ODS polish + reusable confirm modal + file-dialog focus/overwrite fixes.

ODS writer:
- Header row styled bold on a grey background; data rows alternate
  light-grey / white (zebra). Auto-filter buttons enabled per sheet
  via `<table:database-range table:display-filter-buttons="true">`
  — sheet names are now single-quoted in the target-range-address so
  LibreOffice actually parses ranges that contain spaces.
- First row of every sheet frozen via `settings.xml` (view setting).
  The settings layout follows LibreOffice's own writer exactly:
  `xmlns:ooo` + `xmlns:xlink` declared on the root, `ActiveTable` and
  view-level zoom/grid/headers placed *after* the Tables map (the
  order LibreOffice expects to read back). HorizontalSplitMode = 0,
  VerticalSplitMode = 2 → only the first row is frozen, the first
  column scrolls normally. ActiveSplitRange = 2 (bottom-left pane).
  `settings.xml` registered in `META-INF/manifest.xml`.

Reusable Yes/No modal:
- New `screen_confirm.cpp` exposing `Tui::ShowConfirm(msg, on_yes)`.
  Centred `borderRounded` popup, `No` first (safer default), Enter
  confirms the focused button, Esc cancels (treated as No).
- Stacked into the Modal chain in `Run()` (between file-dialog and
  error). The outer `CatchEvent` cedes events when it's open.

File dialog:
- Picks `OK` button focus reliably — previously the focus indices in
  the Renderer were remapped against the Container::Vertical child
  indices, so the OK label only flagged "focused" while the actual
  focused child was the filename input.
- OK button uses a custom `ButtonOption::transform` that renders the
  label transparent when idle, inverted when focused. No more
  cyan-fill, no more double-inversion via FocusLabel.
- After confirmation, if the picked path already exists, pops a
  `ShowConfirm("File … already exists. Overwrite?")` before invoking
  the caller's action.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/imports/ods_writer.cpp

@@ -35,9 +35,46 @@ OdsSheet *OdsWriter::add_sheet(const std::string &name) {
 
 namespace {
 
+// Column-letter encoding (0 → A, 25 → Z, 26 → AA, …). Used to spell out
+// the auto-filter range address.
+std::string col_letter(int c) {
+    std::string s;
+    ++c;
+    while (c > 0) {
+        --c;
+        s = char('A' + c % 26) + s;
+        c /= 26;
+    }
+    return s;
+}
+
+// Append the three styles we use throughout: `hdr` for the first row
+// (bold + grey background), `even` / `odd` for the zebra-striped data
+// rows. Defined as cell-family automatic styles so callers don't need
+// to declare them.
+void append_styles(pugi::xml_node &root) {
+    auto autos = root.append_child("office:automatic-styles");
+    auto add = [&](const char *name, bool bold,
+                    const char *bg) {
+        auto st = autos.append_child("style:style");
+        st.append_attribute("style:name")   = name;
+        st.append_attribute("style:family") = "table-cell";
+        if (bold) {
+            auto tp = st.append_child("style:text-properties");
+            tp.append_attribute("fo:font-weight") = "bold";
+        }
+        auto cp = st.append_child("style:table-cell-properties");
+        cp.append_attribute("fo:background-color") = bg;
+    };
+    add("hdr",  /*bold=*/true,  "#dddddd");
+    add("even", /*bold=*/false, "#f2f2f2");
+    add("odd",  /*bold=*/false, "#ffffff");
+}
+
 // Build the `content.xml` payload for the spreadsheet. Returns the
-// serialised UTF-8 string. The minimum schema the format requires for
+// serialised UTF-8 string. Minimum-but-styled: includes header / zebra
-// a string-only multi-sheet workbook.
+// cell styles and a database-range per sheet so LibreOffice / Excel
+// render auto-filter buttons on the first row.
 std::string build_content_xml(const std::vector<OdsSheet> &sheets) {
     pugi::xml_document doc;
     auto decl = doc.append_child(pugi::node_declaration);
@@ -51,8 +88,14 @@ std::string build_content_xml(const std::vector<OdsSheet> &sheets) {
         "urn:oasis:names:tc:opendocument:xmlns:table:1.0";
     root.append_attribute("xmlns:text") =
         "urn:oasis:names:tc:opendocument:xmlns:text:1.0";
+    root.append_attribute("xmlns:style") =
+        "urn:oasis:names:tc:opendocument:xmlns:style:1.0";
+    root.append_attribute("xmlns:fo") =
+        "urn:oasis:names:tc:opendocument:xmlns:xsl-fo-compatible:1.0";
     root.append_attribute("office:version") = "1.2";
 
+    append_styles(root);
+
     auto body = root.append_child("office:body");
     auto sheet_root = body.append_child("office:spreadsheet");
 
@@ -63,8 +106,12 @@ std::string build_content_xml(const std::vector<OdsSheet> &sheets) {
         int cols = s.cols();
         for (int r = 0; r < rows; ++r) {
             auto row = table.append_child("table:table-row");
+            const char *style = (r == 0)        ? "hdr"
+                              : (r % 2 == 1)    ? "odd"
+                              :                   "even";
             for (int c = 0; c < cols; ++c) {
                 auto cell = row.append_child("table:table-cell");
+                cell.append_attribute("table:style-name") = style;
                 cell.append_attribute("office:value-type") = "string";
                 auto p = cell.append_child("text:p");
                 p.append_child(pugi::node_pcdata).set_value(s.cell(r, c).c_str());
@@ -72,6 +119,40 @@ std::string build_content_xml(const std::vector<OdsSheet> &sheets) {
         }
     }
 
+    // Auto-filter per sheet: one <table:database-range> with display-
+    // filter-buttons=true covering the full grid (header + data). The
+    // range address syntax is `<sheet>.A1:<lastcol><lastrow>`. Sheet
+    // names with spaces or special characters MUST be single-quoted
+    // (and embedded `'` doubled) — without the quotes LibreOffice
+    // silently fails to parse the range and the filter buttons don't
+    // appear. Quoting unconditionally is safe.
+    auto quote_sheet = [](const std::string &name) {
+        std::string out = "'";
+        for (char c : name) {
+            if (c == '\'') out += "''";
+            else out += c;
+        }
+        out += "'";
+        return out;
+    };
+    if (!sheets.empty()) {
+        auto ranges = sheet_root.append_child("table:database-ranges");
+        int idx = 1;
+        for (const auto &s : sheets) {
+            int rows = s.rows();
+            int cols = s.cols();
+            if (rows < 1 || cols < 1) continue;
+            std::string addr = quote_sheet(s.name()) + ".A1:"
+                             + col_letter(cols - 1) + std::to_string(rows);
+            auto dr = ranges.append_child("table:database-range");
+            std::string name = "filter_" + std::to_string(idx++);
+            dr.append_attribute("table:name") = name.c_str();
+            dr.append_attribute("table:display-filter-buttons") = "true";
+            dr.append_attribute("table:target-range-address") = addr.c_str();
+            dr.append_attribute("table:orientation") = "row";
+        }
+    }
+
     std::ostringstream oss;
     // We added the declaration node explicitly above, so pugi will emit
     // it. `format_no_declaration` only suppresses *implicit* injection;
@@ -89,9 +170,95 @@ std::string build_manifest_xml() {
            R"(<manifest:manifest xmlns:manifest="urn:oasis:names:tc:opendocument:xmlns:manifest:1.0" manifest:version="1.2">)" "\n"
            R"(  <manifest:file-entry manifest:full-path="/" manifest:media-type="application/vnd.oasis.opendocument.spreadsheet"/>)" "\n"
            R"(  <manifest:file-entry manifest:full-path="content.xml" manifest:media-type="text/xml"/>)" "\n"
+           R"(  <manifest:file-entry manifest:full-path="settings.xml" manifest:media-type="text/xml"/>)" "\n"
            R"(</manifest:manifest>)" "\n";
 }
 
+// `settings.xml` carries view-only properties — freeze panes is the
+// only thing we need here. Per ODF 1.2 the structure is deeply nested
+// config-item maps; the values that matter for "freeze first row and
+// first column":
+//   HorizontalSplitMode / VerticalSplitMode = 2  (2 = "frozen")
+//   HorizontalSplitPosition / VerticalSplitPosition = 1 (split after
+//     first column / first row)
+//   PositionRight / PositionBottom = 1 (first non-frozen cell at B2)
+std::string build_settings_xml(const std::vector<OdsSheet> &sheets) {
+    pugi::xml_document doc;
+    auto decl = doc.append_child(pugi::node_declaration);
+    decl.append_attribute("version") = "1.0";
+    decl.append_attribute("encoding") = "UTF-8";
+
+    auto root = doc.append_child("office:document-settings");
+    // Namespace cocktail expected by LibreOffice — without `xmlns:ooo`
+    // and `xmlns:xlink` here it silently ignores the view-settings.
+    root.append_attribute("xmlns:config") =
+        "urn:oasis:names:tc:opendocument:xmlns:config:1.0";
+    root.append_attribute("xmlns:xlink") = "http://www.w3.org/1999/xlink";
+    root.append_attribute("xmlns:ooo")   = "http://openoffice.org/2004/office";
+    root.append_attribute("xmlns:office") =
+        "urn:oasis:names:tc:opendocument:xmlns:office:1.0";
+    root.append_attribute("office:version") = "1.2";
+
+    auto settings = root.append_child("office:settings");
+    auto view_set = settings.append_child("config:config-item-set");
+    view_set.append_attribute("config:name") = "ooo:view-settings";
+    auto views = view_set.append_child("config:config-item-map-indexed");
+    views.append_attribute("config:name") = "Views";
+    auto view = views.append_child("config:config-item-map-entry");
+
+    auto add_item = [&](pugi::xml_node &parent, const char *name,
+                         const char *type, const std::string &v) {
+        auto n = parent.append_child("config:config-item");
+        n.append_attribute("config:name") = name;
+        n.append_attribute("config:type") = type;
+        n.append_child(pugi::node_pcdata).set_value(v.c_str());
+    };
+
+    // Inside the View entry, the order matters: ViewId first, then the
+    // Tables map, then ActiveTable + zoom (NOT before Tables — that's
+    // the layout LibreOffice writes itself and reliably reads back).
+    add_item(view, "ViewId", "string", "view1");
+
+    auto tables = view.append_child("config:config-item-map-named");
+    tables.append_attribute("config:name") = "Tables";
+
+    for (const auto &s : sheets) {
+        auto t = tables.append_child("config:config-item-map-entry");
+        t.append_attribute("config:name") = s.name().c_str();
+        // Cursor at A1 (anchors the view state).
+        add_item(t, "CursorPositionX",      "int",   "0");
+        add_item(t, "CursorPositionY",      "int",   "0");
+        // Freeze the first row only: horizontal split off, vertical
+        // split frozen one row in. ActiveSplitRange = 2 (bottom-left
+        // sub-pane = the scrollable data).
+        add_item(t, "HorizontalSplitMode",  "short", "0");
+        add_item(t, "VerticalSplitMode",    "short", "2");
+        add_item(t, "HorizontalSplitPosition", "int", "0");
+        add_item(t, "VerticalSplitPosition",   "int", "1");
+        add_item(t, "ActiveSplitRange",     "short", "2");
+        add_item(t, "PositionLeft",         "int",   "0");
+        add_item(t, "PositionRight",        "int",   "0");
+        add_item(t, "PositionTop",          "int",   "0");
+        add_item(t, "PositionBottom",       "int",   "1");
+        add_item(t, "ZoomType",             "short", "0");
+        add_item(t, "ZoomValue",            "int",   "100");
+        add_item(t, "ShowGrid",             "boolean", "true");
+    }
+
+    if (!sheets.empty()) {
+        add_item(view, "ActiveTable", "string", sheets.front().name());
+    }
+    add_item(view, "ZoomType",            "short", "0");
+    add_item(view, "ZoomValue",           "int",   "100");
+    add_item(view, "ShowGrid",            "boolean", "true");
+    add_item(view, "HasColumnRowHeaders", "boolean", "true");
+    add_item(view, "HasSheetTabs",        "boolean", "true");
+
+    std::ostringstream oss;
+    doc.save(oss, "", pugi::format_raw);
+    return oss.str();
+}
+
 // libzip wrapper for "add a string as a file with the given name". The
 // buffer must outlive zip_close, which is why callers keep a vector of
 // owned strings alive until after the close.
@@ -134,10 +301,12 @@ bool OdsWriter::save(const std::string &path, std::string &error) const {
     std::string mimetype = "application/vnd.oasis.opendocument.spreadsheet";
     std::string manifest = build_manifest_xml();
     std::string content  = build_content_xml(sheets_);
+    std::string settings = build_settings_xml(sheets_);
 
     if (!add_string_entry(zip, "mimetype",                mimetype, /*store=*/true,  error) ||
         !add_string_entry(zip, "META-INF/manifest.xml",   manifest, /*store=*/false, error) ||
-        !add_string_entry(zip, "content.xml",             content,  /*store=*/false, error)) {
+        !add_string_entry(zip, "content.xml",             content,  /*store=*/false, error) ||
+        !add_string_entry(zip, "settings.xml",            settings, /*store=*/false, error)) {
         zip_discard(zip);
         return false;
     }

src/tui/screen_confirm.cpp

@@ -0,0 +1,62 @@
+#include "tui/tui.hpp"
+
+#include <ftxui/component/component.hpp>
+#include <ftxui/component/event.hpp>
+#include <ftxui/dom/elements.hpp>
+
+#include <utility>
+
+using namespace ftxui;
+
+void Tui::ShowConfirm(const std::string &msg, std::function<void()> on_yes) {
+    confirm_message = msg;
+    confirm_on_yes  = std::move(on_yes);
+    confirm_open    = true;
+}
+
+Component Tui::BuildConfirmModal() {
+    // Transparent label idle, inverted when focused.
+    ButtonOption btn_opt;
+    btn_opt.transform = [](const EntryState &s) {
+        Element el = text(s.label);
+        if (s.focused) el = el | inverted;
+        return el;
+    };
+    auto yes = Button(" Yes ", [this]() {
+        // Copy the callback before resetting state so the user can
+        // (re-)open a confirm modal from inside their on_yes handler
+        // without losing the original.
+        auto cb = confirm_on_yes;
+        confirm_on_yes = nullptr;
+        confirm_open = false;
+        if (cb) cb();
+    }, btn_opt);
+    auto no  = Button(" No ",  [this]() {
+        confirm_on_yes = nullptr;
+        confirm_open = false;
+    }, btn_opt);
+    // No first → safer default.
+    auto buttons = Container::Horizontal({no, yes});
+
+    auto handler = CatchEvent(buttons, [this](Event e) {
+        if (e == Event::Escape) {
+            confirm_on_yes = nullptr;
+            confirm_open = false;
+            return true;
+        }
+        return false;
+    });
+
+    return Renderer(handler, [this, yes, no] {
+        return vbox({
+            text(" Confirm ") | bold | center,
+            separator(),
+            paragraph(confirm_message),
+            separator(),
+            hbox({filler(), no->Render(), text("  "), yes->Render(), filler()}),
+            text(" Tab cycle  •  Enter confirm  •  Esc = No ") | dim,
+        }) | borderRounded
+           | size(WIDTH, LESS_THAN, 60)
+           | size(WIDTH, GREATER_THAN, 36);
+    });
+}

src/tui/screen_filedialog.cpp

@@ -83,9 +83,8 @@ void Tui::OpenFileDialog(std::string title,
     }
 
     file_dialog.entry_idx = 0;
-    // Default focus: filename input. With filters present that's slot 2;
+    // Default focus: filename input (Container child 2).
-    // without, slot 1.
+    file_dialog.focus_idx = 2;
-    file_dialog.focus_idx = file_dialog.filters.empty() ? 1 : 2;
     file_dialog.open      = true;
 }
 
@@ -117,7 +116,19 @@ void Tui::ConfirmFileDialog() {
     SaveLastUsed(file_dialog.persist_key,
                  file_dialog.dir, file_dialog.filename);
     file_dialog.open = false;
-    if (cb) cb(full.string());
+
+    auto invoke = [cb, full]() { if (cb) cb(full.string()); };
+
+    // Overwrite guard: if the file already exists, ask before letting
+    // the action proceed. Esc / No cancels; Yes runs the action.
+    std::error_code ec;
+    if (fs::exists(full, ec) && !ec) {
+        ShowConfirm("File '" + full.string() + "' already exists.\n"
+                    "Overwrite?",
+                    invoke);
+        return;
+    }
+    invoke();
 }
 
 Component Tui::BuildFileDialog() {
@@ -146,7 +157,7 @@ Component Tui::BuildFileDialog() {
                                        ext_of(file_dialog.filename));
                 if (i >= 0) file_dialog.filter_idx = i;
             }
-            file_dialog.focus_idx = file_dialog.filters.empty() ? 2 : 3;
+            file_dialog.focus_idx = 3;   // jump to the OK button
             return;
         }
         std::error_code ec;
@@ -165,7 +176,15 @@ Component Tui::BuildFileDialog() {
     // lambda below (FTXUI's plain Toggle API has no on_change hook).
     auto filter_toggle = Toggle(&file_dialog.filter_labels, &file_dialog.filter_idx);
 
-    auto button = Button(" OK ", [this]() { ConfirmFileDialog(); });
+    // Transparent label when idle, inverted (reverse-video) when focused
+    // — clearly visible without painting a colour into the background.
+    ButtonOption btn_opt;
+    btn_opt.transform = [](const EntryState &s) {
+        Element el = text(s.label);
+        if (s.focused) el = el | inverted;
+        return el;
+    };
+    auto button = Button(" OK ", [this]() { ConfirmFileDialog(); }, btn_opt);
 
     auto container = Container::Vertical(
         {filter_toggle, entries_menu, filename_input, button},
@@ -173,14 +192,14 @@ Component Tui::BuildFileDialog() {
 
     auto handler = CatchEvent(container, [this](Event e) {
         if (e == Event::Escape) { file_dialog.open = false; return true; }
-        // The number of focusable slots depends on whether filters are
+        // Container has 4 children at indices 0..3: filter_toggle,
-        // present (4 with, 3 without). Skip slot 0 (filters) when empty.
+        // entries_menu, filename_input, button. `focus_idx` indexes
-        int n = file_dialog.filters.empty() ? 3 : 4;
+        // them directly. When the dialog has no filters, slot 0 is
+        // unused (the toggle isn't rendered) and Tab must skip it.
         int base = file_dialog.filters.empty() ? 1 : 0;
         if (e == Event::Tab) {
             do { file_dialog.focus_idx = (file_dialog.focus_idx + 1) % 4;
             } while (file_dialog.focus_idx < base);
-            (void)n;
             return true;
         }
         if (e == Event::TabReverse) {
@@ -251,23 +270,23 @@ Component Tui::BuildFileDialog() {
         }
         rows.push_back(hbox({text(" dir: ") | dim, text(file_dialog.dir)}));
         rows.push_back(separator());
-        int entries_focus = file_dialog.filters.empty() ? 0 : 1;
+        // Focus index maps directly to the Container::Vertical child
-        int fname_focus   = file_dialog.filters.empty() ? 1 : 2;
+        // index — 1 = entries, 2 = filename, 3 = button (0 = filter
-        int btn_focus     = file_dialog.filters.empty() ? 2 : 3;
+        // toggle, only meaningful when filters are present).
         rows.push_back(FocusLabel(text(" entries "),
-                                  file_dialog.focus_idx == entries_focus) | bold);
+                                  file_dialog.focus_idx == 1) | bold);
         rows.push_back(entries_menu->Render() | vscroll_indicator | yframe
                        | size(HEIGHT, LESS_THAN, 16) | size(HEIGHT, GREATER_THAN, 6));
         rows.push_back(separator());
         rows.push_back(hbox({
-            FocusLabel(text(" filename: "), file_dialog.focus_idx == fname_focus),
+            FocusLabel(text(" filename: "), file_dialog.focus_idx == 2),
             filename_input->Render() | flex,
         }) | border);
         rows.push_back(separator());
-        rows.push_back(hbox({filler(),
+        // The button's own ButtonOption::transform already inverts the
-                             FocusLabel(button->Render(),
+        // label when focused — no outer FocusLabel here (it would
-                                        file_dialog.focus_idx == btn_focus),
+        // double-invert and cancel out).
-                             filler()}));
+        rows.push_back(hbox({filler(), button->Render(), filler()}));
         rows.push_back(status);
         rows.push_back(text(" Tab cycle  •  Enter: cd / pick / confirm  •  Esc cancel ") | dim);
 

src/tui/tui.cpp

@@ -53,13 +53,15 @@ void Tui::Run() {
     auto with_palette = tab | Modal(BuildPaletteModal(), &palette_open);
     auto with_dialog  = with_palette
                       | Modal(BuildFileDialog(), &file_dialog.open);
-    auto with_error   = with_dialog
+    auto with_confirm = with_dialog
+                      | Modal(BuildConfirmModal(), &confirm_open);
+    auto with_error   = with_confirm
                       | Modal(BuildErrorModal(), &error_open);
 
     auto root = CatchEvent(with_error, [this](Event e) {
-        // Modals own their events while open. Error modal has priority.
+        // Modals own their events while open. Error modal sits on top.
-        if (error_open || palette_open || sigtype_dialog_open
+        if (error_open || confirm_open || palette_open
-            || file_dialog.open) return false;
+            || sigtype_dialog_open || file_dialog.open) return false;
 
         // Ctrl-P opens the palette from any screen.
         if (e == Event::CtrlP) { OpenPalette(); return true; }

src/tui/tui.hpp

@@ -112,6 +112,11 @@ class Tui {
     bool error_open = false;
     std::string error_message;
 
+    // ---- Generic Yes/No confirmation dialog (modal) ----
+    bool confirm_open = false;
+    std::string confirm_message;
+    std::function<void()> confirm_on_yes;
+
     // ---- Generic file-picker dialog (modal) ----
     // Reused for any "pick a path" interaction (export, save, restore, …).
     // `persist_key` ties the dir + filename to a key persisted under the
@@ -251,10 +256,15 @@ private:
     ftxui::Component BuildHelpScreen();
     ftxui::Component BuildFileDialog();
     ftxui::Component BuildErrorModal();
+    ftxui::Component BuildConfirmModal();
     // Pop a centred modal with `msg` and an OK button. Esc / Enter close
     // it. Use for actionable failures the user must see (write errors,
     // bad inputs, etc.) — for normal feedback keep `Print()`.
     void ShowError(const std::string &msg);
+    // Pop a centred Yes/No modal. `on_yes` runs only if the user picks
+    // Yes (Esc and No cancel). Use for destructive confirmations
+    // (overwrite a file, delete a snapshot, …).
+    void ShowConfirm(const std::string &msg, std::function<void()> on_yes);
     // Open the picker modal. `persist_key` controls where the last-used
     // dir + filename are stored (one tiny file per key under the user
     // data directory). `on_confirm` runs when the user presses Enter on