From f11afa43114be00434d9cfee6beff19ab47ba8dc Mon Sep 17 00:00:00 2001
From: Samuel <sam.rodr.g@gmail.com>
Date: Mon, 20 Jan 2025 19:25:02 -0300
Subject: [PATCH] Improve cache of font data to use less memory

---
 CHANGELOG.md                          |  1 +
 crates/zng-ext-font/src/lib.rs        |  1 +
 crates/zng-ext-font/src/query_util.rs | 22 +++++++++++++++++++++-
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3e7717287..1cd52fe92 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
 # Unreleased
 
+* Improve cache of font data to use less memory.
 
 # 0.13.7
 
diff --git a/crates/zng-ext-font/src/lib.rs b/crates/zng-ext-font/src/lib.rs
index 8af193ddf..defc818dd 100644
--- a/crates/zng-ext-font/src/lib.rs
+++ b/crates/zng-ext-font/src/lib.rs
@@ -1785,6 +1785,7 @@ impl<I: SliceIndex<[Font]>> std::ops::Index<I> for FontList {
 struct FontFaceLoader {
     custom_fonts: HashMap<FontName, Vec<FontFace>>,
     unregister_requests: Vec<(FontName, ResponderVar<bool>)>,
+
     system_fonts_cache: HashMap<FontName, Vec<SystemFontFace>>,
     list_cache: HashMap<Box<[FontName]>, Vec<FontFaceListQuery>>,
 }
diff --git a/crates/zng-ext-font/src/query_util.rs b/crates/zng-ext-font/src/query_util.rs
index 8b90fc359..921d472ec 100644
--- a/crates/zng-ext-font/src/query_util.rs
+++ b/crates/zng-ext-font/src/query_util.rs
@@ -1,16 +1,22 @@
+use std::path::PathBuf;
+
 #[cfg(not(any(target_arch = "wasm32", target_os = "android")))]
 pub use desktop::*;
 
+use parking_lot::Mutex;
 #[cfg(target_arch = "wasm32")]
 pub use wasm::*;
 
 #[cfg(target_os = "android")]
 pub use android::*;
 
+static DATA_CACHE: Mutex<Vec<(PathBuf, std::sync::Weak<Vec<u8>>)>> = Mutex::new(vec![]);
+
 #[cfg(not(any(target_arch = "wasm32", target_os = "android")))]
 mod desktop {
     use std::{borrow::Cow, path::Path, sync::Arc};
 
+    use zng_layout::unit::ByteUnits;
     use zng_var::ResponseVar;
 
     use crate::{FontDataRef, FontLoadingError, FontName, FontStretch, FontStyle, FontWeight, GlyphLoadingError};
@@ -166,9 +172,23 @@ mod desktop {
                     }
                 }
 
+                for (k, data) in super::DATA_CACHE.lock().iter() {
+                    if *k == *path {
+                        if let Some(data) = data.upgrade() {
+                            return Ok((FontDataRef(data), *font_index));
+                        }
+                    }
+                }
+
                 let bytes = std::fs::read(&*path)?;
+                tracing::debug!("read font `{}:{}`, using {}", path.display(), font_index, bytes.capacity().bytes());
+
+                let data = Arc::new(bytes);
+                let mut cache = super::DATA_CACHE.lock();
+                cache.retain(|(_, v)| v.strong_count() > 0);
+                cache.push((path.to_path_buf(), Arc::downgrade(&data)));
 
-                Ok((FontDataRef(Arc::new(bytes)), *font_index))
+                Ok((FontDataRef(data), *font_index))
             }
             font_kit::handle::Handle::Memory { bytes, font_index } => Ok((FontDataRef(bytes.clone()), *font_index)),
         }