#1209: everything that opens or closes the left panel does so on a phone too

UiState::open_left_panel / close_left_panel set the narrow window's panel along with left_collapsed:
the Assets panel (Shift+I), libraries, file and layer rename, page select, version history, the rail
tabs, the panel's Collapse button and panel.leftSidebar (which toggles what a narrow window shows).
Test: view.assets opens the left panel in a phone-sized window.

crates/ui-egui/src/layers.rs

@@ -118,10 +118,10 @@ pub fn rail(app: &mut FigApp, ui: &mut Ui) {
                 Some(tb) => {
                     // Leaving the version history shows the tab rather than collapsing it.
                     if active {
-                        app.ui.left_collapsed = true;
+                        app.ui.close_left_panel();
                     } else {
                         app.ui.left_tab = tb;
-                        app.ui.left_collapsed = false;
+                        app.ui.open_left_panel();
                     }
                     app.ui.versions = Default::default();
                 }
@@ -161,7 +161,7 @@ pub fn left_panel(app: &mut FigApp, ui: &mut Ui) {
     }
     icons::paint(ui.painter(), hr.shrink(5.0), Icon::Panels, t.icon);
     if hresp.clicked() {
-        app.ui.left_collapsed = true;
+        app.ui.close_left_panel();
     }
     ui.painter().line_segment([head.left_bottom(), head.right_bottom()], Stroke::new(1.0, t.border));
     match app.ui.left_tab {
@@ -612,7 +612,7 @@ pub(crate) fn start_rename(app: &mut FigApp, ids: &[NodeId]) {
     let rows = listed_rows(&doc, page, &app.ui.expanded, &app.ui.layer_filter.trim().to_lowercase());
     let Some(id) = rows.iter().map(|r| r.id).find(|r| ids.contains(r)) else { return };
     app.ui.left_tab = LeftTab::File;
-    app.ui.left_collapsed = false;
+    app.ui.open_left_panel();
     rename_layer(app, id);
 }
 

crates/ui-egui/src/lib.rs

@@ -491,6 +491,22 @@ pub enum MobilePanel {
     Left,
     Right,
 }
+
+impl UiState {
+    /// Opens the left panel; a narrow window shows it in place of the right one.
+    pub fn open_left_panel(&mut self) {
+        self.left_collapsed = false;
+        self.mobile_panel = Some(MobilePanel::Left);
+    }
+
+    /// Closes the left panel.
+    pub fn close_left_panel(&mut self) {
+        self.left_collapsed = true;
+        if self.mobile_panel == Some(MobilePanel::Left) {
+            self.mobile_panel = None;
+        }
+    }
+}
 pub const CANVAS_MIN: f32 = 160.0;
 
 /// The widths the side panels are drawn at in `avail` points (the window less the icon rail), from
@@ -645,6 +661,8 @@ pub struct UiState {
     pub left_collapsed: bool,
     /// The side panel open in a narrow window (a phone), where only one shows at a time.
     pub mobile_panel: Option<MobilePanel>,
+    /// The window was narrow (one side panel at a time) at the last frame.
+    pub narrow: bool,
     pub comments: comments::CommentUi,
     pub versions: versions::VersionUi,
     /// The branch review dialog, while open.
@@ -778,6 +796,7 @@ impl Default for UiState {
             batch_rename: None,
             left_collapsed: false,
             mobile_panel: None,
+            narrow: false,
             comments: comments::CommentUi::default(),
             versions: versions::VersionUi::default(),
             branch_review: None,
@@ -1054,7 +1073,14 @@ impl FigApp {
                 "panel.devMode" => {
                     self.ui.right_tab = if self.ui.right_tab == RightTab::Inspect { RightTab::Design } else { RightTab::Inspect };
                 }
-                "panel.leftSidebar" => self.ui.left_collapsed = !self.ui.left_collapsed,
+                "panel.leftSidebar" => {
+                    let shown = if self.ui.narrow { self.ui.mobile_panel == Some(MobilePanel::Left) } else { !self.ui.left_collapsed };
+                    if shown {
+                        self.ui.close_left_panel();
+                    } else {
+                        self.ui.open_left_panel();
+                    }
+                }
                 "panel.widths" => {
                     let width = |k: &str| r.data.get(k).and_then(Value::as_f64).map(|w| w as f32);
                     let (left, right) = (width("left"), width("right"));
@@ -1069,7 +1095,7 @@ impl FigApp {
                 "panel.layers" => self.ui.left_tab = LeftTab::File,
                 "panel.assets" => {
                     self.ui.left_tab = LeftTab::Assets;
-                    self.ui.left_collapsed = false;
+                    self.ui.open_left_panel();
                     self.ui.versions = Default::default();
                 }
                 "panel.versionHistory" => versions::open(self),
@@ -1078,7 +1104,7 @@ impl FigApp {
                 }
                 "panel.libraries" => {
                     self.ui.left_tab = LeftTab::Assets;
-                    self.ui.left_collapsed = false;
+                    self.ui.open_left_panel();
                     self.ui.libraries = true;
                 }
                 "home" => self.ui.home = true,
@@ -1635,7 +1661,11 @@ impl FigApp {
                 ui.painter().rect(r, 8.0, fill, egui::Stroke::new(1.0, t.border), egui::StrokeKind::Inside);
                 icons::paint(ui.painter(), r.shrink(10.0), icon, if open { t.accent_on } else { t.icon });
                 if resp.clicked() {
-                    self.ui.mobile_panel = if open { None } else { Some(side) };
+                    if side == MobilePanel::Left && !open {
+                        self.ui.open_left_panel();
+                    } else {
+                        self.ui.mobile_panel = if open { None } else { Some(side) };
+                    }
                 }
                 ui.add_space(4.0);
             }
@@ -1696,6 +1726,7 @@ impl FigApp {
         let hidden = self.session.ds().map(|d| d.view.ui_hidden).unwrap_or(false);
         let narrow = !hidden && ui.available_width() < NARROW_WIDTH;
         let mobile = self.ui.mobile_panel.filter(|_| narrow);
+        self.ui.narrow = narrow;
         // A narrow window shows the right panel when its button asks for it, a board's too.
         let right_open = (self.right_panel_shown(hidden) && !narrow) || mobile == Some(MobilePanel::Right);
         if !hidden && (!narrow || mobile == Some(MobilePanel::Left)) {

crates/ui-egui/src/menus.rs

@@ -231,7 +231,7 @@ pub fn invoke(app: &mut FigApp, id: &str) {
         // The file name in the left panel's header turns into its editor, the name selected.
         "file.rename" => {
             app.ui.left_tab = crate::LeftTab::File;
-            app.ui.left_collapsed = false;
+            app.ui.open_left_panel();
             app.ui.rename_file = true;
         }
         "text.link" => app.ui.menu_input = Some(crate::dialogs::MenuInput::Link(String::new())),
@@ -246,7 +246,7 @@ pub fn invoke(app: &mut FigApp, id: &str) {
         "tool.set" => app.ui.tool_flyout = Some("move"),
         "page.select" => {
             app.ui.left_tab = crate::LeftTab::File;
-            app.ui.left_collapsed = false;
+            app.ui.open_left_panel();
             app.ui.pages_open = true;
         }
         // From a menu the link is pasted into the Join dialog (`collab.join {link}` joins directly).

crates/ui-egui/src/panel_width_tests.rs

@@ -254,6 +254,10 @@ fn a_narrow_window_shows_one_side_panel_at_a_time() {
         let w = canvas_width(&mut app, phone);
         assert!((1.0..=60.0).contains(&w), "{side:?}: the open panel leaves {w}");
     }
+    // A command that opens the left panel opens it on a phone too, in place of the right one.
+    app.run("view.assets", json!({}));
+    let w = canvas_width(&mut app, phone);
+    assert!((1.0..=60.0).contains(&w) && app.ui.mobile_panel == Some(MobilePanel::Left), "view.assets leaves {w}");
     app.ui.mobile_panel = Some(MobilePanel::Right);
     let wide = canvas_width(&mut app, vec2(1440.0, 900.0));
     assert!(wide > 600.0 && wide < 1100.0, "a wide window shows both panels beside the canvas ({wide})");

crates/ui-egui/src/versions.rs

@@ -50,7 +50,7 @@ impl Form {
 /// Open the panel (File ▸ Show version history).
 pub fn open(app: &mut FigApp) {
     app.ui.versions.open = true;
-    app.ui.left_collapsed = false;
+    app.ui.open_left_panel();
     app.ui.left_tab = crate::LeftTab::File;
 }