feat: Jetpack Compose reimplementation of GapFillTextView

[Copilot]

Adds a pure-Compose equivalent of GapFillTextView, replacing the View-based span/popup/dialog machinery with idiomatic Compose state, layout, and effect primitives. Also upgrades the build system to support Kotlin + Compose.

Build system

• AGP 3.5.2 → 8.2.2, Gradle 5.4.1 → 8.4, Kotlin 1.9.22, compileSdk/targetSdk 28 → 34, minSdk 15 → 21
• Compose BOM 2024.02.01 added to richtextview module (ui, foundation, material3, runtime, animation)
• Removed bintray/dcendents publishing plugins; namespace moved from AndroidManifest to build.gradle

New files — com.rayworks.library.compose

GapFillParser.kt

Parses raw gap-fill text into a typed segment list. Applies the same normalisation and markdown→HTML conversion (Utils.getHtmlTextWithMarkups) as the original before splitting on {…} patterns.

sealed class Segment {
    data class TextSegment(val html: String) : Segment()
    data class BlankSegment(val index: Int, val defaultPlaceholder: String) : Segment()
}
data class GapFillParsed(val segments: List<Segment>, val errorCorrectionEnabled: Boolean, val totalBlanks: Int)

GapFillState.kt

Compose state holder — filledAnswers and activeBlankIndex backed by mutableStateOf. Includes reset(), firstUnfilledBlankIndex(), and formattedFullText() (regex-based so it handles both {} and {placeholder} blanks).

GapFillAnnotatedString.kt

Builds the AnnotatedString from parsed segments + current state. Handles:

• BLANK string annotations on every blank span for tap resolution
• Correct/wrong/editor colour spans (SpanStyle) on answered blanks
• TextDecoration.Underline for error-correction + review mode
• InlineTextContent + appendInlineContent for the deletion-icon blank
• Spanned → AnnotatedString conversion for StyleSpan / ForegroundColorSpan

GapFillPopup.kt

DropdownMenu-based option picker styled to match popupwnd_bkg.xml (blue, 8dp corners). Deletion option renders an icon+label row. Max 4 items visible before scroll.

GapFillEditorDialog.kt

Dialog-based free-form editor. Background animates blue → orange-red when word limit is exceeded (mirrors rectangle_gapfill_form_bkg*.xml). Dim scrim removed via DialogWindowProvider. Keyboard hidden on dismiss.

GapFillText.kt

Top-level composable + GapFillConfig data class (replaces XML attrs and setter methods).

@Composable
fun GapFillText(
    config: GapFillConfig,
    state: GapFillState = rememberGapFillState(),
    answerChecker: AnswerCorrectionChecker? = null,
    resultObserver: AnswerResultObserver? = null,
    modifier: Modifier = Modifier,
    textStyle: TextStyle = TextStyle.Default,
)

• Tap handling via BasicText + detectTapGestures + TextLayoutResult.getOffsetForPosition
• Idle-detection timer via LaunchedEffect(interactionKey) — restarts on every blank tap, cancelling the previous delay (replaces Handler.postDelayed)
• Full AnswerResultObserver / AnswerCorrectionChecker callback parity with the original
• Outer Box carries the writing_text_frame_bkg border (1dp light-grey stroke, 8dp corners)

All existing Java source files are unchanged.