Cthulhu is no longer a fork. Now it is a screen reader written in Golang.

internal/review/document_caret_text.go

@@ -0,0 +1,112 @@
+// Cthulhu screen reader.
+// Copyright (c) 2026 Storm Dragon
+// Authors: Storm Dragon, Angus Kola
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package review
+
+import (
+	"context"
+	"errors"
+	"unicode"
+	"unicode/utf8"
+
+	"git.stormux.org/storm/cthulhu/internal/atspi"
+)
+
+// Python caret_navigation starts a word move at the adjacent non-space
+// character, rather than the next/previous word boundary. In particular,
+// reversing at the end of a word must read that word, not skip over it.
+func moveCaretText(ctx context.Context, reader DocumentCaretReader, doc atspi.DocumentSnapshot, place *documentPlace, indices []int, current int, backwards, byWord bool) (DocumentCaretMove, error) {
+	step := 1
+	if backwards {
+		step = -1
+	}
+	position := 0
+	for position < len(indices) && indices[position] < current {
+		position++
+	}
+	offset := 0
+	if position < len(indices) && indices[position] == current {
+		offset = place.offset + step
+	} else if backwards {
+		position--
+		if position >= 0 {
+			offset = doc.Nodes[indices[position]].Snapshot.CharacterCount - 1
+		}
+	} else if place.origin == StructuralNavigation {
+		// Structural jumps speak the first descendant at offset zero.
+		offset = 1
+	}
+	for position >= 0 && position < len(indices) {
+		if err := ctx.Err(); err != nil {
+			return DocumentCaretMove{}, err
+		}
+		node := doc.Nodes[indices[position]]
+		if node.Snapshot.CharacterCount == 0 || wholeCaretNode(node.Snapshot) {
+			if node.Reference != place.object {
+				place.object, place.offset, place.origin = node.Reference, 0, CaretNavigation
+				return DocumentCaretMove{Position: documentPosition(doc, *place), Moved: true}, nil
+			}
+			position += step
+			offset = 0
+			if backwards && position >= 0 {
+				offset = doc.Nodes[indices[position]].Snapshot.CharacterCount - 1
+			}
+			continue
+		}
+		if offset >= 0 && offset < node.Snapshot.CharacterCount {
+			character, err := reader.ReadDocumentCaret(ctx, node.Reference, offset, atspi.DocumentCaretCharacter)
+			if err != nil && !errors.Is(err, atspi.ErrNoDocumentCaret) {
+				return DocumentCaretMove{}, err
+			}
+			if err == nil && character.End > character.Start {
+				value, _ := utf8.DecodeRuneInString(character.Text)
+				if character.Text == "" || byWord && unicode.IsSpace(value) || value == '\ufffc' || value == '\ufeff' {
+					offset += step
+					continue
+				}
+				if !byWord {
+					place.object, place.offset, place.origin = node.Reference, character.Start, CaretNavigation
+					return DocumentCaretMove{Position: documentPosition(doc, *place), Text: character.Text, Misspelled: character.Misspelled, Moved: true, Start: character.Start, End: character.End}, nil
+				}
+				word, err := reader.ReadDocumentCaret(ctx, node.Reference, offset, atspi.DocumentCaretWord)
+				if err != nil {
+					return DocumentCaretMove{}, err
+				}
+				if word.Text == "" || word.Start < 0 || word.Start > offset || word.End <= offset || word.End > word.CharacterCount {
+					// Chromium can expose an emoji as a valid character but
+					// return a broken WORD range (for example, end = -1).
+					// Read that character as a unit rather than trapping word
+					// navigation at the same position on every key press.
+					if character.Start < 0 || character.Start > offset || character.End <= offset || character.End > character.CharacterCount {
+						return DocumentCaretMove{}, atspi.ErrNoDocumentCaret
+					}
+					word = character
+				}
+				nextOffset := word.Start
+				if !backwards {
+					nextOffset = word.End
+					// WORD ranges may contain a trailing delimiter. Query its
+					// actual character; spoken word text can be normalized.
+					last, err := reader.ReadDocumentCaret(ctx, node.Reference, word.End-1, atspi.DocumentCaretCharacter)
+					if err != nil {
+						return DocumentCaretMove{}, err
+					}
+					value, _ := utf8.DecodeRuneInString(last.Text)
+					if unicode.IsSpace(value) {
+						nextOffset--
+					}
+				}
+				place.object, place.offset, place.origin = node.Reference, nextOffset, CaretNavigation
+				return DocumentCaretMove{Position: documentPosition(doc, *place), Text: word.Text, Misspelled: word.Misspelled, Moved: true, Start: word.Start, End: word.End}, nil
+			}
+		}
+		position += step
+		offset = 0
+		if backwards && position >= 0 {
+			offset = doc.Nodes[indices[position]].Snapshot.CharacterCount - 1
+		}
+	}
+	return DocumentCaretMove{Position: documentPosition(doc, *place)}, nil
+}