1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
use std::fmt;
use std::io::{self, Write};

use crate::terminal::{BeginSynchronizedUpdate, EndSynchronizedUpdate};

/// An interface for a command that performs an action on the terminal.
///
/// Crossterm provides a set of commands,
/// and there is no immediate reason to implement a command yourself.
/// In order to understand how to use and execute commands,
/// it is recommended that you take a look at [Command API](./index.html#command-api) chapter.
pub trait Command {
    /// Write an ANSI representation of this command to the given writer.
    /// An ANSI code can manipulate the terminal by writing it to the terminal buffer.
    /// However, only Windows 10 and UNIX systems support this.
    ///
    /// This method does not need to be accessed manually, as it is used by the crossterm's [Command API](./index.html#command-api)
    fn write_ansi(&self, f: &mut impl fmt::Write) -> fmt::Result;

    /// Execute this command.
    ///
    /// Windows versions lower than windows 10 do not support ANSI escape codes,
    /// therefore a direct WinAPI call is made.
    ///
    /// This method does not need to be accessed manually, as it is used by the crossterm's [Command API](./index.html#command-api)
    #[cfg(windows)]
    fn execute_winapi(&self) -> io::Result<()>;

    /// Returns whether the ANSI code representation of this command is supported by windows.
    ///
    /// A list of supported ANSI escape codes
    /// can be found [here](https://docs.microsoft.com/en-us/windows/console/console-virtual-terminal-sequences).
    #[cfg(windows)]
    fn is_ansi_code_supported(&self) -> bool {
        super::ansi_support::supports_ansi()
    }
}

impl<T: Command + ?Sized> Command for &T {
    fn write_ansi(&self, f: &mut impl fmt::Write) -> fmt::Result {
        (**self).write_ansi(f)
    }

    #[inline]
    #[cfg(windows)]
    fn execute_winapi(&self) -> io::Result<()> {
        T::execute_winapi(self)
    }

    #[cfg(windows)]
    #[inline]
    fn is_ansi_code_supported(&self) -> bool {
        T::is_ansi_code_supported(self)
    }
}

/// An interface for types that can queue commands for further execution.
pub trait QueueableCommand {
    /// Queues the given command for further execution.
    fn queue(&mut self, command: impl Command) -> io::Result<&mut Self>;
}

/// An interface for types that can directly execute commands.
pub trait ExecutableCommand {
    /// Executes the given command directly.
    fn execute(&mut self, command: impl Command) -> io::Result<&mut Self>;
}

impl<T: Write + ?Sized> QueueableCommand for T {
    /// Queues the given command for further execution.
    ///
    /// Queued commands will be executed in the following cases:
    ///
    /// * When `flush` is called manually on the given type implementing `io::Write`.
    /// * The terminal will `flush` automatically if the buffer is full.
    /// * Each line is flushed in case of `stdout`, because it is line buffered.
    ///
    /// # Arguments
    ///
    /// - [Command](./trait.Command.html)
    ///
    ///     The command that you want to queue for later execution.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use std::io::{self, Write};
    /// use crossterm::{QueueableCommand, style::Print};
    ///
    ///  fn main() -> io::Result<()> {
    ///     let mut stdout = io::stdout();
    ///
    ///     // `Print` will executed executed when `flush` is called.
    ///     stdout
    ///         .queue(Print("foo 1\n".to_string()))?
    ///         .queue(Print("foo 2".to_string()))?;
    ///
    ///     // some other code (no execution happening here) ...
    ///
    ///     // when calling `flush` on `stdout`, all commands will be written to the stdout and therefore executed.
    ///     stdout.flush()?;
    ///
    ///     Ok(())
    ///
    ///     // ==== Output ====
    ///     // foo 1
    ///     // foo 2
    /// }
    /// ```
    ///
    /// Have a look over at the [Command API](./index.html#command-api) for more details.
    ///
    /// # Notes
    ///
    /// * In the case of UNIX and Windows 10, ANSI codes are written to the given 'writer'.
    /// * In case of Windows versions lower than 10, a direct WinAPI call will be made.
    ///     The reason for this is that Windows versions lower than 10 do not support ANSI codes,
    ///     and can therefore not be written to the given `writer`.
    ///     Therefore, there is no difference between [execute](./trait.ExecutableCommand.html)
    ///     and [queue](./trait.QueueableCommand.html) for those old Windows versions.
    fn queue(&mut self, command: impl Command) -> io::Result<&mut Self> {
        #[cfg(windows)]
        if !command.is_ansi_code_supported() {
            // There may be queued commands in this writer, but `execute_winapi` will execute the
            // command immediately. To prevent commands being executed out of order we flush the
            // writer now.
            self.flush()?;
            command.execute_winapi()?;
            return Ok(self);
        }

        write_command_ansi(self, command)?;
        Ok(self)
    }
}

impl<T: Write + ?Sized> ExecutableCommand for T {
    /// Executes the given command directly.
    ///
    /// The given command its ANSI escape code will be written and flushed onto `Self`.
    ///
    /// # Arguments
    ///
    /// - [Command](./trait.Command.html)
    ///
    ///     The command that you want to execute directly.
    ///
    /// # Example
    ///
    /// ```rust
    /// use std::io;
    /// use crossterm::{ExecutableCommand, style::Print};
    ///
    /// fn main() -> io::Result<()> {
    ///      // will be executed directly
    ///       io::stdout()
    ///         .execute(Print("sum:\n".to_string()))?
    ///         .execute(Print(format!("1 + 1= {} ", 1 + 1)))?;
    ///
    ///       Ok(())
    ///
    ///      // ==== Output ====
    ///      // sum:
    ///      // 1 + 1 = 2
    /// }
    /// ```
    ///
    /// Have a look over at the [Command API](./index.html#command-api) for more details.
    ///
    /// # Notes
    ///
    /// * In the case of UNIX and Windows 10, ANSI codes are written to the given 'writer'.
    /// * In case of Windows versions lower than 10, a direct WinAPI call will be made.
    ///     The reason for this is that Windows versions lower than 10 do not support ANSI codes,
    ///     and can therefore not be written to the given `writer`.
    ///     Therefore, there is no difference between [execute](./trait.ExecutableCommand.html)
    ///     and [queue](./trait.QueueableCommand.html) for those old Windows versions.
    fn execute(&mut self, command: impl Command) -> io::Result<&mut Self> {
        self.queue(command)?;
        self.flush()?;
        Ok(self)
    }
}

/// An interface for types that support synchronized updates.
pub trait SynchronizedUpdate {
    /// Performs a set of actions against the given type.
    fn sync_update<T>(&mut self, operations: impl FnOnce(&mut Self) -> T) -> io::Result<T>;
}

impl<W: std::io::Write + ?Sized> SynchronizedUpdate for W {
    /// Performs a set of actions within a synchronous update.
    ///
    /// Updates will be suspended in the terminal, the function will be executed against self,
    /// updates will be resumed, and a flush will be performed.
    ///
    /// # Arguments
    ///
    /// - Function
    ///
    ///     A function that performs the operations that must execute in a synchronized update.
    ///
    /// # Examples
    ///
    /// ```rust
    /// use std::io;
    /// use crossterm::{ExecutableCommand, SynchronizedUpdate, style::Print};
    ///
    /// fn main() -> io::Result<()> {
    ///     let mut stdout = io::stdout();
    ///
    ///     stdout.sync_update(|stdout| {
    ///         stdout.execute(Print("foo 1\n".to_string()))?;
    ///         stdout.execute(Print("foo 2".to_string()))?;
    ///         // The effects of the print command will not be present in the terminal
    ///         // buffer, but not visible in the terminal.
    ///         std::io::Result::Ok(())
    ///     })?;
    ///
    ///     // The effects of the commands will be visible.
    ///
    ///     Ok(())
    ///
    ///     // ==== Output ====
    ///     // foo 1
    ///     // foo 2
    /// }
    /// ```
    ///
    /// # Notes
    ///
    /// This command is performed only using ANSI codes, and will do nothing on terminals that do not support ANSI
    /// codes, or this specific extension.
    ///
    /// When rendering the screen of the terminal, the Emulator usually iterates through each visible grid cell and
    /// renders its current state. With applications updating the screen a at higher frequency this can cause tearing.
    ///
    /// This mode attempts to mitigate that.
    ///
    /// When the synchronization mode is enabled following render calls will keep rendering the last rendered state.
    /// The terminal Emulator keeps processing incoming text and sequences. When the synchronized update mode is disabled
    /// again the renderer may fetch the latest screen buffer state again, effectively avoiding the tearing effect
    /// by unintentionally rendering in the middle a of an application screen update.
    ///
    fn sync_update<T>(&mut self, operations: impl FnOnce(&mut Self) -> T) -> io::Result<T> {
        self.queue(BeginSynchronizedUpdate)?;
        let result = operations(self);
        self.execute(EndSynchronizedUpdate)?;
        Ok(result)
    }
}
/// Writes the ANSI representation of a command to the given writer.
fn write_command_ansi<C: Command>(
    io: &mut (impl io::Write + ?Sized),
    command: C,
) -> io::Result<()> {
    struct Adapter<T> {
        inner: T,
        res: io::Result<()>,
    }

    impl<T: Write> fmt::Write for Adapter<T> {
        fn write_str(&mut self, s: &str) -> fmt::Result {
            self.inner.write_all(s.as_bytes()).map_err(|e| {
                self.res = Err(e);
                fmt::Error
            })
        }
    }

    let mut adapter = Adapter {
        inner: io,
        res: Ok(()),
    };

    command
        .write_ansi(&mut adapter)
        .map_err(|fmt::Error| match adapter.res {
            Ok(()) => panic!(
                "<{}>::write_ansi incorrectly errored",
                std::any::type_name::<C>()
            ),
            Err(e) => e,
        })
}

/// Executes the ANSI representation of a command, using the given `fmt::Write`.
pub(crate) fn execute_fmt(f: &mut impl fmt::Write, command: impl Command) -> fmt::Result {
    #[cfg(windows)]
    if !command.is_ansi_code_supported() {
        return command.execute_winapi().map_err(|_| fmt::Error);
    }

    command.write_ansi(f)
}