Merge pull request #6661 from dotCooCoo/fix/clipboard-read-time-limit

Clipboard: Linux and BSD reads wait 2 s at most for the app that copied

Cargo.lock

@@ -6353,6 +6353,7 @@ dependencies = [
  "winit",
  "winresource",
  "winsafe",
+ "wl-clipboard-rs",
  "x11rb",
  "zbus",
 ]

apps/vectorcraft/Cargo.toml

@@ -113,6 +113,10 @@ wayland-backend = { version = "0.3", features = ["client_system"] }
 # exactly: review the diff before bumping.
 [target.'cfg(any(target_os = "linux", target_os = "freebsd", target_os = "dragonfly", target_os = "netbsd", target_os = "openbsd"))'.dependencies]
 zbus = "=5.19.0"
+# Tells whether arboard reads through the compositor's data-control protocol or through X11, the
+# same check arboard makes (src/clipboard.rs). MIT OR Apache-2.0, already in the build through
+# arboard.
+wl-clipboard-rs = "0.9"
 
 [build-dependencies]
 # Icon + VERSIONINFO for vectorcraft.exe; build.rs only uses it when targeting Windows.

docs/development.md

@@ -122,8 +122,8 @@ On GNOME/Wayland, enable **Preferences › User Interface › System Title Bar**
 
 The window runs natively on Wayland (eframe's `wayland` feature) and on X11. On machines with two GPUs it renders on the one the desktop runs on unless Preferences say otherwise; see [Desktop graphics processor](#desktop-graphics-processor) (#502). The system clipboard (`apps/vectorcraft/src/clipboard.rs`) is arboard with its `wayland-data-control` feature:
 
-- **Clipboard:** under Wayland arboard talks to the compositor through the data-control protocol (wlroots compositors such as Sway and Hyprland, KDE Plasma), so bitmaps (`image/png`), SVG markup and text copied in any app paste (#398). Where the compositor lacks the protocol (GNOME's Mutter, [arboard#223](https://github.com/1Password/arboard/issues/223)), arboard falls back to the X11 clipboard through XWayland, which only holds what X11 apps copied. Where there is no X11 either (the Flatpak on a Wayland session: `--socket=fallback-x11` gives it none), Copy and Paste use the compositor's core data-device protocol on the window's own connection through smithay-clipboard: text only (a copy's text or its SVG markup), and only while the window has focus. smithay-clipboard waits for the owner's data with no limit, so its reads run on a worker thread and a Paste waits 2 s at most: an owner that never sends its data costs one Paste 2 s, and later reads return at once until it answers. A clipboard neither backend opens is tried again after 1 s, doubling to a minute (a Copy or Paste of the user's at most once a second), and logged once when it goes and once when it comes back: before, the background Paste check reconnected and logged a warning every 250 ms. egui's own text paste into fields goes through smithay-clipboard and works either way.
-- **Clipboard owners that never answer (#510):** reading the clipboard waits on the app that owns it: arboard gives up on an X11 owner after 4 s, and a Wayland read waits for the owner to send its data. So on Linux the check that enables the Paste menu items runs on a background thread with a second clipboard handle (`crates/ui-egui/src/clipboard_probe.rs`, installed as `Services::clipboard_probe`), only while nothing is copied in the app and a document is open, and the window keeps drawing. A paste itself still reads on the UI thread, so pasting from such an owner waits for it once. Windows and macOS keep the check on the UI thread: Windows only asks which formats the clipboard holds, macOS asks the pasteboard server.
+- **Clipboard:** under Wayland arboard talks to the compositor through the data-control protocol (wlroots compositors such as Sway and Hyprland, KDE Plasma), so bitmaps (`image/png`), SVG markup and text copied in any app paste (#398). Where the compositor lacks the protocol (GNOME's Mutter, [arboard#223](https://github.com/1Password/arboard/issues/223)), arboard falls back to the X11 clipboard through XWayland, which only holds what X11 apps copied. Where there is no X11 either (the Flatpak on a Wayland session: `--socket=fallback-x11` gives it none), Copy and Paste use the compositor's core data-device protocol on the window's own connection through smithay-clipboard: text only (a copy's text or its SVG markup), and only while the window has focus. smithay-clipboard waits for the owner's data with no limit, so its reads run on a worker thread and the UI thread waits 2 s at most: an owner that never sends its data costs one read 2 s, and later reads return at once until it answers. When a read gets no answer in its 2 s, such as a paste's check whether the clipboard still holds what VectorCraft copied, the paste waits on its background thread for that read's answer, up to 10 s after the read was sent, and pastes the text unless it is empty or what VectorCraft copied. A clipboard neither backend opens is tried again after 1 s, doubling to a minute (a Copy or Paste of the user's at most once a second), and logged once when it goes and once when it comes back: before, the background Paste check reconnected and logged a warning every 250 ms. egui's own text paste into fields goes through smithay-clipboard and works either way.
+- **Clipboard owners that never answer (#510):** reading the clipboard waits on the app that owns it: arboard gives up on an X11 owner after 4 s for each format it tries, and a Wayland read waits for the owner to send its data. So on Linux the check that enables the Paste menu items runs on a background thread with a second clipboard handle (`crates/ui-egui/src/clipboard_probe.rs`, installed as `Services::clipboard_probe`), only while nothing is copied in the app and a document is open, and the window keeps drawing. Every arboard read on Linux and the BSDs, including the UI thread's (a paste, and a Copy or Cut checking what the clipboard held), runs on a worker thread with a handle of its own and waits 2 s at most: an owner that never sends its data costs one read that wait, and later reads fail at once until it answers. A paste's bitmap read waits up to 10 s on the paste's background thread, so the UI thread does not wait for it. When one of a paste's reads gets no answer in its 2 s, or a paste follows a read that has not been answered yet, such as the paste's own check whether the clipboard still holds what VectorCraft copied, the paste waits on that thread for that read's answer, up to 10 s after the read was sent, and pastes what it holds. When the answer is what VectorCraft copied, holds nothing to paste, or does not come, the paste takes the internal clipboard. On X11, quitting within 25 s of a read that got no answer waits for that read to end, so the app's own handle is the last one and hands what it copied to the clipboard manager. Windows and macOS keep the check on the UI thread: Windows only asks which formats the clipboard holds, macOS asks the pasteboard server.
 - **Copied files:** files copied in a file manager (`text/uri-list`; `CF_HDROP` on Windows, file URLs on macOS) paste as the first one that is art (SVG, PDF, EPS, EMF/WMF or a bitmap; a `.ai` or `.ait` file from the editing data it holds, else as the PDF or PostScript it holds), before the clipboard's other formats (which include the files' paths as text).
 - **Dropping files on the window does not work under Wayland:** winit 0.30, which eframe 0.37 runs on, has no Wayland drag and drop ([winit#1881](https://github.com/rust-windowing/winit/issues/1881), added in winit 0.31; [egui#1563](https://github.com/emilk/egui/issues/1563)), so no `dropped_files` arrive. Until eframe moves to winit 0.31: copy the files in the file manager and paste them, use File › Place or Open, or open the window through XWayland, where drops work: set **Preferences › Performance › Linux Display Server** to **X11 (XWayland)** and restart (#1151), or start the app with `WAYLAND_DISPLAY= vectorcraft`. The preference (`linuxDisplayServer`, read at startup in `apps/vectorcraft/src/main.rs`, shown on Linux only) has winit open the window on X11 (`EventLoopBuilderExtX11::with_x11`) when the session is Wayland, `DISPLAY` is set and the X11 libraries winit loads are installed (`apps/vectorcraft/src/xwayland.rs` reads `ldconfig -p` and the usual library directories); otherwise the window opens on Wayland and the log says why. Unlike clearing `WAYLAND_DISPLAY`, it leaves the clipboard on the compositor's own.
 - **Pens and pen displays under Wayland (#491, #2028):** winit 0.30 doesn't bind the Wayland tablet protocol (`zwp_tablet_v2`; tablet input arrives in winit 0.31, [winit#4318](https://github.com/rust-windowing/winit/pull/4318), [egui#7731](https://github.com/emilk/egui/pull/7731)). Since Plasma 6.3, KWin no longer turns tablet input into pointer input for such apps ([kwin!6336](https://invent.kde.org/plasma/kwin/-/merge_requests/6336), commit [25c65abd](https://invent.kde.org/plasma/kwin/-/commit/25c65abddd95eb87fb892a8594faccbf509ff62f)), and GNOME's Mutter does not turn it into pointer input either (that commit's message): on KWin the pen moves the compositor's cursor over the window, but the app gets no motion or presses and shows none of its own cursors. Until eframe moves to winit 0.31, the app runs under XWayland, which supports the tablet protocol and hands the pen to X11 apps as a pointer: Preferences › Performance › Linux Display Server's Automatic (the default) and X11 (XWayland) When a Pen Is Attached (`x11WithPen`) open the window through XWayland when `/proc/bus/input/devices` lists a pen as the app starts, a device with the `BTN_TOOL_PEN` key and the `ABS_X` and `ABS_Y` axes, and log `pen found: opening the window through XWayland`, as PhotoCraft does (#4967; `VECTORCRAFT_NATIVE_WAYLAND=1` keeps the window on Wayland). For a pen attached after the app started, either run the app under XWayland (Preferences › Performance › Linux Display Server › X11 (XWayland); `WAYLAND_DISPLAY= vectorcraft`, or `env -u WAYLAND_DISPLAY vectorcraft`; for a desktop launcher, put `env WAYLAND_DISPLAY=` before the command in its `Exec=` line), or turn KWin's deprecated emulation back on for the whole session by setting `KWIN_WAYLAND_EMULATE_TABLET=1` in KWin's environment (for example in a file under `~/.config/environment.d/` or in `/etc/environment`) and logging in again. The pen then works as a mouse. Under XWayland the app also reads the pen's pressure (next item); with KWin's emulation on native Wayland the pen has no pressure. Other compositors that don't emulate a pointer for tablets behave the same way.