feat: display status message on failed operations in Files app

kernel/src/Api/BuildNo.hpp

@@ -12,4 +12,4 @@
 
 #pragma once
 
-#define MONTAUK_BUILD_NUMBER 264
+#define MONTAUK_BUILD_NUMBER 265

programs/include/montauk/statuscodes.h

@@ -62,7 +62,7 @@ inline const char* GetStatusExplanationText(StatusCodes statusCode) {
         nullptr, // 1
         nullptr, // 2
         nullptr, // 3
-        "The path is protected by the system and can't be modified.", // 4
+        "The path is protected by the system and cannot be modified.", // 4
         nullptr, // 5
         nullptr, // 6
         nullptr, // 7

programs/src/desktop/apps/filemanager/actions.cpp

@@ -73,18 +73,28 @@ void filemanager_finish_rename(FileManagerState* fm) {
     filemanager_build_fullpath(new_path, 512,
                                fm->current_path, fm->rename_buf);
 
-    if (montauk::frename(old_path, new_path) != 0) {
+    montauk::StatusCodes status =
+        filemanager_status_from_result(montauk::frename(old_path, new_path));
+    if (status != montauk::Success && !filemanager_status_is_access_denied(status)) {
         // Fall back to copy + delete for drivers that don't support rename
         if (fm->is_dir[fm->rename_idx]) {
-            if (filemanager_copy_dir_recursive(old_path, new_path))
-                filemanager_delete_recursive(old_path);
+            status = filemanager_copy_dir_recursive(old_path, new_path);
+            if (status == montauk::Success)
+                status = filemanager_delete_recursive(old_path);
         } else {
-            if (filemanager_copy_file(old_path, new_path))
-                montauk::fdelete(old_path);
+            status = filemanager_copy_file(old_path, new_path);
+            if (status == montauk::Success)
+                status = filemanager_status_from_result(montauk::fdelete(old_path));
         }
     }
 
     filemanager_read_dir(fm);
+
+    if (status != montauk::Success) {
+        char heading[192];
+        snprintf(heading, sizeof(heading), "Couldn't rename \"%s\"", path_basename(old_path));
+        filemanager_show_error(fm->desktop, fm, heading, old_path, status);
+    }
 }
 
 void filemanager_cancel_rename(FileManagerState* fm) {
@@ -98,18 +108,25 @@ void filemanager_new_folder(FileManagerState* fm) {
     char name[64] = "New Folder";
     char path[512];
     filemanager_build_fullpath(path, 512, fm->current_path, name);
-    int attempt = 1;
-    // Try creating; if it fails, append a number
-    if (montauk::fmkdir(path) != 0) {
-        for (attempt = 2; attempt <= 99; attempt++) {
-            snprintf(name, 64, "New Folder %d", attempt);
-            filemanager_build_fullpath(path, 512, fm->current_path, name);
-            if (montauk::fmkdir(path) == 0) break;
-        }
+    // Try creating; if it fails (most likely the name is taken), append a
+    // number. An access error fails the same way for every name, so stop.
+    montauk::StatusCodes status = filemanager_status_from_result(montauk::fmkdir(path));
+    for (int attempt = 2; status != montauk::Success &&
+                          !filemanager_status_is_access_denied(status) &&
+                          attempt <= 99; attempt++) {
+        snprintf(name, 64, "New Folder %d", attempt);
+        filemanager_build_fullpath(path, 512, fm->current_path, name);
+        status = filemanager_status_from_result(montauk::fmkdir(path));
     }
 
     filemanager_read_dir(fm);
 
+    if (status != montauk::Success) {
+        filemanager_show_error(fm->desktop, fm, "Couldn't create a new folder",
+                               fm->current_path, status);
+        return;
+    }
+
     // Select the new folder and start rename
     for (int i = 0; i < fm->entry_count; i++) {
         if (montauk::streq(fm->entry_names[i], name)) {
@@ -182,9 +199,15 @@ void filemanager_delete_selected(FileManagerState* fm) {
     }
 
     montauk::mfree(filtered);
-    montauk::fdelete(fullpath);
+    montauk::StatusCodes status = filemanager_status_from_result(montauk::fdelete(fullpath));
     filemanager_clear_multi_selection(fm);
     filemanager_read_dir(fm);
+
+    if (status != montauk::Success) {
+        char heading[192];
+        snprintf(heading, sizeof(heading), "Couldn't delete \"%s\"", path_basename(fullpath));
+        filemanager_show_error(fm->desktop, fm, heading, fullpath, status);
+    }
 }
 
 void filemanager_open_ctx_menu(FileManagerState* fm, int local_x, int local_y, int target_idx) {

programs/src/desktop/apps/filemanager/filemanager_internal.hpp

@@ -8,6 +8,7 @@
 
 #include "../apps_common.hpp"
 #include <gui/mtk/widgets.hpp>
+#include <montauk/statuscodes.h>
 
 namespace filemanager {
 
@@ -230,9 +231,27 @@ void filemanager_read_virtual_view(FileManagerState* fm, FileManagerVirtualViewK
 void filemanager_read_apps(FileManagerState* fm);
 void filemanager_read_system_configuration(FileManagerState* fm);
 
-bool filemanager_delete_recursive(const char* path);
-bool filemanager_copy_file(const char* src, const char* dst);
-bool filemanager_copy_dir_recursive(const char* src, const char* dst);
+// Map a raw syscall result (kernel StatusCodes are negative) to a userspace
+// montauk::StatusCodes. Non-negative results (handles, counts) are Success.
+inline montauk::StatusCodes filemanager_status_from_result(int rc) {
+    if (rc >= 0) return montauk::Success;
+    int code = -rc;
+    if (code > montauk::OutOfMemory) return montauk::GenericFailure;
+    return (montauk::StatusCodes)code;
+}
+
+// The path itself may not be modified. Falling back to copy + delete after a
+// failed rename cannot help here and would leave a duplicate behind.
+inline bool filemanager_status_is_access_denied(montauk::StatusCodes status) {
+    return status == montauk::SystemIntegrityError ||
+           status == montauk::PermissionDenied ||
+           status == montauk::CapabilityDenied;
+}
+
+// These return the first failure encountered (Success when everything worked).
+montauk::StatusCodes filemanager_delete_recursive(const char* path);
+montauk::StatusCodes filemanager_copy_file(const char* src, const char* dst);
+montauk::StatusCodes filemanager_copy_dir_recursive(const char* src, const char* dst);
 
 void filemanager_do_copy(FileManagerState* fm);
 void filemanager_do_cut(FileManagerState* fm);
@@ -254,6 +273,13 @@ void filemanager_show_multi_properties(FileManagerState* fm,
 void filemanager_show_directory_delete_confirmation(FileManagerState* fm, int target_idx);
 void filemanager_show_bulk_delete_confirmation(FileManagerState* fm,
                                                const int* indices, int count);
+// Graphical error popup for a failed file operation. `heading` says what
+// failed, `path` (optional) names the item, and a non-Success `status` adds
+// montauk::GetStatusExplanationText() as the cause. `owner_app_data` is only
+// used to center the popup and may be null or stale.
+void filemanager_show_error(DesktopState* ds, const void* owner_app_data,
+                            const char* heading, const char* path,
+                            montauk::StatusCodes status);
 
 void filemanager_push_history(FileManagerState* fm);
 void filemanager_navigate(FileManagerState* fm, const char* name);

programs/src/desktop/apps/filemanager/fileop.cpp

@@ -33,6 +33,12 @@ struct FileOpJob {
     volatile int finished;    // worker -> UI
     volatile char current[128]; // basename of the item in progress (worker writes)
 
+    // Failures, written by the worker and read on the UI thread only after
+    // the worker has finished (joined), so they need no synchronization.
+    int  failed_count;
+    montauk::StatusCodes first_error;
+    char first_error_path[256];
+
     int tid;
     int last_drawn_done;      // dialog redraw tracking
     int mouse_x, mouse_y;
@@ -65,6 +71,42 @@ static bool fileop_path_is_dir(const char* path) {
     return montauk::readdir(path, probe, 1) >= 0;
 }
 
+static const char* fileop_error_verb(int kind) {
+    switch (kind) {
+    case FILE_OP_COPY:   return "copy";
+    case FILE_OP_MOVE:   return "move";
+    case FILE_OP_DELETE: return "delete";
+    default:             return "process";
+    }
+}
+
+static void fileop_record_status(FileOpJob* job, const char* path,
+                                 montauk::StatusCodes status) {
+    if (status == montauk::Success) return;
+    if (job->failed_count++ == 0) {
+        job->first_error = status;
+        montauk::strncpy(job->first_error_path, path, sizeof(job->first_error_path) - 1);
+        job->first_error_path[sizeof(job->first_error_path) - 1] = '\0';
+    }
+}
+
+// Show an error popup for a finished job that had failures. UI thread only,
+// after the worker has been joined.
+static void fileop_report_errors(FileOpJob* job) {
+    if (!job || job->failed_count <= 0) return;
+
+    char heading[192];
+    if (job->failed_count == 1) {
+        snprintf(heading, sizeof(heading), "Couldn't %s \"%s\"",
+                 fileop_error_verb(job->kind), path_basename(job->first_error_path));
+    } else {
+        snprintf(heading, sizeof(heading), "Couldn't %s %d of %d items",
+                 fileop_error_verb(job->kind), job->failed_count, job->count);
+    }
+    filemanager_show_error(job->desktop, job->owner, heading,
+                           job->first_error_path, job->first_error);
+}
+
 // ============================================================================
 // Worker thread
 // ============================================================================
@@ -78,7 +120,7 @@ static int fileop_worker(void* arg) {
         fileop_set_current(job, base);
 
         if (job->kind == FILE_OP_DELETE) {
-            filemanager_delete_recursive(src);
+            fileop_record_status(job, src, filemanager_delete_recursive(src));
             job->files_done = i + 1;
             continue;
         }
@@ -90,24 +132,31 @@ static int fileop_worker(void* arg) {
 
         bool is_dir = fileop_path_is_dir(src);
         if (is_dir && fileop_path_same_or_descendant(dst, src)) {
+            // Refuse to copy a directory into itself.
+            fileop_record_status(job, src, montauk::InvalidArgument);
             job->files_done = i + 1;
-            continue; // refuse to copy a directory into itself
+            continue;
         }
 
+        montauk::StatusCodes status;
         if (job->kind == FILE_OP_MOVE) {
             // Try a rename first: an instant same-volume move with no copying.
-            if (montauk::frename(src, dst) == 0) { job->files_done = i + 1; continue; }
-            // Cross-volume (or driver without rename): fall back to copy + delete.
-            bool ok = is_dir ? filemanager_copy_dir_recursive(src, dst)
-                             : filemanager_copy_file(src, dst);
-            if (ok) {
-                if (is_dir) filemanager_delete_recursive(src);
-                else        montauk::fdelete(src);
+            status = filemanager_status_from_result(montauk::frename(src, dst));
+            if (status != montauk::Success && !filemanager_status_is_access_denied(status)) {
+                // Cross-volume (or driver without rename): fall back to copy + delete.
+                status = is_dir ? filemanager_copy_dir_recursive(src, dst)
+                                : filemanager_copy_file(src, dst);
+                if (status == montauk::Success) {
+                    status = is_dir
+                        ? filemanager_delete_recursive(src)
+                        : filemanager_status_from_result(montauk::fdelete(src));
+                }
             }
         } else { // FILE_OP_COPY
-            if (is_dir) filemanager_copy_dir_recursive(src, dst);
-            else        filemanager_copy_file(src, dst);
+            status = is_dir ? filemanager_copy_dir_recursive(src, dst)
+                            : filemanager_copy_file(src, dst);
         }
+        fileop_record_status(job, src, status);
         job->files_done = i + 1;
     }
 
@@ -278,6 +327,10 @@ static void fileop_dialog_on_close(Window* win) {
         filemanager_read_dir(owner);
     }
 
+    // Opening the popup here is safe: desktop_close_window() only shifts the
+    // window array after on_close returns, and the new window moves with it.
+    fileop_report_errors(job);
+
     if (job->paths) montauk::mfree(job->paths);
     montauk::mfree(job);
     win->app_data = nullptr;
@@ -332,6 +385,7 @@ static bool fileop_launch(FileOpJob* job) {
             filemanager_clear_multi_selection(owner);
             filemanager_read_dir(owner);
         }
+        fileop_report_errors(job);
         if (job->paths) montauk::mfree(job->paths);
         montauk::mfree(job);
         return true;
@@ -348,6 +402,7 @@ static bool fileop_launch(FileOpJob* job) {
             filemanager_clear_multi_selection(owner);
             filemanager_read_dir(owner);
         }
+        fileop_report_errors(job);
         if (job->paths) montauk::mfree(job->paths);
         montauk::mfree(job);
         return true;
@@ -389,17 +444,30 @@ bool filemanager_start_paste_job(FileManagerState* fm) {
         if (sz <= FILEOP_INLINE_MAX_BYTES) {
             char dst[512];
             filemanager_build_fullpath(dst, 512, fm->current_path, path_basename(src));
+            montauk::StatusCodes status = montauk::Success;
             if (!montauk::streq(dst, src)) {
                 if (is_cut) {
-                    if (montauk::frename(src, dst) != 0) {
-                        if (filemanager_copy_file(src, dst)) montauk::fdelete(src);
+                    status = filemanager_status_from_result(montauk::frename(src, dst));
+                    if (status != montauk::Success &&
+                        !filemanager_status_is_access_denied(status)) {
+                        status = filemanager_copy_file(src, dst);
+                        if (status == montauk::Success)
+                            status = filemanager_status_from_result(montauk::fdelete(src));
                     }
                 } else {
-                    filemanager_copy_file(src, dst);
+                    status = filemanager_copy_file(src, dst);
                 }
             }
             if (is_cut) fm->clipboard_count = 0;
             filemanager_read_dir(fm);
+
+            if (status != montauk::Success) {
+                char heading[192];
+                snprintf(heading, sizeof(heading), "Couldn't %s \"%s\"",
+                         fileop_error_verb(is_cut ? FILE_OP_MOVE : FILE_OP_COPY),
+                         path_basename(src));
+                filemanager_show_error(fm->desktop, fm, heading, src, status);
+            }
             return true;
         }
     }

programs/src/desktop/apps/filemanager/filesystem.cpp

@@ -427,7 +427,8 @@ void filemanager_read_system_configuration(FileManagerState* fm) {
 // (each up to 255 chars, directory entries keep their trailing '/'). Pages the
 // directory fully so there is no fixed entry cap. Returns the child count and
 // stores the malloc'd buffer in *out (caller frees with montauk::mfree); the
-// buffer is null when the count is 0. Returns -1 if the path is not readable.
+// buffer is null when the count is 0. Returns the (negative) readdir status if
+// the path is not readable.
 static int filemanager_read_all_children(const char* dir, char (**out)[256]) {
     *out = nullptr;
 
@@ -459,7 +460,7 @@ static int filemanager_read_all_children(const char* dir, char (**out)[256]) {
 
     for (;;) {
         int got = montauk::readdir_at(dir, names, BATCH, count);
-        if (got < 0) { if (!any) return -1; break; }
+        if (got < 0) { if (!any) return got; break; }
         any = true;
         if (got == 0) break;
 
@@ -494,17 +495,19 @@ static int filemanager_read_all_children(const char* dir, char (**out)[256]) {
     return count;
 }
 
-bool filemanager_delete_recursive(const char* path) {
+montauk::StatusCodes filemanager_delete_recursive(const char* path) {
     // Try deleting as a file (or empty directory) first
-    if (montauk::fdelete(path) == 0) return true;
+    montauk::StatusCodes status = filemanager_status_from_result(montauk::fdelete(path));
+    if (status == montauk::Success) return status;
 
     // If that failed, it may be a non-empty directory -- snapshot all children
     // first (the directory shrinks as we delete, so we cannot page while
     // deleting), then delete each.
     char (*children)[256] = nullptr;
     int count = filemanager_read_all_children(path, &children);
-    if (count < 0) return false;
+    if (count < 0) return status;
 
+    montauk::StatusCodes child_status = montauk::Success;
     for (int i = 0; i < count; i++) {
         char child[512];
         montauk::strcpy(child, path);
@@ -517,30 +520,35 @@ bool filemanager_delete_recursive(const char* path) {
         int clen = montauk::slen(child);
         if (clen > 0 && child[clen - 1] == '/') child[clen - 1] = '\0';
 
-        filemanager_delete_recursive(child);
+        montauk::StatusCodes s = filemanager_delete_recursive(child);
+        if (s != montauk::Success && child_status == montauk::Success) child_status = s;
     }
 
     if (children) montauk::mfree(children);
 
     // Now the directory should be empty -- delete it
-    return montauk::fdelete(path) == 0;
+    status = filemanager_status_from_result(montauk::fdelete(path));
+    // A child that could not be deleted keeps the directory non-empty; its
+    // status explains the failure better than the directory's own.
+    if (status != montauk::Success && child_status != montauk::Success) return child_status;
+    return status;
 }
 
-bool filemanager_copy_file(const char* src, const char* dst) {
-    if (!src || !dst || montauk::streq(src, dst)) return false;
+montauk::StatusCodes filemanager_copy_file(const char* src, const char* dst) {
+    if (!src || !dst || montauk::streq(src, dst)) return montauk::InvalidArgument;
 
     int sfd = montauk::open(src);
-    if (sfd < 0) return false;
+    if (sfd < 0) return filemanager_status_from_result(sfd);
     uint64_t size = montauk::getsize(sfd);
 
     // Create destination
     int dfd = montauk::fcreate(dst);
     if (dfd < 0) {
         montauk::close(sfd);
-        return false;
+        return filemanager_status_from_result(dfd);
     }
 
-    bool ok = true;
+    montauk::StatusCodes status = montauk::Success;
     if (size > 0) {
         static constexpr uint64_t COPY_CHUNK = 64 * 1024;
         uint64_t buf_size = size < COPY_CHUNK ? size : COPY_CHUNK;
@@ -549,7 +557,7 @@ bool filemanager_copy_file(const char* src, const char* dst) {
             montauk::close(sfd);
             montauk::close(dfd);
             montauk::fdelete(dst);
-            return false;
+            return montauk::OutOfMemory;
         }
 
         uint64_t off = 0;
@@ -558,9 +566,15 @@ bool filemanager_copy_file(const char* src, const char* dst) {
             if (todo64 > buf_size) todo64 = buf_size;
             int todo = (int)todo64;
             int got = montauk::read(sfd, buf, off, todo64);
-            if (got != todo) { ok = false; break; }
+            if (got != todo) {
+                status = got < 0 ? filemanager_status_from_result(got) : montauk::IoFailure;
+                break;
+            }
             int wrote = montauk::fwrite(dfd, buf, off, todo64);
-            if (wrote != todo) { ok = false; break; }
+            if (wrote != todo) {
+                status = wrote < 0 ? filemanager_status_from_result(wrote) : montauk::IoFailure;
+                break;
+            }
             off += todo64;
         }
 
@@ -569,23 +583,23 @@ bool filemanager_copy_file(const char* src, const char* dst) {
 
     montauk::close(sfd);
     montauk::close(dfd);
-    if (!ok) {
-        montauk::fdelete(dst);
-        return false;
-    }
-    return true;
+    if (status != montauk::Success) montauk::fdelete(dst);
+    return status;
 }
 
 // Recursive directory copy
-bool filemanager_copy_dir_recursive(const char* src, const char* dst) {
-    if (!src || !dst || montauk::streq(src, dst)) return false;
+montauk::StatusCodes filemanager_copy_dir_recursive(const char* src, const char* dst) {
+    if (!src || !dst || montauk::streq(src, dst)) return montauk::InvalidArgument;
 
+    // Ignore the result: the destination may already exist (merge). If it
+    // truly could not be created, the child copies fail and report why.
     montauk::fmkdir(dst);
 
     char (*children)[256] = nullptr;
     int count = filemanager_read_all_children(src, &children);
-    if (count < 0) return false;
+    if (count < 0) return filemanager_status_from_result(count);
 
+    montauk::StatusCodes status = montauk::Success;
     for (int i = 0; i < count; i++) {
         bool child_is_dir = false;
         char basename[256];
@@ -601,15 +615,15 @@ bool filemanager_copy_dir_recursive(const char* src, const char* dst) {
         filemanager_build_fullpath(src_child, 512, src, basename);
         filemanager_build_fullpath(dst_child, 512, dst, basename);
 
-        if (child_is_dir)
-            filemanager_copy_dir_recursive(src_child, dst_child);
-        else
-            filemanager_copy_file(src_child, dst_child);
+        montauk::StatusCodes s = child_is_dir
+            ? filemanager_copy_dir_recursive(src_child, dst_child)
+            : filemanager_copy_file(src_child, dst_child);
+        if (s != montauk::Success && status == montauk::Success) status = s;
     }
 
     if (children) montauk::mfree(children);
 
-    return true;
+    return status;
 }
 
 } // namespace filemanager

programs/src/desktop/apps/filemanager/properties.cpp

@@ -490,15 +490,34 @@ static void delete_confirm_apply(FileDeleteConfirmDialogState* st) {
     if (!started) {
         // Fallback: delete synchronously (e.g. another operation is running).
         bool any = false;
+        int failed = 0;
+        const char* first_failed_path = nullptr;
+        montauk::StatusCodes first_error = montauk::Success;
         for (int i = 0; i < n; i++) {
             const char* p = (st->count > 0) ? st->paths[i] : st->path;
             if (!p || !p[0]) continue;
-            if (filemanager_delete_recursive(p)) any = true;
+            montauk::StatusCodes status = filemanager_delete_recursive(p);
+            if (status == montauk::Success) {
+                any = true;
+            } else if (failed++ == 0) {
+                first_failed_path = p;
+                first_error = status;
+            }
         }
         if (owner && any) {
             filemanager_clear_multi_selection(owner);
             filemanager_read_dir(owner);
         }
+        if (failed > 0) {
+            char heading[192];
+            if (failed == 1)
+                snprintf(heading, sizeof(heading), "Couldn't delete \"%s\"",
+                         path_basename(first_failed_path));
+            else
+                snprintf(heading, sizeof(heading), "Couldn't delete %d of %d items", failed, n);
+            filemanager_show_error(st->desktop, st->owner, heading,
+                                   first_failed_path, first_error);
+        }
     }
 
     if (owner && owner->delete_confirm_dialog == st)
@@ -753,6 +772,214 @@ void filemanager_show_bulk_delete_confirmation(FileManagerState* fm,
     win->on_close = delete_confirm_on_close;
 }
 
+// ===== File operation error dialog =====
+
+struct FileErrorDialogState {
+    DesktopState* desktop;
+    Color accent;
+    int mouse_x;
+    int mouse_y;
+
+    char heading[192];     // what failed, e.g. "Couldn't delete "foo""
+    char path[256];        // the item involved (optional)
+    char cause[4][160];    // wrapped GetStatusExplanationText() lines
+    int  cause_lines;
+    SvgIcon icon;          // owned
+};
+
+static constexpr int kErrorDialogW = 440;
+static constexpr int kErrorTextX = 80;
+static constexpr int kErrorTop = 22;
+
+// Greedy word wrap of `src` into at most `max_lines` lines no wider than
+// `max_w`. A word that cannot fit on a line of its own, and any text left over
+// for the last line, is ellipsized.
+static int error_wrap_text(const char* src, char (*lines)[160], int max_lines, int max_w) {
+    int count = 0;
+    int pos = 0;
+    while (src[pos] && count < max_lines) {
+        while (src[pos] == ' ') pos++;
+        if (!src[pos]) break;
+
+        if (count == max_lines - 1) {
+            props_fit_text(src + pos, lines[count++], 160, max_w);
+            break;
+        }
+
+        // Extend the line one word at a time while it still fits.
+        char buf[160];
+        int best = -1;
+        int end = pos;
+        for (;;) {
+            while (src[end] && src[end] != ' ') end++;
+            int n = end - pos;
+            if (n > 159) break;
+            montauk::memcpy(buf, src + pos, n);
+            buf[n] = '\0';
+            if (text_width(buf) > max_w) break;
+            best = end;
+            if (!src[end]) break;
+            end++;
+        }
+
+        if (best < 0) {
+            // The first word alone is too wide: truncate it and skip past it.
+            int word_end = pos;
+            while (src[word_end] && src[word_end] != ' ') word_end++;
+            int n = word_end - pos;
+            if (n > 159) n = 159;
+            montauk::memcpy(buf, src + pos, n);
+            buf[n] = '\0';
+            props_fit_text(buf, lines[count++], 160, max_w);
+            pos = word_end;
+        } else {
+            int n = best - pos;
+            montauk::memcpy(lines[count], src + pos, n);
+            lines[count][n] = '\0';
+            count++;
+            pos = best;
+        }
+    }
+    return count;
+}
+
+// Top-down text layout shared by the draw path and the window sizing.
+static int error_path_y(int fh) { return kErrorTop + fh + 8; }
+static int error_cause_y(const FileErrorDialogState* st, int fh) {
+    return st->path[0] ? error_path_y(fh) + fh + 12 : error_path_y(fh);
+}
+
+static Rect error_ok_button_rect(int content_w, int content_h) {
+    return {content_w - 96, content_h - 42, 80, 28};
+}
+
+static void error_on_draw(Window* win, Framebuffer& fb) {
+    (void)fb;
+    FileErrorDialogState* st = (FileErrorDialogState*)win->app_data;
+    if (!st) return;
+
+    Canvas c(win);
+    mtk::Theme theme = mtk::make_theme(st->accent);
+    c.fill(theme.window_bg);
+
+    int pad = 16;
+    int fh = system_font_height();
+    int text_w = c.w - kErrorTextX - pad;
+
+    if (st->icon.pixels) {
+        c.icon(pad + (48 - st->icon.width) / 2,
+               kErrorTop + (48 - st->icon.height) / 2,
+               st->icon);
+    } else {
+        c.fill_rounded_rect(pad, kErrorTop, 48, 48, 24, theme.danger);
+        c.text(pad + (48 - text_width("!")) / 2, kErrorTop + (48 - fh) / 2, "!",
+               theme.danger_fg);
+    }
+
+    char fit[192];
+    props_fit_text(st->heading, fit, sizeof(fit), text_w);
+    c.text(kErrorTextX, kErrorTop, fit, theme.text);
+
+    if (st->path[0]) {
+        props_fit_text(st->path, fit, sizeof(fit), text_w);
+        c.text(kErrorTextX, error_path_y(fh), fit, theme.text_muted);
+    }
+
+    int y = error_cause_y(st, fh);
+    for (int i = 0; i < st->cause_lines; i++) {
+        c.text(kErrorTextX, y, st->cause[i], theme.text);
+        y += fh + 6;
+    }
+
+    Rect ok = error_ok_button_rect(c.w, c.h);
+    mtk::draw_button(c, ok, "OK", mtk::BUTTON_PRIMARY,
+                     mtk::widget_state(false, ok.contains(st->mouse_x, st->mouse_y), true),
+                     theme);
+}
+
+static void error_on_mouse(Window* win, MouseEvent& ev) {
+    FileErrorDialogState* st = (FileErrorDialogState*)win->app_data;
+    if (!st) return;
+
+    mtk::DesktopHost host(win);
+    int mx = 0;
+    int my = 0;
+    if (!host.map_mouse(ev, &mx, &my)) return;
+
+    Rect ok = error_ok_button_rect(win->content_w, win->content_h);
+    bool old_hover = ok.contains(st->mouse_x, st->mouse_y);
+    bool new_hover = ok.contains(mx, my);
+    st->mouse_x = mx;
+    st->mouse_y = my;
+    if (old_hover != new_hover) host.invalidate();
+
+    if (ev.left_pressed() && new_hover)
+        props_close_self(st->desktop, st);
+}
+
+static void error_on_key(Window* win, const montauk::abi::KeyEvent& key) {
+    FileErrorDialogState* st = (FileErrorDialogState*)win->app_data;
+    if (!st || !key.pressed) return;
+    if (key.scancode == 0x01 || key.ascii == '\n' || key.ascii == '\r')
+        props_close_self(st->desktop, st);
+}
+
+static void error_on_close(Window* win) {
+    FileErrorDialogState* st = (FileErrorDialogState*)win->app_data;
+    if (!st) return;
+    if (st->icon.pixels) svg_free(st->icon);
+    montauk::mfree(st);
+    win->app_data = nullptr;
+}
+
+void filemanager_show_error(DesktopState* ds, const void* owner_app_data,
+                            const char* heading, const char* path,
+                            montauk::StatusCodes status) {
+    if (!ds) return;
+
+    FileErrorDialogState* st =
+        (FileErrorDialogState*)montauk::malloc(sizeof(FileErrorDialogState));
+    if (!st) return;
+    montauk::memset(st, 0, sizeof(FileErrorDialogState));
+    st->desktop = ds;
+    st->accent = ds->settings.accent_color;
+    props_copy(st->heading, sizeof(st->heading), heading ? heading : "The operation failed");
+    props_copy(st->path, sizeof(st->path), path);
+
+    int content_w = kErrorDialogW - 2 * gui::BORDER_WIDTH;
+    if (status != montauk::Success) {
+        st->cause_lines = error_wrap_text(montauk::GetStatusExplanationText(status),
+                                          st->cause, 4, content_w - kErrorTextX - 16);
+    }
+
+    st->icon = svg_load("0:/os/icons/dialog-error.svg", 48, 48, colors::ICON_COLOR);
+
+    int fh = system_font_height();
+    int text_bottom = error_cause_y(st, fh) + st->cause_lines * (fh + 6);
+    int body_bottom = kErrorTop + 48;
+    if (text_bottom > body_bottom) body_bottom = text_bottom;
+    int content_h = body_bottom + 18 /*gap*/ + 28 /*button*/ + 14 /*bottom margin*/;
+    int w = kErrorDialogW;
+    int h = content_h + gui::TITLEBAR_HEIGHT + gui::BORDER_WIDTH;
+    int wx = 0;
+    int wy = 0;
+    props_center_dialog(ds, owner_app_data, w, h, &wx, &wy);
+
+    int idx = desktop_create_window(ds, "Error", wx, wy, w, h);
+    if (idx < 0) {
+        if (st->icon.pixels) svg_free(st->icon);
+        montauk::mfree(st);
+        return;
+    }
+
+    Window* win = &ds->windows[idx];
+    win->app_data = st;
+    win->on_draw = error_on_draw;
+    win->on_mouse = error_on_mouse;
+    win->on_key = error_on_key;
+    win->on_close = error_on_close;
+}
+
 // ===== Multi-item Properties dialog =====
 
 struct MultiPropertiesDialogState {

scripts/copy_icons.sh

@@ -161,6 +161,7 @@ ICONS=(
     "categories/scalable/utilities-log-viewer.svg"
     "apps/scalable/sleep.svg"
     "apps/scalable/kolourpaint.svg" # paint app
+    "apps/scalable/dialog-error.svg" # Files error popup
     "panel/sensors-temperature-symbolic.svg" # temperature panel icon
     "actions/symbolic/view-paged-symbolic.svg" # page view toggle (word processor)
 )