On desktop, replace Gdx clipboard with a proxy using AWT (#11857)

desktop/src/com/unciv/app/desktop/AwtClipboard.kt

@@ -0,0 +1,42 @@
+package com.unciv.app.desktop
+
+import java.awt.Toolkit
+import java.awt.datatransfer.DataFlavor
+import java.awt.datatransfer.StringSelection
+import java.awt.datatransfer.Clipboard as ClipboardAwt
+import com.badlogic.gdx.utils.Clipboard as ClipboardGdx
+
+/**
+ *  A plug-in replacement for Gdx Lwjgl3Clipboard that goes through AWT instead of GLFW and removes the stack size limitation.
+ *
+ *  Gdx.app.clipboard on desktop is a Lwjgl3Clipboard instance, which allocates a buffer on the stack for UTF8 conversion at the Lwjgl3-GLFW interface.
+ *  The default stack size is a severe limitation, which we **originally** treated by increasing the limit, which can only be done statically at launch time:
+```
+         // 386 is an almost-arbitrary choice from the saves I had at the moment and their GZipped size.
+         // There must be a reason for lwjgl3 being so stingy, which for me meant to stay conservative.
+         System.setProperty("org.lwjgl.system.stackSize", "384")
+```
+ *  - See [setContents](https://github.com/libgdx/libgdx/blob/master/backends/gdx-backend-lwjgl3/src/com/badlogic/gdx/backends/lwjgl3/Lwjgl3Clipboard.java#L40)
+ *  - See [glfwSetClipboardString](https://github.com/LWJGL/lwjgl3/blob/master/modules/lwjgl/glfw/src/generated/java/org/lwjgl/glfw/GLFW.java#L5068-L5077)
+ *  - See [Higher available clipboard size](https://github.com/orgs/LWJGL/discussions/769)
+ */
+class AwtClipboard : ClipboardGdx {
+    // A lazy seems to work too, but not keeping a reference when not active is safer (also debuggable while a lazy is not):
+    private val clipboard: ClipboardAwt
+        get() = Toolkit.getDefaultToolkit().systemClipboard
+
+    override fun hasContents(): Boolean {
+        return DataFlavor.stringFlavor in clipboard.availableDataFlavors
+    }
+
+    override fun getContents(): String? {
+        val transferable = clipboard.getContents(null)
+        if (!transferable.isDataFlavorSupported(DataFlavor.stringFlavor)) return null
+        return transferable.getTransferData(DataFlavor.stringFlavor) as String
+    }
+
+    override fun setContents(content: String?) {
+        val selection = StringSelection(content)  // Yes this supports null
+        clipboard.setContents(selection, selection)
+    }
+}

desktop/src/com/unciv/app/desktop/DesktopLauncher.kt

@@ -36,10 +36,6 @@ internal object DesktopLauncher {
         // Solves a rendering problem in specific GPUs and drivers.
         // For more info see https://github.com/yairm210/Unciv/pull/3202 and https://github.com/LWJGL/lwjgl/issues/119
         System.setProperty("org.lwjgl.opengl.Display.allowSoftwareOpenGL", "true")
-        // This setting (default 64) limits clipboard transfers. Value in kB!
-        // 386 is an almost-arbitrary choice from the saves I had at the moment and their GZipped size.
-        // There must be a reason for lwjgl3 being so stingy, which for me meant to stay conservative.
-        System.setProperty("org.lwjgl.system.stackSize", "384")
 
         val isRunFromJAR = DesktopLauncher.javaClass.`package`.specificationVersion != null
         ImagePacker.packImages(isRunFromJAR)

desktop/src/com/unciv/app/desktop/HardenGdxAudio.kt

@@ -6,10 +6,18 @@ import com.badlogic.gdx.backends.lwjgl3.Lwjgl3ApplicationConfiguration
 import com.badlogic.gdx.backends.lwjgl3.audio.OpenALLwjgl3Audio
 import com.badlogic.gdx.backends.lwjgl3.audio.OpenALMusic
 import com.badlogic.gdx.utils.Array
+import com.badlogic.gdx.utils.Clipboard
 import com.unciv.ui.audio.MusicController
 
 /**
- *  Problem: Not all exceptions playing Music can be caught on the desktop platform using a try-catch around the play method.
+ *  ### Notes
+ *  - Since this is the one replacement wrapping Lwjgl3Application that will be running Unciv-desktop, and we want to replace Gdx.app.clipboard,
+ *    the hook for [AwtClipboard] is implemented here as [getClipboard] override.
+ *  - ***This class is never properly initialized before use!*** (because the super constructor runs until the game is quit.)
+ *    Therefore, fields must be initialized on-demand or from upstream UncivGame
+ *
+ *  ### Problem
+ *  Not all exceptions playing Music can be caught on the desktop platform using a try-catch around the play method.
  *  Unciv 3.17.13 to 4.0.5 all exacerbated the problem due to using Music from various threads - and Gdx documents it isn't threadsafe.
  *  But even with that fixed, music streams can have codec failures _after_ the first buffer's worth of data, so the problem is only mitigated.
  *
@@ -18,7 +26,7 @@ import com.unciv.ui.audio.MusicController
  *
  *  This catches those Exceptions and reports them through a callback mechanism, and also provides a callback from the app loop
  *  that allows MusicController to make its Music calls on a thread guaranteed to be safe for OpenALMusic.
- * #
+ *
  *  ### Approach:
  *  - Subclass [OpenALLwjgl3Audio] overriding [update][OpenALLwjgl3Audio.update] with equivalent code catching any Exceptions and Errors
  *  - Get the framework to use the subclassed Audio by overriding Lwjgl3ApplicationBase.createAudio
@@ -46,6 +54,7 @@ class HardenGdxAudio(
 ) : Lwjgl3Application(game, config) {
     private var updateCallback: (()->Unit)? = null
     private var exceptionHandler: ((Throwable, Music)->Unit)? = null
+    private lateinit var awtClipboard: AwtClipboard  // normal initialization won't run, including initializing lazy delegates!
 
     /** Hooks part 1
      *
@@ -69,6 +78,12 @@ class HardenGdxAudio(
         this.exceptionHandler = exceptionHandler
     }
 
+    /** This redirects `Gdx.app.clipboard` on desktop to our [AwtClipboard] replacement */
+    override fun getClipboard(): Clipboard {
+        if (!::awtClipboard.isInitialized) awtClipboard = AwtClipboard()
+        return awtClipboard
+    }
+
     /**
      *  Desktop implementation of the [Audio][com.badlogic.gdx.Audio] interface that
      *  unlike its superclass catches exceptions and allows passing them into application code for handling.