Add error applet support + error applet panic hook

ctru-rs/src/applets/error.rs

@@ -0,0 +1,146 @@
+//! Error applet
+//!
+//! This applet displays error text as a pop-up message on the lower screen.
+use crate::services::{apt::Apt, gfx::Gfx};
+
+use ctru_sys::errorConf;
+
+/// Configuration struct to set up the Error applet.
+#[doc(alias = "errorConf")]
+pub struct PopUp {
+    state: Box<errorConf>,
+}
+
+/// The kind of error applet to display.
+#[doc(alias = "errorType")]
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+#[repr(u32)]
+pub enum Kind {
+    /// Error text is centered in the error applet window.
+    Center = ctru_sys::ERROR_TEXT,
+    /// Error text starts at the top of the error applet window.
+    Top = ctru_sys::ERROR_TEXT_WORD_WRAP,
+}
+
+/// Error returned by an unsuccessful [`PopUp::launch()`].
+#[doc(alias = "errorReturnCode")]
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+#[repr(i8)]
+pub enum Error {
+    /// Unknown error occurred.
+    Unknown = ctru_sys::ERROR_UNKNOWN,
+    /// Operation not supported.
+    NotSupported = ctru_sys::ERROR_NOT_SUPPORTED,
+    /// Home button pressed while [`PopUp`] was running.
+    HomePressed = ctru_sys::ERROR_HOME_BUTTON,
+    /// Power button pressed while [`PopUp`] was running.
+    PowerPressed = ctru_sys::ERROR_POWER_BUTTON,
+    /// Reset button pressed while [`PopUp`] was running.
+    ResetPressed = ctru_sys::ERROR_SOFTWARE_RESET,
+}
+
+impl PopUp {
+    /// Initialize the error applet with the provided text kind.
+    #[doc(alias = "errorInit")]
+    pub fn new(kind: Kind) -> Self {
+        let mut state = Box::<errorConf>::default();
+
+        unsafe { ctru_sys::errorInit(state.as_mut(), kind as _, 0) };
+
+        Self { state }
+    }
+
+    /// Sets the error text to display.
+    #[doc(alias = "errorText")]
+    pub fn set_text(&mut self, text: &str) {
+        for (idx, code_unit) in text
+            .encode_utf16()
+            .chain(std::iter::once(0))
+            .take(self.state.Text.len() - 1)
+            .enumerate()
+        {
+            self.state.Text[idx] = code_unit;
+        }
+    }
+
+    /// Launches the error applet.
+    #[doc(alias = "errorDisp")]
+    pub fn launch(&mut self, _apt: &Apt, _gfx: &Gfx) -> Result<(), Error> {
+        unsafe { ctru_sys::errorDisp(self.state.as_mut()) }
+
+        match self.state.returnCode {
+            ctru_sys::ERROR_NONE | ctru_sys::ERROR_SUCCESS => Ok(()),
+            ctru_sys::ERROR_NOT_SUPPORTED => Err(Error::NotSupported),
+            ctru_sys::ERROR_HOME_BUTTON => Err(Error::HomePressed),
+            ctru_sys::ERROR_POWER_BUTTON => Err(Error::PowerPressed),
+            ctru_sys::ERROR_SOFTWARE_RESET => Err(Error::ResetPressed),
+            _ => Err(Error::Unknown),
+        }
+    }
+
+    /// Launches the error applet without requiring an [`Apt`] or [`Gfx`] handle.
+    ///
+    /// # Safety
+    ///
+    /// Causes undefined behavior if the aforementioned services are not actually active when the applet launches.
+    unsafe fn launch_unchecked(&mut self) {
+        unsafe { ctru_sys::errorDisp(self.state.as_mut()) };
+    }
+}
+
+/// Sets a custom [panic hook](https://doc.rust-lang.org/std/panic/fn.set_hook.html) that uses the error applet to display panic messages.
+///
+/// You can also choose to have the previously registered panic hook called along with the error applet message, which can be useful
+/// if you want to use output redirection to display panic messages over `3dslink` or `GDB`.
+///
+/// If the [`Gfx`] service is not initialized during a panic, the error applet will not be displayed and the old
+/// panic hook will be called.
+///
+/// You can use [`std::panic::take_hook`](https://doc.rust-lang.org/std/panic/fn.take_hook.html) to unregister the panic hook
+/// set by this function.
+pub fn set_panic_hook(call_old_hook: bool) {
+    use crate::services::gfx::GFX_ACTIVE;
+    use std::sync::TryLockError;
+
+    let old_hook = std::panic::take_hook();
+
+    std::panic::set_hook(Box::new(move |panic_info| {
+        let thread = std::thread::current();
+
+        let name = thread.name().unwrap_or("<unnamed>");
+
+        // If we get a `WouldBlock` error, we know that the `Gfx` service has been initialized.
+        // Otherwise fallback to printing over stderr.
+        if let (Err(TryLockError::WouldBlock), Ok(_apt)) = (GFX_ACTIVE.try_lock(), Apt::new()) {
+            if call_old_hook {
+                old_hook(panic_info);
+            }
+
+            let payload = format!("thread '{name}' {panic_info}");
+
+            let mut popup = PopUp::new(Kind::Top);
+
+            popup.set_text(&payload);
+
+            unsafe {
+                popup.launch_unchecked();
+            }
+        } else {
+            old_hook(panic_info);
+        }
+    }));
+}
+
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::NotSupported => write!(f, "operation not supported"),
+            Self::HomePressed => write!(f, "home button pressed while error applet was running"),
+            Self::PowerPressed => write!(f, "power button pressed while error applet was running"),
+            Self::ResetPressed => write!(f, "reset button pressed while error applet was running"),
+            Self::Unknown => write!(f, "an unknown error occurred"),
+        }
+    }
+}
+
+impl std::error::Error for Error {}

ctru-rs/src/applets/mod.rs

@@ -8,5 +8,6 @@
 //!
 //! Applets block execution of the thread that launches them as long as the user doesn't close the applet.
 
+pub mod error;
 pub mod mii_selector;
 pub mod swkbd;

ctru-rs/src/services/gfx.rs

@@ -239,7 +239,7 @@ pub struct Gfx {
     _service_handler: ServiceReference,
 }
 
-static GFX_ACTIVE: Mutex<()> = Mutex::new(());
+pub(crate) static GFX_ACTIVE: Mutex<()> = Mutex::new(());
 
 impl Gfx {
     /// Initialize a new default service handle.

ctru-sys/build.rs

@@ -79,6 +79,8 @@ fn main() {
         .blocklist_type("u(8|16|32|64)")
         .blocklist_type("__builtin_va_list")
         .blocklist_type("__va_list")
+        .blocklist_type("errorReturnCode")
+        .blocklist_type("errorScreenFlag")
         .opaque_type("MiiData")
         .derive_default(true)
         .wrap_static_fns(true)

ctru-sys/src/lib.rs

@@ -16,6 +16,24 @@
 pub mod result;
 pub use result::*;
 
+// Fun fact: C compilers are allowed to represent enums as the smallest integer type that can hold all of its variants,
+// meaning that enums are allowed to be the size of a `c_short` or a `c_char` rather than the size of a `c_int`.
+// Libctru's `errorConf` struct contains two enums that depend on this narrowing property for size and alignment purposes,
+// and since `bindgen` generates all enums with `c_int` sizing, we have to blocklist those types and manually define them
+// here with the proper size.
+pub const ERROR_UNKNOWN: errorReturnCode = -1;
+pub const ERROR_NONE: errorReturnCode = 0;
+pub const ERROR_SUCCESS: errorReturnCode = 1;
+pub const ERROR_NOT_SUPPORTED: errorReturnCode = 2;
+pub const ERROR_HOME_BUTTON: errorReturnCode = 10;
+pub const ERROR_SOFTWARE_RESET: errorReturnCode = 11;
+pub const ERROR_POWER_BUTTON: errorReturnCode = 12;
+pub type errorReturnCode = libc::c_schar;
+
+pub const ERROR_NORMAL: errorScreenFlag = 0;
+pub const ERROR_STEREO: errorScreenFlag = 1;
+pub type errorScreenFlag = libc::c_char;
+
 include!(concat!(env!("OUT_DIR"), "/bindings.rs"));
 
 /// In lieu of a proper errno function exposed by libc