508004 2025-08-08 03:13:02 +0000 XWayland application somtimes failed to write clipboard with focus changed 2025-10-11 20:03:54 +0000 1 1 4 Plasma kwin xwayland 6.4.80 Arch Linux Linux RESOLVED FIXED wayland-only HI normal --- 1 tsicliu kwin-bugs-null 4wy78uwh kde nate https://invent.kde.org/plasma/kwin/-/commit/3976a8c08695ad0f3c1d10b410b44a72599dddae 6.5.0 0 oldest_to_newest 2445944 0 183873 tsicliu 2025-08-08 03:13:02 +0000 Created attachment 183873 demo and clipboard selection monitor **Bug Description** When an XWayland application attempts to write to the clipboard while KWin currently holds clipboard data provided by a Wayland-native application, a focus change occurring during the write process will often cause the write to fail. More precisely, the write is overwritten by `kwin_wayland`. **Reproduction Demo** I wrote a demo application to reproduce this issue: * The **main window** monitors and displays the current clipboard content. * It contains a **button** that opens a popup window for writing to the clipboard. * Clicking the button opens a window with a text input field and a button, prompting the user to enter some text. * After entering text, pressing the button writes the text to the clipboard and closes the popup window, causing a focus change. **Observed Behavior** * If the clipboard initially contains content copied from a **Wayland-native** application, after performing the above steps, there is a high probability that the main window still shows the old Wayland-provided clipboard content instead of the newly written text. * If we first use `xclip` to set the clipboard to something written by an **XWayland** application and then repeat the steps, the main window correctly shows the new text every time. **Additional Investigation** I also wrote a **clipboard selection monitor**. When the clipboard contains Wayland-provided content: * The clipboard selection is briefly owned by the demo, but is then immediately re-owned by `kwin_wayland`. When the clipboard contains XWayland-provided content: * This re-ownership does not occur. Looking into KWin’s source code, I found that: * When KWin receives a **selection change** from an XWayland client, it does not update the selection immediately. https://github.com/KDE/kwin/blob/e39731feabc643db9c5a6d8c945c29209a047158/src/xwayland/clipboard.cpp#L117 * Instead, it waits until a **selection property change** event is received to obtain a new offer and update the selection. https://github.com/KDE/kwin/blob/e39731feabc643db9c5a6d8c945c29209a047158/src/xwayland/clipboard.cpp#L133 * Between these two events, other events (e.g., focus changes) can occur. * If the focus changes before the new offer is obtained, `kwin_wayland` calls `checkWlSource`, which writes the Wayland-side clipboard content back into XWayland, overwriting the new content from the XWayland application. https://github.com/KDE/kwin/blob/e39731feabc643db9c5a6d8c945c29209a047158/src/xwayland/clipboard.cpp#L73 **Attachments** 1. The demo application described above. * Depends on Qt6 Widgets and is built with CMake. 2. The clipboard selection monitor program. * Depends on libxcb, libxcb-xfixes, and libxcb-res. * Can be built with: ```bash g++ clipboard_xres_with_targets.cpp -o xcb_clipboard_monitor -lxcb -lxcb-xfixes -lxcb-res ``` 2446522 1 nate 2025-08-11 15:21:57 +0000 In progress with https://invent.kde.org/plasma/kwin/-/merge_requests/7990 2459853 2 vlad.zahorodnii 2025-10-06 14:02:43 +0000 Git commit 3976a8c08695ad0f3c1d10b410b44a72599dddae by Vlad Zahorodnii. Committed on 06/10/2025 at 13:25. Pushed by vladz into branch 'Plasma/6.5'. xwayland: Decouple selection sync'ing from focus changes The current selection should be unaffected by the active window. For example, if a client sets a selection and then active window changes, that selection should still remain set. The current selection should only change when it's set explicitly (either by an X or a Wayland client). Regarding snooping clipboard contents, our SelectionRequest handler has a guard to protect us against that case. (cherry picked from commit 947d2c5ad0746d807b04f6bb382e1d4ddb1b7f29) M +9 -51 src/xwayland/clipboard.cpp M +0 -6 src/xwayland/clipboard.h M +8 -49 src/xwayland/primary.cpp M +0 -6 src/xwayland/primary.h https://invent.kde.org/plasma/kwin/-/commit/3976a8c08695ad0f3c1d10b410b44a72599dddae 183873 2025-08-08 03:13:02 +0000 2025-08-08 03:13:02 +0000 demo and clipboard selection monitor attachment.tar.gz application/x-gzip 3319 tsicliu H4sIAAAAAAAAA+0a7XLaSDK/eYoJd/EKB2OBHe8WTtgiGGe52IABr53yplSyGMc6C0krDf643dyD 3LPcO90rXPfMSBoJITv7eVelrsSImZ7+7p6eEZZj+5eeGcyN+4CGxp3Nrg1mBp8oCxuW7z/7LUAH 2Nvdxc/m16909RMf9161dp81X+m7r5rN1t4e4DX3dJgm+m/C/RFYhqAuIc9YaFtFeI/N/5/CX2zX cpZzSl7fW5fb8L9x3alkBq/sexqujgdiUBm1vZAF1FyomFerQzBiu5/UkVtqMS9QR5auHbJ5mqm1 utBi9oJ2UiIsTNf2U+wiCSq+PTcYgdg+s925dze2528fzic01EAdw/JcF8SwPRdwNvFbneD4HceF MfFQIz9VCABOYcZYjk1dZgDl0KcWoOEHeSOxEBoCBcYEhXoyszDDGxg/7701Jv2p0Tsa9IczY3Bg HHen742jUa97FA2OBwd83ef9Sor/j0saPCRSgECed2NTEEQ8APl1qJpQslknGyh0bb+YcEB95wFt wx8K6ApMSV1IUSfu0nF8Fkgm9hXRnnO0WmyNgLJl4BI9o2Bi4FvTWVLDZjQwIVpAEnwskoP/l+ia 4CbYX3kB0fb5+kZAF/trmbn0nmkbiFerKS5F8fniucnMrQ5aT/ryyc4kGxsxuSJ1xV+Hup/YdcKz RjpvSFMVCUHEN/xVjJJLTyF0oX/cTxG5CihNGSvjHyCfjH8WMSk8trIy8ShgQDq32yKDMQUNP/As GoaGay6ocflgAF0tViDSjC+yZQ0h1mLu2C7Vqtu4eLtKXgoE5hmCsMaXviTVbYlalZKozJGhMgqy cKJyRZ3P18lXP+hfpdXA8QZd+OxBq5FvSfXUvXG9O7dK2pJkRklrGQRoeixRkXwpvfgEI0AE/BWP aOlMEeMLsskWBoxGmI5nmQ5H34D1Kq4nWEmTeWEo5uCBvH4tUPylkEoTNOuk+uLD1ovF1os5efFd +8Vx+8W0mtYdVjeAolbjWmJsQU4tRDHlj2tLKPwNoRZdwya7iWZS66ftQhi6glR+2VIwZD3R66BD APmgcWrCXUrpUmnmVqwVhKcWqsgWmODd2ejYGI6G/YSxNAh+ACe+ZKuD3/YLk0NgRKEjNsLXShh1 uInDpe97AaPzqDkr3LKkKCF15CwOpEIvjw9Ui6XDZPUVbkNiIcjpI33+II3IZcLv3HiK+UML9OTi iCeJL4gEnseUiswHa7wMJQTi7ZZBquG3mKOLy6D+z7M8gRFOiJXSm+ik3mj8wTicgKfG3QmU3XpM E2KIS7fVQZHqqTKXgM6jrcn/6euQkNHZYHgwOoPi3p1OjcFwfDozRqcz+EjzMW7tcGk6BeyS2MuG lXS7IcMrTjuhbXXWnbzrz+KsVRZCpfRpwB7WrTyf9o+Mg+6sW1W5wuQtrDLiEJLoigFTwVVPCVhP c5XeOJ2gE4zZ4LiviHnlLMPryKN8dHubnJk245v0NOIy9Jh99RCv4tFgWwa95RWWbPIHUE9aUNC/ u7YdSjQtmuTxBaQNIC2WCsYre7tYAV6joQ+JAGXpwadkg/xTv/9Gr0W7PFiu35sNRkOoBLPB4Yfs dmwumYdpw8sBLzs+JL1hmSF7LZIiMqHLtUu06QgBMhswShZSaDeidShI2g/QVRBEieyPGClfZGVM DMp3ZIEY12IcMVIFWcVLKnISFmnHr4n0XwBx0cU/Ii/11m7GQLnKxJsAV0bdCVbRpEaK2tn9IOuP hGieZTkWhJ5D3Tyeqd5OpbRNQvsf1LvSkkTO4R+pKzN9Ez9D3iCYDHIjjrNovqPlS6CyjpIwC7xj RlVsYKBD60xeo1b75OVLe53mqju4DLzVi4NL+aYYJ0aUvuBKXdgf1+ifzyP2efItj0XK6Yo4RU5X nZ/QKDIBgthbsXt0TAvaXdO60ZTNV1sVjZtAYfDrcimffhR6CptagcoIvI1R8Ndjf86dyR/lVJUo XKW6uo6vySuTCJfQEtykhxMKydMKjc/JFjin4BvvId1WRIUu3cNFnROsxhRZmLarqX3uap8mo1FO RC1/XvOZWX9thgYNAuiexM6lxB2PJwsmsc+H04l5CZsf7EByNT6ew+YQwMbe+MGtJtaRWjRTJviV DaBySldGHu8GCztJhdK6rhGJxpii7VLaGnGVJS8KwA5h0tm8gk0l9wYkjQatYKuwe0nsJpbTe0Zd JJAUJSkFzCjGTPBQM8ltQxEaTrbKkUSh8fPPRPmKez8NMaLXhsb5ISKTmCOcQOHccmvaDoZMcWzg 3yUE+TegiGR6afIWRxXhyg5CJtqZ1VbWiq6cc7rR3tFg/HbUnRzkdrL2wgweclaNJ4Pj7uRD3MGi hRQub9JHNjRYTCszt95oh2AeOsckAu5iV3pCFqGpdloG1oT4pu/8cHDenyrdY/977Iv5LdG0P1Mm RmfD/mQ/G72i41O6R9uFA720BT/PJCauc8a1X0JDmmiFwmrIC0N5S8YNdVHFj/zLD5z/SI7sECIP r0iwq0i6We8Omnq8KnA/0bDREOZVG3kWLKnqocKTwLpmP/EYTyRR/aMNI56LYlySxfb/DSk6FShr ka667k0qU17mB0HREWLtCSLlzacfJNRbKlgL1LXssSKOIH7VlaQlaT/Sh6xQknHE6USJStqwQQ3f DyHAq5mGkxtvqyNi4bnImGxmRqDed+bc6otojojldAmqHXxsatASSK4DewHIW3BNWeMqyBvANZS/ ICWqBVZNKKCvBP6Im0co3Cb6fTW+27um9/gcaf0IXTIeHIAi8eo5tfAZFHx0obCLXCyshxNJ0qqw vbn+3kneHMi6vnrTFbsxDqs1Z7Hn0YtLeUm7rilPO4eQacSSyGuUdo5HEfghSGzwmJgbhEEUSKZF J4AMQ24xls8ivz9OEeBfqDt3crpkQh0oMU9T++L5RzL0Ip3l/gVGACUxRAGxUX2U3+Z2usleJ8Dv nRDxRRFULmoGoIbmemJHqRVpoZ4KnnYssMOoa1e2k9Sbjj/7ne6XQO/YvKG4IYcNds9+Hx7F7/91 PXn/39pt7uw805utHX2nfP//R4C1AP8bC9u1F0t8H/Lj0obk0b7vT6bQlZCdRnOvVoE98O8Y8L2o KTj0rGV4QBceOeoO35123/WnpHd+XqtU4BSn9Y677/sGfDems+7wANoG0vy6tmbKmPRPTgeT/gEZ DVWc7ulsNOn1ckaPR2K0cgXbn+Gb1o35iWonbI/EpHqj4zH0DEMoa2f2nJfnSsWcz+F0Qq0lw2OO 9tefxpPR36D7Mobd476oA3hyx5+9VABd1HXDsd0b+HMZmIENPUXeKmDdbks+uPLP9umXQKTx78nj kfzf3fu6JfK/tbertzD/my19r8z/PwKSn8mcdH3fsS0TN1H15zMncdanRo8hcET/mRoew+Hw7ZKx DI3v33r3R+YD7P+p4SPzkjrpEdul/bmdRptBg5D6ddDJdwq9iuWYYUgGeIIVEkFX5i8vQRlyItJS NiQnxugt5m5FzIqjjLJOS3Qlm8oZOqKy6ZtB6jVT8uOVdoSkCZwanJuNmISmHKeUC4boyDKzGRSk as+DE56LPzRi4uIuWlStqdcM+GpA29HxFUhLV2ZicoeO+QnqIdYk/oslpR8X50mHWw7VoHdE8Y3G ru0wD/2SHxI5NneZVvWhy4JGj18b4J0XCt6u1omkEBEQnLY6UHuleTgxlcdC3D3E9GUAaI9SkgtX 5b3k8RcRTCJSq54FK6Z9gsiCnson6gDFTJ1sKFygzYXYuqFzQblOLvDjo5Y9ICjhgUcbNsOfGkmd tjoMv2Uv4y3HC6mmDH5O+lM4Zt+ajIqYVuNY4SOQYxPjHGcHXet+lEZJXitZpAwWZFKClVJWOMWC AAlMR2aS9I34tv/U8EzRSMdQXoz2xPmCxMb4z7//9RR/S2pfElgjn7qikshD+S+LKwiDnqrjisYK Yqp0JKbPqRW7WCtaup62mHoNe/JuaSvln4ewrFzqoqU/hxCLzckjNi8tFOKYG/GCdhvvtnv8gi9O j41E9nY7h8NvnXfClbas+tKZ6iagSJ99AS+xeL52GZxYQRAqSm3XOIAjKKMjt4dZmn2PKvawdjuE Q65Dp9ce016BVy4ikqtyZhheY1bl3HvEGCYcf7ECRBlYhBuYdrqQIHwuLCwkdDwWikS/9ex5fjAo OpxMxcUaE+85UuWOychJopFnXFIH83OXvOTU1hU9nvZY1Dix/eJKiBUvbiiqvA1eeFZVeYOHD3AG sOry12vwfHvxMf4ZFfjavdWqJzPjZNw1xkfd2eFocgx5X723LuGjKcVU+ypi+r4maCI1iaFU1zv5 w5WG6u/ol2K+38Dzi/wR3p/dOZZQQgkllFBCCSWUUEIJJZRQQgkllFBCCSWUUEIJJZRQQgkllFBC Cf8r8F9RiZb+AFAAAA==