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

internal/app/text_selection.go

@@ -0,0 +1,91 @@
+// Copyright (c) 2026 Storm Dragon
+// Authors: Storm Dragon, Angus Kola
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package app
+
+import (
+	"strings"
+	"unicode/utf8"
+
+	"git.stormux.org/storm/cthulhu/internal/atspi"
+)
+
+// textSelection tracks only the focused text object. Its cached content is
+// bounded by the native snapshot and is retired when focus changes.
+type textSelection struct {
+	id         atspi.ObjectID
+	start, end int
+	text       string
+}
+
+const selectionFragmentLimit = 120
+const lineSelectionFragmentLimit = 4096
+
+func (selection *textSelection) reset(snapshot atspi.Snapshot) {
+	selection.id = snapshot.ID()
+	selection.start, selection.end = snapshot.SelectionStart, snapshot.SelectionEnd
+	selection.text = snapshot.SelectionText
+}
+
+func (selection *textSelection) changed(snapshot atspi.Snapshot) string {
+	return selection.changedWithLimit(snapshot, selectionFragmentLimit)
+}
+
+func (selection *textSelection) changedWithLimit(snapshot atspi.Snapshot, fragmentLimit int) string {
+	start, end := snapshot.SelectionStart, snapshot.SelectionEnd
+	if selection.id != snapshot.ID() {
+		selection.reset(snapshot)
+		return ""
+	}
+	oldStart, oldEnd, oldText := selection.start, selection.end, selection.text
+	selection.reset(snapshot)
+	if start == oldStart && end == oldEnd && oldText == snapshot.SelectionText {
+		return ""
+	}
+	if end <= start {
+		if oldEnd > oldStart {
+			return "selection removed"
+		}
+		return ""
+	}
+	if oldEnd <= oldStart {
+		return selectionFragment(snapshot.SelectionText, "selected", fragmentLimit)
+	}
+	var changes []string
+	if start > oldStart {
+		changes = append(changes, selectionFragment(selectionSlice(oldText, 0, min(oldEnd, start)-oldStart), "unselected", fragmentLimit))
+	}
+	if end < oldEnd {
+		changes = append(changes, selectionFragment(selectionSlice(oldText, max(oldStart, end)-oldStart, oldEnd-oldStart), "unselected", fragmentLimit))
+	}
+	if start < oldStart {
+		changes = append(changes, selectionFragment(selectionSlice(snapshot.SelectionText, 0, min(end, oldStart)-start), "selected", fragmentLimit))
+	}
+	if end > oldEnd {
+		changes = append(changes, selectionFragment(selectionSlice(snapshot.SelectionText, max(start, oldEnd)-start, end-start), "selected", fragmentLimit))
+	}
+	if len(changes) == 0 {
+		return "selection changed"
+	}
+	return strings.Join(changes, ", ")
+}
+
+func selectionSlice(value string, start, end int) string {
+	runes := []rune(value)
+	if start < 0 || end > len(runes) || start >= end {
+		return ""
+	}
+	return string(runes[start:end])
+}
+
+func selectionFragment(value, change string, limit int) string {
+	if utf8.RuneCountInString(value) > limit {
+		return change
+	}
+	value = strings.Join(strings.Fields(value), " ")
+	if value == "" {
+		return change
+	}
+	return value + " " + change
+}