tauri-workspace/core/tauri/src/window/scripts/drag.js

// Copyright 2019-2023 Tauri Programme within The Commons Conservancy
// SPDX-License-Identifier: Apache-2.0
// SPDX-License-Identifier: MIT

document.addEventListener("mousedown", (e) => {
  if (e.target.hasAttribute("data-tauri-drag-region") && e.button === 0) {
    // prevents text cursor
    e.preventDefault();
    // fix #2549: double click on drag region edge causes content to maximize without window sizing change
    // https://github.com/tauri-apps/tauri/issues/2549#issuecomment-1250036908
    e.stopImmediatePropagation();

    // start dragging if the element has a `tauri-drag-region` data attribute and maximize on double-clicking it
    const cmd = e.detail === 2 ? "internal_toggle_maximize" : "start_dragging";
    window.__TAURI_INVOKE__("plugin:window|" + cmd);
  }
});