Improve SplitPaneState (#3974)

Improve `SplitPane` programmatic configuration through changes in
`SplitPaneState`.
Add programmatic `SplitPane` programmatic configuration changes to demo.

---------

Co-authored-by: vdshb <github.com/vdshb>

components/SplitPane/demo/src/jvmMain/kotlin/org/jetbrains/compose/splitpane/demo/Main.kt

@@ -1,17 +1,34 @@
 package org.jetbrains.compose.splitpane.demo
 
 import androidx.compose.foundation.background
-import androidx.compose.foundation.layout.*
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxHeight
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.width
+import androidx.compose.material.Button
 import androidx.compose.material.MaterialTheme
-import androidx.compose.runtime.*
+import androidx.compose.material.OutlinedTextField
+import androidx.compose.material.Text
+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.graphics.Color
 import androidx.compose.ui.graphics.SolidColor
 import androidx.compose.ui.input.pointer.PointerIcon
 import androidx.compose.ui.input.pointer.pointerHoverIcon
+import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.window.singleWindowApplication
-import org.jetbrains.compose.splitpane.*
+import org.jetbrains.compose.splitpane.ExperimentalSplitPaneApi
+import org.jetbrains.compose.splitpane.HorizontalSplitPane
+import org.jetbrains.compose.splitpane.VerticalSplitPane
+import org.jetbrains.compose.splitpane.rememberSplitPaneState
 import java.awt.Cursor
 
 private fun Modifier.cursorForHorizontalResize(): Modifier =
@@ -24,40 +41,69 @@ fun main() = singleWindowApplication(
     MaterialTheme {
         val splitterState = rememberSplitPaneState()
         val hSplitterState = rememberSplitPaneState()
-        HorizontalSplitPane(
-            splitPaneState = splitterState
-        ) {
-            first(20.dp) {
-                Box(Modifier.background(Color.Red).fillMaxSize())
-            }
-            second(50.dp) {
-                VerticalSplitPane(splitPaneState = hSplitterState) {
-                    first(50.dp) {
-                        Box(Modifier.background(Color.Blue).fillMaxSize())
-                    }
-                    second(20.dp) {
-                        Box(Modifier.background(Color.Green).fillMaxSize())
-                    }
+        var delta by remember { mutableStateOf("20") }
+        var percentage by remember { mutableStateOf("0.20") }
+        Row {
+            Column(verticalArrangement = Arrangement.spacedBy(10.dp), modifier = Modifier.padding(10.dp).width(180.dp)) {
+                Text("Action panel", fontWeight = FontWeight.Bold)
+                Button(onClick = { splitterState.moveEnabled = !splitterState.moveEnabled }) {
+                    Text(if (splitterState.moveEnabled) "Freeze V" else "Unfreeze V")
+                }
+                Button(onClick = { hSplitterState.moveEnabled = !hSplitterState.moveEnabled }) {
+                    Text(if (hSplitterState.moveEnabled) "Freeze H" else "Unfreeze H")
+                }
+
+                OutlinedTextField(value = delta, onValueChange = { delta = it }, label = { Text("Delta") })
+                Button(onClick = { delta.toFloatOrNull()?.let { splitterState.dispatchRawMovement(it) } }) {
+                    Text("Add delta V")
+                }
+                Button(onClick = { delta.toFloatOrNull()?.let { hSplitterState.dispatchRawMovement(it) } }) {
+                    Text("Add delta H")
+                }
+
+                OutlinedTextField(value = percentage, onValueChange = { percentage = it }, label = { Text("Fraction") })
+                Button(onClick = { percentage.toFloatOrNull()?.let { splitterState.positionPercentage = it } }) {
+                    Text("Set fraction V")
+                }
+                Button(onClick = { percentage.toFloatOrNull()?.let { hSplitterState.positionPercentage = it } }) {
+                    Text("Set fraction H")
                 }
             }
-            splitter {
-                visiblePart {
-                    Box(
-                        Modifier
-                            .width(1.dp)
-                            .fillMaxHeight()
-                            .background(MaterialTheme.colors.background)
-                    )
+            HorizontalSplitPane(
+                splitPaneState = splitterState
+            ) {
+                first(20.dp) {
+                    Box(Modifier.background(Color.Red).fillMaxSize())
                 }
-                handle {
-                    Box(
-                        Modifier
-                            .markAsHandle()
-                            .cursorForHorizontalResize()
-                            .background(SolidColor(Color.Gray), alpha = 0.50f)
-                            .width(9.dp)
-                            .fillMaxHeight()
-                    )
+                second(50.dp) {
+                    VerticalSplitPane(splitPaneState = hSplitterState) {
+                        first(50.dp) {
+                            Box(Modifier.background(Color.Blue).fillMaxSize())
+                        }
+                        second(20.dp) {
+                            Box(Modifier.background(Color.Green).fillMaxSize())
+                        }
+                    }
+                }
+                splitter {
+                    visiblePart {
+                        Box(
+                            Modifier
+                                .width(1.dp)
+                                .fillMaxHeight()
+                                .background(MaterialTheme.colors.background)
+                        )
+                    }
+                    handle {
+                        Box(
+                            Modifier
+                                .markAsHandle()
+                                .cursorForHorizontalResize()
+                                .background(SolidColor(Color.Gray), alpha = 0.50f)
+                                .width(9.dp)
+                                .fillMaxHeight()
+                        )
+                    }
                 }
             }
         }

components/SplitPane/library/src/commonMain/kotlin/org/jetbrains/compose/splitpane/SplitPaneState.kt

@@ -11,10 +11,11 @@ class SplitPaneState(
 ) {
 
     var moveEnabled by mutableStateOf(moveEnabled)
-        internal set
 
-    var positionPercentage by mutableStateOf(initialPositionPercentage)
-        internal set
+    private var _positionPercentage by mutableStateOf(initialPositionPercentage)
+    var positionPercentage: Float
+        get() = _positionPercentage
+        set(value) { _positionPercentage = value.coerceIn(0f, 1f) }
 
     internal var minPosition: Float = 0f