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Specification 6.0 · Not released · Tested product 5.21.3

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    Library · std.typeset

    BreakPolicy.protectFittingLatin

    Protects fitting alphabetic runs from fallback breaks.

    BreakPolicy.protectFittingLatin: bool
    Receiver
    BreakPolicy
    Minimum arity
    0
    Maximum arity
    0

    Declaration and parameters

    Link

    Availability

    Included by default: Pending

    Import std.typeset in language mode 5.21.

    The current compiler selects std/typeset.tpz for this language mode. Availability in other released editions and inclusion in each installed distribution are Pending.

    Source evidence

    Receiver

    BreakPolicy

    Parameter constraints

    BreakPolicy supplies every classification choice explicitly. rules selects the character boundary policy. mode selects word protection. The two choices are independent and neither consults the host locale.

    forbidBefore and forbidAfter contain Unicode scalar values. Each integer must be between zero and 1114111 and outside 55296 through 57343. Invalid values return TypesetError.InvalidPolicy. Ordering and duplicate entries do not change membership.

    At an ordinary interior boundary, forbidAfter checks the final scalar on the left and forbidBefore checks the first scalar on the right. These custom bans filter admitted candidates and do not create candidates. They do not replace non-tailorable Unicode decisions.

    The shaping boundary mask can remove an ordinary candidate. A mask conflict with a mandatory or non-tailorable required Unicode opportunity returns TypesetError.InvalidInput. A generated hyphen or character mode never bypasses a false mask entry.

    generatedHyphenEnds contains exclusive interior cluster indices. Both neighboring clusters must consist of Unicode Alphabetic scalars or the apostrophes U+0027 and U+2019. An out of range index or nonword neighbor returns TypesetError.InvalidInput. Duplicate indices have no additional effect.

    A generated index changes a missing or HardFallback candidate to LatinSoftHyphen when Unicode permits tailoring there. It does not replace another category or a non-tailorable prohibition. The selected locale, custom bans, shaping mask, and short-word policy still apply. The function does not insert text or measure a hyphen glyph.

    narrowestWordTarget and bodyWordTarget are independent nonnegative point lengths. A negative target returns TypesetError.InvalidPolicy. Zero is accepted and equality with a target counts as fitting.

    For a HardFallback inside a contiguous run of Alphabetic or apostrophe clusters, protectFittingLatin suppresses the break when the measured run width is at most narrowestWordTarget. Word mode also suppresses that break when the run width is at most bodyWordTarget. Character mode removes this second word-fit test while retaining all other constraints.

    Word mode can add emergency boundaries inside an oversized word whose width exceeds bodyWordTarget. Unicode modes retain non-tailorable prohibitions and locale bans. Unicode16Ko also preserves a fitting whitespace-delimited Hangul run at bodyWordTarget.

    With preserveShortWords, an interior boundary between nonwhitespace clusters is suppressed when their whitespace-delimited run has at most three Alphabetic or Number scalars. It is also suppressed when that run fits bodyWordTarget. These tests include generated hyphens. Mandatory and non-tailorable required Unicode opportunities retain their priority.

    Result

    The declared result type is bool.

    Effects

    Failures

    Result and effects

    Link

    Select this field from a value of its named type without call parentheses.

    For a HardFallback within a run of Alphabetic or apostrophe clusters, true suppresses the candidate when the run fits narrowestWordTarget. The predicate uses Unicode Alphabetic data despite the historical field name.

    Resolved contracts

    Link

    Related entries

    Link

    std.typeset

    Apply word policy without crossing protected cluster boundaries

    Link
    Ruletopaz.stdlib.contract.typeset-break-policy.rule

    Apply word policy without crossing protected cluster boundaries

    BreakPolicy supplies every classification choice explicitly. rules selects the character boundary policy. mode selects word protection. The two choices are independent and neither consults the host locale.

    forbidBefore and forbidAfter contain Unicode scalar values. Each integer must be between zero and 1114111 and outside 55296 through 57343. Invalid values return TypesetError.InvalidPolicy. Ordering and duplicate entries do not change membership.

    At an ordinary interior boundary, forbidAfter checks the final scalar on the left and forbidBefore checks the first scalar on the right. These custom bans filter admitted candidates and do not create candidates. They do not replace non-tailorable Unicode decisions.

    The shaping boundary mask can remove an ordinary candidate. A mask conflict with a mandatory or non-tailorable required Unicode opportunity returns TypesetError.InvalidInput. A generated hyphen or character mode never bypasses a false mask entry.

    generatedHyphenEnds contains exclusive interior cluster indices. Both neighboring clusters must consist of Unicode Alphabetic scalars or the apostrophes U+0027 and U+2019. An out of range index or nonword neighbor returns TypesetError.InvalidInput. Duplicate indices have no additional effect.

    A generated index changes a missing or HardFallback candidate to LatinSoftHyphen when Unicode permits tailoring there. It does not replace another category or a non-tailorable prohibition. The selected locale, custom bans, shaping mask, and short-word policy still apply. The function does not insert text or measure a hyphen glyph.

    narrowestWordTarget and bodyWordTarget are independent nonnegative point lengths. A negative target returns TypesetError.InvalidPolicy. Zero is accepted and equality with a target counts as fitting.

    For a HardFallback inside a contiguous run of Alphabetic or apostrophe clusters, protectFittingLatin suppresses the break when the measured run width is at most narrowestWordTarget. Word mode also suppresses that break when the run width is at most bodyWordTarget. Character mode removes this second word-fit test while retaining all other constraints.

    Word mode can add emergency boundaries inside an oversized word whose width exceeds bodyWordTarget. Unicode modes retain non-tailorable prohibitions and locale bans. Unicode16Ko also preserves a fitting whitespace-delimited Hangul run at bodyWordTarget.

    With preserveShortWords, an interior boundary between nonwhitespace clusters is suppressed when their whitespace-delimited run has at most three Alphabetic or Number scalars. It is also suppressed when that run fits bodyWordTarget. These tests include generated hyphens. Mandatory and non-tailorable required Unicode opportunities retain their priority.

    Why

    Word fitting and character breaking answer different layout needs. Explicit thresholds let callers retain fitting words while admitting emergency breaks in oversized text. Applying shaping and punctuation constraints after candidate generation prevents a convenience option from splitting protected text.

    Source evidence

    Keep generated hyphens behind the shaping mask

    Link
    main.tpzKeep generated hyphens behind the shaping maskOpen in Playground
    1. import std.typeset as ts
    2. import std.io
    3. import std.test
    4. let clusters = [ts.BreakCluster { text: "a", advance: 1pt, trackingAfter: 0pt }, ts.BreakCluster { text: "b", advance: 1pt, trackingAfter: 0pt }]
    5. let selected = ts.BreakPolicy {
    6. mode: ts.BreakMode.Character(),
    7. rules: ts.KinsokuRules.AtlasDefault(),
    8. forbidBefore: [],
    9. forbidAfter: [],
    10. boundaryAllowed: [false, true],
    11. generatedHyphenEnds: [1, 1],
    12. protectFittingLatin: false,
    13. preserveShortWords: false,
    14. narrowestWordTarget: 0pt,
    15. bodyWordTarget: 0pt
    16. }
    17. let breaks = test.assertOk(ts.classifyBreaks(clusters, selected))
    18. for boundary in (breaks) {
    19. io.writeLine("{boundary.unitEnd}")
    20. }
    Expected outputexit 0
    2
    
    $ topaz run main.tpz · target product 5.21.3
    Expected result

    Expected result

    Execution completes. Exit code 0.

    Expected stdout
    1. 2
    Source evidence

    Keep a word together at the fitting threshold

    Link
    main.tpzKeep a word together at the fitting thresholdOpen in Playground
    1. import std.typeset as ts
    2. import std.io
    3. import std.test
    4. let clusters = [ts.BreakCluster { text: "a", advance: 1pt, trackingAfter: 0pt }, ts.BreakCluster { text: "b", advance: 1pt, trackingAfter: 0pt }, ts.BreakCluster { text: "c", advance: 1pt, trackingAfter: 0pt }, ts.BreakCluster { text: "d", advance: 1pt, trackingAfter: 0pt }]
    5. let fitting = ts.BreakPolicy {
    6. mode: ts.BreakMode.Word(),
    7. rules: ts.KinsokuRules.AtlasDefault(),
    8. forbidBefore: [],
    9. forbidAfter: [],
    10. boundaryAllowed: [true, true, true, true],
    11. generatedHyphenEnds: [],
    12. protectFittingLatin: false,
    13. preserveShortWords: false,
    14. narrowestWordTarget: 0pt,
    15. bodyWordTarget: 4pt
    16. }
    17. let oversized = ts.BreakPolicy {
    18. mode: ts.BreakMode.Word(),
    19. rules: ts.KinsokuRules.AtlasDefault(),
    20. forbidBefore: [],
    21. forbidAfter: [],
    22. boundaryAllowed: [true, true, true, true],
    23. generatedHyphenEnds: [],
    24. protectFittingLatin: false,
    25. preserveShortWords: false,
    26. narrowestWordTarget: 0pt,
    27. bodyWordTarget: 3pt
    28. }
    29. let guarded = ts.BreakPolicy {
    30. mode: ts.BreakMode.Character(),
    31. rules: ts.KinsokuRules.AtlasDefault(),
    32. forbidBefore: [],
    33. forbidAfter: [],
    34. boundaryAllowed: [true, true, true, true],
    35. generatedHyphenEnds: [],
    36. protectFittingLatin: true,
    37. preserveShortWords: false,
    38. narrowestWordTarget: 4pt,
    39. bodyWordTarget: 0pt
    40. }
    41. let a = test.assertOk(ts.classifyBreaks(clusters, fitting))
    42. let b = test.assertOk(ts.classifyBreaks(clusters, oversized))
    43. let c = test.assertOk(ts.classifyBreaks(clusters, guarded))
    44. io.writeLine("{a.length} {b.length} {c.length}")
    Expected outputexit 0
    1 4 1
    
    $ topaz run main.tpz · target product 5.21.3
    Expected result

    Expected result

    Execution completes. Exit code 0.

    Expected stdout
    1. 1 4 1
    Source evidence

    Classify one generated hyphen boundary despite duplicate input indices

    Link
    main.tpzClassify one generated hyphen boundary despite duplicate input indicesOpen in Playground
    1. import std.typeset as ts
    2. import std.io
    3. import std.test
    4. let clusters = [ts.BreakCluster { text: "a", advance: 1pt, trackingAfter: 0pt }, ts.BreakCluster { text: "b", advance: 1pt, trackingAfter: 0pt }, ts.BreakCluster { text: "c", advance: 1pt, trackingAfter: 0pt }, ts.BreakCluster { text: "d", advance: 1pt, trackingAfter: 0pt }]
    5. let selected = ts.BreakPolicy {
    6. mode: ts.BreakMode.Word(),
    7. rules: ts.KinsokuRules.AtlasDefault(),
    8. forbidBefore: [],
    9. forbidAfter: [],
    10. boundaryAllowed: [true, true, true, true],
    11. generatedHyphenEnds: [2, 2],
    12. protectFittingLatin: true,
    13. preserveShortWords: false,
    14. narrowestWordTarget: 4pt,
    15. bodyWordTarget: 4pt
    16. }
    17. let breaks = test.assertOk(ts.classifyBreaks(clusters, selected))
    18. for boundary in (breaks) {
    19. let category = match (boundary.kind) {
    20. case LatinSoftHyphen() => "hyphen"
    21. case ForcedEnd() => "end"
    22. case _ => "unexpected kind"
    23. }
    24. io.writeLine("{boundary.unitEnd} {category}")
    25. }
    Expected outputexit 0
    2 hyphen
    4 end
    
    $ topaz run main.tpz · target product 5.21.3
    Expected result

    Expected result

    Execution completes. Exit code 0.

    Expected stdout
    1. 2 hyphen
    2. 4 end
    Source evidence

    Preserve a word of three counted scalars

    Link
    main.tpzPreserve a word of three counted scalarsOpen in Playground
    1. import std.typeset as ts
    2. import std.io
    3. import std.test
    4. let clusters = [ts.BreakCluster { text: "a", advance: 1pt, trackingAfter: 0pt }, ts.BreakCluster { text: "b", advance: 1pt, trackingAfter: 0pt }, ts.BreakCluster { text: "c", advance: 1pt, trackingAfter: 0pt }]
    5. let selected = ts.BreakPolicy {
    6. mode: ts.BreakMode.Character(),
    7. rules: ts.KinsokuRules.AtlasDefault(),
    8. forbidBefore: [],
    9. forbidAfter: [],
    10. boundaryAllowed: [true, true, true],
    11. generatedHyphenEnds: [],
    12. protectFittingLatin: false,
    13. preserveShortWords: true,
    14. narrowestWordTarget: 0pt,
    15. bodyWordTarget: 0pt
    16. }
    17. let breaks = test.assertOk(ts.classifyBreaks(clusters, selected))
    18. io.writeLine("{breaks.length} {breaks[0].unitEnd}")
    Expected outputexit 0
    1 3
    
    $ topaz run main.tpz · target product 5.21.3
    Expected result

    Expected result

    Execution completes. Exit code 0.

    Expected stdout
    1. 1 3
    Source evidence

    Distinguish invalid policy values from invalid generated boundaries

    Link
    main.tpzDistinguish invalid policy values from invalid generated boundariesOpen in Playground
    1. import std.typeset as ts
    2. import std.io
    3. import std.test
    4. function outcome(value: Result<Array<ts.BreakOpportunity>, ts.TypesetError>) -> string {
    5. match (value) {
    6. case Ok(_) => "Ok"
    7. case Err(InvalidInput(_)) => "InvalidInput"
    8. case Err(InvalidPolicy(_)) => "InvalidPolicy"
    9. case Err(_) => "unexpected error"
    10. }
    11. }
    12. let clusters = [ts.BreakCluster { text: "a", advance: 1pt, trackingAfter: 0pt }, ts.BreakCluster { text: "b", advance: 1pt, trackingAfter: 0pt }]
    13. let target = ts.BreakPolicy {
    14. mode: ts.BreakMode.Character(),
    15. rules: ts.KinsokuRules.AtlasDefault(),
    16. forbidBefore: [],
    17. forbidAfter: [],
    18. boundaryAllowed: [true, true],
    19. generatedHyphenEnds: [],
    20. protectFittingLatin: false,
    21. preserveShortWords: false,
    22. narrowestWordTarget: 0pt,
    23. bodyWordTarget: -1pt
    24. }
    25. let scalar = ts.BreakPolicy {
    26. mode: ts.BreakMode.Character(),
    27. rules: ts.KinsokuRules.AtlasDefault(),
    28. forbidBefore: [55296],
    29. forbidAfter: [],
    30. boundaryAllowed: [true, true],
    31. generatedHyphenEnds: [],
    32. protectFittingLatin: false,
    33. preserveShortWords: false,
    34. narrowestWordTarget: 0pt,
    35. bodyWordTarget: 0pt
    36. }
    37. let boundary = ts.BreakPolicy {
    38. mode: ts.BreakMode.Character(),
    39. rules: ts.KinsokuRules.AtlasDefault(),
    40. forbidBefore: [],
    41. forbidAfter: [],
    42. boundaryAllowed: [true, true],
    43. generatedHyphenEnds: [2],
    44. protectFittingLatin: false,
    45. preserveShortWords: false,
    46. narrowestWordTarget: 0pt,
    47. bodyWordTarget: 0pt
    48. }
    49. io.writeLine(outcome(ts.classifyBreaks(clusters, target)))
    50. io.writeLine(outcome(ts.classifyBreaks(clusters, scalar)))
    51. io.writeLine(outcome(ts.classifyBreaks(clusters, boundary)))
    Expected outputexit 0
    InvalidPolicy
    InvalidPolicy
    InvalidInput
    
    $ topaz run main.tpz · target product 5.21.3
    Expected result

    Expected result

    Execution completes. Exit code 0.

    Expected stdout
    1. InvalidPolicy
    2. InvalidPolicy
    3. InvalidInput
    Source evidence

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