Trait druid::piet::cairo::glib::bitflags::_core::fmt::Debug

1.0.0 · source ·

pub trait Debug {
    // Required method
    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>;
}

Expand description

? formatting.

Debug should format the output in a programmer-facing, debugging context.

Generally speaking, you should just derive a Debug implementation.

When used with the alternate format specifier #?, the output is pretty-printed.

For more information on formatters, see the module-level documentation.

This trait can be used with #[derive] if all fields implement Debug. When derived for structs, it will use the name of the struct, then {, then a comma-separated list of each field’s name and Debug value, then }. For enums, it will use the name of the variant and, if applicable, (, then the Debug values of the fields, then ).

Stability

Derived Debug formats are not stable, and so may change with future Rust versions. Additionally, Debug implementations of types provided by the standard library (std, core, alloc, etc.) are not stable, and may also change with future Rust versions.

Examples

Deriving an implementation:

#[derive(Debug)]
struct Point {
    x: i32,
    y: i32,
}

let origin = Point { x: 0, y: 0 };

assert_eq!(format!("The origin is: {origin:?}"), "The origin is: Point { x: 0, y: 0 }");

Manually implementing:

use std::fmt;

struct Point {
    x: i32,
    y: i32,
}

impl fmt::Debug for Point {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Point")
         .field("x", &self.x)
         .field("y", &self.y)
         .finish()
    }
}

let origin = Point { x: 0, y: 0 };

assert_eq!(format!("The origin is: {origin:?}"), "The origin is: Point { x: 0, y: 0 }");

There are a number of helper methods on the Formatter struct to help you with manual implementations, such as debug_struct.

Types that do not wish to use the standard suite of debug representations provided by the Formatter trait (debug_struct, debug_tuple, debug_list, debug_set, debug_map) can do something totally custom by manually writing an arbitrary representation to the Formatter.

impl fmt::Debug for Point {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "Point [{} {}]", self.x, self.y)
    }
}

Debug implementations using either derive or the debug builder API on Formatter support pretty-printing using the alternate flag: {:#?}.

Pretty-printing with #?:

#[derive(Debug)]
struct Point {
    x: i32,
    y: i32,
}

let origin = Point { x: 0, y: 0 };

assert_eq!(format!("The origin is: {origin:#?}"),
"The origin is: Point {
    x: 0,
    y: 0,
}");

Required Methods§

source

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

Examples

use std::fmt;

struct Position {
    longitude: f32,
    latitude: f32,
}

impl fmt::Debug for Position {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_tuple("")
         .field(&self.longitude)
         .field(&self.latitude)
         .finish()
    }
}

let position = Position { longitude: 1.987, latitude: 2.983 };
assert_eq!(format!("{position:?}"), "(1.987, 2.983)");

assert_eq!(format!("{position:#?}"), "(
    1.987,
    2.983,
)");

Implementors§

Trait druid::piet::cairo::glib::bitflags::_core::fmt::Debug

Stability

Examples

Required Methods§

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Examples

Implementors§

impl Debug for Code

impl Debug for druid::Color

impl Debug for druid::Cursor

impl Debug for Handled

impl Debug for InternalEvent

impl Debug for InternalLifeCycle

impl Debug for druid::Location

impl Debug for MouseButton

impl Debug for druid::PlatformError

impl Debug for RawMods

impl Debug for RawWindowHandle

impl Debug for SysMods

impl Debug for Target

impl Debug for druid::Value

impl Debug for WindowSizePolicy

impl Debug for druid::WindowState

impl Debug for BarHeldState

impl Debug for BarHoveredState

impl Debug for ScrollbarsEnabled

impl Debug for druid::tests::helpers::Record

impl Debug for druid::text::Attribute

impl Debug for druid::text::Direction

impl Debug for druid::text::ImeInvalidation

impl Debug for Movement

impl Debug for druid::text::TextAction

impl Debug for VerticalMovement

impl Debug for WritingDirection

impl Debug for Axis

impl Debug for CrossAxisAlignment

impl Debug for KnobStyle

impl Debug for LineBreaking

impl Debug for MainAxisAlignment

impl Debug for TabsEdge

impl Debug for TabsTransition

impl Debug for druid::widget::prelude::Event

impl Debug for LifeCycle

impl Debug for ColorParseError

impl Debug for druid::piet::Error

impl Debug for FixedGradient

impl Debug for FontStyle

impl Debug for druid::piet::ImageFormat

impl Debug for druid::piet::LineCap

impl Debug for druid::piet::LineJoin

impl Debug for PaintBrush

impl Debug for ScaleMode

impl Debug for TextAlignment

impl Debug for druid::piet::TextAttribute

impl Debug for druid::piet::image_crate::ColorType

impl Debug for DynamicImage

impl Debug for ExtendedColorType

impl Debug for ImageError

impl Debug for druid::piet::image_crate::ImageFormat

impl Debug for ImageOutputFormat

impl Debug for ImageFormatHint

impl Debug for LimitErrorKind

impl Debug for ParameterErrorKind

impl Debug for UnsupportedErrorKind

impl Debug for druid::piet::image_crate::flat::Error

impl Debug for NormalForm

impl Debug for druid::piet::image_crate::imageops::FilterType

impl Debug for druid::piet::kurbo::PathEl

impl Debug for druid::piet::kurbo::PathSeg

impl Debug for druid::piet::kurbo::SvgParseError

impl Debug for Antialias

impl Debug for druid::piet::cairo::BorrowError

impl Debug for Content

impl Debug for druid::piet::cairo::DeviceType

impl Debug for druid::piet::cairo::Error

impl Debug for Extend

impl Debug for druid::piet::cairo::FillRule

impl Debug for druid::piet::cairo::Filter

impl Debug for FontSlant

impl Debug for FontType