Implement drag-and-drop functionality for split view and refine CSS styles for better layout and visibility

src/browser/base/content/main-popupset-inc-xhtml.patch

@@ -1,8 +1,8 @@
 diff --git a/browser/base/content/main-popupset.inc.xhtml b/browser/base/content/main-popupset.inc.xhtml
-index e5f3424eaeeec0ba552537f167dd99e912216d94..4bdfcdb23fe9c44ad3d4de273c64f4cc31cb4034 100644
+index 959c523b21c642f29353b9de37b3ce6b5505b01b..0d151ad345dde47467432196ed76f4320b4b92cc 100644
 --- a/browser/base/content/main-popupset.inc.xhtml
 +++ b/browser/base/content/main-popupset.inc.xhtml
-@@ -181,6 +181,10 @@
+@@ -206,6 +206,10 @@
             hidden="true"
             tabspecific="true"
             aria-labelledby="editBookmarkPanelTitle">
@@ -13,7 +13,7 @@ index e5f3424eaeeec0ba552537f167dd99e912216d94..4bdfcdb23fe9c44ad3d4de273c64f4cc
        <box class="panel-header">
          <html:h1>
            <html:span id="editBookmarkPanelTitle"/>
-@@ -206,6 +210,7 @@
+@@ -231,6 +235,7 @@
                    class="footer-button"/>
          </html:moz-button-group>
        </vbox>
@@ -21,7 +21,7 @@ index e5f3424eaeeec0ba552537f167dd99e912216d94..4bdfcdb23fe9c44ad3d4de273c64f4cc
      </panel>
    </html:template>
  
-@@ -535,6 +540,8 @@
+@@ -565,6 +570,8 @@
  
  #include popup-notifications.inc.xhtml
  

src/browser/base/content/zen-styles/zen-decks.css

@@ -248,3 +248,34 @@
     outline-color: var(--toolbarbutton-active-outline-color);
   }
 }
+
+#zen-split-view-fake-browser {
+  position: absolute;
+  height: 100%;
+  background: rgba(255, 255, 255, 0.1);
+  border-radius: var(--zen-native-inner-radius);
+  box-shadow: var(--zen-big-shadow);
+  pointer-events: none;
+  overflow: hidden;
+
+  &::after {
+    content: '';
+    position: absolute;
+    top: 50%;
+    left: 50%;
+    transform: translate(-50%, -50%);
+    width: 3.5rem;
+    height: 3.5rem;
+    background: var(--zen-split-view-fake-icon);
+    background-size: contain;
+    background-repeat: no-repeat;
+    background-position: center;
+    opacity: 0.8;
+    transition: opacity 0.2s;
+    transition-delay: 0.1s;
+
+    @starting-style {
+      opacity: 0;
+    }
+  }
+}

src/browser/base/content/zen-styles/zen-workspaces.css

@@ -9,6 +9,7 @@
   justify-content: center;
   align-items: center;
   display: flex;
+  font-size: x-small;
 
   position: relative;
 

src/browser/base/zen-components/ZenSidebarManager.mjs

@@ -102,7 +102,7 @@ class ZenBrowserManagerSidebar extends ZenDOMOperatedFeature {
   syncPinnedState() {
     const sidebar = document.getElementById('zen-sidebar-web-panel');
     const pinButton = document.getElementById('zen-sidebar-web-panel-pinned');
-    
+
     if (sidebar.hasAttribute('pinned')) {
       pinButton.setAttribute('pinned', 'true');
     } else {

src/browser/base/zen-components/ZenViewSplitter.mjs

@@ -84,6 +84,10 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
     this.initializeContextMenu();
     this.insertPageActionButton();
     this.insertIntoContextMenu();
+
+    // Add drag over listener to the browser view
+    this.tabBrowserPanel.addEventListener('dragenter', this.onBrowserDragOverToSplit.bind(this));
+    this.tabBrowserPanel.addEventListener('dragleave', this.onBrowserDragEndToSplit.bind(this));
   }
 
   insertIntoContextMenu() {
@@ -142,6 +146,111 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
     }
   }
 
+  onBrowserDragOverToSplit(event) {
+    var dt = event.dataTransfer;
+    var draggedTab;
+    if (dt.mozTypesAt(0)[0] == TAB_DROP_TYPE) {
+      // tab copy or move
+      draggedTab = dt.mozGetDataAt(TAB_DROP_TYPE, 0);
+      // not our drop then
+      if (!draggedTab || gBrowser.selectedTab.hasAttribute('zen-empty-tab')) {
+        return;
+      }
+      draggedTab.container._finishMoveTogetherSelectedTabs(draggedTab);
+    }
+    if (!draggedTab || this._canDrop || this._hasAnimated || this.fakeBrowser) {
+      return;
+    }
+    const currentView = this._data[this.currentView];
+    if (currentView?.tabs.length >= this.MAX_TABS) {
+      return;
+    }
+    this._canDrop = true;
+    // wait some time before showing the split view
+    this._showSplitViewTimeout = setTimeout(() => {
+      this._hasAnimated = true;
+      const panelsWidth = gBrowser.tabbox.getBoundingClientRect().width;
+      const halfWidth = panelsWidth / 2;
+      this.fakeBrowser = document.createXULElement('vbox');
+      const padding = Services.prefs.getIntPref('zen.theme.content-element-separation', 0);
+      this.fakeBrowser.setAttribute('flex', '1');
+      this.fakeBrowser.id = 'zen-split-view-fake-browser';
+      gBrowser.tabbox.appendChild(this.fakeBrowser);
+      this.fakeBrowser.style.setProperty('--zen-split-view-fake-icon', `url(${draggedTab.getAttribute('image')})`);
+      Promise.all([
+        gZenUIManager.motion.animate(
+          gBrowser.tabbox,
+          {
+            paddingLeft: [0, `${halfWidth}px`],
+          },
+          {
+            duration: 0.1,
+            easing: 'ease-out',
+          }
+        ),
+        gZenUIManager.motion.animate(
+          this.fakeBrowser,
+          {
+            width: [0, `${halfWidth - padding * 2}px`],
+            marginLeft: [0, `${-(halfWidth - padding)}px`],
+          },
+          {
+            duration: 0.1,
+            easing: 'ease-out',
+          }
+        ),
+      ]).then(() => {});
+    }, 100);
+  }
+
+  onBrowserDragEndToSplit(event) {
+    if (!this._canDrop) {
+      return;
+    }
+    const panelsRect = gBrowser.tabbox.getBoundingClientRect();
+    // this event is fired even though we are still in the "allowed" area
+    if (event.target !== this.tabBrowserPanel) {
+      return;
+    }
+    this._canDrop = false;
+    if (this._showSplitViewTimeout) {
+      clearTimeout(this._showSplitViewTimeout);
+    }
+    if (!this._hasAnimated) {
+      return;
+    }
+    setTimeout(() => {
+      const panelsWidth = panelsRect.width;
+      const halfWidth = panelsWidth / 2;
+      const padding = Services.prefs.getIntPref('zen.theme.content-element-separation', 0);
+      Promise.all([
+        gZenUIManager.motion.animate(
+          gBrowser.tabbox,
+          {
+            paddingLeft: [`${halfWidth}px`, 0],
+          },
+          {
+            duration: 0.1,
+            easing: 'ease-out',
+          }
+        ),
+        gZenUIManager.motion.animate(
+          this.fakeBrowser,
+          {
+            width: [`${halfWidth - padding * 2}px`, 0],
+            marginLeft: [`${-(halfWidth - padding)}px`, 0],
+          },
+          {
+            duration: 0.1,
+            easing: 'ease-out',
+          }
+        ),
+      ]).then(() => {
+        this._mayabeRemoveFakeBrowser();
+      });
+    }, 100);
+  }
+
   /**
    * Remove a SplitNode from its tree and the view
    * @param {SplitNode} toRemove
@@ -699,6 +808,7 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
       this.updateSplitView(tab);
       tab.linkedBrowser.docShellIsActive = true;
     }
+    this._mayabeRemoveFakeBrowser();
   }
 
   /**
@@ -1282,6 +1392,16 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
     }
   };
 
+  _mayabeRemoveFakeBrowser() {
+    if (this.fakeBrowser) {
+      this.fakeBrowser.remove();
+      this.fakeBrowser = null;
+      gBrowser.tabbox.removeAttribute('style');
+      delete this._canDrop;
+      delete this._hasAnimated;
+    }
+  }
+
   /**
    * @description moves the tab to the split view if dragged on a browser
    * @param event - The event
@@ -1289,6 +1409,8 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
    * @returns {boolean} true if the tab was moved to the split view
    */
   moveTabToSplitView(event, draggedTab) {
+    this._mayabeRemoveFakeBrowser();
+
     const dropTarget = document.elementFromPoint(event.clientX, event.clientY);
     const browser = dropTarget?.closest('browser');
 
@@ -1336,24 +1458,22 @@ class ZenViewSplitter extends ZenDOMOperatedFeature {
         }
       } else {
         // Create new split view with layout based on drop position
-        let gridType;
-        switch (hoverSide) {
-          case 'left':
-          case 'right':
-            gridType = 'vsep';
-            break;
-          case 'top':
-          case 'bottom':
-            gridType = 'hsep';
-            break;
-          default:
-            gridType = 'grid';
-        }
+        let gridType = 'vsep';
+        //switch (hoverSide) {
+        //  case 'left':
+        //  case 'right':
+        //    gridType = 'vsep';
+        //    break;
+        //  case 'top':
+        //  case 'bottom':
+        //    gridType = 'hsep';
+        //    break;
+        //  default:
+        //    gridType = 'grid';
+        //}
 
-        // Put tabs in correct order based on drop side
-        const tabs = ['left', 'top'].includes(hoverSide) ? [draggedTab, droppedOnTab] : [droppedOnTab, draggedTab];
-
-        this.splitTabs(tabs, gridType);
+        // Put tabs always as if it was dropped from the left
+        this.splitTabs([draggedTab, droppedOnTab], gridType);
       }
     }
     return true;

src/browser/themes/shared/zen-icons/icons.css

@@ -1140,6 +1140,7 @@ menupopup > menuitem:is([type='checkbox']) .menu-iconic-left {
 }
 
 #toolbar-context-toggle-vertical-tabs,
-#toolbar-context-customize-sidebar {
-  display: none;
+#toolbar-context-customize-sidebar,
+#sidebarRevampSeparator {
+  display: none !important;
 }