feat: add kernel clipboard manager

Adds a global kernel clipboard with write/read/len syscalls (IDs 54-56).
Exposes sys_clipboard_write/read/len() in userland libc and ui_clipboard_set/get()
in libui. Includes cliptest app for runtime verification (PASS confirmed in QEMU).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/sys/syscall.c

@@ -27,6 +27,7 @@
 #include "app_metadata.h"
 #include "disk.h"
 #include "mkfs_fat32.h"
+#include "spinlock.h"
 
 #define SYSTEM_CMD_DISK_GET_COUNT  100
 #define SYSTEM_CMD_DISK_GET_INFO   101
@@ -2207,6 +2208,39 @@ static uint64_t sys_cmd_get_keyboard_layout(const syscall_args_t *args) {
     return (uint64_t)keymap_get_current();
 }
 
+#define CLIPBOARD_MAX_SIZE 4096
+static char g_clipboard[CLIPBOARD_MAX_SIZE];
+static int  g_clipboard_len = 0;
+static spinlock_t g_clipboard_lock = SPINLOCK_INIT;
+
+static uint64_t sys_cmd_clipboard_write(const syscall_args_t *args) {
+    const char *buf = (const char *)args->arg2;
+    int len = (int)args->arg3;
+    if (!buf || len <= 0) return 0;
+    if (len > CLIPBOARD_MAX_SIZE) len = CLIPBOARD_MAX_SIZE;
+    uint64_t flags = spinlock_acquire_irqsave(&g_clipboard_lock);
+    for (int i = 0; i < len; i++) g_clipboard[i] = buf[i];
+    g_clipboard_len = len;
+    spinlock_release_irqrestore(&g_clipboard_lock, flags);
+    return (uint64_t)len;
+}
+
+static uint64_t sys_cmd_clipboard_read(const syscall_args_t *args) {
+    char *buf = (char *)args->arg2;
+    int max_len = (int)args->arg3;
+    if (!buf || max_len <= 0) return 0;
+    uint64_t flags = spinlock_acquire_irqsave(&g_clipboard_lock);
+    int n = g_clipboard_len < max_len ? g_clipboard_len : max_len;
+    for (int i = 0; i < n; i++) buf[i] = g_clipboard[i];
+    spinlock_release_irqrestore(&g_clipboard_lock, flags);
+    return (uint64_t)n;
+}
+
+static uint64_t sys_cmd_clipboard_len(const syscall_args_t *args) {
+    (void)args;
+    return (uint64_t)g_clipboard_len;
+}
+
 typedef struct {
     char     devname[16];
     char     label[32];
@@ -2484,6 +2518,9 @@ static const syscall_handler_fn sys_cmd_table[SYS_CMD_TABLE_SIZE] = {
     [SYSTEM_CMD_PARALLEL_RUN]        = sys_cmd_parallel_run,
     [SYSTEM_CMD_SET_KEYBOARD_LAYOUT] = sys_cmd_set_keyboard_layout,
     [SYSTEM_CMD_GET_KEYBOARD_LAYOUT] = sys_cmd_get_keyboard_layout,
+    [SYSTEM_CMD_CLIPBOARD_WRITE]     = sys_cmd_clipboard_write,
+    [SYSTEM_CMD_CLIPBOARD_READ]      = sys_cmd_clipboard_read,
+    [SYSTEM_CMD_CLIPBOARD_LEN]       = sys_cmd_clipboard_len,
     [SYSTEM_CMD_SET_MOUSE_CURSOR_SCALE] = sys_cmd_set_mouse_cursor_scale,
     [SYSTEM_CMD_GET_MOUSE_CURSOR_SCALE] = sys_cmd_get_mouse_cursor_scale,
     [SYSTEM_CMD_TTY_CREATE]          = sys_cmd_tty_create,

src/sys/syscall.h

@@ -127,6 +127,10 @@ typedef struct {
 #define SYSTEM_CMD_GET_ELF_METADATA 76
 #define SYSTEM_CMD_GET_ELF_PRIMARY_IMAGE 77
 
+#define SYSTEM_CMD_CLIPBOARD_WRITE  54
+#define SYSTEM_CMD_CLIPBOARD_READ   55
+#define SYSTEM_CMD_CLIPBOARD_LEN    56
+
 void syscall_init(void);
 uint64_t syscall_handler_c(registers_t *regs);
 

src/userland/gui/cliptest.c

@@ -0,0 +1,61 @@
+// Copyright (c) 2026 BoredOS Contributors
+// This software is released under the GNU General Public License v3.0. See LICENSE file for details.
+// This header needs to maintain in any file it is present in, as per the GPL license terms.
+// BOREDOS_APP_DESC: Clipboard integration test.
+// BOREDOS_APP_ICONS: /Library/images/icons/colloid/copyq.png
+#include "libc/syscall.h"
+#include "libc/libui.h"
+#include "libc/string.h"
+#include <stdbool.h>
+#include <stdint.h>
+
+#define WIN_W 400
+#define WIN_H 200
+#define BG    0xFF1E1E2E
+#define WHITE 0xFFCDD6F4
+#define GREEN 0xFFA6E3A1
+#define RED   0xFFF38BA8
+#define GREY  0xFF45475A
+
+static void draw(ui_window_t win, const char *written, const char *read_back, bool match) {
+    ui_draw_rect(win, 0, 0, WIN_W, WIN_H, BG);
+
+    ui_draw_string(win, 10, 20, "Clipboard Test", WHITE);
+
+    ui_draw_string(win, 10, 60, "Written:", GREY);
+    ui_draw_string(win, 90, 60, written, WHITE);
+
+    ui_draw_string(win, 10, 90, "Read back:", GREY);
+    ui_draw_string(win, 90, 90, read_back, WHITE);
+
+    ui_draw_string(win, 10, 130, "Result:", GREY);
+    if (match)
+        ui_draw_string(win, 90, 130, "PASS - write/read match", GREEN);
+    else
+        ui_draw_string(win, 90, 130, "FAIL - mismatch!", RED);
+
+    ui_mark_dirty(win, 0, 0, WIN_W, WIN_H);
+}
+
+int main(void) {
+    const char *test_str = "Hello, Clipboard!";
+    char read_buf[64] = {0};
+
+    ui_clipboard_set(test_str);
+    int n = ui_clipboard_get(read_buf, sizeof(read_buf));
+
+    bool match = (n > 0) && (strcmp(test_str, read_buf) == 0);
+
+    ui_window_t win = ui_window_create("Clipboard Test", 100, 100, WIN_W, WIN_H);
+
+    draw(win, test_str, read_buf, match);
+
+    gui_event_t ev;
+    while (1) {
+        if (!ui_get_event(win, &ev)) { sys_yield(); continue; }
+        if (ev.type == GUI_EVENT_CLOSE) break;
+        if (ev.type == GUI_EVENT_PAINT) draw(win, test_str, read_buf, match);
+    }
+
+    return 0;
+}

src/userland/libc/libui.c

@@ -102,3 +102,15 @@ void ui_window_set_resizable(ui_window_t win, bool resizable) {
 void ui_set_font(ui_window_t win, const char *path) {
     syscall3(SYS_GUI, GUI_CMD_SET_FONT, (uint64_t)win, (uint64_t)path);
 }
+
+void ui_clipboard_set(const char *text) {
+    if (!text) return;
+    int len = 0;
+    while (text[len]) len++;
+    sys_clipboard_write(text, len + 1);
+}
+
+int ui_clipboard_get(char *buf, int max_len) {
+    if (!buf || max_len <= 0) return 0;
+    return sys_clipboard_read(buf, max_len);
+}

src/userland/libc/libui.h

@@ -75,4 +75,8 @@ void ui_window_set_title(ui_window_t win, const char *title);
 void ui_window_set_resizable(ui_window_t win, bool resizable);
 void ui_set_font(ui_window_t win, const char *path);
 
+// Clipboard API — text only, null-terminated strings
+void ui_clipboard_set(const char *text);
+int  ui_clipboard_get(char *buf, int max_len);
+
 #endif

src/userland/libc/syscall.c

@@ -89,6 +89,18 @@ int sys_system(int cmd, uint64_t arg1, uint64_t arg2, uint64_t arg3, uint64_t ar
     return (int)syscall5(SYS_SYSTEM, (uint64_t)cmd, arg1, arg2, arg3, arg4);
 }
 
+int sys_clipboard_write(const char *buf, int len) {
+    return sys_system(SYSTEM_CMD_CLIPBOARD_WRITE, (uint64_t)buf, (uint64_t)len, 0, 0);
+}
+
+int sys_clipboard_read(char *buf, int max_len) {
+    return sys_system(SYSTEM_CMD_CLIPBOARD_READ, (uint64_t)buf, (uint64_t)max_len, 0, 0);
+}
+
+int sys_clipboard_len(void) {
+    return sys_system(SYSTEM_CMD_CLIPBOARD_LEN, 0, 0, 0, 0);
+}
+
 int sys_open(const char *path, const char *mode) {
     return (int)syscall3(SYS_FS, FS_CMD_OPEN, (uint64_t)path, (uint64_t)mode);
 }

src/userland/libc/syscall.h

@@ -108,6 +108,10 @@
 #define SYSTEM_CMD_GET_ELF_METADATA 76
 #define SYSTEM_CMD_GET_ELF_PRIMARY_IMAGE 77
 
+#define SYSTEM_CMD_CLIPBOARD_WRITE  54
+#define SYSTEM_CMD_CLIPBOARD_READ   55
+#define SYSTEM_CMD_CLIPBOARD_LEN    56
+
 #define SPAWN_FLAG_TERMINAL 0x1
 #define SPAWN_FLAG_INHERIT_TTY 0x2
 #define SPAWN_FLAG_TTY_ID 0x4
@@ -309,4 +313,9 @@ int sys_disk_sync(const char *mountpoint);
 int sys_disk_rescan(const char *devname);
 int sys_disk_replace_kernel(const char *src_path, const char *esp_mountpoint);
 
+// Clipboard API
+int sys_clipboard_write(const char *buf, int len);
+int sys_clipboard_read(char *buf, int max_len);
+int sys_clipboard_len(void);
+
 #endif