Reveal a screen's controls when a laser lands on them

Hidden controls were taken out of SteamVR, so only ft-screens' own
proximity test could bring them back, and that test didn't match every
controller's laser. They now stay in place fully transparent while
hidden, and SteamVR's hover event on one reveals them, for any laser.

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

screens/vr.cpp

@@ -12,7 +12,7 @@
 //   - a resize tab on the bottom right corner: drag it to set the width (the height
 //     follows the screen's resolution).
 //   The controls are translucent, like SteamVR's own, and brighten under a laser. They
-//   are invisible until a laser (a controller's, or the 3D mouse's) passes very close to
+//   are invisible until a laser (a controller's, or the 3D mouse's) lands on or passes very close to
 //   one of them (UpdateControls).
 //   - pin to a wrist: while carrying a screen, sweep the laser (the line from the carrying
 //     device to the bar) across your other controller. A ring around each controller
@@ -672,9 +672,9 @@ void UpdateLasers() {
     }
 }
 
-// The controls are invisible until a laser passes very close to one of them (within
-// `reach`, about 1.5 times a button's size); they stay kControlsLinger ticks after it
-// leaves, and while in use.
+// The controls are invisible until a laser is on one of them (SteamVR's hover event) or
+// passes very close (within `reach`, about 1.5 times a button's size); they stay
+// kControlsLinger ticks after it leaves, and while in use.
 void UpdateControls() {
     std::vector<Mat> lasers;
     for (vr::TrackedDeviceIndex_t i = 1; i < vr::k_unMaxTrackedDeviceCount; ++i) {
@@ -711,18 +711,17 @@ void UpdateControls() {
         }
         const bool inUse = s.drag != Drag::None || s.hover[0] || s.hover[1] || s.hover[2] || s.hover[3];
         const bool want = s.visible && (inUse || g_tick < s.nearUntil);
-        const float before = s.controls;
-        s.controls = std::clamp(s.controls + (want ? 0.2f : -0.1f), 0.f, 1.f);
-        if (s.controls == before) continue;
-        if (s.controls > 0 && !s.controlsUp) {
+        // The controls stay shown while their screen is, just fully transparent when not
+        // wanted: SteamVR's laser still hits them, and the hover event brings them in, for
+        // any device's laser, whatever its shape.
+        if (s.visible && !s.controlsUp) {
             for (auto o : s.Controls()) vr::VROverlay()->ShowOverlay(o);
             s.controlsUp = true;
+            ApplyAlpha(s);
         }
-        ApplyAlpha(s);
-        if (s.controls == 0 && s.controlsUp) {
-            for (auto o : s.Controls()) vr::VROverlay()->HideOverlay(o);
-            s.controlsUp = false;
-        }
+        const float before = s.controls;
+        s.controls = std::clamp(s.controls + (want ? 0.2f : -0.1f), 0.f, 1.f);
+        if (s.controls != before) ApplyAlpha(s);
     }
 }