feat: WIP add custom proc to handle titlebar content

IN PROGRESS. Not working yet.

Author: alexfacciorusso

settings.gradle.kts

@@ -8,4 +8,8 @@ pluginManagement {
 }
 
 rootProject.name = "ComposeWindowStyler"
-include("window-styler", "window-styler-demo")
+include(
+    "window-styler",
+    "window-styler-demo",
+    "window-styler-demo-transparent",
+)

window-styler-demo-transparent/build.gradle.kts

@@ -0,0 +1,39 @@
+import org.jetbrains.compose.desktop.application.dsl.TargetFormat
+
+// Suppress annotation is a workaround for a bug.
+@Suppress("DSL_SCOPE_VIOLATION")
+plugins {
+    alias(libs.plugins.kotlin.multiplatform)
+    alias(libs.plugins.compose)
+}
+
+kotlin {
+    jvmToolchain(17)
+
+    jvm {
+        withJava()
+    }
+
+    sourceSets {
+        named("jvmMain") {
+            dependencies {
+                implementation(compose.desktop.currentOs)
+
+                implementation(project(":window-styler"))
+            }
+        }
+    }
+}
+
+compose.desktop {
+    application {
+        mainClass = "MainKt"
+
+        nativeDistributions {
+            targetFormats(TargetFormat.Msi)
+
+            packageName = "window-styler-demo-transparent"
+            packageVersion = "1.0.0"
+        }
+    }
+}

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

@@ -0,0 +1,35 @@
+import androidx.compose.desktop.ui.tooling.preview.Preview
+import androidx.compose.foundation.isSystemInDarkTheme
+import androidx.compose.material.Button
+import androidx.compose.material.MaterialTheme
+import androidx.compose.material.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.window.Window
+import androidx.compose.ui.window.application
+import com.mayakapps.compose.windowstyler.WindowBackdrop
+import com.mayakapps.compose.windowstyler.WindowStyle
+
+@Composable
+@Preview
+fun App() {
+    Button(onClick = {}) {
+        Text("Button")
+    }
+}
+
+fun main() = application {
+    Window(
+        onCloseRequest = ::exitApplication,
+        title = "Compose Window Styler Demo",
+    ) {
+        WindowStyle(
+            isDarkTheme = isSystemInDarkTheme(),
+            backdropType = WindowBackdrop.Mica,
+            manageTitlebar = true
+        )
+
+        MaterialTheme {
+            App()
+        }
+    }
+}

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

@@ -15,8 +15,9 @@ fun WindowScope.WindowStyle(
     isDarkTheme: Boolean = false,
     backdropType: WindowBackdrop = WindowBackdrop.Default,
     frameStyle: WindowFrameStyle = WindowFrameStyle(),
+    manageTitlebar: Boolean = false,
 ) {
-    val manager = remember { WindowStyleManager(window, isDarkTheme, backdropType, frameStyle) }
+    val manager = remember { WindowStyleManager(window, isDarkTheme, backdropType, frameStyle, manageTitlebar) }
 
     LaunchedEffect(isDarkTheme) {
         manager.isDarkTheme = isDarkTheme

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

@@ -13,12 +13,13 @@ import java.awt.Window
  */
 fun WindowStyleManager(
     window: Window,
-    isDarkTheme: Boolean = false,
-    backdropType: WindowBackdrop = WindowBackdrop.Default,
-    frameStyle: WindowFrameStyle = WindowFrameStyle(),
+    isDarkTheme: Boolean,
+    backdropType: WindowBackdrop,
+    frameStyle: WindowFrameStyle,
+    manageTitlebar: Boolean,
 ) = when (hostOs) {
-    OS.Windows -> WindowsWindowStyleManager(window, isDarkTheme, backdropType, frameStyle)
-    else -> StubWindowStyleManager(isDarkTheme, backdropType, frameStyle)
+    OS.Windows -> WindowsWindowStyleManager(window, isDarkTheme, backdropType, frameStyle, manageTitlebar)
+    else -> StubWindowStyleManager(isDarkTheme, backdropType, frameStyle, manageTitlebar)
 }
 
 /**
@@ -46,10 +47,17 @@ interface WindowStyleManager {
      * The style of the window frame which includes the title bar and window border. See [WindowFrameStyle].
      */
     var frameStyle: WindowFrameStyle
+
+    /**
+     * Whether to manage the title bar of the window. If set to `true`, the title bar will be hidden and the window
+     * will need to manage its own title.
+     */
+    var manageTitlebar: Boolean
 }
 
 internal class StubWindowStyleManager(
     override var isDarkTheme: Boolean,
     override var backdropType: WindowBackdrop,
     override var frameStyle: WindowFrameStyle,
+    override var manageTitlebar: Boolean,
 ) : WindowStyleManager

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

@@ -0,0 +1,47 @@
+package com.mayakapps.compose.windowstyler.windows
+
+import com.mayakapps.compose.windowstyler.windows.jna.Dwm
+import com.mayakapps.compose.windowstyler.windows.jna.User32
+import com.sun.jna.platform.win32.WinDef
+import com.sun.jna.platform.win32.WinUser
+
+private const val WM_NCCALCSIZE = 0x0083
+private const val WM_NCHITTEST = 0x0084
+
+class CustomDecorationWindowProc private constructor(private val hwnd: WinDef.HWND) : WinUser.WindowProc {
+    private val defWndProc = User32.setWindowProc(hwnd, this)
+
+    override fun callback(hWnd: WinDef.HWND, uMsg: Int, wParam: WinDef.WPARAM, lParam: WinDef.LPARAM): WinDef.LRESULT {
+        if (Dwm.callDefaultWindowHitProc(hwnd, uMsg, wParam, lParam)) {
+            return WinDef.LRESULT(0)
+        }
+
+        return when (uMsg) {
+            WM_NCCALCSIZE -> {
+                WinDef.LRESULT(0)
+            }
+
+            WM_NCHITTEST -> {
+                User32.callWindowProc(defWndProc, hWnd, uMsg, wParam, lParam)
+            }
+
+            WinUser.WM_DESTROY -> {
+                User32.setWindowProc(hWnd, defWndProc)
+                WinDef.LRESULT(-1)
+            }
+
+            else -> {
+                User32.callWindowProc(defWndProc, hWnd, uMsg, wParam, lParam)
+            }
+        }
+    }
+
+    companion object {
+        /**
+         * Installs a [CustomDecorationWindowProc] for the given window.
+         *
+         * @param hwnd The window handle.
+         */
+        fun install(hwnd: WinDef.HWND) = CustomDecorationWindowProc(hwnd)
+    }
+}

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

@@ -8,12 +8,19 @@ import com.mayakapps.compose.windowstyler.windows.jna.enums.DwmSystemBackdrop
 import com.mayakapps.compose.windowstyler.windows.jna.enums.DwmWindowAttribute
 import com.sun.jna.platform.win32.WinDef
 
-internal class WindowsBackdropApis(private val hwnd: WinDef.HWND) {
+internal class WindowsBackdropApis private constructor(private val hwnd: WinDef.HWND) {
     private var isSystemBackdropSet = false
     private var isMicaEnabled = false
     private var isAccentPolicySet = false
     private var isSheetOfGlassApplied = false
 
+    companion object {
+        /**
+         * Instantiate [WindowsBackdropApis] for the given window and install it.
+         */
+        fun install(hwnd: WinDef.HWND) = WindowsBackdropApis(hwnd)
+    }
+
     fun setSystemBackdrop(systemBackdrop: DwmSystemBackdrop) {
         createSheetOfGlassEffect()
         if (Dwm.setSystemBackdrop(hwnd, systemBackdrop)) {

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

@@ -3,7 +3,15 @@ package com.mayakapps.compose.windowstyler.windows
 import androidx.compose.ui.awt.ComposeWindow
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.isSpecified
-import com.mayakapps.compose.windowstyler.*
+import com.mayakapps.compose.windowstyler.ColorableWindowBackdrop
+import com.mayakapps.compose.windowstyler.WindowBackdrop
+import com.mayakapps.compose.windowstyler.WindowCornerPreference
+import com.mayakapps.compose.windowstyler.WindowFrameStyle
+import com.mayakapps.compose.windowstyler.WindowStyleManager
+import com.mayakapps.compose.windowstyler.hackContentPane
+import com.mayakapps.compose.windowstyler.isTransparent
+import com.mayakapps.compose.windowstyler.isUndecorated
+import com.mayakapps.compose.windowstyler.setComposeLayerTransparency
 import com.mayakapps.compose.windowstyler.windows.jna.Dwm
 import com.mayakapps.compose.windowstyler.windows.jna.enums.AccentFlag
 import com.mayakapps.compose.windowstyler.windows.jna.enums.DwmWindowAttribute
@@ -20,16 +28,18 @@ import javax.swing.SwingUtilities
  */
 class WindowsWindowStyleManager(
     window: Window,
-    isDarkTheme: Boolean = false,
-    backdropType: WindowBackdrop = WindowBackdrop.Default,
-    frameStyle: WindowFrameStyle = WindowFrameStyle(),
+    isDarkTheme: Boolean,
+    backdropType: WindowBackdrop,
+    frameStyle: WindowFrameStyle,
+    manageTitlebar: Boolean,
 ) : WindowStyleManager {
 
     private val hwnd: HWND = window.hwnd
     private val isUndecorated = window.isUndecorated
     private var wasAero = false
 
-    private val backdropApis = WindowsBackdropApis(hwnd)
+    private val backdropApis = WindowsBackdropApis.install(hwnd)
+    private val customDecorationWindowProc = if (manageTitlebar) CustomDecorationWindowProc.install(hwnd) else null
 
     override var isDarkTheme: Boolean = isDarkTheme
         set(value) {
@@ -59,6 +69,17 @@ class WindowsWindowStyleManager(
             }
         }
 
+    override var manageTitlebar: Boolean = manageTitlebar
+        get() = field
+        set(value) {
+            field = if (value) {
+                true
+            } else {
+                // TODO: reset the window proc to the default one
+                false
+            }
+        }
+
     init {
         // invokeLater is called to make sure that ComposeLayer was initialized first
         SwingUtilities.invokeLater {
@@ -193,6 +214,7 @@ class WindowsWindowStyleManager(
                 if (this is ThemedAcrylic) themedTransparent
                 else WindowBackdrop.Transparent(color)
             }
+
             else -> WindowBackdrop.Default
         }.fallbackIfUnsupported()
     }

window-styler/src/jvmMain/kotlin/com/mayakapps/compose/windowstyler/windows/jna/Dwm.kt

@@ -9,14 +9,17 @@ import com.sun.jna.PointerType
 import com.sun.jna.platform.win32.W32Errors
 import com.sun.jna.platform.win32.WinDef
 import com.sun.jna.platform.win32.WinDef.HWND
+import com.sun.jna.platform.win32.WinDef.LPARAM
+import com.sun.jna.platform.win32.WinDef.LRESULT
+import com.sun.jna.platform.win32.WinDef.WPARAM
 import com.sun.jna.platform.win32.WinNT.HRESULT
 import com.sun.jna.ptr.IntByReference
 import com.sun.jna.win32.StdCallLibrary
 import com.sun.jna.win32.W32APIOptions
 
 internal object Dwm {
-    fun extendFrameIntoClientArea(hwnd: HWND, margin: Int = 0) =
-        extendFrameIntoClientArea(hwnd, margin, margin, margin, margin)
+    fun extendFrameIntoClientArea(hwnd: HWND, allMargins: Int = 0) =
+        extendFrameIntoClientArea(hwnd, allMargins, allMargins, allMargins, allMargins)
 
     fun extendFrameIntoClientArea(
         hwnd: HWND,
@@ -47,6 +50,11 @@ internal object Dwm {
     fun setWindowAttribute(hwnd: HWND, attribute: DwmWindowAttribute, value: Int) =
         setWindowAttribute(hwnd, attribute, IntByReference(value), INT_SIZE)
 
+    fun callDefaultWindowHitProc(hwnd: HWND, msg: Int, wParam: WPARAM, lParam: LPARAM): Boolean {
+        val dwmDefWindowProc = DwmImpl.DwmDefWindowProc(hwnd, msg, wParam, lParam)
+        return dwmDefWindowProc != LRESULT(0)
+    }
+
     private fun setWindowAttribute(
         hwnd: HWND,
         attribute: DwmWindowAttribute,
@@ -67,4 +75,5 @@ private object DwmImpl : DwmApi by Native.load("dwmapi", DwmApi::class.java, W32
 private interface DwmApi : StdCallLibrary {
     fun DwmExtendFrameIntoClientArea(hwnd: HWND, margins: Margins): HRESULT
     fun DwmSetWindowAttribute(hwnd: HWND, attribute: Int, value: PointerType?, valueSize: Int): HRESULT
+    fun DwmDefWindowProc(hwnd: HWND, msg: Int, wParam: WPARAM, lParam: LPARAM): LRESULT
 }