perf(menu): improves menu performance and fixes some edge cases

src/components/menu/menu-gestures.ts

@@ -47,6 +47,11 @@ export class MenuContentGesture extends SlideEdgeGesture {
   // Set CSS, then wait one frame for it to apply before sliding starts
   onSlideBeforeStart(ev: any) {
     console.debug('menu gesture, onSlideBeforeStart', this.menu.side);
+    this.menu.swipeBeforeStart();
+  }
+
+  onSlideStart() {
+    console.debug('menu gesture, onSlideStart', this.menu.side);
     this.menu.swipeStart();
   }
 

src/components/menu/menu.ts

@@ -438,12 +438,24 @@ export class Menu {
   /**
    * @private
    */
-  swipeStart() {
-    // user started swiping the menu open/close
-    if (this.canSwipe()) {
-      this._before();
-      this._getType().setProgressStart(this.isOpen);
+  swipeBeforeStart() {
+    if (!this.canSwipe()) {
+      assert(false, 'canSwipe() has to be true');
+      return;
     }
+    this._before();
+  }
+
+  /**
+   * @private
+   */
+  swipeStart() {
+    // user actively dragging the menu
+    if (!this._isAnimating) {
+      assert(false, '_isAnimating has to be true');
+      return;
+    }
+    this._getType().setProgressStart(this.isOpen);
   }
 
   /**
@@ -452,6 +464,7 @@ export class Menu {
   swipeProgress(stepValue: number) {
     // user actively dragging the menu
     if (!this._isAnimating) {
+      assert(false, '_isAnimating has to be true');
       return;
     }
     this._getType().setProgessStep(stepValue);

src/components/toolbar/toolbar.ios.scss

@@ -80,11 +80,12 @@ $navbar-ios-height:                         $toolbar-ios-height !default;
 }
 
 .toolbar-title-ios {
+  margin-top: 1px;
+
   font-size: $toolbar-ios-title-font-size;
   font-weight: $toolbar-ios-title-font-weight;
   text-align: $toolbar-ios-title-text-align;
   color: $toolbar-ios-title-text-color;
-  margin-top: 1px;
 
   pointer-events: auto;
 }