Skia: Use parley for text layout

cc #9559

Author: tronical

internal/renderers/skia/Cargo.toml

@@ -35,7 +35,7 @@ unstable-wgpu-26 = [
 default = []
 
 [dependencies]
-i-slint-core = { workspace = true, features = ["default", "box-shadow-cache"] }
+i-slint-core = { workspace = true, features = ["default", "box-shadow-cache", "shared-parley"] }
 i-slint-core-macros = { workspace = true, features = ["default"] }
 i-slint-common = { workspace = true, features = ["default"] }
 
@@ -49,7 +49,7 @@ pin-weak = "1"
 scoped-tls-hkt = "0.1"
 raw-window-handle = { version = "0.6", features = ["std"] }
 
-skia-safe = { version = "0.88", features = ["textlayout", "gl"] }
+skia-safe = { version = "0.88", features = ["gl"] }
 glow = { workspace = true }
 unicode-segmentation = { workspace = true }
 
@@ -89,10 +89,17 @@ metal = { version = "0.31", optional = true }
 foreign-types = { version = "0.5.0", optional = true }
 wgpu-26 = { workspace = true, optional = true, features = ["metal"] }
 
+read-fonts = { version = "0.35" }
+write-fonts = { version = "0.43" }
+
 [target.'cfg(not(any(target_vendor = "apple", target_family = "windows")))'.dependencies]
 skia-safe = { version = "0.88", features = ["gl", "vulkan"] }
 wgpu-26 = { workspace = true, optional = true, features = ["vulkan"] }
 
+[target.'cfg(any(target_os = "ios", target_os="windows", target_os="android"))'.dependencies]
+# Text layout is enabled here just so that we can make use of the pre-built Skia libraries.
+skia-safe = { version = "0.88", features = ["textlayout"] }
+
 [build-dependencies]
 cfg_aliases = { workspace = true }
 

internal/renderers/skia/font_cache.rs

@@ -0,0 +1,56 @@
+// Copyright © SixtyFPS GmbH <[email protected]>
+// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-2.0 OR LicenseRef-Slint-Software-3.0
+
+use i_slint_core::textlayout::sharedparley::parley;
+use std::cell::RefCell;
+use std::collections::HashMap;
+
+pub struct FontCache {
+    font_mgr: skia_safe::FontMgr,
+    fonts: HashMap<(u64, u32), Option<skia_safe::Typeface>>,
+}
+
+impl Default for FontCache {
+    fn default() -> Self {
+        Self { font_mgr: skia_safe::FontMgr::new(), fonts: Default::default() }
+    }
+}
+
+impl FontCache {
+    pub fn font(&mut self, font: &parley::Font) -> Option<skia_safe::Typeface> {
+        self.fonts
+            .entry((font.data.id(), font.index))
+            .or_insert_with(|| {
+                let typeface = self.font_mgr.new_from_data(
+                    font.data.as_ref(),
+                    if font.index > 0 { Some(font.index as _) } else { None },
+                );
+
+                // Due to  https://issues.skia.org/issues/310510989, fonts from true type collections
+                // with an index > 0 fail to load on macOS. As a workaround, we manually extract the font from the
+                // collection and load it as a single font.
+                #[cfg(target_vendor = "apple")]
+                if font.index > 0 && typeface.is_none() {
+                    {
+                        if let Some(typeface) = read_fonts::CollectionRef::new(font.data.as_ref())
+                            .ok()
+                            .and_then(|ttc| ttc.get(font.index).ok())
+                            .map(|ttf| {
+                                write_fonts::FontBuilder::new().copy_missing_tables(ttf).build()
+                            })
+                            .and_then(|new_ttf| self.font_mgr.new_from_data(&new_ttf, None))
+                        {
+                            return Some(typeface);
+                        }
+                    }
+                }
+
+                typeface
+            })
+            .clone()
+    }
+}
+
+thread_local! {
+    pub static FONT_CACHE: RefCell<FontCache> = RefCell::new(Default::default())
+}