feat(workspace): add app-drawer toolbar button for Quick Access panel

Add a grid icon above the profile button in the right toolbar that
toggles the Quick Access (default) panel. The button shows a
selected/pressed state when the panel is open and deselects when the
panel is hidden or another panel opens.

Also remove unused $pluginIconsBar variable in MainViewManager tests
and add 5 integration tests for the new button behavior.

Author: abose

src/styles/images/app-drawer.svg

@@ -31,7 +31,8 @@ define(function (require, exports, module) {
         CommandManager = require("command/CommandManager"),
         Strings = require("strings"),
         WorkspaceManager = require("view/WorkspaceManager"),
-        PanelView = require("view/PanelView");
+        PanelView = require("view/PanelView"),
+        ExtensionUtils = require("utils/ExtensionUtils");
 
     /**
      * Descriptors for each launcher button.
@@ -177,14 +178,43 @@ define(function (require, exports, module) {
             }
         });
 
-        // Auto-hide when any other panel is shown.
-        // hide() is a no-op if the panel is already closed, so no guard needed.
+        // Create the app-drawer toolbar icon above the profile button
+        const iconURL = ExtensionUtils.getModulePath(module, "../styles/images/app-drawer.svg");
+        const $drawerBtn = $("<a>")
+            .attr({
+                id: "app-drawer-button",
+                href: "#",
+                title: Strings.BOTTOM_PANEL_DEFAULT_TITLE
+            })
+            .css({
+                "background-image": "url('" + iconURL + "')",
+                "background-position": "center",
+                "background-size": "16px"
+            })
+            .prependTo($("#main-toolbar .bottom-buttons"));
+
+        $drawerBtn.on("click", function () {
+            if (_panel.isVisible()) {
+                _panel.hide();
+            } else {
+                _panel.show();
+            }
+        });
+
+        // Auto-hide when any other panel is shown; update drawer button state.
         PanelView.on(PanelView.EVENT_PANEL_SHOWN, function (event, panelID) {
             if (panelID !== WorkspaceManager.DEFAULT_PANEL_ID) {
                 _panel.hide();
             } else {
                 _updateButtonVisibility();
             }
+            $drawerBtn.toggleClass("selected-button", panelID === WorkspaceManager.DEFAULT_PANEL_ID);
+        });
+
+        PanelView.on(PanelView.EVENT_PANEL_HIDDEN, function (event, panelID) {
+            if (panelID === WorkspaceManager.DEFAULT_PANEL_ID) {
+                $drawerBtn.removeClass("selected-button");
+            }
         });
 
         // Initial visibility update and set up live observers

src/view/DefaultPanelView.js

@@ -1304,7 +1304,6 @@ define(function (require, exports, module) {
             it("should clamp panel width when shown after window was resized", function () {
                 // Panel is hidden; compute what the max toolbar width would be
                 const sidebarWidth = _$("#sidebar").outerWidth() || 0;
-                const $pluginIconsBar = _$("#plugin-icons-bar");
                 const maxToolbarWidth = Math.min(
                     testWindow.innerWidth * 0.75,
                     testWindow.innerWidth - sidebarWidth - 100
@@ -1334,5 +1333,75 @@ define(function (require, exports, module) {
                 expect(rightOffset).toEqual($mainToolbar.width());
             });
         });
+
+        describe("Quick Access panel (app drawer button)", function () {
+            const DEFAULT_PANEL_ID = "workspace.defaultPanel";
+
+            function getDrawerButton() {
+                return _$("#app-drawer-button");
+            }
+
+            function isDefaultPanelVisible() {
+                return _$("#default-panel").is(":visible");
+            }
+
+            function isDrawerSelected() {
+                return getDrawerButton().hasClass("selected-button");
+            }
+
+            beforeEach(function () {
+                // Ensure a clean state: hide any open panels
+                const panel = WorkspaceManager.getPanelForID(DEFAULT_PANEL_ID);
+                if (panel && panel.isVisible()) {
+                    panel.hide();
+                }
+            });
+
+            it("should have the app-drawer button in the toolbar", function () {
+                expect(getDrawerButton().length).toBe(1);
+            });
+
+            it("should open Quick Access panel on drawer button click", function () {
+                expect(isDefaultPanelVisible()).toBeFalse();
+
+                getDrawerButton().click();
+
+                expect(isDefaultPanelVisible()).toBeTrue();
+            });
+
+            it("should show selected state when panel is open", function () {
+                expect(isDrawerSelected()).toBeFalse();
+
+                getDrawerButton().click();
+
+                expect(isDrawerSelected()).toBeTrue();
+            });
+
+            it("should close Quick Access panel on second click", function () {
+                getDrawerButton().click();
+                expect(isDefaultPanelVisible()).toBeTrue();
+                expect(isDrawerSelected()).toBeTrue();
+
+                getDrawerButton().click();
+
+                expect(isDefaultPanelVisible()).toBeFalse();
+                expect(isDrawerSelected()).toBeFalse();
+            });
+
+            it("should deselect drawer when another panel opens", async function () {
+                getDrawerButton().click();
+                expect(isDefaultPanelVisible()).toBeTrue();
+                expect(isDrawerSelected()).toBeTrue();
+
+                // Open a different panel (Problems)
+                await CommandManager.execute(Commands.VIEW_TOGGLE_PROBLEMS);
+
+                expect(isDefaultPanelVisible()).toBeFalse();
+                expect(isDrawerSelected()).toBeFalse();
+
+                // Clean up: close Problems panel
+                await CommandManager.execute(Commands.VIEW_TOGGLE_PROBLEMS);
+            });
+        });
     });
 });