Rework transparent effect

window-styler-demo/src/jvmMain/kotlin/Main.kt

@@ -60,7 +60,8 @@ val backdropOptions = listOf(
     WindowBackdrop.Default to "Default",
     WindowBackdrop.Solid(Color.Red) to "Solid Red",
     WindowBackdrop.Solid(Color.Blue) to "Solid Blue",
-    WindowBackdrop.Transparent to "Transparent",
+    WindowBackdrop.Transparent(Color.Transparent) to "Transparent",
+    WindowBackdrop.Transparent(Color.Yellow.copy(alpha = 0.25F)) to "Yellow Transparent",
     WindowBackdrop.Aero to "Aero",
     WindowBackdrop.Acrylic(Color.Magenta.copy(alpha = 0.25F)) to "Acrylic Magenta",
     WindowBackdrop.Acrylic(Color.Cyan.copy(alpha = 0.25F)) to "Acrylic Cyan",

window-styler/src/jvmMain/kotlin/com/mayakapps/compose/windowstyler/NativeUtils.kt

@@ -34,6 +34,7 @@ internal fun WindowBackdrop.toDwmSystemBackdrop(): DwmSystemBackdrop =
 internal fun WindowBackdrop.toAccentState(): AccentState =
     when (this) {
         is WindowBackdrop.Default, is WindowBackdrop.Solid -> AccentState.ACCENT_ENABLE_GRADIENT
+        is WindowBackdrop.Transparent -> AccentState.ACCENT_ENABLE_TRANSPARENTGRADIENT
         is WindowBackdrop.Aero -> AccentState.ACCENT_ENABLE_BLURBEHIND
         is WindowBackdrop.Acrylic -> AccentState.ACCENT_ENABLE_ACRYLICBLURBEHIND
         else -> AccentState.ACCENT_DISABLED

window-styler/src/jvmMain/kotlin/com/mayakapps/compose/windowstyler/Utils.kt

@@ -15,4 +15,9 @@ internal fun Color.toAbgr(): Int {
             ((color[2] * 255.0f + 0.5f).toInt() shl 16) or
             ((color[1] * 255.0f + 0.5f).toInt() shl 8) or
             (color[0] * 255.0f + 0.5f).toInt()
-}
+}
+
+// For some reason, passing 0 (fully transparent black) to the setAccentPolicy with
+// transparent accent policy results in solid red color. As a workaround, we pass
+// fully transparent white which has the same visual effect.
+internal fun Color.toAbgrForTransparent() = if (alpha == 0F) 0x00FFFFFF else toAbgr()

window-styler/src/jvmMain/kotlin/com/mayakapps/compose/windowstyler/WindowBackdrop.kt

@@ -5,7 +5,7 @@ import androidx.compose.ui.graphics.Color
 sealed interface WindowBackdrop {
     object Default : WindowBackdrop
     data class Solid(override val color: Color) : ColorableWindowBackdrop
-    object Transparent : WindowBackdrop
+    data class Transparent(override val color: Color) : ColorableWindowBackdrop
     object Aero : WindowBackdrop
     data class Acrylic(override val color: Color) : ColorableWindowBackdrop
     object Mica : WindowBackdrop
@@ -14,4 +14,4 @@ sealed interface WindowBackdrop {
 
 internal interface ColorableWindowBackdrop : WindowBackdrop {
     val color: Color
-}
+}

window-styler/src/jvmMain/kotlin/com/mayakapps/compose/windowstyler/WindowStyle.kt

@@ -29,6 +29,19 @@ fun FrameWindowScope.WindowStyle(
     if (windowsBuild >= 17763) {
         LaunchedEffect(isDarkTheme) {
             setImmersiveDarkModeEnabled(hwnd, isDarkTheme)
+
+            // For some reason, using setImmersiveDarkModeEnabled after setting accent policy to transparent
+            // results in solid red backdrop. So, we have to reset the transparent backdrop after using it.
+            val finalLastEffect = lastEffect
+            if (finalLastEffect is WindowBackdrop.Transparent) {
+                setAccentPolicy(hwnd, AccentState.ACCENT_DISABLED)
+                setAccentPolicy(
+                    hwnd = hwnd,
+                    accentState = backdropType.toAccentState(),
+                    accentFlags = setOf(AccentFlag.DRAW_ALL_BORDERS),
+                    color = finalLastEffect.color.toAbgrForTransparent(),
+                )
+            }
         }
     }
 
@@ -43,8 +56,6 @@ fun FrameWindowScope.WindowStyle(
             // Set [ACCENT_DISABLED] as [ACCENT_POLICY] to apply styles properly.
             setAccentPolicy(hwnd, AccentState.ACCENT_DISABLED)
 
-            if (backdropType is WindowBackdrop.Transparent) return@invokeLater
-
             // Only on later Windows 11 versions and if effect is WindowEffect.mica,
             // WindowEffect.acrylic or WindowEffect.tabbed, otherwise fallback to old
             // approach.
@@ -73,16 +84,22 @@ fun FrameWindowScope.WindowStyle(
                         setMicaEffectEnabled(hwnd, false)
                     }
 
+                    val color = when (backdropType) {
+                        is WindowBackdrop.Transparent -> backdropType.color.toAbgrForTransparent()
+                        is ColorableWindowBackdrop -> backdropType.color.toAbgr()
+                        else -> 0x7FFFFFFF
+                    }
+
                     setAccentPolicy(
                         hwnd = hwnd,
                         accentState = backdropType.toAccentState(),
                         accentFlags = setOf(AccentFlag.DRAW_ALL_BORDERS),
-                        color = (backdropType as? ColorableWindowBackdrop)?.color?.toAbgr() ?: 0x0FFFFFFF,
+                        color = color,
                     )
                 }
             }
 
             lastEffect = backdropType
         }
     }
-}
+}