feat: added immersive window support for VR race views

- Introduced a new configuration option for immersive window mode in runtime_config.h.
- Updated the parsing and setting functions to handle the immersive window state.
- Modified the OpenXR backend to support rendering with the immersive window, blending the race view with the surrounding environment.
- Enhanced the settings overlay to allow users to select between immersive, immersive window, and flat screen race views.
- Implemented GPU rendering logic for the immersive window mask, ensuring correct visual output in various rendering paths.
- Added tests to validate the immersive window functionality and its interaction with existing race view settings.

android/app/src/main/java/org/wiicompiled/quest/launcher/SettingsPage.kt

@@ -116,14 +116,28 @@ class SettingsPage(
     private fun buildVr() {
         // Flat Screen mode keeps races on the menu screen, which none of the race view rows reach.
         val immersive = { c: TomlConfig -> !(c.bool("vr", "flat_screen") ?: false) }
+        // The immersive window is still the stereo race view, seen through the race HUD's screen.
+        val window = { c: TomlConfig -> immersive(c) && (c.bool("vr", "immersive_window") ?: false) }
         val firstPerson = { c: TomlConfig -> immersive(c) && (c.bool("vr", "first_person") ?: false) }
         // The steering wheel and hand steering belong to the cockpit seat.
         val cockpit = { c: TomlConfig -> firstPerson(c) && stringIndex(c, "vr", "first_person_seat", SEATS) == 0 }
         section(R.string.section_vr_camera) {
-            toggle(
-                R.string.vr_flat_screen, R.string.vr_flat_screen_helper,
-                read = { !immersive(it) },
-                write = { c, value -> c.setBool("vr", "flat_screen", value) },
+            // One setting in two keys, read as runtime_config.h's VrRaceView reads them: Flat
+            // Screen mode wins over the immersive window.
+            choice(
+                R.string.vr_race_view, R.string.vr_race_view_helper,
+                listOf(R.string.vr_race_view_immersive, R.string.vr_race_view_window, R.string.vr_race_view_flat),
+                read = {
+                    when {
+                        !immersive(it) -> 2
+                        window(it) -> 1
+                        else -> 0
+                    }
+                },
+                write = { c, index ->
+                    c.setBool("vr", "flat_screen", index == 2)
+                    c.setBool("vr", "immersive_window", index == 1)
+                },
             )
             choice(
                 R.string.vr_camera, R.string.vr_camera_helper,
@@ -217,11 +231,12 @@ class SettingsPage(
             )
         }
         section(R.string.section_vr_screen) {
+            // The immersive window is that screen and always carries the HUD.
             toggle(
                 R.string.vr_hud_screen, R.string.vr_hud_screen_helper,
                 read = { it.bool("vr", "hud_virtual_screen") ?: true },
                 write = { c, value -> c.setBool("vr", "hud_virtual_screen", value) },
-                enabledIf = immersive,
+                enabledIf = { immersive(it) && !window(it) },
             )
             slider(
                 R.string.vr_hud_distance, R.string.vr_hud_distance_helper, 0.5, 5.0, 0.1,

android/app/src/main/res/values/strings.xml

@@ -508,8 +508,11 @@
 
     <!-- VR tab -->
     <string name="section_vr_camera">Camera</string>
-    <string name="vr_flat_screen">Flat Screen mode</string>
-    <string name="vr_flat_screen_helper">Plays races on the same flat screen as the menus instead of all around you. The camera settings below do not apply while it is on.</string>
+    <string name="vr_race_view">Race view</string>
+    <string name="vr_race_view_helper">Immersive plays races all around you in stereo. Immersive window keeps that stereo view but shows it only through a window where the menu screen sits, with your room around it. Flat screen plays races on the menu screen; the camera settings below do not apply to it.</string>
+    <string name="vr_race_view_immersive">Immersive</string>
+    <string name="vr_race_view_window">Immersive window</string>
+    <string name="vr_race_view_flat">Flat screen</string>
     <string name="vr_camera">Camera</string>
     <string name="vr_camera_helper">Ride behind the kart like the game, or sit in the driver\'s seat.</string>
     <string name="vr_camera_chase">Chase camera</string>
@@ -562,7 +565,7 @@
     <string name="vr_hud_width">Screen width</string>
     <string name="vr_hud_width_helper">How wide the menu screen and race HUD are.</string>
     <string name="vr_passthrough">Passthrough around the menu screen</string>
-    <string name="vr_passthrough_helper">Shows your room through the headset\'s cameras around the menus instead of black. Races stay fully virtual, except in Flat Screen mode.</string>
+    <string name="vr_passthrough_helper">Shows your room through the headset\'s cameras around the menus instead of black. Immersive races stay fully virtual; the immersive window and the flat screen race have the room around them too.</string>
 
     <!-- Graphics tab -->
     <string name="section_graphics">Rendering</string>