Add the ability to load application fonts by path

The viewer command line tool also gains the ability to specify them via `--app-font=/path/to/font.ttf` , which can be specified multiple times.

api/sixtyfps-rs/lib.rs

@@ -178,6 +178,15 @@ pub fn register_application_font_from_memory(
     sixtyfps_rendering_backend_default::backend().register_application_font_from_memory(data)
 }
 
+/// This function can be used to register a custom TrueType font with SixtyFPS,
+/// for use with the `font-family` property. The provided path must refer to a valid TrueType
+/// font.
+pub fn register_application_font_from_path<P: AsRef<std::path::Path>>(
+    path: P,
+) -> Result<(), Box<dyn std::error::Error>> {
+    sixtyfps_rendering_backend_default::backend().register_application_font_from_path(path.as_ref())
+}
+
 // FIXME: this should not be in this namespace
 // but the name is `sixtyfps::StateInfo` in builtin.60
 #[doc(hidden)]

sixtyfps_runtime/corelib/backend.rs

@@ -11,6 +11,8 @@ LICENSE END */
 The backend is the abstraction for crates that need to do the actual drawing and event loop
 */
 
+use std::path::Path;
+
 use crate::window::ComponentWindow;
 
 /// Interface implemented by backends
@@ -30,6 +32,14 @@ pub trait Backend: Send + Sync {
         data: &'static [u8],
     ) -> Result<(), Box<dyn std::error::Error>>;
 
+    /// This function can be used to register a custom TrueType font with SixtyFPS,
+    /// for use with the `font-family` property. The provided path must refer to a valid TrueType
+    /// font.
+    fn register_application_font_from_path(
+        &'static self,
+        path: &Path,
+    ) -> Result<(), Box<dyn std::error::Error>>;
+
     fn set_clipboard_text(&'static self, text: String);
     fn clipboard_text(&'static self) -> Option<String>;
 }

sixtyfps_runtime/interpreter/lib.rs

@@ -213,3 +213,9 @@ pub async fn load(
 pub fn run_event_loop() {
     sixtyfps_rendering_backend_default::backend().run_event_loop();
 }
+
+pub fn register_application_font_from_path<P: AsRef<std::path::Path>>(
+    path: P,
+) -> Result<(), Box<dyn std::error::Error>> {
+    sixtyfps_rendering_backend_default::backend().register_application_font_from_path(path.as_ref())
+}

sixtyfps_runtime/rendering_backends/gl/fonts.rs

@@ -33,6 +33,17 @@ pub fn register_application_font_from_memory(
     Ok(())
 }
 
+pub fn register_application_font_from_path(
+    path: &std::path::Path,
+) -> Result<(), Box<dyn std::error::Error>> {
+    // Should use FontDb::load_font_file but that requires the `fs` feature, for which I can't figure
+    // out how to exclude it from the wasm build. It's inclusion implies mmap, which doesn't compile
+    // with wasm.
+    let data = std::fs::read(path)?;
+    APPLICATION_FONTS.with(|fontdb| fontdb.borrow_mut().load_font_data(data));
+    Ok(())
+}
+
 pub(crate) fn try_load_app_font(
     canvas: &CanvasRc,
     request: &FontRequest,

sixtyfps_runtime/rendering_backends/gl/lib.rs

@@ -1438,6 +1438,13 @@ impl sixtyfps_corelib::backend::Backend for Backend {
         self::register_application_font_from_memory(data)
     }
 
+    fn register_application_font_from_path(
+        &'static self,
+        path: &std::path::Path,
+    ) -> Result<(), Box<dyn std::error::Error>> {
+        self::register_application_font_from_path(path)
+    }
+
     fn set_clipboard_text(&'static self, text: String) {
         use copypasta::ClipboardProvider;
         CLIPBOARD.with(|clipboard| clipboard.borrow_mut().set_contents(text).ok());

sixtyfps_runtime/rendering_backends/qt/lib.rs

@@ -98,6 +98,17 @@ pub const HAS_NATIVE_STYLE: bool = cfg!(not(no_qt));
 /// False if the backend was compiled without Qt so it wouldn't do anything
 pub const IS_AVAILABLE: bool = cfg!(not(no_qt));
 
+#[cfg(unix)]
+fn path_to_bytes<'a>(path: &'a std::path::Path) -> &'a [u8] {
+    use std::os::unix::ffi::OsStrExt;
+    path.as_os_str().as_bytes()
+}
+
+#[cfg(not(unix))]
+fn path_to_bytes<'a>(path: &'a std::path::Path) -> &'a [u8] {
+    path.to_string_lossy().to_string().as_bytes()
+}
+
 pub struct Backend;
 impl sixtyfps_corelib::backend::Backend for Backend {
     fn create_window(&'static self) -> ComponentWindow {
@@ -138,6 +149,22 @@ impl sixtyfps_corelib::backend::Backend for Backend {
         Ok(())
     }
 
+    fn register_application_font_from_path(
+        &'static self,
+        _path: &std::path::Path,
+    ) -> Result<(), Box<dyn std::error::Error>> {
+        #[cfg(not(no_qt))]
+        {
+            use cpp::cpp;
+            let encoded_path: qttypes::QByteArray = path_to_bytes(_path).into();
+            cpp! {unsafe [encoded_path as "QByteArray"] {
+                ensure_initialized();
+                QFontDatabase::addApplicationFont(QFile::decodeName(encoded_path));
+            } }
+        };
+        Ok(())
+    }
+
     fn set_clipboard_text(&'static self, _text: String) {
         #[cfg(not(no_qt))]
         {

tools/viewer/main.rs

@@ -20,12 +20,26 @@ struct Cli {
     /// The style name (empty, or 'qt')
     #[structopt(long, name = "style name", default_value)]
     style: String,
+
+    /// An optional application font
+    #[structopt(long, name = "application font")]
+    app_font: Option<Vec<String>>,
 }
 
 fn main() -> std::io::Result<()> {
     let args = Cli::from_args();
     let source = std::fs::read_to_string(&args.path)?;
 
+    args.app_font.map(|fonts| {
+        fonts.iter().for_each(|font_path| {
+            if let Err(app_font_err) =
+                sixtyfps_interpreter::register_application_font_from_path(&font_path)
+            {
+                eprintln!("Error loading app font {}: {}", font_path, app_font_err);
+            }
+        });
+    });
+
     let mut compiler_config = sixtyfps_compilerlib::CompilerConfiguration::new(
         sixtyfps_compilerlib::generator::OutputFormat::Interpreter,
     );