Fix build on QNX

- The memmap2 dependecy doesn't compile on QNX, so disable fontdb's memmap feature on QNX (besides WASM)
- Assume the availability of the Noto Sans font from the fonts system package

internal/common/Cargo.toml

@@ -30,4 +30,7 @@ cfg-if = { version = "1", optional = true }
 libloading = { version = "0.8.0", optional = true }
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
-fontdb = { workspace = true, optional = true, default-features = true }
+fontdb = { workspace = true, optional = true, features = ["std", "fs", "fontconfig"] }
+
+[target.'cfg(all(not(target_arch = "wasm32"), not(target_os = "nto")))'.dependencies]
+fontdb = { workspace = true, optional = true, features = ["memmap"] }

internal/common/sharedfontdb.rs

@@ -17,6 +17,7 @@ pub struct FontDatabase {
         target_vendor = "apple",
         target_arch = "wasm32",
         target_os = "android",
+        target_os = "nto",
     )))]
     pub fontconfig_fallback_families: Vec<String>,
     // Default font families to use instead of SansSerif when SLINT_DEFAULT_FONT env var is set.
@@ -64,6 +65,7 @@ thread_local! {
     target_vendor = "apple",
     target_arch = "wasm32",
     target_os = "android",
+    target_os = "nto",
 )))]
 mod fontconfig;
 
@@ -117,15 +119,20 @@ fn init_fontdb() -> FontDatabase {
         target_vendor = "apple",
         target_arch = "wasm32",
         target_os = "android",
+        target_os = "nto",
     )))]
     let mut fontconfig_fallback_families = Vec::new();
 
-    #[cfg(target_arch = "wasm32")]
+    #[cfg(any(target_arch = "wasm32", target_os = "nto"))]
     {
         let data = include_bytes!("sharedfontdb/DejaVuSans.ttf");
         font_db.load_font_data(data.to_vec());
         font_db.set_sans_serif_family("DejaVu Sans");
     }
+    #[cfg(target_os = "nto")]
+    {
+        font_db.set_sans_serif_family("Noto Sans");
+    }
     #[cfg(target_os = "android")]
     {
         font_db.load_fonts_dir("/system/fonts");
@@ -146,6 +153,7 @@ fn init_fontdb() -> FontDatabase {
                 target_vendor = "apple",
                 target_arch = "wasm32",
                 target_os = "android",
+                target_os = "nto",
             )))] {
                 match fontconfig::find_families("sans-serif") {
                     Ok(mut fallback_families) => {
@@ -179,6 +187,7 @@ fn init_fontdb() -> FontDatabase {
             target_vendor = "apple",
             target_arch = "wasm32",
             target_os = "android",
+            target_os = "nto",
         )))]
         fontconfig_fallback_families,
         default_font_family_ids,
@@ -203,7 +212,13 @@ pub fn register_font_from_path(path: &std::path::Path) -> Result<(), Box<dyn std
         for face_info in db.faces() {
             match &face_info.source {
                 fontdb::Source::Binary(_) => {}
-                fontdb::Source::File(loaded_path) | fontdb::Source::SharedFile(loaded_path, ..) => {
+                fontdb::Source::File(loaded_path) => {
+                    if *loaded_path == requested_path {
+                        return Ok(());
+                    }
+                }
+                #[cfg(not(target_os = "nto"))]
+                fontdb::Source::SharedFile(loaded_path, ..) => {
                     if *loaded_path == requested_path {
                         return Ok(());
                     }

internal/renderers/femtovg/fonts.rs

@@ -232,13 +232,13 @@ impl FontCache {
         // replacing files. Unlinking OTOH is safe and doesn't destroy the file mapping,
         // the backing file becomes an orphan in a special area of the file system. That works
         // on Unixy platforms and on Windows the default file flags prevent the deletion.
-        #[cfg(not(target_arch = "wasm32"))]
+        #[cfg(all(not(target_arch = "wasm32"), not(target_os = "nto")))]
         let (shared_data, face_index) = unsafe {
             sharedfontdb::FONT_DB.with_borrow_mut(|db| {
                 db.make_mut().make_shared_face_data(fontdb_face_id).expect("unable to mmap font")
             })
         };
-        #[cfg(target_arch = "wasm32")]
+        #[cfg(any(target_arch = "wasm32", target_os = "nto"))]
         let (shared_data, face_index) = crate::sharedfontdb::FONT_DB.with_borrow(|db| {
             db.face_source(fontdb_face_id)
                 .map(|(source, face_index)| {
@@ -456,6 +456,7 @@ impl FontCache {
         target_vendor = "apple",
         target_arch = "wasm32",
         target_os = "android",
+        target_os = "nto",
     )))]
     fn font_fallbacks_for_request(
         &self,
@@ -489,6 +490,21 @@ impl FontCache {
             .collect()
     }
 
+    #[cfg(target_os = "nto")]
+    fn font_fallbacks_for_request(
+        &self,
+        _family: Option<&SharedString>,
+        _pixel_size: PhysicalLength,
+        _primary_font: &LoadedFont,
+        _reference_text: &str,
+    ) -> Vec<SharedString> {
+        [SharedString::from("Noto Sans")]
+            .iter()
+            .filter(|family_name| self.is_known_family(&family_name))
+            .cloned()
+            .collect()
+    }
+
     fn is_known_family(&self, family: &str) -> bool {
         self.available_families.contains(family)
     }