feat(gui,core): larger icon sizes in My files

The icon grid's size slider stops at 256 px instead of 144 px, which is
big enough to tell photos apart by their thumbnail. Thumbnails are
512 px, so they stay sharp at that size on a 2x screen. Names may wrap
wider on the larger tiles.

Ctrl+plus, Ctrl+minus and Ctrl+0 step and reset the size while the grid
is shown, as they do in Photos. The size is saved in the config as
files_view.icon_size once the slider rests; configs without it keep the
72 px default.

crates/pdfs-gui/src/app/main.rs

@@ -488,6 +488,7 @@ fn build_window(app: &adw::Application) {
             empty_actions: browser_widgets.empty_actions.clone(),
             summary: browser_widgets.summary.clone(),
             zoom: browser_widgets.zoom.clone(),
+            zoom_save: RefCell::new(None),
         },
         details: DetailsState {
             details: browser_widgets.details,
@@ -1523,6 +1524,9 @@ fn show_shortcuts(window: &adw::ApplicationWindow) {
                 ("<Alt>Left <Alt>Right", gettext_noop("Back / forward")),
                 ("<Alt>Up", gettext_noop("Parent folder")),
                 ("<Control>1 <Control>2", gettext_noop("Grid / list")),
+                ("<Control>plus", gettext_noop("Larger thumbnails")),
+                ("<Control>minus", gettext_noop("Smaller thumbnails")),
+                ("<Control>0", gettext_noop("Reset thumbnail size")),
                 ("F2", gettext_noop("Rename")),
                 ("Delete", gettext_noop("Move to Trash")),
                 ("Escape", gettext_noop("Clear the selection")),
@@ -1588,6 +1592,21 @@ fn install_shortcuts(ui: &Rc<Ui>, window: &adw::ApplicationWindow) {
                 ui.browser.search.grab_focus();
             }
             gtk4::gdk::Key::n | gtk4::gdk::Key::N if ctrl && on_browser => prompt_new_folder(&ui),
+            gtk4::gdk::Key::plus | gtk4::gdk::Key::equal | gtk4::gdk::Key::KP_Add
+                if ctrl && on_browser && !ui.browser.files.shows_list() =>
+            {
+                zoom_files(&ui, 1)
+            }
+            gtk4::gdk::Key::minus | gtk4::gdk::Key::KP_Subtract
+                if ctrl && on_browser && !ui.browser.files.shows_list() =>
+            {
+                zoom_files(&ui, -1)
+            }
+            gtk4::gdk::Key::_0 | gtk4::gdk::Key::KP_0
+                if ctrl && on_browser && !ui.browser.files.shows_list() =>
+            {
+                zoom_files(&ui, 0)
+            }
             gtk4::gdk::Key::_1 | gtk4::gdk::Key::_2 if ctrl && on_browser => set_files_view(
                 &ui,
                 FilesView {

crates/pdfs-gui/src/app/pages/browser.rs

@@ -77,6 +77,8 @@ pub(crate) struct BrowserState {
     /// zoom value, and Proton account storage usage.
     pub(crate) summary: gtk4::Label,
     pub(crate) zoom: gtk4::Scale,
+    /// Saves the zoom once the slider rests, not on every step.
+    pub(crate) zoom_save: RefCell<Option<glib::SourceId>>,
 }
 
 /// Idle pause after the last keystroke before a search query is sent, so typing
@@ -87,9 +89,11 @@ pub(crate) const SEARCH_DEBOUNCE: Duration = Duration::from_millis(250);
 pub(crate) const SEARCH_LIMIT: usize = 200;
 
 /// Browser grid thumbnail size controlled by the bottom zoom slider. The
-/// default preserves the former fixed 72 px presentation.
+/// default preserves the former fixed 72 px presentation. The largest size is
+/// big enough to tell photos apart by their thumbnail, and thumbnails are
+/// 512 px, so they stay sharp up to it on a 2× screen.
 pub(crate) const GRID_THUMB_MIN: i32 = 48;
-pub(crate) const GRID_THUMB_MAX: i32 = 144;
+pub(crate) const GRID_THUMB_MAX: i32 = 256;
 pub(crate) const GRID_THUMB_DEFAULT: i32 = 72;
 pub(crate) const GRID_THUMB_STEP: i32 = 8;
 
@@ -801,6 +805,7 @@ pub(crate) fn wire_browser(ui: &Rc<Ui>) {
             &[],
         )));
         ui_zoom.browser.files.set_thumbnail_size(size);
+        save_icon_size(&ui_zoom, size);
     });
 
     files
@@ -1306,6 +1311,11 @@ pub(crate) fn wire_browser_actions(ui: &Rc<Ui>, build_thumbnails: &gtk4::Button)
 
     let view = ui.dirs.load_config().files_view;
     ui.browser.view.set(view);
+    if let Some(size) = view.icon_size {
+        ui.browser
+            .zoom
+            .set_value(f64::from(size.clamp(GRID_THUMB_MIN, GRID_THUMB_MAX)));
+    }
     let layout = gio::SimpleAction::new_stateful(
         "view",
         Some(glib::VariantTy::STRING),
@@ -1407,6 +1417,41 @@ pub(crate) fn wire_browser_actions(ui: &Rc<Ui>, build_thumbnails: &gtk4::Button)
     ui.browser.content.add_controller(drop);
 }
 
+/// Remember the grid's icon size, once the slider has rested for a moment.
+fn save_icon_size(ui: &Rc<Ui>, size: i32) {
+    let mut view = ui.browser.view.get();
+    if view.icon_size == Some(size) {
+        return;
+    }
+    view.icon_size = Some(size);
+    ui.browser.view.set(view);
+    if let Some(source) = ui.browser.zoom_save.borrow_mut().take() {
+        source.remove();
+    }
+    let ui_save = ui.clone();
+    let source = glib::timeout_add_local_once(Duration::from_millis(500), move || {
+        ui_save.browser.zoom_save.borrow_mut().take();
+        let mut config = ui_save.dirs.load_config();
+        config.files_view.icon_size = ui_save.browser.view.get().icon_size;
+        if let Err(e) = ui_save.dirs.save_config(&config) {
+            tracing::warn!("cannot save the icon size: {e}");
+        }
+    });
+    *ui.browser.zoom_save.borrow_mut() = Some(source);
+}
+
+/// Step the grid's icon size by `steps` slider notches; `0` resets it.
+pub(crate) fn zoom_files(ui: &Rc<Ui>, steps: i32) {
+    let zoom = &ui.browser.zoom;
+    let size = if steps == 0 {
+        GRID_THUMB_DEFAULT
+    } else {
+        (zoom.value().round() as i32 + steps * GRID_THUMB_STEP)
+            .clamp(GRID_THUMB_MIN, GRID_THUMB_MAX)
+    };
+    zoom.set_value(f64::from(size));
+}
+
 fn layout_name(view: FilesView) -> &'static str {
     if view.list { "list" } else { "grid" }
 }

crates/pdfs-gui/src/app/widgets/file_list.rs

@@ -478,7 +478,7 @@ pub(crate) fn text_column(
 
 fn resize_grid_tile(thumbnail: &gtk4::Overlay, label: &gtk4::Label, size: i32) {
     resize_file_thumbnail(thumbnail, size, grid_fallback_size(size));
-    let name_width = (size / 6 + 1).clamp(8, 24);
+    let name_width = (size / 6 + 1).clamp(8, 40);
     label.set_width_chars(name_width);
     label.set_max_width_chars(name_width);
 }