Floating windows: fix the scale crash, the click offset, and placement

- KWin's nested backend makes an output the size it's configured to times its
  scale, so after Meta+scroll every size ft-floatd sent was multiplied again,
  and an odd result disconnected KWin (buffer not divisible by its scale).
  ft-floatd now asks for sizes in the output's scaled terms (kwin_size), and
  asks again after each scale change.
- SteamVR reports mouse positions on a panel with texture bounds in the whole
  texture, not the crop, so clicks on a floating window landed up to ~200 px
  off. The mouse scale is now the buffer's size, as on a screen.
- A floated window starts 30 cm in front of its screen (was 5 cm), so it's
  easy to point at apart from the screen behind it.
- No 1 s wait before a spare turns on (a disabled output never commits), and
  the login splash on the spares isn't taken for floating windows.

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

screens/compositor.c

@@ -434,8 +434,10 @@ static int control_readable(int fd, uint32_t mask, void *data) {
         int value, index, w, h;
         double scale;
         if (sscanf(buf, "size %d %d %d", &index, &w, &h) == 3) {
-            // A new resolution for a screen, live: KWin resizes the screen to match.
-            if (index < 1 || index > MAX_SCREENS || !s->screens[index - 1] || w < 320 || h < 200 || w > 16384 ||
+            // A new resolution for a screen, live: KWin resizes the screen to match. (KWin makes
+            // it this size times its scale; ft-floatd sends spares' sizes divided by theirs.)
+            const int min_w = index - 1 < s->n_config ? 320 : 64, min_h = index - 1 < s->n_config ? 200 : 64;
+            if (index < 1 || index > MAX_SCREENS || !s->screens[index - 1] || w < min_w || h < min_h || w > 16384 ||
                 h > 16384) {
                 snprintf(reply, sizeof reply, "error bad screen or size");
             } else {

screens/vr.cpp

@@ -276,10 +276,8 @@ struct Screen {
         return width > 0 ? metres * height / width : metres * 9 / 16;
     }
     // Buffer pixels from OpenVR's mouse position on the panel (its origin is bottom left).
-    void ToBuffer(double mx, double my, double *x, double *y) const {
-        if (floating && cropW > 0) *x = cropX + mx, *y = cropY + cropH - my;
-        else *x = mx, *y = height - my;
-    }
+    // A cropped panel too: SteamVR gives the position in the whole texture, not the crop.
+    void ToBuffer(double mx, double my, double *x, double *y) const { *x = mx, *y = height - my; }
     std::array<vr::VROverlayHandle_t, 6> Controls() const {
         return {bar, curveButton, rollButton, handle, dockButton, closeButton};
     }
@@ -1150,14 +1148,15 @@ void Push(Screen &s, double notches) {
 
 // ---------------------------------------------------------------- floating windows
 
-// Show the window's rectangle of the buffer, and map the mouse to it (see ToBuffer).
-// Texture bounds are fractions of the buffer, v from the top.
+// Show the window's rectangle of the buffer. Texture bounds are fractions of the buffer, v
+// from the top. SteamVR reports mouse positions in the whole texture (the bounds applied), so
+// the mouse scale is the buffer's size, as on a screen (see ToBuffer).
 void CropOverlay(vr::VROverlayHandle_t o, const Screen &s, int x, int y, int w, int h) {
     if (s.width <= 0 || s.height <= 0 || w <= 0 || h <= 0) return;
     vr::VRTextureBounds_t b = {float(x) / s.width, float(y) / s.height, float(x + w) / s.width,
                                float(y + h) / s.height};
     vr::VROverlay()->SetOverlayTextureBounds(o, &b);
-    vr::HmdVector2_t scale = {float(w), float(h)};
+    vr::HmdVector2_t scale = {float(s.width), float(s.height)};
     vr::VROverlay()->SetOverlayMouseScale(o, &scale);
 }
 
@@ -1571,15 +1570,11 @@ void ft_vr_poll(void (*handle)(const struct ft_event *, void *), void *data) {
     RefreshPoses();
     for (auto &[index, s] : g_screens) {
         vr::VREvent_t ev;
-        // The screen itself: input for KWin.
         // The screen itself (and a floating window's popups): input for KWin.
-        auto panelEvent = [&](const vr::VREvent_t &ev, bool sub, const Sub *from) {
+        auto panelEvent = [&](const vr::VREvent_t &ev, bool sub) {
             ft_event e{};
             e.screen = index;
-            auto at = [&] {
-                if (from) e.x = from->x + ev.data.mouse.x, e.y = from->y + from->h - ev.data.mouse.y;
-                else s.ToBuffer(ev.data.mouse.x, ev.data.mouse.y, &e.x, &e.y);
-            };
+            auto at = [&] { s.ToBuffer(ev.data.mouse.x, ev.data.mouse.y, &e.x, &e.y); };
             switch (ev.eventType) {
                 case vr::VREvent_MouseMove:
                     if (s.titleCarry) return;  // KWin's pointer stays where the title bar was pressed
@@ -1624,9 +1619,9 @@ void ft_vr_poll(void (*handle)(const struct ft_event *, void *), void *data) {
             }
             handle(&e, data);
         };
-        while (vr::VROverlay()->PollNextOverlayEvent(s.overlay, &ev, sizeof ev)) panelEvent(ev, false, nullptr);
+        while (vr::VROverlay()->PollNextOverlayEvent(s.overlay, &ev, sizeof ev)) panelEvent(ev, false);
         for (const auto &[k, sub] : s.subs)
-            while (vr::VROverlay()->PollNextOverlayEvent(sub.overlay, &ev, sizeof ev)) panelEvent(ev, true, &sub);
+            while (vr::VROverlay()->PollNextOverlayEvent(sub.overlay, &ev, sizeof ev)) panelEvent(ev, true);
         // The controls light up under a laser.
         auto hover = [&](int k) {
             const bool on = ev.eventType == vr::VREvent_MouseMove || ev.eventType == vr::VREvent_FocusEnter;