Add prominent shutter speed display

app/src/main/java/eu/wa5p/lightmeter/MainActivity.kt

@@ -23,9 +23,11 @@ import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
 import eu.wa5p.lightmeter.ui.theme.LightMeterTheme
 import kotlin.math.abs
 
@@ -34,6 +36,30 @@ const val TAG: String = "lightmeter MainActivity"
 private val commonIsoValues = listOf(50, 100, 200, 400, 800, 1600, 3200, 6400)
 private val commonApertureValues = listOf(0.85, 1.4, 2.0, 2.8, 4.0, 5.6, 8.0, 11.0, 16.0, 22.0)
 
+data class ShutterSpeed(val value: Double, val label: String)
+val shutterSpeeds = listOf(
+    ShutterSpeed(1.0 / 8000, "1/8000 s"),
+    ShutterSpeed(1.0 / 4000, "1/4000 s"),
+    ShutterSpeed(1.0 / 2000, "1/2000 s"),
+    ShutterSpeed(1.0 / 1000, "1/1000 s"),
+    ShutterSpeed(1.0 / 500, "1/500 s"),
+    ShutterSpeed(1.0 / 250, "1/250 s"),
+    ShutterSpeed(1.0 / 125, "1/125 s"),
+    ShutterSpeed(1.0 / 60, "1/60 s"),
+    ShutterSpeed(1.0 / 30, "1/30 s"),
+    ShutterSpeed(1.0 / 15, "1/15 s"),
+    ShutterSpeed(1.0 / 8, "1/8 s"),
+    ShutterSpeed(1.0 / 4, "1/4 s"),
+    ShutterSpeed(1.0 / 2, "1/2 s"),
+    ShutterSpeed(1.0, "1 s"),
+    ShutterSpeed(2.0, "2 s"),
+    ShutterSpeed(4.0, "4 s"),
+    ShutterSpeed(8.0, "8 s"),
+    ShutterSpeed(15.0, "15 s"),
+    ShutterSpeed(30.0, "30 s"),
+    ShutterSpeed(60.0, "60 s")
+)
+
 class MainActivity : ComponentActivity(), SensorEventListener {
     private lateinit var sensorManager: SensorManager
     private var illuminanceSensor: Sensor? = null
@@ -151,6 +177,37 @@ fun LightmeterListItemPreview() {
     }
 }
 
+private fun formatShutterSpeed(shutterSpeed: Double): String {
+    val closestShutterSpeed = shutterSpeeds.minByOrNull {
+        abs(it.value - shutterSpeed)
+    }
+
+    return closestShutterSpeed?.label ?: "Unknown"
+}
+
+@Composable
+fun ShutterSpeed(state: MutableState<LightmeterState>) {
+    Row(modifier = Modifier.padding(bottom = 8.dp)) {
+        Text(
+            modifier = Modifier
+                .weight(0.5f)
+                .padding(all = 8.dp),
+            textAlign = TextAlign.Center,
+            fontWeight = FontWeight.Bold,
+            fontSize = 24.sp,
+            text = formatShutterSpeed(state.value.shutterSpeed)
+        )
+    }
+}
+
+@Preview(showBackground = true)
+@Composable
+fun PreviewShutterSpeed() {
+    LightMeterTheme {
+        ShutterSpeed(state = previewlightmeterState)
+    }
+}
+
 @Composable
 fun IsoSlider(state: MutableState<LightmeterState>, recalculateShutterSpeed: () -> Unit) {
     // Convert common ISO values to the range used by the slider
@@ -284,6 +341,13 @@ fun LightmeterHomeScreen(
             )
         }
         
+        Column (
+            modifier = Modifier.padding(top = 64.dp),
+            verticalArrangement = Arrangement.Center
+        ) {
+            ShutterSpeed(state = state)
+        }
+
         Column(
             modifier = Modifier.padding(top = 64.dp),
             verticalArrangement = Arrangement.Bottom