servo/components/gfx/text/util.rs

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

use text::glyph::CharIndex;

#[derive(PartialEq, Eq, Copy)]
pub enum CompressionMode {
    CompressNone,
    CompressWhitespace,
    CompressWhitespaceNewline,
    DiscardNewline
}

// ported from Gecko's nsTextFrameUtils::TransformText.
//
// High level TODOs:
//
// * Issue #113: consider incoming text state (arabic, etc)
//               and propagate outgoing text state (dual of above)
//
// * Issue #114: record skipped and kept chars for mapping original to new text
//
// * Untracked: various edge cases for bidi, CJK, etc.
pub fn transform_text(text: &str,
                      mode: CompressionMode,
                      incoming_whitespace: bool,
                      output_text: &mut String,
                      new_line_pos: &mut Vec<CharIndex>)
                      -> bool {
    let out_whitespace = match mode {
        CompressionMode::CompressNone | CompressionMode::DiscardNewline => {
            let mut new_line_index = CharIndex(0);
            for ch in text.chars() {
                if is_discardable_char(ch, mode) {
                    // TODO: record skipped char
                } else {
                    // TODO: record kept char
                    if ch == '\t' {
                        // TODO: set "has tab" flag
                    } else if ch == '\n' {
                        // Save new-line's position for line-break
                        // This value is relative(not absolute)
                        new_line_pos.push(new_line_index);
                        new_line_index = CharIndex(0);
                    }

                    if ch != '\n' {
                        new_line_index = new_line_index + CharIndex(1);
                    }
                    output_text.push(ch);
                }
            }
            text.len() > 0 && is_in_whitespace(text.char_at_reverse(0), mode)
        },

        CompressionMode::CompressWhitespace | CompressionMode::CompressWhitespaceNewline => {
            let mut in_whitespace: bool = incoming_whitespace;
            for ch in text.chars() {
                // TODO: discard newlines between CJK chars
                let mut next_in_whitespace: bool = is_in_whitespace(ch, mode);

                if !next_in_whitespace {
                    if is_always_discardable_char(ch) {
                        // revert whitespace setting, since this char was discarded
                        next_in_whitespace = in_whitespace;
                        // TODO: record skipped char
                    } else {
                        // TODO: record kept char
                        output_text.push(ch);
                    }
                } else { /* next_in_whitespace; possibly add a space char */
                    if in_whitespace {
                        // TODO: record skipped char
                    } else {
                        // TODO: record kept char
                        output_text.push(' ');
                    }
                }
                // save whitespace context for next char
                in_whitespace = next_in_whitespace;
            } /* /for str::each_char */
            in_whitespace
        }
    };

    return out_whitespace;

    fn is_in_whitespace(ch: char, mode: CompressionMode) -> bool {
        match (ch, mode) {
            (' ', _)  => true,
            ('\t', _) => true,
            ('\n', CompressionMode::CompressWhitespaceNewline) => true,
            (_, _)    => false
        }
    }

    fn is_discardable_char(ch: char, mode: CompressionMode) -> bool {
        if is_always_discardable_char(ch) {
            return true;
        }
        match mode {
            CompressionMode::DiscardNewline | CompressionMode::CompressWhitespaceNewline => ch == '\n',
            _ => false
        }
    }

    fn is_always_discardable_char(_ch: char) -> bool {
        // TODO: check for bidi control chars, soft hyphens.
        false
    }
}

pub fn float_to_fixed(before: int, f: f64) -> i32 {
    ((1i32 << before as uint) as f64 * f) as i32
}

pub fn fixed_to_float(before: int, f: i32) -> f64 {
    f as f64 * 1.0f64 / ((1i32 << before as uint) as f64)
}

pub fn fixed_to_rounded_int(before: int, f: i32) -> int {
    let half = 1i32 << (before-1) as uint;
    if f > 0i32 {
        ((half + f) >> before as uint) as int
    } else {
       -((half - f) >> before as uint) as int
    }
}

#[test]
fn test_transform_compress_none() {
    let test_strs = [
        "  foo bar",
        "foo bar  ",
        "foo\n bar",
        "foo \nbar",
        "  foo  bar  \nbaz",
        "foo bar baz",
        "foobarbaz\n\n",
    ];

    let mode = CompressionMode::CompressNone;
    for &test in test_strs.iter() {
        let mut new_line_pos = vec![];
        let mut trimmed_str = String::new();
        transform_text(test, mode, true, &mut trimmed_str, &mut new_line_pos);
        assert_eq!(trimmed_str.as_slice(), test)
    }
}

#[test]
fn test_transform_discard_newline() {
    let test_strs = [
        ("  foo bar",
         "  foo bar"),

        ("foo bar  ",
         "foo bar  "),

        ("foo\n bar",
         "foo bar"),

        ("foo \nbar",
         "foo bar"),

        ("  foo  bar  \nbaz",
         "  foo  bar  baz"),

        ("foo bar baz",
         "foo bar baz"),

        ("foobarbaz\n\n",
         "foobarbaz"),
    ];

    let mode = CompressionMode::DiscardNewline;
    for &(test, oracle) in test_strs.iter() {
        let mut new_line_pos = vec![];
        let mut trimmed_str = String::new();
        transform_text(test, mode, true, &mut trimmed_str, &mut new_line_pos);
        assert_eq!(trimmed_str.as_slice(), oracle)
    }
}

#[test]
fn test_transform_compress_whitespace() {
    let test_strs = [
        ("  foo bar",
         "foo bar"),

        ("foo bar  ",
         "foo bar "),

        ("foo\n bar",
         "foo\n bar"),

        ("foo \nbar",
         "foo \nbar"),

        ("  foo  bar  \nbaz",
         "foo bar \nbaz"),

        ("foo bar baz",
         "foo bar baz"),

        ("foobarbaz\n\n",
         "foobarbaz\n\n"),
    ];

    let mode = CompressionMode::CompressWhitespace;
    for &(test, oracle) in test_strs.iter() {
        let mut new_line_pos = vec![];
        let mut trimmed_str = String::new();
        transform_text(test, mode, true, &mut trimmed_str, &mut new_line_pos);
        assert_eq!(&*trimmed_str, oracle)
    }
}

#[test]
fn test_transform_compress_whitespace_newline() {
    let test_strs = vec![
        ("  foo bar",
         "foo bar"),

        ("foo bar  ",
         "foo bar "),

        ("foo\n bar",
         "foo bar"),

        ("foo \nbar",
         "foo bar"),

        ("  foo  bar  \nbaz",
         "foo bar baz"),

        ("foo bar baz",
         "foo bar baz"),

        ("foobarbaz\n\n",
         "foobarbaz "),
    ];

    let mode = CompressionMode::CompressWhitespaceNewline;
    for &(test, oracle) in test_strs.iter() {
        let mut new_line_pos = vec![];
        let mut trimmed_str = String::new();
        transform_text(test, mode, true, &mut trimmed_str, &mut new_line_pos);
        assert_eq!(&*trimmed_str, oracle)
    }
}

#[test]
fn test_transform_compress_whitespace_newline_no_incoming() {
    let test_strs = [
        ("  foo bar",
         " foo bar"),

        ("\nfoo bar",
         " foo bar"),

        ("foo bar  ",
         "foo bar "),

        ("foo\n bar",
         "foo bar"),

        ("foo \nbar",
         "foo bar"),

        ("  foo  bar  \nbaz",
         " foo bar baz"),

        ("foo bar baz",
         "foo bar baz"),

        ("foobarbaz\n\n",
         "foobarbaz "),
    ];

    let mode = CompressionMode::CompressWhitespaceNewline;
    for &(test, oracle) in test_strs.iter() {
        let mut new_line_pos = vec![];
        let mut trimmed_str = String::new();
        transform_text(test, mode, false, &mut trimmed_str, &mut new_line_pos);
        assert_eq!(trimmed_str.as_slice(), oracle)
    }
}