Fix Ctrl+key combos inserting characters in text fields on Wayland

On native Wayland, GLFW fires a separate char event after the "main" key
event, leading to quirky behaviour (eg. with `Ctrl+a`). This new mixin
fixes it by cancelling the secondary key event if the Ctrl modifier is
set.

Author: Tmpod

src/main/java/net/vulkanmod/mixin/wayland/KeyboardHandlerM.java

@@ -0,0 +1,31 @@
+package net.vulkanmod.mixin.wayland;
+
+import net.minecraft.client.KeyboardHandler;
+import net.minecraft.client.input.CharacterEvent;
+import net.vulkanmod.config.Platform;
+import org.lwjgl.glfw.GLFW;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+@Mixin(KeyboardHandler.class)
+public class KeyboardHandlerM {
+
+    /**
+     * Ensures Ctrl-based shortcuts work correctly.
+     *
+     * On native Wayland (i.e. not XWayland), GLFW fires both a key event and a char callback event
+     * when a Ctrl+key combination is pressed, because the compositor delivers the unmodified
+     * character as a separate char event regardless of held modifiers. This causes both the
+     * shortcut action and a character insertion to happen simultaneously (e.g. Ctrl+v pastes and appends 'v').
+     *
+     * This mixin cancels that char event if the Ctrl modifier is set, thus fixing the issue.
+     */
+    @Inject(method = "charTyped", at = @At("HEAD"), cancellable = true)
+    private void cancelCtrlCharTyped(long window, CharacterEvent event, CallbackInfo ci) {
+        if (Platform.isWayLand() && (event.modifiers() & GLFW.GLFW_MOD_CONTROL) != 0) {
+            ci.cancel();
+        }
+    }
+}

src/main/resources/vulkanmod.mixins.json

@@ -98,6 +98,7 @@
     "vertex.VertexMultiConsumersM$SheetDecalM",
 
     "wayland.InputConstantsM",
+    "wayland.KeyboardHandlerM",
     "wayland.MinecraftMixin",
 
     "texture.mip.MipmapGeneratorM",