Implement posix app loading (#643)

- Added POSIX desktop support for SDK builds, application packaging, and integration testing.
- Added POSIX filesystem partitions and improved application path handling.
- Added simulator support for loading and running applications dynamically.
- Improved simulator task stack handling and display startup reliability.
- Improved simulator display scaling, resizing, high-DPI support, and pointer accuracy.
- Fixed LVGL timers and input polling on POSIX. (fixes simulator with Linux on some Intel graphics platforms)
- Standardized data paths across platforms.
- Logging now works via separate task: this allows apps to write to log without it affecting their stdout (for apps that output text as relevant date for other apps, like the File Selection app)
- Fixes for app stdio

Tactility/CMakeLists.txt

@@ -88,6 +88,7 @@ else ()
 
     list(APPEND REQUIRES_LIST
         platform-posix
+        app-posix-module
         freertos_kernel
         cJSON
         lvgl
@@ -181,6 +182,34 @@ else ()
     target_include_directories(Tactility PUBLIC Include/)
     target_include_directories(Tactility PRIVATE Private/)
     target_link_libraries(Tactility PRIVATE ${TACTILITY_REQUIRES_LIST})
+    # Exports Tactility's own symbols (-rdynamic) so a dlopen()ed app-posix-module app can resolve
+    # calls back into it - the OS-native equivalent of app-esp32-module's custom symbol resolver.
+    set_target_properties(Tactility PROPERTIES ENABLE_EXPORTS ON)
+    # Routes every pthread_attr_setstack() call (FreeRTOS's POSIX port hands each task a stack
+    # carved out of its own heap through this) to __wrap_pthread_attr_setstack() in
+    # Platforms/platform-posix/source/pthread_stack_wrap.c, which no-ops it - see that file for why.
+    # --wrap is a GNU ld option; Apple's linker doesn't support it.
+    if (NOT APPLE)
+        target_link_options(Tactility PRIVATE "-Wl,--wrap=pthread_attr_setstack")
+        # Routes every read()/write()/close() call to Tactility/Source/AppStdioWrap.cpp's
+        # __wrap_read/write/close(), which forward into app_io_read/write/close() - the fd-table
+        # dispatch that lets an app's own stdio (e.g. a fileselection dialog's printf'd result
+        # path) reach an AppStream a parent bound via app_manager_start_with_streams(). Mirrors
+        # what ESP-IDF's build already does for the ESP32 target (see top-level CMakeLists.txt).
+        target_link_options(Tactility PRIVATE "-Wl,--wrap=read" "-Wl,--wrap=write" "-Wl,--wrap=close")
+        # glibc's printf/fprintf/etc don't call the public write() symbol internally (they're
+        # already compiled into libc.so, out of --wrap's reach), so the read/write/close wrap
+        # above can't see them. Newlib (ESP-IDF) doesn't have this gap - its stdio does call the
+        # wrappable syscall stubs - so this block is POSIX-only. Wrapping these symbols instead
+        # redirects OUR OWN calls to them (the only ones --wrap can rewrite) through
+        # AppStdioWrap.cpp's __wrap_* functions, which check the target stream (stdout/stdin) and
+        # fall back to the real libc function for any other FILE*.
+        target_link_options(Tactility PRIVATE
+            "-Wl,--wrap=printf" "-Wl,--wrap=fprintf" "-Wl,--wrap=vprintf" "-Wl,--wrap=vfprintf"
+            "-Wl,--wrap=puts" "-Wl,--wrap=fputs" "-Wl,--wrap=putchar" "-Wl,--wrap=fputc"
+            "-Wl,--wrap=getchar" "-Wl,--wrap=fgetc" "-Wl,--wrap=fgets"
+        )
+    endif ()
 endif ()
 
 #

Tactility/Include/Tactility/app/fileselection/FileSelection.h

@@ -1,29 +1,36 @@
 #pragma once
 
+#include <cstddef>
 #include <cstdint>
-#include <string>
+
+#include <app/stream.h>
+#include <tactility/concurrent/task_event_group.h>
 
 namespace tt::app::fileselection {
 
 /**
  * Show a file selection dialog that allows the user to select an existing file, as a modal
- * child of @a callerAppInstanceId (see app_manager_start_for_result()). Result (0 = Ok,
- * 1 = Cancelled) is delivered back via APP_EVENT_RESULT once this app's thread exits - call
- * getLastPath() right after receiving it, on result == 0. The caller must call
- * app_manager_stop() on the returned instance id once that event arrives, to fully reap this
- * instance.
+ * child of @a callerAppInstanceId (see app_manager_start_for_result_with_streams()). Result
+ * (0 = Ok, 1 = Cancelled) is delivered back via APP_EVENT_RESULT once this app's thread exits.
+ * On result == 0, read the picked path with app_stream_read(&stream, ...) then
+ * app_stream_unsubscribe(&stream); on any other result, just app_stream_unsubscribe(&stream).
+ * The caller must call app_manager_stop() on the returned instance id once that event arrives,
+ * to fully reap this instance.
+ * @param[in,out] stream caller-owned storage bound to the started app's stdout; must stay valid
+ * until app_stream_unsubscribe() is called on it (see above).
+ * @param[in] buffer caller-owned backing storage for @a stream's ring buffer; must stay valid
+ * for the same duration as @a stream.
+ * @param[in] bufferCapacity size of @a buffer in bytes.
+ * @param[in] eventGroup the caller's own event group, reused for the stream's readiness bits
+ * (see app_stream_subscribe()) - the caller isn't required to actually wait on them itself.
  * @return the new app instance id
  */
-uint32_t startForExistingFile(uint32_t callerAppInstanceId);
+uint32_t startForExistingFile(uint32_t callerAppInstanceId, AppStream& stream, void* buffer, size_t bufferCapacity, TaskEventGroup* eventGroup);
 
 /**
  * Same as startForExistingFile(), but also allows picking a path that doesn't exist yet (for
  * "save as"-style flows).
  */
-uint32_t startForExistingOrNewFile(uint32_t callerAppInstanceId);
-
-/** @return the path picked by the last FileSelection dialog that closed with result == Ok. Only
- * one dialog is expected to be open at a time. */
-std::string getLastPath();
+uint32_t startForExistingOrNewFile(uint32_t callerAppInstanceId, AppStream& stream, void* buffer, size_t bufferCapacity, TaskEventGroup* eventGroup);
 
 } // namespace

Tactility/Private/Tactility/PartitionsPosix.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#ifndef ESP_PLATFORM
+
+namespace tt {
+
+bool initPartitionsPosix();
+
+} // namespace
+
+#endif // ESP_PLATFORM

Tactility/Source/AppStdioWrap.cpp

@@ -1,6 +1,9 @@
 // SPDX-License-Identifier: Apache-2.0
-#ifdef ESP_PLATFORM
 
+// Paired with -Wl,--wrap=read/write/close - see Tactility/CMakeLists.txt (POSIX) and the
+// top-level CMakeLists.txt (ESP32) for where that's applied. On a platform where it isn't
+// (currently: macOS, whose linker doesn't support --wrap), these are simply never called - real
+// read()/write()/close() calls go straight through unredirected.
 #include <app/io.h>
 
 #include <sys/types.h>
@@ -21,4 +24,177 @@ int __wrap_close(int fd) {
 
 }
 
-#endif // ESP_PLATFORM
+// region glibc stdio wraps
+//
+// glibc's printf/fprintf/etc are compiled into libc.so and call an internal, non-exported write()
+// alias - --wrap=write (above) can't reach that call, only calls WE make to the public symbol.
+// These wraps instead redirect calls WE make to printf/fprintf/etc, the same trick as read/write/
+// close above. Newlib (ESP-IDF) doesn't have this gap - its stdio does call the wrappable syscall
+// stubs - so Tactility/CMakeLists.txt only applies the matching -Wl,--wrap= flags on POSIX.
+//
+// Scoped to the printf/getc families only: fread/fwrite take an arbitrary FILE* and are already
+// used sitewide for real file I/O (e.g. File.cpp's readBinaryInternal), so wrapping them would
+// route every such call through this file's stdin/stdout check - a correctness risk for unrelated
+// code that isn't worth taking here. putc/getc are excluded too since glibc defines them as
+// macros, not real calls, so wrapping those symbols wouldn't reliably intercept them.
+
+#if !defined(ESP_PLATFORM) && !defined(__APPLE__)
+
+#include <cstdarg>
+#include <cstdio>
+#include <cstring>
+#include <memory>
+#include <unistd.h>
+
+extern "C" {
+int __real_vfprintf(FILE* stream, const char* format, va_list args);
+int __real_fputs(const char* s, FILE* stream);
+int __real_fputc(int c, FILE* stream);
+int __real_fgetc(FILE* stream);
+char* __real_fgets(char* buffer, int size, FILE* stream);
+}
+
+namespace {
+
+void writeAllToStdout(const void* data, size_t size) {
+    const auto* bytes = static_cast<const char*>(data);
+    size_t remaining = size;
+    while (remaining > 0) {
+        ssize_t written = app_io_write(STDOUT_FILENO, bytes, remaining);
+        if (written <= 0) {
+            break;
+        }
+        bytes += written;
+        remaining -= static_cast<size_t>(written);
+    }
+}
+
+// Formats into stdout via app_io_write() rather than through a FILE*'s own buffering, since that
+// buffering is exactly what glibc's internal write() call sidesteps --wrap for in the first place.
+int formatToStdout(const char* format, va_list args) {
+    char stackBuffer[256];
+    va_list argsForStack;
+    va_copy(argsForStack, args);
+    int needed = vsnprintf(stackBuffer, sizeof(stackBuffer), format, argsForStack);
+    va_end(argsForStack);
+    if (needed < 0) {
+        return needed;
+    }
+    if (static_cast<size_t>(needed) < sizeof(stackBuffer)) {
+        writeAllToStdout(stackBuffer, static_cast<size_t>(needed));
+        return needed;
+    }
+    auto heapBuffer = std::make_unique<char[]>(static_cast<size_t>(needed) + 1);
+    va_list argsForHeap;
+    va_copy(argsForHeap, args);
+    vsnprintf(heapBuffer.get(), static_cast<size_t>(needed) + 1, format, argsForHeap);
+    va_end(argsForHeap);
+    writeAllToStdout(heapBuffer.get(), static_cast<size_t>(needed));
+    return needed;
+}
+
+int readOneFromStdin(char& out) {
+    return static_cast<int>(app_io_read(STDIN_FILENO, &out, 1));
+}
+
+} // namespace
+
+extern "C" {
+
+int __wrap_vprintf(const char* format, va_list args) {
+    return formatToStdout(format, args);
+}
+
+int __wrap_printf(const char* format, ...) {
+    va_list args;
+    va_start(args, format);
+    int result = formatToStdout(format, args);
+    va_end(args);
+    return result;
+}
+
+int __wrap_vfprintf(FILE* stream, const char* format, va_list args) {
+    if (stream == stdout) {
+        return formatToStdout(format, args);
+    }
+    return __real_vfprintf(stream, format, args);
+}
+
+int __wrap_fprintf(FILE* stream, const char* format, ...) {
+    va_list args;
+    va_start(args, format);
+    int result = (stream == stdout) ? formatToStdout(format, args) : __real_vfprintf(stream, format, args);
+    va_end(args);
+    return result;
+}
+
+int __wrap_puts(const char* s) {
+    writeAllToStdout(s, strlen(s));
+    writeAllToStdout("\n", 1);
+    return 0;
+}
+
+int __wrap_fputs(const char* s, FILE* stream) {
+    if (stream == stdout) {
+        writeAllToStdout(s, strlen(s));
+        return 0;
+    }
+    return __real_fputs(s, stream);
+}
+
+int __wrap_putchar(int c) {
+    auto ch = static_cast<char>(c);
+    writeAllToStdout(&ch, 1);
+    return c;
+}
+
+int __wrap_fputc(int c, FILE* stream) {
+    if (stream == stdout) {
+        return __wrap_putchar(c);
+    }
+    return __real_fputc(c, stream);
+}
+
+int __wrap_getchar() {
+    char c;
+    return readOneFromStdin(c) == 1 ? static_cast<unsigned char>(c) : EOF;
+}
+
+int __wrap_fgetc(FILE* stream) {
+    if (stream == stdin) {
+        return __wrap_getchar();
+    }
+    return __real_fgetc(stream);
+}
+
+char* __wrap_fgets(char* buffer, int size, FILE* stream) {
+    if (stream != stdin) {
+        return __real_fgets(buffer, size, stream);
+    }
+    if (size <= 0) {
+        return nullptr;
+    }
+    int i = 0;
+    for (; i < size - 1; ++i) {
+        char c;
+        if (readOneFromStdin(c) != 1) {
+            break;
+        }
+        buffer[i] = c;
+        if (c == '\n') {
+            ++i;
+            break;
+        }
+    }
+    if (i == 0) {
+        return nullptr;
+    }
+    buffer[i] = '\0';
+    return buffer;
+}
+
+}
+
+#endif // !ESP_PLATFORM && !__APPLE__
+
+// endregion

Tactility/Source/DeprecatedPaths.cpp

@@ -52,11 +52,7 @@ std::string getUserDataRootPath() {
 }
 
 std::string getDataPath() {
-#ifdef ESP_PLATFORM
     return getUserDataRootPath() + "/tactility";
-#else
-    return "data";
-#endif
 }
 
 std::string getTempPath() {

Tactility/Source/MountPoints.cpp

@@ -18,7 +18,11 @@ std::vector<dirent> getFileSystemDirents() {
         if (!file_system_is_mounted(fs)) return true;
         char path[128];
         if (file_system_get_path(fs, path, sizeof(path)) != ERROR_NONE) return true;
-        auto mount_name = std::string(path).substr(1);
+        // ESP32 mount paths are short names ("/system"); POSIX file systems can return a full
+        // absolute host path instead, so take the last path component either way.
+        auto path_str = std::string(path);
+        auto slash_pos = path_str.find_last_of('/');
+        auto mount_name = slash_pos == std::string::npos ? path_str : path_str.substr(slash_pos + 1);
         if (!config::SHOW_SYSTEM_PARTITION && mount_name.starts_with(SYSTEM_PARTITION_NAME)) return true;
         auto dir_entry = dirent {
             .d_ino = 2,

Tactility/Source/PartitionsPosix.cpp

@@ -0,0 +1,103 @@
+#ifndef ESP_PLATFORM
+
+#include <Tactility/PartitionsPosix.h>
+#include <Tactility/MountPoints.h>
+
+#include <tactility/error.h>
+#include <tactility/filesystem/file_system.h>
+#include <tactility/log.h>
+
+#include <cerrno>
+#include <climits>
+#include <cstdlib>
+#include <cstring>
+
+namespace tt {
+
+constexpr auto* TAG = "Partitions";
+
+// region file_system stub
+
+// A plain host directory has no real mount/unmount step to perform - "mounted" here just tracks
+// whether file_system_remove()'s precondition (must be unmounted first) has been satisfied.
+struct DirectoryFsData {
+    char path[PATH_MAX];
+    bool mounted;
+};
+
+static DirectoryFsData system_fs_data;
+static DirectoryFsData data_fs_data;
+static FileSystem* system_fs = nullptr;
+static FileSystem* data_fs = nullptr;
+
+static error_t mount(void* data) {
+    static_cast<DirectoryFsData*>(data)->mounted = true;
+    return ERROR_NONE;
+}
+
+static error_t unmount(void* data) {
+    static_cast<DirectoryFsData*>(data)->mounted = false;
+    return ERROR_NONE;
+}
+
+static bool is_mounted(void* data) {
+    return static_cast<DirectoryFsData*>(data)->mounted;
+}
+
+static error_t get_path(void* data, char* out_path, size_t out_path_size) {
+    auto* fs_data = static_cast<DirectoryFsData*>(data);
+    if (strlen(fs_data->path) >= out_path_size) {
+        return ERROR_BUFFER_OVERFLOW;
+    }
+    strcpy(out_path, fs_data->path);
+    return ERROR_NONE;
+}
+
+static const FileSystemApi directory_fs_api = {
+    .mount = mount,
+    .unmount = unmount,
+    .is_mounted = is_mounted,
+    .get_path = get_path,
+};
+
+// endregion file_system stub
+
+// relative_path is resolved against the process' current working directory (the simulator is
+// expected to run with Data/ as its working directory, so file::SYSTEM_PARTITION_NAME/
+// DATA_PARTITION_NAME here match file::MOUNT_POINT_SYSTEM/MOUNT_POINT_DATA).
+static FileSystem* registerDirectoryFs(const char* relativePath, DirectoryFsData* outData) {
+    if (realpath(relativePath, outData->path) == nullptr) {
+        LOG_E(TAG, "Failed to resolve '%s' to an absolute path: %s", relativePath, strerror(errno));
+        return nullptr;
+    }
+    outData->mounted = true;
+    return file_system_add(&directory_fs_api, outData);
+}
+
+static void unregisterDirectoryFs(FileSystem* fs) {
+    if (fs == nullptr) {
+        return;
+    }
+    file_system_unmount(fs);
+    file_system_remove(fs);
+}
+
+bool initPartitionsPosix() {
+    system_fs = registerDirectoryFs(file::SYSTEM_PARTITION_NAME, &system_fs_data);
+    if (system_fs == nullptr) {
+        return false;
+    }
+
+    data_fs = registerDirectoryFs(file::DATA_PARTITION_NAME, &data_fs_data);
+    if (data_fs == nullptr) {
+        unregisterDirectoryFs(system_fs);
+        system_fs = nullptr;
+        return false;
+    }
+
+    return true;
+}
+
+} // namespace
+
+#endif // ESP_PLATFORM

Tactility/Source/Tactility.cpp

@@ -4,13 +4,27 @@
 #include <app_esp32/module.h>
 #endif
 
+#if __has_include(<unistd.h>) && not defined(ESP_PLATFORM)
+#define TT_IS_POSIX 1
+#else
+#define TT_IS_POSIX 0
+#endif
+
+#if TT_IS_POSIX or defined(ESP_PLATFORM) // esp-idf supports certain posix symbols
+#include <posix_symbols/module.h>
+#endif
+
+#if TT_IS_POSIX
+#include <app_posix/module.h>
+#include <Tactility/PartitionsPosix.h>
+#endif
+
 #include <format>
 #include <memory>
 #include <string>
 #include <vector>
 
 #include <app/event.h>
-#include <app/install.h>
 #include <app/manager.h>
 #include <app/manifest.h>
 #include <app/module.h>
@@ -19,7 +33,6 @@
 
 #include <Tactility/CpuAffinity.h>
 #include <Tactility/DeprecatedPaths.h>
-#include <Tactility/LogMessages.h>
 #include <Tactility/MountPoints.h>
 #include <Tactility/TactilityConfig.h>
 #include <Tactility/bluetooth/Bluetooth.h>
@@ -35,7 +48,10 @@
 #include <Tactility/service/audio/Audio.h>
 #include <Tactility/settings/DisplaySettings.h>
 #include <Tactility/settings/TimePrivate.h>
+
+#ifdef CONFIG_TT_TOUCH_CALIBRATION_SUPPORTED
 #include <Tactility/settings/TouchCalibrationSettings.h>
+#endif
 
 #include <c_symbols/module.h>
 #include <cpp_symbols/module.h>
@@ -47,7 +63,6 @@
 #include <gps_meshtastic/module.h>
 #include <http/module.h>
 #include <mbedtls/module.h>
-#include <posix_symbols/module.h>
 #include <pthread/module.h>
 
 #include <crypt/module.h>
@@ -501,7 +516,9 @@ void run(Module* const dtsModules[], const DtsDevice dtsDevices[]) {
 
     // C/C++/Posix symbols
     check(module_ensure_started(&c_symbols_module) == ERROR_NONE);
+#if TT_IS_POSIX or defined(ESP_PLATFORM) // esp-idf supports certain posix symbols
     check(module_ensure_started(&posix_symbols_module) == ERROR_NONE);
+#endif
     check(module_ensure_started(&cpp_symbols_module) == ERROR_NONE);
     // OS level symbols
     check(module_ensure_started(&freertos_module) == ERROR_NONE);
@@ -516,10 +533,14 @@ void run(Module* const dtsModules[], const DtsDevice dtsDevices[]) {
     check(module_ensure_started(&gps_meshtastic_module) == ERROR_NONE);
 #ifdef ESP_PLATFORM
     check(module_ensure_started(&app_esp32_module) == ERROR_NONE);
+#elif TT_IS_POSIX
+    check(module_ensure_started(&app_posix_module) == ERROR_NONE);
 #endif
 
 #ifdef ESP_PLATFORM
     initEsp();
+#elif TT_IS_POSIX
+    check(initPartitionsPosix(), "Failed to init partitions");
 #endif
 
     settings::initTimeZone();

Tactility/Source/app/files/View.cpp

@@ -24,6 +24,7 @@
 #include <cstdio>
 #include <cstring>
 #include <fcntl.h>
+#include <format>
 #include <unistd.h>
 
 namespace tt::app::files {
@@ -174,43 +175,22 @@ static bool copyRecursive(const std::string& src, const std::string& dst) {
 
 void View::viewFile(const std::string& path, const std::string& filename) {
     std::string file_path = path + "/" + filename;
-
-    // For PC we need to make the path relative to the current work directory,
-    // because that's how LVGL maps its 'drive letter' to the file system.
-    std::string processed_filepath;
-    if (kernel::getPlatform() == kernel::PlatformSimulator) {
-        char cwd[PATH_MAX];
-        if (getcwd(cwd, sizeof(cwd)) == nullptr) {
-            LOG_E(TAG, "Failed to get current working directory");
-            return;
-        }
-        if (!file_path.starts_with(cwd)) {
-            LOG_E(TAG, "Can only work with files in working directory %s", cwd);
-            return;
-        }
-        processed_filepath = file_path.substr(strlen(cwd));
-    } else {
-        processed_filepath = file_path;
-    }
-
     LOG_I(TAG, "Clicked %s", file_path.c_str());
 
     if (isSupportedAppFile(filename)) {
-#ifdef ESP_PLATFORM
         // install(filename);
         auto message = std::format("Do you want to install {}?", filename);
-        installAppPath = processed_filepath;
+        installAppPath = file_path;
         auto choices = std::vector<std::string> {"Yes", "No"};
         installDialogId = alertdialog::start(appInstanceId, "Install?", message, choices);
-#endif
     } else if (isSupportedImageFile(filename)) {
-        imageviewer::start(processed_filepath);
+        imageviewer::start(file_path);
     } else if (isSupportedTextFile(filename)) {
         if (kernel::getPlatform() == kernel::PlatformEsp) {
-            notes::start(processed_filepath);
+            notes::start(file_path);
         } else {
             // Remove forward slash, because we need a relative path
-            notes::start(processed_filepath.substr(1));
+            notes::start(file_path.substr(1));
         }
     } else {
         LOG_W(TAG, "Opening files of this type is not supported");

Tactility/Source/app/fileselection/FileSelection.cpp

@@ -1,18 +1,23 @@
+#include "Tactility/app/fileselection/FileSelection.h"
 #include "Tactility/app/fileselection/FileSelectionPrivate.h"
 #include "Tactility/app/fileselection/View.h"
 #include "Tactility/app/fileselection/State.h"
 
 #include <app/event.h>
+#include <app/io.h>
 #include <app/manager.h>
 #include <app/manifest.h>
 #include <app/scheduler.h>
+#include <app/stream.h>
 
 #include <lvgl_window_manager/window_manager.h>
 
 #include <tactility/check.h>
 
+#include <cstdio>
 #include <memory>
 #include <string>
+#include <unistd.h>
 
 namespace tt::app::fileselection {
 
@@ -27,20 +32,11 @@ struct Context {
     Mode mode;
     std::shared_ptr<State> state;
     std::unique_ptr<View> view;
-    // The eventual appMain() return value - see AlertDialog.cpp's Context::result for why this
-    // is a plain (non-atomic) field safely shared between the LVGL thread (writer, before
-    // emitting APP_EVENT_CLOSE) and this app's own thread (reader, after waking from it).
-    int32_t result = 1; // Cancelled - safety-net default if closed without picking a file
+    std::string resultPath;
+    int32_t resultCode = 1; // 1 means Cancelled
 };
 
 
-// The last picked path. Static rather than per-instance: simple, and in practice only one
-// FileSelection dialog is ever open at a time. Written on the LVGL thread (View's select-button
-// callback, before emitting APP_EVENT_CLOSE); read by the parent via getLastPath() after
-// receiving that event - safe without a lock for the same reason Context::result is (see
-// AlertDialog.cpp).
-std::string lastPath;
-
 void createWidgets(lv_obj_t* parent, void* userData) {
     auto* ctx = static_cast<Context*>(userData);
     ctx->view->init(parent, ctx->mode);
@@ -52,16 +48,11 @@ int32_t appMain(int argc, char* argv[]) {
 
     Context ctx {};
     ctx.appInstanceId = appInstanceId;
-    ctx.mode = (argc > 0 && std::string(argv[0]) == "existing_or_new") ? Mode::ExistingOrNew : Mode::Existing;
+    ctx.mode = (argc > 0 && std::string(argv[0]) == "--existing-or-new") ? Mode::ExistingOrNew : Mode::Existing;
     ctx.state = std::make_shared<State>();
     ctx.view = std::make_unique<View>(appInstanceId, ctx.state, [&ctx, appInstanceId](const std::string& path) {
-        // Runs on the LVGL task (View::onSelectButtonPressed) - must NOT call app_manager_stop()
-        // here: that bound-waits (thread_join) for this app's own thread to finish, which needs
-        // the LVGL lock (window_manager_remove()) - but this callback runs ON the LVGL task,
-        // which would deadlock against itself. The caller reaps this instance via
-        // app_manager_stop() after it receives the APP_EVENT_RESULT instead.
-        lastPath = path;
-        ctx.result = 0;
+        ctx.resultPath = path;
+        ctx.resultCode = 0;
         app_event_emit_close(appInstanceId);
     });
 
@@ -91,27 +82,42 @@ int32_t appMain(int argc, char* argv[]) {
     check(app_event_unsubscribe(&sub) == ERROR_NONE);
     task_event_group_destruct(&event_group);
 
-    return ctx.result;
+    if (ctx.resultCode == 0) {
+        // The parent captures this via an AppStream bound to our stdout (see startWithMode()) -
+        // see AppStdioWrap.cpp for how printf() itself gets routed there on POSIX.
+        LOG_I(TAG, "Result: %s", ctx.resultPath.c_str());
+        printf("%s", ctx.resultPath.c_str());
+    }
+
+    return ctx.resultCode;
 }
 
 } // namespace
 
-std::string getLastPath() {
-    return lastPath;
-}
+namespace {
 
-uint32_t startForExistingFile(uint32_t callerAppInstanceId) {
-    const char* argv[] = { "existing" };
+uint32_t startWithMode(const char* modeArg, uint32_t callerAppInstanceId, AppStream& stream, void* buffer, size_t bufferCapacity, TaskEventGroup* eventGroup) {
+    const char* argv[] = { modeArg };
+    AppStreamBinding binding = {
+        .producer_fd = STDOUT_FILENO,
+        .stream = &stream,
+        .buffer = buffer,
+        .buffer_capacity = bufferCapacity,
+        .event_group = eventGroup,
+    };
     uint32_t instanceId = 0;
-    app_manager_start_for_result(manifest.id, callerAppInstanceId, 1, argv, &instanceId);
+    app_manager_start_for_result_with_streams(manifest.id, callerAppInstanceId, 1, argv, &binding, 1, &instanceId);
     return instanceId;
 }
 
-uint32_t startForExistingOrNewFile(uint32_t callerAppInstanceId) {
-    const char* argv[] = { "existing_or_new" };
-    uint32_t instanceId = 0;
-    app_manager_start_for_result(manifest.id, callerAppInstanceId, 1, argv, &instanceId);
-    return instanceId;
+} // namespace
+
+uint32_t startForExistingFile(uint32_t callerAppInstanceId, AppStream& stream, void* buffer, size_t bufferCapacity, TaskEventGroup* eventGroup) {
+    return startWithMode("--existing", callerAppInstanceId, stream, buffer, bufferCapacity, eventGroup);
+}
+
+uint32_t startForExistingOrNewFile(uint32_t callerAppInstanceId, AppStream& stream, void* buffer, size_t bufferCapacity, TaskEventGroup* eventGroup) {
+    return startWithMode("--existing-or-new", callerAppInstanceId, stream, buffer, bufferCapacity, eventGroup);
 }
 
 extern const ::AppManifest manifest = {

Tactility/Source/app/fileselection/State.cpp

@@ -33,7 +33,7 @@ std::string State::getSelectedChildPath() const {
 }
 
 bool State::setEntriesForPath(const std::string& path) {
-    LOG_I(TAG, "Changing path: %s -> %s", current_path.c_str(), path.c_str());
+    LOG_D(TAG, "Changing path: %s -> %s", current_path.c_str(), path.c_str());
 
     auto lock = mutex.asScopedLock();
     if (!lock.lock(100)) {
@@ -47,7 +47,6 @@ bool State::setEntriesForPath(const std::string& path) {
      */
     bool show_custom_root = (kernel::getPlatform() == kernel::PlatformEsp) && (path == "/");
     if (show_custom_root) {
-        LOG_I(TAG, "Setting custom root");
         dir_entries = file::getFileSystemDirents();
         current_path = path;
         selected_child_entry = "";
@@ -56,7 +55,6 @@ bool State::setEntriesForPath(const std::string& path) {
         dir_entries.clear();
         int count = file::scandir(path, dir_entries, &file::direntFilterDotEntries, file::direntSortAlphaAndType);
         if (count >= 0) {
-            LOG_I(TAG, "%s has %d entries", path.c_str(), count);
             current_path = path;
             selected_child_entry = "";
             return true;
@@ -69,7 +67,7 @@ bool State::setEntriesForPath(const std::string& path) {
 
 bool State::setEntriesForChildPath(const std::string& childPath) {
     auto path = file::getChildPath(current_path, childPath);
-    LOG_I(TAG, "Navigating from %s to %s", current_path.c_str(), path.c_str());
+    LOG_D(TAG, "Navigating from %s to %s", current_path.c_str(), path.c_str());
     return setEntriesForPath(path);
 }
 

Tactility/Source/app/fileselection/View.cpp

@@ -60,12 +60,15 @@ void View::onTapFile(const std::string& path, const std::string& filename) {
             LOG_E(TAG, "Can only work with files in working directory %s", cwd);
             return;
         }
-        processed_filepath = file_path.substr(strlen(cwd));
+        // MountPoints.h's MOUNT_POINT_DATA/MOUNT_POINT_SYSTEM have no leading slash on POSIX
+        // (fopen() resolves relative to cwd there), unlike ESP32's real VFS mount points - so
+        // strip the separator too, not just cwd itself.
+        processed_filepath = file_path.substr(strlen(cwd) + 1);
     } else {
         processed_filepath = file_path;
     }
 
-    LOG_I(TAG, "Clicked %s", processed_filepath.c_str());
+    LOG_D(TAG, "Clicked %s", processed_filepath.c_str());
 
     lv_textarea_set_text(path_textarea, processed_filepath.c_str());
 }
@@ -73,7 +76,7 @@ void View::onTapFile(const std::string& path, const std::string& filename) {
 void View::onDirEntryPressed(uint32_t index) {
     dirent dir_entry;
     if (state->getDirent(index, dir_entry)) {
-        LOG_I(TAG, "Pressed %s %d", dir_entry.d_name, (int)dir_entry.d_type);
+        LOG_D(TAG, "Pressed %s %d", dir_entry.d_name, (int)dir_entry.d_type);
         state->setSelectedChildEntry(dir_entry.d_name);
         using namespace tt::file;
         switch (dir_entry.d_type) {
@@ -146,7 +149,7 @@ void View::createDirEntryWidget(lv_obj_t* list, dirent& dir_entry) {
 
 void View::onNavigateUpPressed() {
     if (state->getCurrentPath() != "/") {
-        LOG_I(TAG, "Navigating upwards");
+        LOG_D(TAG, "Navigating upwards");
         std::string new_absolute_path;
         if (string::getPathParent(state->getCurrentPath(), new_absolute_path)) {
             state->setEntriesForPath(new_absolute_path);

Tactility/Source/app/notes/Notes.cpp

@@ -1,4 +1,7 @@
 #include <Tactility/app/notes/Notes.h>
+
+#include "Tactility/app/alertdialog/AlertDialog.h"
+
 #include <Tactility/app/fileselection/FileSelection.h>
 #include <Tactility/file/File.h>
 
@@ -6,6 +9,7 @@
 #include <app/manager.h>
 #include <app/manifest.h>
 #include <app/scheduler.h>
+#include <app/stream.h>
 
 #include <lvgl_window_manager/window_manager.h>
 
@@ -25,6 +29,7 @@ namespace {
 
 struct Context {
     uint32_t appInstanceId;
+    TaskEventGroup* eventGroup = nullptr;
 
     lv_obj_t* uiCurrentFileName = nullptr;
     lv_obj_t* uiDropDownMenu = nullptr;
@@ -35,6 +40,10 @@ struct Context {
 
     uint32_t loadFileLaunchId = 0;
     uint32_t saveFileLaunchId = 0;
+    AppStream loadResultStream {};
+    uint8_t loadResultBuffer[256] {};
+    AppStream saveResultStream {};
+    uint8_t saveResultBuffer[256] {};
 };
 
 
@@ -90,11 +99,11 @@ void appNotesEventCb(lv_event_t* e) {
                     lvgl_lock();
                     ctx->saveBuffer = lv_textarea_get_text(ctx->uiNoteText);
                     lvgl_unlock();
-                    ctx->saveFileLaunchId = fileselection::startForExistingOrNewFile(ctx->appInstanceId);
+                    ctx->saveFileLaunchId = fileselection::startForExistingOrNewFile(ctx->appInstanceId, ctx->saveResultStream, ctx->saveResultBuffer, sizeof(ctx->saveResultBuffer), ctx->eventGroup);
                     LOG_I(TAG, "launched with id %u", ctx->saveFileLaunchId);
                     break;
                 case 3: // Load
-                    ctx->loadFileLaunchId = fileselection::startForExistingFile(ctx->appInstanceId);
+                    ctx->loadFileLaunchId = fileselection::startForExistingFile(ctx->appInstanceId, ctx->loadResultStream, ctx->loadResultBuffer, sizeof(ctx->loadResultBuffer), ctx->eventGroup);
                     LOG_I(TAG, "launched with id %u", ctx->loadFileLaunchId);
                     break;
             }
@@ -102,7 +111,7 @@ void appNotesEventCb(lv_event_t* e) {
             auto* cont = lv_event_get_current_target_obj(e);
             if (obj == cont) return;
             if (lv_obj_get_child(cont, 1)) {
-                ctx->saveFileLaunchId = fileselection::startForExistingOrNewFile(ctx->appInstanceId);
+                ctx->saveFileLaunchId = fileselection::startForExistingOrNewFile(ctx->appInstanceId, ctx->saveResultStream, ctx->saveResultBuffer, sizeof(ctx->saveResultBuffer), ctx->eventGroup);
                 LOG_I(TAG, "launched with id %u", ctx->saveFileLaunchId);
             } else { //Reset
                 resetFileContent(ctx);
@@ -189,6 +198,7 @@ int32_t appMain(int argc, char* argv[]) {
 
     TaskEventGroup event_group {};
     task_event_group_construct(&event_group);
+    ctx.eventGroup = &event_group;
 
     AppEventSubscription sub {};
     check(app_event_subscribe(&sub, &event_group) == ERROR_NONE);
@@ -206,23 +216,35 @@ int32_t appMain(int argc, char* argv[]) {
                     shouldClose = true;
                     break;
                 case APP_EVENT_RESULT:
-                    LOG_I(TAG, "Result for launch id %u", event.result.launch_id);
+                    LOG_I(TAG, "Result for launch id %u = %u", event.result.launch_id, event.result.result);
                     if (event.result.launch_id == ctx.loadFileLaunchId) {
                         ctx.loadFileLaunchId = 0;
                         if (event.result.result == 0 /* Ok */) {
-                            auto path = fileselection::getLastPath();
+                            char destination[sizeof(ctx.loadResultBuffer)];
+                            size_t length = app_stream_read(&ctx.loadResultStream, destination, sizeof(destination));
+                            app_stream_unsubscribe(&ctx.loadResultStream);
+                            auto path = std::string(destination, length);
+                            LOG_I(TAG, "Path: '%s'", path.c_str());
                             if (!path.empty()) {
                                 openFile(&ctx, path);
                             }
+                        } else {
+                            app_stream_unsubscribe(&ctx.loadResultStream);
                         }
                     } else if (event.result.launch_id == ctx.saveFileLaunchId) {
                         ctx.saveFileLaunchId = 0;
                         if (event.result.result == 0 /* Ok */) {
-                            auto path = fileselection::getLastPath();
+                            char destination[sizeof(ctx.saveResultBuffer)];
+                            size_t length = app_stream_read(&ctx.saveResultStream, destination, sizeof(destination));
+                            app_stream_unsubscribe(&ctx.saveResultStream);
+                            auto path = std::string(destination, length);
                             // Must re-open file, because the UI was cleared after opening the dialog.
+                            LOG_I(TAG, "Path: '%s'", path.c_str());
                             if (!path.empty() && saveFile(&ctx, path)) {
                                 openFile(&ctx, path);
                             }
+                        } else {
+                            app_stream_unsubscribe(&ctx.saveResultStream);
                         }
                     }
                     app_manager_stop(event.result.launch_id);

Tactility/Source/file/File.cpp

@@ -66,7 +66,6 @@ int scandir(
     ScandirFilter filterMethod,
     ScandirSort sortMethod
 ) {
-    LOG_I(TAG, "scandir start");
     DIR* dir = opendir(path.c_str());
     if (dir == nullptr) {
         LOG_E(TAG, "Failed to open dir %s", path.c_str());
@@ -86,7 +85,6 @@ int scandir(
         std::ranges::sort(outList, sortMethod);
     }
 
-    LOG_I(TAG, "scandir finish");
     return outList.size();
 }
 

Tactility/Tests/CMakeLists.txt

@@ -19,11 +19,25 @@ target_include_directories(TactilityTests PRIVATE ${CMAKE_CURRENT_LIST_DIR}/../P
 
 add_test(NAME TactilityTests COMMAND TactilityTests)
 
+# Matches Tactility/CMakeLists.txt's own set of --wrap flags: this binary also compiles
+# AppStdioWrap.cpp and links app-module (whose io.cpp calls __real_read/write/close() on
+# non-Apple POSIX - see TT_APP_IO_WRAPS_STDIO in Modules/app-module/CMakeLists.txt), so it
+# needs the same wraps applied or those go unresolved.
+if (NOT APPLE)
+    target_link_options(TactilityTests PRIVATE
+        "-Wl,--wrap=pthread_attr_setstack" "-Wl,--wrap=read" "-Wl,--wrap=write" "-Wl,--wrap=close"
+        "-Wl,--wrap=printf" "-Wl,--wrap=fprintf" "-Wl,--wrap=vprintf" "-Wl,--wrap=vfprintf"
+        "-Wl,--wrap=puts" "-Wl,--wrap=fputs" "-Wl,--wrap=putchar" "-Wl,--wrap=fputc"
+        "-Wl,--wrap=getchar" "-Wl,--wrap=fgetc" "-Wl,--wrap=fgets"
+    )
+endif ()
+
 target_link_libraries(TactilityTests PRIVATE
     TactilityKernel
     TactilityKernelCpp
     TactilityFreeRtos
     platform-posix
+    app-posix-module
     lvgl-module
     lvgl-window-manager-module
     app-module