WIP: try to reduce use of eval() for TabsInTitlebar hack

content/treestyletab/windowHelper.js

@@ -49,6 +49,50 @@ var TreeStyleTabWindowHelper = {
 					'$& gBrowser.treeStyleTab.position != "top" ? 0 : '
 				));
 			}, 'treeStyleTab');
+/*
+			TabsInTitlebar.__treestyletab__update = TabsInTitlebar._update;
+			TabsInTitlebar._update = function(...aArgs) {
+				// See: https://dxr.mozilla.org/mozilla-central/rev/dbe4b47941c7b3d6298a0ead5e40dd828096c808/browser/base/content/browser-tabsintitlebar.js#104
+				let isForce = aArgs[0];
+				let shouldFixMargin = (
+					gBrowser.treeStyleTab.position != 'top' &&
+					!window.fullScreen &&
+					this._initialized &&
+					(
+						isForce ||
+						(
+							this._lastSizeMode != document.documentElement.getAttribute('sizemode') &&
+							this._lastSizeMode != 'fullscreen'
+						)
+					) &&
+					Object.keys(this._disallowed).length === 0
+				);
+				if (!shouldFixMargin)
+					return this.__treestyletab__update(...aArgs);
+
+				// reset needless margins around the titlebar, from non-top tab bar
+
+				let titlebarContent = document.getElementById('titlebar-content');
+				let titlebarContentHeight = titlebarContent.getBoundingClientRect().height;
+
+				let fullTabsHeight = (function() {
+						let tabsToolbar = document.getElementById('TabsToolbar');
+						let tabsStyles = window.getComputedStyle(tabsToolbar);
+						let verticalMargins = parseFloat(tabsStyles.marginBottom) + parseFloat(tabsStyles.marginTop);
+						return tabsToolbar.getBoundingClientRect().height + verticalMargins;
+					})();
+
+				let result = this.__treestyletab__update(...aArgs);
+
+				let titlebar = document.getElementById('titlebar');
+				let currentMargin = parseFloat(titlebar.style.marginBottom.replace('px', ''));
+				if (-titlebarContentHeight != currentMargin) {
+					titlebar.style.marginBottom = (currentMargin + fullTabsHeight) + 'px';
+				}
+
+				return result;
+			};
+*/
 		}
 
 		window.__treestyletab__BrowserOpenTab = window.BrowserOpenTab;