Fix Open dialog directory precedence and add recent-folder fallback

docs/domain/file-io.md

@@ -11,6 +11,13 @@
 - If temp-file setup fails, saving falls back to writing the target directly. After a successful temp-file write, replacement tries `ReplaceFileW` for an existing target, then `MoveFileExW` with replace/write-through flags; a replacement failure makes the save fail.
 - `Globals.dwLastError` holds the Win32 error. In `FileSave()`, check `ERROR_ACCESS_DENIED` and `ERROR_PATH_NOT_FOUND` before the generic fallback.
 
+## Open-dialog initial directory
+
+- `OpenFileDlg()` / `_ResolveOpenInitialDir()` in `src\Dialogs.c` prefer an explicit initial path, then the current file's directory, `Settings.DefaultDirectoryOverride`, and `Settings2.DefaultDirectory`.
+- With none of those available and `Settings.SaveRecentFiles` enabled, Open uses the newest MRU entry's parent directory if it exists (the file itself need not exist). Otherwise it uses `Paths.WorkingDirectory`. It does not search older MRU entries.
+- MRU paths must be sanitized, unquoted, and expanded with `Path_AbsoluteFromApp(..., true)` before taking the parent directory with the drive-root-safe `_GetParentDir()`. An unavailable parent clears the candidate so the shared resolver supplies the working directory. Save dialogs do not use history.
+- An invalid final directory still falls back to Documents; Save also requires a writable directory. Focused coverage: `test\TestOpenDialogDirectory.ps1`.
+
 ## File watching
 
 `InstallFileWatching()` uses `FindFirstChangeNotificationW` on the parent directory. Stop watching with `InstallFileWatching(false)` before saving, then reinstall it with `InstallFileWatching(true)` afterward.

docs/domain/startup-and-window-lifecycle.md

@@ -17,3 +17,7 @@ The runtime toggle is `IDM_EDIT_TOGGLE_PASTEBOARD`; `/B` enables Pasteboard Mode
 - If there is no acknowledging target, the launched process adopts the AppID and opens a new window.
 - The handoff to `DialogNewWindow` passes `-n` semantics, so a taskbar new-window request bypasses `ReuseWindow`.
 - Every AppUserModel property set through the window property store must be cleared in `ClearWindowAppUserModelID()` during `WM_DESTROY`.
+
+## Startup with a directory argument
+
+- A directory passed as the startup path opens the file dialog rooted in that directory (`Notepad3.c` startup path handling). `OpenFileDlg()` may receive the same `HPATHL` as both output and initial-directory input; it must copy the initial directory before clearing the output path (`Dialogs.c`).

readme/MenuEntriesAndCmds.md

@@ -563,8 +563,10 @@ Editor behaviour, persistence, and platform integration. Most items are toggles
 
 | Menu | Description |
 |---|---|
-| **Set to Current File's Directory** | Bind the *Open* / *Save As* default to the current file's directory. |
-| **Reset to Default** | Restore the standard "Documents" default. |
+| **Set to Current File's Directory** | Store the current file's directory as the *Open* / *Save As* default when no file is open. This is a fixed directory, not a setting that tracks later files. |
+| **Reset to Default** | Clear the menu-set directory override and return to the configured `DefaultDirectory` or the normal fallback. |
+
+An explicitly supplied directory (for example, a directory command-line argument) takes precedence over these defaults, as does the directory of an open file. With no current file or configured default, **Open** can use the most recent file's directory when **Remember Recent Files** is enabled. See [file-dialog starting directories](paths/FilePathHandling.md#file-dialog-starting-directory) for the full order and fallbacks.
 
 ### Remember
 

readme/config/Configuration.md

@@ -120,6 +120,10 @@ This pattern is used by **Shift+F5** to update timestamps, e.g., `$Date: 2018/04
 
 Default directory for open/save dialogs when no file is open. Paths can be relative to the Notepad3 program directory.
 
+**Settings → Default Directory → Set to Current File's Directory** stores a separate override (`DefaultDirectoryOverride` under `[Settings]`); **Reset to Default** clears that override without changing this key. An explicit directory or the currently open file's directory takes precedence over both defaults.
+
+If neither default is defined, **Open** tries the most recent file's existing directory when **Remember Recent Files** is enabled, then the working directory. This history fallback does not apply to **Save As**. See [file-dialog starting directories](../paths/FilePathHandling.md#file-dialog-starting-directory).
+
 #### `DefaultExtension=txt`
 
 Default extension for saved files (omit the leading dot).

readme/faq/FAQ.md

@@ -190,6 +190,8 @@ Yes. Notepad3 always looks beside the exe first — `%APPDATA%` is only consulte
 
 `DefaultDirectory=` and `DefaultExtension=txt` under `[Settings2]`.
 
+You can also choose **Settings → Default Directory → Set to Current File's Directory** to store a fixed default folder. With no current file and no default folder defined, **Open** tries the most recent file's directory if **Remember Recent Files** is enabled, then the working directory. See [file-dialog starting directories](../paths/FilePathHandling.md#file-dialog-starting-directory).
+
 ### How do I customize the date/time format for "Update Timestamps" (Shift+F5)?
 
 You need to define **both** of the following in `[Settings2]`:

readme/paths/FilePathHandling.md

@@ -284,6 +284,25 @@ The Recent Files list in the File menu is persisted in `Notepad3.ini` under
 `[Recent Files]`. Disable persistence with the `NoSaveRecent` setting.
 Entries can be removed individually from the MRU dialog.
 
+### File-dialog starting directory
+
+The **Open** dialog chooses its starting directory in this order:
+
+1. An explicitly supplied directory. Passing a directory rather than a file on the command line opens the dialog there.
+2. The directory of the currently open file.
+3. The fixed directory stored by **Settings → Default Directory → Set to Current File's Directory**.
+4. `DefaultDirectory` under `[Settings2]`.
+5. The most recent file's parent directory, if **Remember Recent Files** is enabled and that directory still exists.
+6. The process working directory (set by the launcher, such as a shortcut's **Start in** folder).
+
+To start Notepad3 with the Open dialog in the current directory, run `Notepad3.exe .`.
+
+The recent file itself need not still exist. Only the newest history entry is considered; a missing directory falls back to the working directory rather than searching older entries. If the final directory is unavailable, the dialog falls back to **Documents**.
+
+**Save As** uses the same defaults but does not use recent-file history, and falls back to **Documents** if the selected directory is not writable. **Reset to Default** clears only the menu-set override; it does not clear `DefaultDirectory` or force **Documents**.
+
+Starting without a file or directory argument does not itself display the Open dialog. **Autoload Recent File** is a separate option that loads the newest history entry at startup; if loaded, that file's directory applies as the current-file directory above.
+
 ### Portable & redirected INI
 
 By default `Notepad3.ini` lives next to `Notepad3.exe` (portable mode). The
@@ -304,7 +323,7 @@ descriptions.
 |---|---|
 | `AtomicFileSave` | Two-phase Save (temp file + ReplaceFileW). |
 | `ResolveUNCPaths` | When opening a UNC path that's actually a mapped drive's share, prefer the drive-letter form for display. |
-| `DefaultDirectory` | Initial directory of the **Open…** dialog. |
+| `DefaultDirectory` | Default directory for **Open…** / **Save As** when no file is open; see [starting-directory precedence](#file-dialog-starting-directory). |
 | `OpenWithDir` | Directory used by **Open with…**. |
 | `FavoritesDir` | Where the Favorites list lives. |
 | `GrepWinPath` | Override the grepWin executable lookup. |

src/Dialogs.c

@@ -7457,6 +7457,26 @@ static void _CanonicalizeInitialDir(HPATHL hpth_in_out, bool bMustBeWritable)
     }
 }
 
+static void _ResolveOpenInitialDir(HPATHL hpth_in_out)
+{
+    if (Path_IsEmpty(hpth_in_out) && Path_IsEmpty(Paths.CurrentFile) &&
+        Path_IsEmpty(Settings.DefaultDirectoryOverride) && Path_IsEmpty(Settings2.DefaultDirectory) &&
+        Settings.SaveRecentFiles && MRU_Count(Globals.pFileMRU) > 0) {
+        LPWSTR const fileBuf = Path_WriteAccessBuf(hpth_in_out, PATHLONG_MAX_CCH);
+        int const fileLength = MRU_Enum(Globals.pFileMRU, 0, fileBuf, (int)Path_GetBufCount(hpth_in_out));
+        Path_Sanitize(hpth_in_out);
+        if (fileLength > 0) {
+            Path_UnQuoteSpaces(hpth_in_out);
+            Path_AbsoluteFromApp(hpth_in_out, true);
+            _GetParentDir(hpth_in_out);
+        }
+        if (!Path_IsExistingDirectory(hpth_in_out)) {
+            Path_Empty(hpth_in_out, false);
+        }
+    }
+    _CanonicalizeInitialDir(hpth_in_out, false);
+}
+
 
 // ============================================================================
 //
@@ -7691,15 +7711,15 @@ bool OpenFileDlg(HWND hwnd, HPATHL hfile_pth_io, const HPATHL hinidir_pth)
     if (!hfile_pth_io) {
         return false;
     }
+    HPATHL hpth_dir = Path_Copy(hinidir_pth);
     if (!Path_IsEmpty(hinidir_pth)) {
         Path_Empty(hfile_pth_io, false);
     }
     WCHAR szDefExt[64] = { L'\0' };
     WCHAR szFilter[EXTENSIONS_FILTER_BUFFER];
     Style_GetFileFilterStr(szFilter, COUNTOF(szFilter), szDefExt, COUNTOF(szDefExt), false);
 
-    HPATHL hpth_dir = Path_Copy(hinidir_pth);
-    _CanonicalizeInitialDir(hpth_dir, false);
+    _ResolveOpenInitialDir(hpth_dir);
 
     LPCWSTR defExt = StrIsNotEmpty(szDefExt) ? szDefExt : Settings2.DefaultExtension;
     LPCWSTR initDir = Path_IsNotEmpty(hpth_dir) ? Path_Get(hpth_dir) : NULL;