new: mark muted characters

shared/src/commonMain/kotlin/fr/ajaury/gwenedeg/player/ui/SubtitleList.kt

@@ -36,6 +36,7 @@ import androidx.compose.ui.unit.Density
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
 import fr.ajaury.gwenedeg.core.model.Phrase
+import fr.ajaury.gwenedeg.player.ui.components.TranscriptionText
 import fr.ajaury.gwenedeg.preferences.model.SubtitlePreferences
 import fr.ajaury.gwenedeg.subtitle.model.SubtitleLine
 import fr.ajaury.gwenedeg.theme.ChomBevTheme
@@ -194,10 +195,10 @@ private fun TranscriptionLine(
     text: String,
     contentColor: Color,
 ) {
-    Text(
+    TranscriptionText(
         text = text,
-        style = MaterialTheme.typography.bodyLarge.copy(fontSize = 20.sp),
         color = contentColor,
+        style = MaterialTheme.typography.bodyLarge.copy(fontSize = 20.sp),
         textAlign = TextAlign.Center,
     )
 }
@@ -234,8 +235,8 @@ private val previewSubtitleLines =
         SubtitleLine(
             startTime = 7350.milliseconds,
             phrase = Phrase(
-                transcription = "Kenavo emberr !",
+                transcription = "Tomm eo ma(n) divskouarn",
-                translation = "À ce soir !",
+                translation = "J'ai chaud aux oreilles",
             ),
         ),
     )

shared/src/commonMain/kotlin/fr/ajaury/gwenedeg/player/ui/components/TranscriptionText.kt

@@ -0,0 +1,159 @@
+package fr.ajaury.gwenedeg.player.ui.components
+
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.text.InlineTextContent
+import androidx.compose.foundation.text.appendInlineContent
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.platform.LocalDensity
+import androidx.compose.ui.text.Placeholder
+import androidx.compose.ui.text.PlaceholderVerticalAlign
+import androidx.compose.ui.text.TextStyle
+import androidx.compose.ui.text.buildAnnotatedString
+import androidx.compose.ui.text.rememberTextMeasurer
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.tooling.preview.Preview
+import androidx.compose.ui.unit.em
+import androidx.compose.ui.unit.sp
+import fr.ajaury.gwenedeg.theme.ChomBevTheme
+
+/**
+ * Matches a liaison/optional letter written between parentheses in a transcription, e.g. the `n`
+ * in `ma(n)`. The captured group is the letter itself, without the surrounding parentheses.
+ */
+private val MUTED_LETTER_REGEX = Regex("""\(([A-Za-z])\)""")
+
+/** Diacritic drawn above an optional letter to mark that it is only sounded on liaison. */
+private const val MUTED_LETTER_MARK = "ø"
+
+/**
+ * Renders a transcription, giving special treatment to letters written between parentheses
+ * (liaison consonants such as the `n` in `ma(n)`): the parentheses are dropped, the letter is
+ * shown in a muted grey and topped with a small [MUTED_LETTER_MARK].
+ *
+ * Optional letters are emitted as inline content so the line still wraps like normal text.
+ */
+@Composable
+fun TranscriptionText(
+    text: String,
+    color: Color,
+    style: TextStyle,
+    modifier: Modifier = Modifier,
+    textAlign: TextAlign = TextAlign.Center,
+) {
+    val matches = remember(text) { MUTED_LETTER_REGEX.findAll(text).toList() }
+
+    if (matches.isEmpty()) {
+        Text(
+            text = text,
+            color = color,
+            style = style,
+            textAlign = textAlign,
+            modifier = modifier,
+        )
+        return
+    }
+
+    // Muted grey that still follows the surrounding line's dimming (current vs. inactive line).
+    val markColor = color.copy(alpha = color.alpha * 0.6f)
+
+    val annotatedText = buildAnnotatedString {
+        var cursor = 0
+        matches.forEachIndexed { index, match ->
+            append(text.substring(cursor, match.range.first))
+            appendInlineContent(id = inlineId(index), alternateText = match.groupValues[1])
+            cursor = match.range.last + 1
+        }
+        append(text.substring(cursor))
+    }
+
+    val density = LocalDensity.current
+    val textMeasurer = rememberTextMeasurer()
+
+    val inlineContent = matches
+        .mapIndexed { index, match ->
+            val letter = match.groupValues[1]
+            // Reserve exactly the letter's advance width (in em, so it is font-scale independent); the
+            // taller placeholder leaves room for the mark above. Aligning to the text bottom keeps the
+            // letter's baseline in step with the rest of the line.
+            val letterWidthEm = remember(letter, style) {
+                val letterWidthPx = textMeasurer.measure(text = letter, style = style).size.width
+                val fontSizePx = with(density) { style.fontSize.toPx() }
+                letterWidthPx / fontSizePx
+            }
+
+            inlineId(index) to InlineTextContent(
+                placeholder = Placeholder(
+                    width = letterWidthEm.em,
+                    height = 1.7.em,
+                    placeholderVerticalAlign = PlaceholderVerticalAlign.TextBottom,
+                ),
+            ) {
+                OptionalLetter(letter = letter, color = markColor, style = style)
+            }
+        }.toMap()
+
+    Text(
+        text = annotatedText,
+        color = color,
+        style = style,
+        textAlign = textAlign,
+        inlineContent = inlineContent,
+        modifier = modifier,
+    )
+}
+
+@Composable
+private fun OptionalLetter(
+    letter: String,
+    color: Color,
+    style: TextStyle,
+) {
+    Box(modifier = Modifier.fillMaxSize()) {
+        Text(
+            text = MUTED_LETTER_MARK,
+            color = color,
+            style = style.copy(fontSize = style.fontSize * 0.75f, lineHeight = 10.sp),
+            modifier = Modifier.align(Alignment.TopCenter),
+        )
+        Text(
+            text = letter,
+            color = color,
+            // Tight line height so the glyph's baseline lands where the surrounding line expects it.
+            style = style.copy(lineHeight = style.fontSize),
+            modifier = Modifier.align(Alignment.BottomCenter),
+        )
+    }
+}
+
+private fun inlineId(index: Int): String = "optional-letter-$index"
+
+@Preview(backgroundColor = 0xFFFFFFFF)
+@Composable
+private fun TranscriptionTextPreview() {
+    ChomBevTheme {
+        TranscriptionText(
+            text = "Tomm eo ma(n) divskouarn, penn ma fri",
+            color = MaterialTheme.colorScheme.onSurface,
+            style = MaterialTheme.typography.bodyLarge.copy(fontSize = 20.sp),
+        )
+    }
+}
+
+@Preview(backgroundColor = 0xFFFFFFFF)
+@Composable
+private fun TranscriptionTextNoOptionalLetterPreview() {
+    ChomBevTheme {
+        TranscriptionText(
+            text = "Demat deoc'h !",
+            color = MaterialTheme.colorScheme.onSurface,
+            style = MaterialTheme.typography.bodyLarge.copy(fontSize = 20.sp),
+        )
+    }
+}