Merge PR #22 (ehippy: lazy susan, Meta+Alt+Tab spins the panels around you) into experimental

Conflicts with experimental's pause_toggle, steam_menu and command: actions and its
AnnounceOverlay: both kept. The spin bindings join the Meta tap in the defaults, spinning
doesn't need pointer mode, and like other actions it does nothing while Frametop is paused.
AnnounceOverlay now sends through the PR's SendPointer.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

screens/compositor.c

@@ -346,6 +346,20 @@ static void handle_vr_event(const struct ft_event *e, void *data) {
     if (e->screen < 0 || e->screen >= MAX_SCREENS || !s->screens[e->screen]) return;
     struct screen *sc = s->screens[e->screen];
     struct wlr_surface *surface = sc->toplevel->base->surface;
+    if (e->type == FT_FRONT) {
+        // A spin brought this panel to the front: typing goes to it, as after a click there,
+        // and ft-floatd makes its window (or the top one on a screen) KWin's active window.
+        wlr_seat_keyboard_notify_enter(s->seat, surface, NULL, 0, NULL);
+        s->keys_clicked = true;
+        char msg[32];
+        snprintf(msg, sizeof msg, "front %d", e->screen + 1);
+        struct sockaddr_un addr = {.sun_family = AF_UNIX};
+        const char name[] = "frametop_float";
+        memcpy(addr.sun_path + 1, name, sizeof name - 1);
+        sendto(s->relay_fd, msg, strlen(msg), MSG_DONTWAIT, (struct sockaddr *)&addr,
+               offsetof(struct sockaddr_un, sun_path) + 1 + sizeof name - 1);
+        return;
+    }
     const uint32_t t = now_ms();
     const double x = e->x / s->scale[e->screen], y = e->y / s->scale[e->screen];  // KWin's units
     switch (e->type) {

screens/vr.cpp

@@ -1008,19 +1008,21 @@ void SendFloat(const std::string &msg) {
         std::printf("to ft-floatd: %s\n", msg.c_str());
 }
 
-// A new panel: the pointer helper reads SteamVR's list of panels only every 20 s, so it's told
-// at once ("overlay <key>"), or the mouse couldn't click a menu until then.
-void AnnounceOverlay(const char *key) {
+// To the pointer helper (@ft_pointer_helper), from an unbound socket.
+void SendPointer(const std::string &msg) {
     static const int fd = socket(AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
     sockaddr_un addr{};
     addr.sun_family = AF_UNIX;
     const char name[] = "ft_pointer_helper";
     std::memcpy(addr.sun_path + 1, name, sizeof name - 1);
-    const std::string msg = std::string("overlay ") + key;
     sendto(fd, msg.data(), msg.size(), MSG_DONTWAIT, reinterpret_cast<sockaddr *>(&addr),
            socklen_t(offsetof(sockaddr_un, sun_path) + 1 + sizeof name - 1));
 }
 
+// A new panel: the pointer helper reads SteamVR's list of panels only every 20 s, so it's told
+// at once ("overlay <key>"), or the mouse couldn't click a menu until then.
+void AnnounceOverlay(const char *key) { SendPointer(std::string("overlay ") + key); }
+
 // Where a device's ray meets the screen's plane, in the screen's x (right) and y (up),
 // metres from its centre.
 bool RayOnPlane(const Mat &p, const Mat &d, double *x, double *y) {
@@ -1488,6 +1490,137 @@ Screen *Find(int one_based) {
     return it == g_screens.end() ? nullptr : &it->second;
 }
 
+// ---------------------------------------------------------------- the lazy susan
+// "spin next|prev|<degrees>": the panels in the room (screens and floating windows, not
+// pinned ones) turn together about a vertical axis through your head, so the next panel to
+// your right (next) or left (prev) glides to straight ahead, or the ring turns by that many
+// degrees (positive turns it left, like next). Their arrangement stays as it is: the room
+// turns instead of you. A spin that arrives during one adds to it, from where the panels are
+// headed, so quick taps carry on smoothly. Grabbing a panel, or a command that places it,
+// takes it out of the spin where it is. The 3D mouse's pointer goes to straight ahead.
+constexpr double kSpinSeconds = 0.3;  // how long a spin takes
+constexpr double kSpinAhead = 8;      // degrees: a panel this near straight ahead is the current one
+constexpr double kSpinFocus = 30;     // degrees: when a spin settles, the panel this near ahead gets typing
+
+struct Spin {
+    bool on = false;
+    double cx = 0, cz = 0;    // the axis
+    double from = 0, to = 0;  // radians, turned from the poses in base (positive: to the left)
+    Clock::time_point start;
+    std::map<int, Mat> base;  // index -> its pose before the spin
+    int front = -1;           // settled: this panel came to the front (ft_vr_poll reports it)
+} g_spin;
+
+// p turned a radians about the vertical axis through (cx, cz); positive turns it to the left.
+Mat Turned(const Mat &p, double a, double cx, double cz) {
+    const double c = std::cos(a), s = std::sin(a);
+    Mat r = Identity();
+    r.m[0][0] = float(c), r.m[0][2] = float(s);
+    r.m[2][0] = float(-s), r.m[2][2] = float(c);
+    r.m[0][3] = float(cx - c * cx - s * cz);
+    r.m[2][3] = float(cz + s * cx - c * cz);
+    return Mul(r, p);
+}
+
+bool Spinnable(const Screen &s) { return s.pinned == kNone && (!s.floating || s.floatOn) && s.drag == Drag::None; }
+
+double SpinNow() {
+    if (!g_spin.on) return g_spin.to;
+    const double t = std::min(1.0, std::chrono::duration<double>(Clock::now() - g_spin.start).count() / kSpinSeconds);
+    return g_spin.from + (g_spin.to - g_spin.from) * t * t * (3 - 2 * t);
+}
+
+void UpdateSpin() {
+    if (!g_spin.on) return;
+    const double a = SpinNow();
+    const bool done = Clock::now() - g_spin.start >= std::chrono::duration<double>(kSpinSeconds);
+    for (auto it = g_spin.base.begin(); it != g_spin.base.end();) {
+        auto s = g_screens.find(it->first);
+        if (s == g_screens.end() || !Spinnable(s->second)) {
+            it = g_spin.base.erase(it);  // grabbed, pinned, or gone: it stays where it is now
+            continue;
+        }
+        SetAbsolute(s->second, Turned(it->second, a, g_spin.cx, g_spin.cz));
+        ++it;
+    }
+    if (done) {
+        // The panel now nearest straight ahead (of where you face) gets typing and the active window.
+        Mat head;
+        double nearest = kSpinFocus;
+        if (DevicePose(vr::k_unTrackedDeviceIndex_Hmd, &head)) {
+            for (const auto &[i, p] : g_spin.base) {
+                const auto it = g_screens.find(i);
+                Mat q;
+                if (it == g_screens.end() || !it->second.visible || !ScreenPose(it->second, &q)) continue;
+                double f[3] = {-head.m[0][2], 0, -head.m[2][2]};
+                double d[3] = {q.m[0][3] - head.m[0][3], 0, q.m[2][3] - head.m[2][3]};
+                const double fl = std::sqrt(Dot3(f, f)), dl = std::sqrt(Dot3(d, d));
+                if (fl < 1e-6 || dl < 1e-6) continue;
+                const double a = std::acos(std::clamp(Dot3(f, d) / (fl * dl), -1.0, 1.0)) * 180 / M_PI;
+                if (a < nearest) nearest = a, g_spin.front = i;
+            }
+        }
+        g_spin.on = false;
+        g_spin.base.clear();
+        ArrangeDesktopSoon();  // KWin's outputs follow where the screens are now
+    }
+}
+
+void SpinCommand(const char *arg, char *reply, int size) {
+    Mat head;
+    if (!DevicePose(vr::k_unTrackedDeviceIndex_Hmd, &head))
+        return (void)std::snprintf(reply, size, "error no head pose (headset off?)");
+    if (g_spin.on) {
+        g_spin.from = SpinNow();  // carry on from where the panels are now
+    } else {
+        g_spin.base.clear();
+        for (auto &[i, s] : g_screens) {
+            Mat p;
+            if (Spinnable(s) && ScreenPose(s, &p)) g_spin.base[i] = p;
+        }
+        g_spin.cx = head.m[0][3], g_spin.cz = head.m[2][3];
+        g_spin.from = g_spin.to = 0;
+    }
+    if (g_spin.base.empty()) return (void)std::snprintf(reply, size, "error nothing to spin");
+    double turn;  // degrees, positive to the left
+    const bool next = !std::strcmp(arg, "next");
+    if (next || !std::strcmp(arg, "prev")) {
+        // Each visible panel's bearing from where you face, to the right positive, as it will
+        // be when the spin so far ends; the nearest one past straight ahead comes to the front.
+        double fx = -head.m[0][2], fz = -head.m[2][2];
+        const double n = std::sqrt(fx * fx + fz * fz) + 1e-9;
+        fx /= n, fz /= n;
+        const double rx = -fz, rz = fx;
+        double best = 0;
+        bool found = false;
+        for (const auto &[i, p] : g_spin.base) {
+            const auto s = g_screens.find(i);
+            if (s == g_screens.end() || !s->second.visible) continue;
+            const Mat q = Turned(p, g_spin.to, g_spin.cx, g_spin.cz);
+            const double dx = q.m[0][3] - head.m[0][3], dz = q.m[2][3] - head.m[2][3];
+            double a = std::atan2(dx * rx + dz * rz, dx * fx + dz * fz) * 180 / M_PI;
+            if (!next) a = -a;
+            if (a <= kSpinAhead) a += 360;
+            if (!found || a < best) best = a, found = true;
+        }
+        if (!found || best >= 360 - kSpinAhead) {
+            if (!g_spin.on) g_spin.base.clear();
+            return (void)std::snprintf(reply, size, "ok 0 (no other panel)");
+        }
+        if (best > 180) best -= 360;  // the short way round
+        turn = next ? best : -best;
+    } else {
+        char *end;
+        turn = std::strtod(arg, &end);
+        if (end == arg || *end) return (void)std::snprintf(reply, size, "error spin next|prev|<degrees>");
+    }
+    g_spin.to += turn * M_PI / 180;
+    g_spin.start = Clock::now();
+    g_spin.on = true;
+    SendPointer("recenter");  // the 3D mouse's pointer stays in front of you, on what comes there
+    std::snprintf(reply, size, "ok %.1f", turn);
+}
+
 uint32_t LinuxButton(uint32_t vrButton) {
     switch (vrButton) {
         case vr::VRMouseButton_Right: return BTN_RIGHT;
@@ -2134,6 +2267,14 @@ void ft_vr_poll(void (*handle)(const struct ft_event *, void *), void *data) {
         handle(&e, data);
     }
     ++g_tick;
+    UpdateSpin();
+    if (g_spin.front >= 0) {
+        ft_event e{};
+        e.type = FT_FRONT;
+        e.screen = g_spin.front;
+        g_spin.front = -1;
+        handle(&e, data);
+    }
     UpdateGame();
     UpdateArrange();
     UpdateVisibility();
@@ -2210,6 +2351,8 @@ void ft_vr_keyboard_hide(void) {
 //                             ~100 ms (it landed on something else), KWin gets it anyway
 //   state         -> "ok <mode> <manual 0|1> <wrist deg> <gesture hand> <gesture deg>
 //                     <controllers> <game running 0|1> <ingames>"
+//   spin next|prev|<degrees>  turn every panel in the room about your head (see the lazy
+//                             susan) -> "ok <degrees turned>"
 //   cutouts on|off|state      hand cutouts (see handcut.h) -> "ok <on|off> <ready|idle|unavailable>
 //                             <last composite ms> ms, predict <on|off> lead <ms> ms"
 //   cutouts predict on|off    move the hands ahead along their velocity (on by default)
@@ -2247,6 +2390,7 @@ void ft_vr_command(const char *cmd, char *reply, int size) {
         Screen *s = Find(n);
         if (!s) return (void)std::snprintf(reply, size, "error no screen %d", n);
         EndDrag(*s);
+        g_spin.base.erase(n - 1);
         SetAbsolute(*s, PanelPose(x, y, z, yaw, pitch, roll));
         std::snprintf(reply, size, "ok");
     } else if (std::sscanf(cmd, "width %d %lf", &n, &w) == 2) {
@@ -2413,6 +2557,7 @@ void ft_vr_command(const char *cmd, char *reply, int size) {
         Mat m{};
         for (int k = 0; k < 12; ++k) m.m[k / 4][k % 4] = r[k];
         EndDrag(*s);
+        g_spin.base.erase(n - 1);
         SetAbsolute(*s, m);
         std::snprintf(reply, size, "ok");
     } else if (int k0; std::sscanf(cmd, "sub %d %d %d %d %d %d", &n, &k0, &x0, &y0, &w0, &h0) == 6 ||
@@ -2440,6 +2585,8 @@ void ft_vr_command(const char *cmd, char *reply, int size) {
         if ((g_press.buttons & ButtonBit(BTN_LEFT)) && g_press.device != kNone && !IsHandController(g_press.device))
             g_press.upAt = g_tick + 9;
         std::snprintf(reply, size, "ok");
+    } else if (std::sscanf(cmd, "spin %15s", word) == 1) {
+        SpinCommand(word, reply, size);
     } else if (std::strncmp(cmd, "state", 5) == 0) {
         std::snprintf(reply, size, "ok %s %d %.0f %s %.0f %s %d %s", ModeName(), g_manual ? 1 : 0, g_wristAngle,
                       g_gestureHand.c_str(), g_gestureAngle, LasersName(), g_gameRunning ? 1 : 0,

screens/vr.h

@@ -17,7 +17,8 @@ struct ft_dmabuf {
     int fd[4];
 };
 
-enum ft_event_type { FT_MOTION, FT_BUTTON, FT_SCROLL, FT_LEAVE, FT_QUIT, FT_KEY, FT_KEYBOARD_CLOSED };
+// FT_FRONT: a spin (the lazy susan) brought panel `screen` to straight ahead: typing goes there.
+enum ft_event_type { FT_MOTION, FT_BUTTON, FT_SCROLL, FT_LEAVE, FT_QUIT, FT_KEY, FT_KEYBOARD_CLOSED, FT_FRONT };
 
 struct ft_event {
     enum ft_event_type type;