refactor: Update error messages for more information on how to debug …

…issues

jpegxl-rs/src/decode/event.rs

@@ -0,0 +1,38 @@
+use std::ffi::c_int;
+
+/// Target of the color profile.
+pub use jpegxl_sys::decode::JxlColorProfileTarget as ColorProfileTarget;
+
+use super::{ColorEncodingConfig, Config};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Event {
+    BasicInfo,
+    ColorEncoding(ColorEncodingConfig),
+}
+
+impl From<Event> for c_int {
+    fn from(value: Event) -> Self {
+        match value {
+            Event::BasicInfo => 0x40,
+            Event::ColorEncoding { .. } => 0x100,
+        }
+    }
+}
+
+pub(crate) fn parse_events<I>(iter: I) -> (c_int, Config)
+where
+    I: IntoIterator<Item = Event>,
+{
+    iter.into_iter()
+        .fold((0, Config::default()), |(flag, config), x| {
+            let flag = flag | c_int::from(x);
+            let config = match x {
+                Event::ColorEncoding(val) => Config {
+                    color_profile: Some(val),
+                },
+                _ => config,
+            };
+            (flag, config)
+        })
+}

jpegxl-rs/src/errors.rs

@@ -28,14 +28,19 @@ pub enum DecodeError {
     #[error("Cannot create a decoder")]
     CannotCreateDecoder,
     /// Unknown Error
-    #[error("Generic Error")]
+    #[error(
+        "Generic Error. Please build `libjxl` from source (using `vendored` feature) 
+        in debug mode to get more information. Check `stderr` for any internal error messages."
+    )]
     GenericError,
     /// Invalid input
     #[error("The input does not contain a valid codestream or container")]
     InvalidInput,
     /// Unsupported Pixel bit width
     #[error("Unsupported Pixel bit width: {0}")]
     UnsupportedBitWidth(u32),
+    #[error("Invalid usage of the library, please file an issus: {0}")]
+    InvalidUsage(&'static str),
     /// Unknown status
     #[error("Unknown status: `{0:?}`")]
     UnknownStatus(JxlDecoderStatus),
@@ -49,7 +54,10 @@ pub enum EncodeError {
     #[error("Cannot create an encoder")]
     CannotCreateEncoder,
     /// Generic Error
-    #[error("Generic Error")]
+    #[error(
+        "Generic Error. Please build `libjxl` from source (using `vendored` feature) 
+        in debug mode to get more information. Check `stderr` for any internal error messages."
+    )]
     GenericError,
     /// Not Supported
     #[error("Encoder does not support it (yet)")]
@@ -66,7 +74,8 @@ pub enum EncodeError {
     /// Input is invalid (e.g. corrupt JPEG file or ICC profile)
     #[error("Input is invalid")]
     BadInput,
-    /// The encoder API is used in an incorrect way. In this case, a debug build of libjxl should output a specific error message
+    /// The encoder API is used in an incorrect way. In this case,
+    /// a debug build of libjxl should output a specific error message
     #[error("The encoder API is used in an incorrect way")]
     ApiUsage,
     /// Unknown status