22acc9f0ae4e5ef

Hack around unsupported glyphs (#618)

Currently, if we get a glyph which the current font "doesn't support"
(such as if that font only supports bitmap images, which we don't), then
the entire transforms stream gets misaligned. That leads to some funny
rendering, such as
![Screenshot of the mason example, with misaligned text, some upside
down characters and incorrect looking
layout.](https://github.com/linebender/vello/assets/36049421/87e84446-7959-48db-9744-f3eac5dad3ff)

This PR works around this, by instead of skipping these glyphs,
inserting an empty encoding into their location.

vello_encoding/src/resolve.rs

diff --git a/vello_encoding/src/resolve.rs b/vello_encoding/src/resolve.rs
index c627c20..626e79c 100644
--- a/vello_encoding/src/resolve.rs
+++ b/vello_encoding/src/resolve.rs
@@ -438,9 +438,14 @@
                     };
                     let glyph_start = self.glyphs.len();
                     for glyph in glyphs {
-                        let Some((encoding, stream_sizes)) = session.get_or_insert(glyph.id) else {
-                            continue;
-                        };
+                        let (encoding, stream_sizes) =
+                            session.get_or_insert(glyph.id).unwrap_or_else(|| {
+                                // HACK: We pretend that the encoding was empty.
+                                // In theory, we should be able to skip this glyph, but there is also
+                                // a corresponding entry in `resources`, which means that we would
+                                // need to make the patching process skip this glyph.
+                                (Arc::new(Encoding::new()), StreamOffsets::default())
+                            });
                         run_sizes.add(&stream_sizes);
                         self.glyphs.push(encoding);
                     }