6 files changed, 364 insertions, 56 deletions

diff --git a/src/backends/dialog.rs b/src/backends/dialog.rs
index e681caf..668cf57 100644
--- a/src/backends/dialog.rs
+++ b/src/backends/dialog.rs
@@ -3,7 +3,7 @@
 
 use std::process;
 
-use crate::{Choice, Error, Input, Message, Password, Question, Result};
+use crate::{Choice, Error, FileSelection, Input, Message, Password, Question, Result};
 
 /// The `dialog` backend.
 ///
@@ -19,11 +19,7 @@ pub struct Dialog {
 impl Dialog {
     /// Creates a new `Dialog` instance without configuration.
     pub fn new() -> Dialog {
-        Dialog {
-            backtitle: None,
-            height: "0".to_string(),
-            width: "0".to_string(),
-        }
+        Default::default()
     }
 
     /// Sets the backtitle for the dialog boxes.
@@ -87,6 +83,16 @@ impl AsRef<Dialog> for Dialog {
     }
 }
 
+impl Default for Dialog {
+    fn default() -> Self {
+        Dialog {
+            backtitle: None,
+            height: "0".to_string(),
+            width: "0".to_string(),
+        }
+    }
+}
+
 fn require_success(status: process::ExitStatus) -> Result<()> {
     if status.success() {
         Ok(())
@@ -111,19 +117,17 @@ fn get_choice(status: process::ExitStatus) -> Result<Choice> {
 fn get_stderr(output: process::Output) -> Result<Option<String>> {
     if output.status.success() {
         String::from_utf8(output.stderr)
-            .map(|s| Some(s))
-            .map_err(|err| Error::from(err))
-    } else {
-        if let Some(code) = output.status.code() {
-            match code {
-                0 => Ok(None),
-                1 => Ok(None),
-                255 => Ok(None),
-                _ => Err(Error::from(("dialog", output.status))),
-            }
-        } else {
-            Err(Error::from(("dialog", output.status)))
+            .map(Some)
+            .map_err(Error::from)
+    } else if let Some(code) = output.status.code() {
+        match code {
+            0 => Ok(None),
+            1 => Ok(None),
+            255 => Ok(None),
+            _ => Err(Error::from(("dialog", output.status))),
         }
+    } else {
+        Err(Error::from(("dialog", output.status)))
     }
 }
 
@@ -156,4 +160,11 @@ impl super::Backend for Dialog {
         self.execute(args, vec![], &question.title)
             .and_then(|output| get_choice(output.status))
     }
+
+    fn show_file_selection(&self, file_selection: &FileSelection) -> Result<Option<String>> {
+        let dir = file_selection.path_to_string().ok_or("path not valid")?;
+        let args = vec!["--fselect", &dir];
+        self.execute(args, vec![], &file_selection.title)
+            .and_then(get_stderr)
+    }
 }
diff --git a/src/backends/kdialog.rs b/src/backends/kdialog.rs
new file mode 100644
index 0000000..21928f8
--- /dev/null
+++ b/src/backends/kdialog.rs
@@ -0,0 +1,152 @@
+// Copyright (C) 2019 Robin Krahl <robin.krahl@ireas.org>
+// Copyright (C) 2019 Stephan Sokolow <http://www.ssokolow.com/ContactMe>
+// SPDX-License-Identifier: MIT
+
+use std::process;
+
+use crate::{
+    Choice, Error, FileSelection, FileSelectionMode, Input, Message, Password, Question, Result,
+};
+
+/// Subprocess exit codes
+///
+/// Note: `kdialog` doesn't have a fixed correspondence between button labels and status codes.
+/// The following mappings occur:
+///
+/// - Yes/No = `0`/`1`
+/// - Yes/No/Cancel = `0`/`1`/`2`
+/// - OK/Cancel = `0`/`1`
+const OK: i32 = 0;
+const CANCEL: i32 = 1;
+
+/// The `kdialog` backend.
+///
+/// This backend uses the external `kdialog` program to display KDE dialog boxes.
+#[derive(Debug, Default)]
+pub struct KDialog {
+    icon: Option<String>,
+    // TODO: --dontagain
+}
+
+impl KDialog {
+    /// Creates a new `KDialog` instance without configuration.
+    pub fn new() -> KDialog {
+        Default::default()
+    }
+
+    /// Sets the icon in the dialog box's titlebar and taskbar button.
+    ///
+    /// The icon can be either a name from the user's configured icon theme, such as `error` or
+    /// `info` or the path to an image to use.
+    ///
+    /// The default image depends on the dialog type.
+    pub fn set_icon(&mut self, icon: impl Into<String>) {
+        self.icon = Some(icon.into());
+    }
+
+    pub(crate) fn is_available() -> bool {
+        super::is_available("kdialog")
+    }
+
+    fn execute(&self, args: Vec<&str>, title: &Option<String>) -> Result<process::Output> {
+        let mut command = process::Command::new("kdialog");
+
+        if let Some(ref icon) = self.icon {
+            command.arg("--icon");
+            command.arg(icon);
+        }
+        if let Some(ref title) = title {
+            command.arg("--title");
+            command.arg(title);
+        }
+
+        command.args(args);
+        command.output().map_err(Error::IoError)
+    }
+}
+
+impl AsRef<KDialog> for KDialog {
+    fn as_ref(&self) -> &Self {
+        self
+    }
+}
+
+fn require_success(status: process::ExitStatus) -> Result<()> {
+    if status.success() {
+        Ok(())
+    } else if let Some(code) = status.code() {
+        match code {
+            CANCEL => Ok(()),
+            _ => Err(Error::from(("kdialog", status))),
+        }
+    } else {
+        Err(Error::from(("kdialog", status)))
+    }
+}
+
+fn get_choice(status: process::ExitStatus) -> Result<Choice> {
+    if let Some(code) = status.code() {
+        match code {
+            OK => Ok(Choice::Yes),
+            CANCEL => Ok(Choice::No),
+            _ => Err(Error::from(("kdialog", status))),
+        }
+    } else {
+        Err(Error::from(("kdialog", status)))
+    }
+}
+
+fn get_stdout(output: process::Output) -> Result<Option<String>> {
+    if output.status.success() {
+        String::from_utf8(output.stdout)
+            .map(|s| Some(s.trim_end_matches('\n').to_string()))
+            .map_err(Error::from)
+    } else if let Some(code) = output.status.code() {
+        match code {
+            OK => Ok(None),
+            CANCEL => Ok(None),
+            _ => Err(Error::from(("kdialog", output.status))),
+        }
+    } else {
+        Err(Error::from(("kdialog", output.status)))
+    }
+}
+
+impl super::Backend for KDialog {
+    fn show_input(&self, input: &Input) -> Result<Option<String>> {
+        let mut args = vec!["--inputbox", &input.text];
+        if let Some(ref default) = input.default {
+            args.push(default);
+        }
+        self.execute(args, &input.title).and_then(get_stdout)
+    }
+
+    fn show_message(&self, message: &Message) -> Result<()> {
+        let args = vec!["--msgbox", &message.text];
+        self.execute(args, &message.title)
+            .and_then(|output| require_success(output.status))
+            .map(|_| ())
+    }
+
+    fn show_password(&self, password: &Password) -> Result<Option<String>> {
+        let args = vec!["--password", &password.text];
+        self.execute(args, &password.title).and_then(get_stdout)
+    }
+
+    fn show_question(&self, question: &Question) -> Result<Choice> {
+        let args = vec!["--yesno", &question.text];
+        self.execute(args, &question.title)
+            .and_then(|output| get_choice(output.status))
+    }
+
+    fn show_file_selection(&self, file_selection: &FileSelection) -> Result<Option<String>> {
+        let dir = file_selection.path_to_string().ok_or("path not valid")?;
+        let option = match file_selection.mode {
+            FileSelectionMode::Open => "--getopenfilename",
+            FileSelectionMode::Save => "--getsavefilename",
+        };
+        let args = vec![option, &dir];
+        self.execute(args, &file_selection.title)
+            .and_then(get_stdout)
+    }
+}
diff --git a/src/backends/mod.rs b/src/backends/mod.rs
index 5ae3cef..09013b1 100644
--- a/src/backends/mod.rs
+++ b/src/backends/mod.rs
@@ -2,10 +2,12 @@
 // SPDX-License-Identifier: MIT
 
 mod dialog;
+mod kdialog;
 mod stdio;
 mod zenity;
 
 pub use crate::backends::dialog::Dialog;
+pub use crate::backends::kdialog::KDialog;
 pub use crate::backends::stdio::Stdio;
 pub use crate::backends::zenity::Zenity;
 
@@ -21,7 +23,7 @@ use crate::Result;
 /// backend and create an instance manually.  To use a backend, pass it to the [`show_with`][]
 /// method of a dialog box.
 ///
-/// [`default_backend`]: ../function.default_backend.html
+/// [`default_backend`]: ../fn.default_backend.html
 /// [`show_with`]: ../trait.DialogBox.html#method.show_with
 pub trait Backend {
     /// Shows the given input dialog and returns the input.
@@ -35,11 +37,14 @@ pub trait Backend {
 
     /// Shows the given question dialog and returns the choice.
     fn show_question(&self, question: &super::Question) -> Result<super::Choice>;
+
+    /// Shows the given file selection dialog and returns the file name.
+    fn show_file_selection(&self, file_selection: &super::FileSelection) -> Result<Option<String>>;
 }
 
 pub(crate) fn is_available(name: &str) -> bool {
     if let Ok(path) = env::var("PATH") {
-        for part in path.split(":") {
+        for part in path.split(':') {
             if path::Path::new(part).join(name).exists() {
                 return true;
             }
@@ -51,6 +56,7 @@ pub(crate) fn is_available(name: &str) -> bool {
 pub(crate) fn from_str(s: &str) -> Option<Box<dyn Backend>> {
     match s.to_lowercase().as_ref() {
         "dialog" => Some(Box::new(Dialog::new())),
+        "kdialog" => Some(Box::new(KDialog::new())),
         "stdio" => Some(Box::new(Stdio::new())),
         "zenity" => Some(Box::new(Zenity::new())),
         _ => None,
diff --git a/src/backends/stdio.rs b/src/backends/stdio.rs
index 6838ef1..627714a 100644
--- a/src/backends/stdio.rs
+++ b/src/backends/stdio.rs
@@ -3,19 +3,19 @@
 
 use std::io::{self, Write};
 
-use crate::{Choice, Input, Message, Password, Question, Result};
+use crate::{Choice, FileSelection, Input, Message, Password, Question, Result};
 
 /// The fallback backend using standard input and output.
 ///
 /// This backend is intended as a fallback backend to use if no other backend is available.  The
 /// dialogs are printed to the standard output and user input is read from the standard input.
-#[derive(Debug)]
+#[derive(Debug, Default)]
 pub struct Stdio {}
 
 impl Stdio {
     /// Creates a new `Stdio` instance.
     pub fn new() -> Stdio {
-        Stdio {}
+        Default::default()
     }
 }
 
@@ -35,7 +35,7 @@ fn print_title(title: &Option<String>) {
 fn read_input() -> Result<String> {
     let mut input = String::new();
     io::stdin().read_line(&mut input)?;
-    Ok(input.trim_end_matches("\n").to_string())
+    Ok(input.trim_end_matches('\n').to_string())
 }
 
 fn parse_choice(input: &str) -> Choice {
@@ -86,4 +86,17 @@ impl super::Backend for Stdio {
         io::stdout().flush()?;
         Ok(parse_choice(&read_input()?))
     }
+
+    fn show_file_selection(&self, file_selection: &FileSelection) -> Result<Option<String>> {
+        let dir = file_selection.path_to_string().ok_or("path not valid")?;
+        print_title(&file_selection.title);
+        print!("{} [{}]: ", file_selection.text, dir);
+        io::stdout().flush()?;
+        let result = read_input()?;
+        if result.starts_with('/') {
+            Ok(Some(result))
+        } else {
+            Ok(Some(dir + &result))
+        }
+    }
 }
diff --git a/src/backends/zenity.rs b/src/backends/zenity.rs
index 85206b3..ac0f98f 100644
--- a/src/backends/zenity.rs
+++ b/src/backends/zenity.rs
@@ -3,12 +3,14 @@
 
 use std::process;
 
-use crate::{Choice, Error, Input, Message, Password, Question, Result};
+use crate::{
+    Choice, Error, FileSelection, FileSelectionMode, Input, Message, Password, Question, Result,
+};
 
 /// The `zenity` backend.
 ///
 /// This backend uses the external `zenity` program to display GTK+ dialog boxes.
-#[derive(Debug)]
+#[derive(Debug, Default)]
 pub struct Zenity {
     icon: Option<String>,
     width: Option<String>,
@@ -19,17 +21,12 @@ pub struct Zenity {
 impl Zenity {
     /// Creates a new `Zenity` instance without configuration.
     pub fn new() -> Zenity {
-        Zenity {
-            icon: None,
-            width: None,
-            height: None,
-            timeout: None,
-        }
+        Default::default()
     }
 
     /// Sets the icon of the dialog box.
     ///
-    /// The icon can either be one of `error`, `info`, `question` or `warning, or the path to an
+    /// The icon can either be one of `error`, `info`, `question` or `warning`, or the path to an
     /// image to use.  The default image depends on the dialog type.
     pub fn set_icon(&mut self, icon: impl Into<String>) {
         self.icon = Some(icon.into());
@@ -101,15 +98,13 @@ impl AsRef<Zenity> for Zenity {
 fn require_success(status: process::ExitStatus) -> Result<()> {
     if status.success() {
         Ok(())
-    } else {
-        if let Some(code) = status.code() {
-            match code {
-                5 => Ok(()),
-                _ => Err(Error::from(("zenity", status))),
-            }
-        } else {
-            Err(Error::from(("zenity", status)))
+    } else if let Some(code) = status.code() {
+        match code {
+            5 => Ok(()),
+            _ => Err(Error::from(("zenity", status))),
         }
+    } else {
+        Err(Error::from(("zenity", status)))
     }
 }
 
@@ -130,18 +125,16 @@ fn get_stdout(output: process::Output) -> Result<Option<String>> {
     if output.status.success() {
         String::from_utf8(output.stdout)
             .map(|s| Some(s.trim_end_matches('\n').to_string()))
-            .map_err(|err| Error::from(err))
-    } else {
-        if let Some(code) = output.status.code() {
-            match code {
-                0 => Ok(None),
-                1 => Ok(None),
-                5 => Ok(None),
-                _ => Err(Error::from(("zenity", output.status))),
-            }
-        } else {
-            Err(Error::from(("zenity", output.status)))
+            .map_err(Error::from)
+    } else if let Some(code) = output.status.code() {
+        match code {
+            0 => Ok(None),
+            1 => Ok(None),
+            5 => Ok(None),
+            _ => Err(Error::from(("zenity", output.status))),
         }
+    } else {
+        Err(Error::from(("zenity", output.status)))
     }
 }
 
@@ -172,4 +165,14 @@ impl super::Backend for Zenity {
         self.execute(args, &question.title)
             .and_then(|output| get_choice(output.status))
     }
+
+    fn show_file_selection(&self, file_selection: &FileSelection) -> Result<Option<String>> {
+        let dir = file_selection.path_to_string().ok_or("path not valid")?;
+        let mut args = vec!["--file-selection", "--filename", &dir];
+        if file_selection.mode == FileSelectionMode::Save {
+            args.push("--save");
+        }
+        self.execute(args, &file_selection.title)
+            .and_then(get_stdout)
+    }
 }
diff --git a/src/lib.rs b/src/lib.rs
index f4ac763..aa19105 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -7,6 +7,7 @@
 //!
 //! The `dialog` crate can be used to display different types of dialog boxes.  The supported types
 //! are:
+//! - [`FileSelection`][]: a file chooser dialog box
 //! - [`Input`][]: a text input dialog
 //! - [`Message`][]: a simple message box
 //! - [`Password`][]: a password input dialog
@@ -15,6 +16,8 @@
 //! These dialog boxes can be displayed using various backends:
 //! - [`Dialog`][]: uses `dialog` to display ncurses-based dialog boxes (requires the external
 //!   `dialog` tool)
+//! - [`KDialog`][]: uses `kdialog` to display Qt-based dialog boxes (requires the external
+//!   `kdialog` tool)
 //! - [`Stdio`][]: prints messages to the standard output and reads user input form standard input
 //!   (intended as a fallback backend)
 //! - [`Zenity`][]: uses `zenity` to display GTK-based dialog boxes (requires the external `zenity`
@@ -68,10 +71,12 @@
 //! ```
 //!
 //! [`Dialog`]: backends/struct.Dialog.html
+//! [`FileSelection`]: struct.FileSelection.html
 //! [`Input`]: struct.Input.html
 //! [`Message`]: struct.Message.html
 //! [`Password`]: struct.Password.html
 //! [`Question`]: struct.Question.html
+//! [`KDialog`]: backends/struct.KDialog.html
 //! [`Stdio`]: backends/struct.Stdio.html
 //! [`Zenity`]: backends/struct.Zenity.html
 //! [`default_backend`]: fn.default_backend.html
@@ -89,7 +94,11 @@ mod error;
 /// [`Backend`]: trait.Backend.html
 pub mod backends;
 
-use std::env;
+use dirs;
+use std::{
+    env,
+    path::{Path, PathBuf},
+};
 
 pub use crate::error::{Error, Result};
 
@@ -339,19 +348,121 @@ impl DialogBox for Question {
     }
 }
 
+/// The type of a file selection dialog.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum FileSelectionMode {
+    /// An Open File dialog, meaning that the user can only select an existing file.
+    Open,
+    /// A Save File dialog, meaning that the user is allowed to select a non-existing file.
+    Save,
+}
+
+/// A file chooser dialog box.
+///
+/// This dialog box opens a file choser with an optional title in the specified path.  If the path
+/// is not specified, it defaults to the user’s home directory.
+///
+/// The backends might support multiple operation modes, for example open or save dialogs.  You can
+/// select a mode using the [`FileSelectionMode`][] enum, though the backend might ignore the mode
+/// and just display a simple file dialog.  Per default, the mode is set to `Open`.
+///
+/// # Example
+///
+/// ```no_run
+/// use dialog::DialogBox;
+///
+/// let choice = dialog::FileSelection::new("Please select a file")
+///     .title("File Selection")
+///     .path("/home/user/Downloads")
+///     .show()
+///     .expect("Could not display dialog box");
+/// println!("The user chose: {:?}", choice);
+/// ```
+///
+/// [`FileSelectionMode`]: enum.FileSelectionMode.html
+pub struct FileSelection {
+    text: String,
+    title: Option<String>,
+    path: Option<PathBuf>,
+    mode: FileSelectionMode,
+}
+
+impl FileSelection {
+    /// Creates a new file chooser with the given path.
+    pub fn new(text: impl Into<String>) -> FileSelection {
+        FileSelection {
+            text: text.into(),
+            title: None,
+            path: dirs::home_dir(),
+            mode: FileSelectionMode::Open,
+        }
+    }
+
+    /// Sets the title of this file chooser dialog box.
+    ///
+    /// This method returns a reference to `self` to enable chaining.
+    pub fn title(&mut self, title: impl Into<String>) -> &mut FileSelection {
+        self.title = Some(title.into());
+        self
+    }
+
+    /// Sets the path of this file chooser dialog box.
+    ///
+    /// This method returns a reference to `self` to enable chaining.
+    pub fn path(&mut self, path: impl AsRef<Path>) -> &mut FileSelection {
+        self.path = Some(path.as_ref().to_path_buf());
+        self
+    }
+
+    /// Gets the path of this file chooser dialog box.
+    ///
+    /// This method returns the validated directory as a `String`.
+    pub fn path_to_string(&self) -> Option<String> {
+        match self.path {
+            Some(ref path) if path.is_dir() => {
+                // The backends expect a trailing / after the directory
+                path.to_str().map(|s| s.to_string() + "/")
+            }
+            _ => None,
+        }
+    }
+
+    /// Sets the operation mode of the file chooser.
+    ///
+    /// This method returns a reference to `self` to enable chaining.
+    pub fn mode(&mut self, mode: FileSelectionMode) -> &mut FileSelection {
+        self.mode = mode;
+        self
+    }
+}
+
+impl DialogBox for FileSelection {
+    type Output = Option<String>;
+
+    fn show_with<B>(&self, backend: impl AsRef<B>) -> Result<Self::Output>
+    where
+        B: backends::Backend + ?Sized,
+    {
+        backend.as_ref().show_file_selection(self)
+    }
+}
+
 /// Creates a new instance of the default backend.
 ///
 /// The following steps are performed to determine the default backend:
 /// - If the `DIALOG` environment variable is set to a valid backend name, this backend is used.
 ///   A valid backend name is the name of a struct in the `backends` module implementing the
 ///   `Backend` trait in any case.
-/// - If the `DISPLAY` environment variable is set, the first available backend from this list is
-///   used:
-///   - [`Zenity`][]
+/// - If the `DISPLAY` environment variable is set, the following resolution algorithm is used:
+///   - If the `XDG_CURRENT_DESKTOP` environment variable is set to `KDE`, [`KDialog`][] is used.
+///   - Otherwise, the first available backend from this list is used:
+///     - [`Zenity`][]
+///     - [`KDialog`][]
 /// - If the [`Dialog`][] backend is available, it is used.
 /// - Otherwise, a [`Stdio`][] instance is returned.
 ///
 /// [`Dialog`]: backends/struct.Dialog.html
+/// [`KDialog`]: backends/struct.KDialog.html
 /// [`Stdio`]: backends/struct.Stdio.html
 /// [`Zenity`]: backends/struct.Zenity.html
 pub fn default_backend() -> Box<dyn backends::Backend> {
@@ -363,9 +474,21 @@ pub fn default_backend() -> Box<dyn backends::Backend> {
 
     if let Ok(display) = env::var("DISPLAY") {
         if !display.is_empty() {
+            // Prefer KDialog if the user is logged into a KDE session
+            let kdialog_available = backends::KDialog::is_available();
+            if let Ok(desktop) = env::var("XDG_CURRENT_DESKTOP") {
+                if kdialog_available && desktop == "KDE" {
+                    return Box::new(backends::KDialog::new());
+                }
+            }
+
             if backends::Zenity::is_available() {
                 return Box::new(backends::Zenity::new());
             }
+
+            if kdialog_available {
+                return Box::new(backends::KDialog::new());
+            }
         }
     }