feat: add data-tauri-drag-region="deep" (#15062)

* feat: add `data-tauri-drag-region="deep"`

supersedes #6362

* Update data-tauri-drag-region-deep.md

* summary is also clickable

---------

Co-authored-by: Lucas Nogueira <lucas@tauri.app>

.changes/data-tauri-drag-region-deep.md

@@ -0,0 +1,5 @@
+---
+"tauri": minor:feat
+---
+
+Add `data-tauri-drag-region="deep"` so clicks on non-clickable children will drag as well. Can still opt out of drag on some regions using `data-tauri-drag-region="false"`

crates/tauri/src/window/scripts/drag.js

@@ -3,30 +3,78 @@
 // SPDX-License-Identifier: MIT
 
 ;(function () {
-  const osName = __TEMPLATE_os_name__
-
   //-----------------------//
   // drag on mousedown and maximize on double click on Windows and Linux
-  // while macOS macos maximization should be on mouseup and if the mouse
+  // while macOS maximization should be on mouseup and if the mouse
   // moves after the double click, it should be cancelled (see https://github.com/tauri-apps/tauri/issues/8306)
   //-----------------------//
   const TAURI_DRAG_REGION_ATTR = 'data-tauri-drag-region'
 
+  function isClickableElement(el) {
+    const tag = el.tagName && el.tagName.toLowerCase()
+
+    return (
+      tag === 'a'
+      || tag === 'button'
+      || tag === 'input'
+      || tag === 'select'
+      || tag === 'textarea'
+      || tag === 'label'
+      || tag === 'summary'
+      || (el.hasAttribute('contenteditable')
+        && el.getAttribute('contenteditable') !== 'false')
+      || (el.hasAttribute('tabindex') && el.getAttribute('tabindex') !== '-1')
+    )
+  }
+
+  // Walk the composed path from target upward. If a clickable element or a
+  // data-tauri-drag-region="false" element is encountered, return false (don't drag).
+  // Otherwise return true.
+  //
+  // Supported values for data-tauri-drag-region:
+  //   (bare / no value) → self: only direct clicks on this element trigger drag
+  //   "deep"            → deep: clicks anywhere in the subtree trigger drag
+  //   "false"           → disabled: drag is blocked here (and for ancestors)
+  function isDragRegion(composedPath) {
+    for (const el of composedPath) {
+      if (!(el instanceof HTMLElement)) continue
+
+      // if we hit a clickable element or a disabled drag region, don't drag
+      if (
+        isClickableElement(el)
+        || el.getAttribute(TAURI_DRAG_REGION_ATTR) === 'false'
+      ) {
+        return false
+      }
+
+      const attr = el.getAttribute(TAURI_DRAG_REGION_ATTR)
+      if (attr !== null) {
+        // deep: the whole subtree is a drag region
+        if (attr === 'deep') return true
+        // bare (or any unrecognized value): self-only
+        if (el === composedPath[0]) return true
+        // click was on a child of a self-only region — stop walking, don't drag
+        return false
+      }
+    }
+
+    return false
+  }
+
+  const osName = __TEMPLATE_os_name__
+
   // initial mousedown position for macOS
   let initialX = 0
   let initialY = 0
 
   document.addEventListener('mousedown', (e) => {
-    const attr = e.target.getAttribute(TAURI_DRAG_REGION_ATTR)
     if (
-      // element has the magic data attribute
-      attr !== null
-      //  and not false
-      && attr !== 'false'
-      // and was left mouse button
-      && e.button === 0
+      // was left mouse button
+      e.button === 0
       // and was normal click to drag or double click to maximize
       && (e.detail === 1 || e.detail === 2)
+      // and is drag region
+      && isDragRegion(e.composedPath())
     ) {
       // macOS maximization happens on `mouseup`,
       // so we save needed state and early return
@@ -48,23 +96,21 @@
       window.__TAURI_INTERNALS__.invoke('plugin:window|' + cmd)
     }
   })
+
   // on macOS we maximize on mouseup instead, to match the system behavior where maximization can be canceled
   // if the mouse moves outside the data-tauri-drag-region
   if (osName === 'macos') {
     document.addEventListener('mouseup', (e) => {
-      const attr = e.target.getAttribute(TAURI_DRAG_REGION_ATTR)
       if (
-        // element has the magic data attribute
-        attr !== null
-        // and not false
-        && attr !== 'false'
-        // and was left mouse button
-        && e.button === 0
+        // was left mouse button
+        e.button === 0
         // and was double click
         && e.detail === 2
         // and the cursor hasn't moved from initial mousedown
         && e.clientX === initialX
         && e.clientY === initialY
+        // and the event path contains a drag region (with no clickable element in between)
+        && isDragRegion(e.composedPath())
       ) {
         window.__TAURI_INTERNALS__.invoke(
           'plugin:window|internal_toggle_maximize'