Fix SwingPanel size not scaling according to LocalDensity (#3033)

Author: m-sasha

compose/ui/ui/src/desktopMain/kotlin/androidx/compose/ui/viewinterop/SwingInteropViewHolder.desktop.kt

@@ -33,6 +33,7 @@ import androidx.compose.ui.layout.findRootCoordinates
 import androidx.compose.ui.unit.Density
 import androidx.compose.ui.unit.IntRect
 import androidx.compose.ui.util.fastForEach
+import androidx.compose.ui.window.density
 import java.awt.Component
 import java.awt.event.FocusEvent
 import java.awt.event.FocusListener
@@ -89,13 +90,13 @@ internal class SwingInteropViewHolder<T : Component>(
     override fun layoutAccordingTo(layoutCoordinates: LayoutCoordinates) {
         val rootCoordinates = layoutCoordinates.findRootCoordinates()
 
+        val awtToComposeScale = container.root.density
         val clippedBounds = rootCoordinates
             .localBoundingBoxOf(layoutCoordinates, clipBounds = true)
-            .round(density)
-
+            .round(awtToComposeScale)
         val bounds = rootCoordinates
             .localBoundingBoxOf(layoutCoordinates, clipBounds = false)
-            .round(density)
+            .round(awtToComposeScale)
 
         clipBounds = clippedBounds // Clipping area for skia canvas
 

compose/ui/ui/src/desktopTest/kotlin/androidx/compose/ui/awt/SwingPanelTest.kt

@@ -24,6 +24,11 @@ import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.offset
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.verticalScroll
+import androidx.compose.runtime.CompositionLocalProvider
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableFloatStateOf
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.layout.LayoutBoundsHolder
 import androidx.compose.ui.layout.layoutBounds
@@ -37,13 +42,16 @@ import androidx.compose.ui.unit.DpSize
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.window.Window
 import androidx.compose.ui.window.WindowState
+import androidx.compose.ui.window.roundToDimension
 import androidx.compose.ui.window.runApplicationTest
 import java.awt.BorderLayout
 import java.awt.Dimension
+import java.awt.Graphics
 import java.awt.Point
 import java.awt.event.MouseAdapter
 import java.awt.event.MouseEvent
 import java.awt.event.MouseWheelEvent
+import javax.swing.JComponent
 import javax.swing.JLabel
 import javax.swing.JPanel
 import javax.swing.SwingUtilities
@@ -208,4 +216,46 @@ class SwingPanelTest {
         awaitIdle()
         assertTrue(scrollState.value > 0, "Compose did not scroll; SwingPanel blocked the event")
     }
+
+    @Test
+    fun swingPanelRespondsToDensityChange() = runApplicationTest {
+        val swingComponent = object: JComponent() {
+            override fun paint(g: Graphics) {
+                g.color = java.awt.Color.RED
+                g.fillRect(0, 0, width, height)
+            }
+        }
+        val swingElementSize = DpSize(200.dp, 200.dp)
+
+        var densityScale by mutableFloatStateOf(1f)
+        launchTestWindowApplication(
+            state = WindowState(size = DpSize(500.dp, 500.dp))
+        ) {
+            Box(
+                modifier = Modifier.fillMaxSize(),
+                contentAlignment = Alignment.Center
+            ) {
+                val density = LocalDensity.current.density
+                CompositionLocalProvider(LocalDensity provides Density(densityScale * density)) {
+                    SwingPanel(
+                        modifier = Modifier.size(swingElementSize),
+                        factory = { swingComponent }
+                    )
+                }
+            }
+        }
+
+        awaitIdle()
+        assertEquals(
+            expected = swingElementSize.roundToDimension(),
+            actual = swingComponent.size
+        )
+
+        densityScale = 2f
+        awaitIdle()
+        assertEquals(
+            expected = (swingElementSize * densityScale).roundToDimension(),
+            actual = swingComponent.size
+        )
+    }
 }