feat: async loading of files

src/jvmMain/kotlin/ui/controls/Controls.kt

@@ -2,6 +2,7 @@ package ui.controls
 
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.wrapContentSize
 import androidx.compose.material3.OutlinedButton
 import androidx.compose.material3.Text
@@ -16,7 +17,7 @@ import viewmodel.FilesViewModel
 fun Controls(viewModel: FilesViewModel) {
     Row(
         horizontalArrangement = Arrangement.spacedBy(8.dp),
-        modifier = Modifier.wrapContentSize(align = Alignment.Companion.CenterStart, unbounded = true),
+        modifier = Modifier.wrapContentSize(align = Alignment.Companion.CenterStart, unbounded = true).height(40.dp),
     ) {
         OpenFileButton(viewModel)
         SaveButton(viewModel)

src/jvmMain/kotlin/ui/controls/OpenFileButton.kt

@@ -1,13 +1,25 @@
 package ui.controls
 
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.aspectRatio
+import androidx.compose.foundation.layout.fillMaxHeight
+import androidx.compose.foundation.layout.width
 import androidx.compose.material3.Button
+import androidx.compose.material3.CircularProgressIndicator
+import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.scale
+import androidx.compose.ui.unit.dp
 import androidx.compose.ui.window.AwtWindow
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
 import viewmodel.FileTypes
 import viewmodel.FilesViewModel
 import java.awt.FileDialog
@@ -18,19 +30,34 @@ import java.nio.file.Path
 @Composable
 fun OpenFileButton(viewModel: FilesViewModel) {
     var isOpen by remember { mutableStateOf(false) }
+    var loadCount by remember { mutableStateOf(0) }
 
     if (isOpen) {
         FileDialog(
             onCloseRequest = { directory, file ->
                 isOpen = false
                 if (directory != null && file != null) {
-                    viewModel.loadFile(Path.of(directory, file))
+                    CoroutineScope(Dispatchers.Default).launch {
+                        loadCount++
+                        try {
+                            viewModel.loadFile(Path.of(directory, file))
+                        } finally {
+                            loadCount--
+                        }
+                    }
                 }
             },
         )
     }
 
     Button(onClick = { isOpen = true }) {
+        if (loadCount > 0) {
+            CircularProgressIndicator(
+                color = MaterialTheme.colorScheme.inverseOnSurface,
+                modifier = Modifier.fillMaxHeight().aspectRatio(1f).scale(0.9f),
+            )
+            Spacer(Modifier.width(16.dp))
+        }
         Text("Open file")
     }
 }