feat(android): expose secondary-screen touch events

docs/modding.md

@@ -221,10 +221,11 @@ the finished `worldCanvas` and `uiCanvas` with their SGB `zones` / `worldZones`,
 `worldActive`, the frame metrics (`ww`, `wh`, `pw`, `ph`, `ox`, `oy`, `vpw`,
 `vph`, `scale`, `Sx`, `Sy`, `dpiX`, `dpiY`), `renderer:blitCanvas(...)` for a
 palette-correct blit of either canvas into an arbitrary screen rect, and the
-`secondScreen` bridge (`available()` / `push(imageData, w, h)` / `setEnabled`)
-for driving a second physical display. This is what lets a mod lay the two
-passes out as two stacked Game Boy screens, or push one onto a second screen,
-without the engine knowing the layout.
+`secondScreen` bridge (`available()` / `push(imageData, w, h)` / `pollTouch()` /
+`setEnabled`) for driving a second physical display. `pollTouch()` returns the
+oldest queued event as `"action,x,y"` in submitted-frame coordinates, or `nil`.
+This is what lets a mod lay the two passes out as two stacked Game Boy screens,
+or push one onto a second screen, without the engine knowing the layout.
 
 `screen.render_visible` receives `(next, state)` while the main screen is being
 composed. Return `false` to omit that state from drawing, opacity selection and

mobile/android/love/src/jni/love/src/common/android.cpp

@@ -1003,4 +1003,33 @@ void love_android_secondary_enable(int on)
 	env->DeleteLocalRef(activity);
 }
 
+extern "C" __attribute__((visibility("default")))
+const char *love_android_poll_secondary_touch()
+{
+	static thread_local std::string event;
+	event.clear();
+	JNIEnv *env = (JNIEnv*) SDL_AndroidGetJNIEnv();
+	jclass activity = env->FindClass("org/love2d/android/GameActivity");
+	jmethodID method = env->GetStaticMethodID(activity, "pollSecondaryDisplayTouch",
+		"()Ljava/lang/String;");
+	if (!method)
+		env->ExceptionClear();
+	else
+	{
+		jstring value = (jstring) env->CallStaticObjectMethod(activity, method);
+		if (value)
+		{
+			const char *utf = env->GetStringUTFChars(value, nullptr);
+			if (utf)
+			{
+				event = utf;
+				env->ReleaseStringUTFChars(value, utf);
+			}
+			env->DeleteLocalRef(value);
+		}
+	}
+	env->DeleteLocalRef(activity);
+	return event.empty() ? nullptr : event.c_str();
+}
+
 #endif // LOVE_ANDROID

mobile/android/love/src/main/java/org/love2d/android/GameActivity.java

@@ -1325,6 +1325,9 @@ public class GameActivity extends SDLActivity {
     // in src/jni/love/src/common/android.cpp.
     private static volatile SecondaryPresentation secondaryPresentation;
     private static volatile boolean secondaryEnabled = false;
+    private static final int MAX_SECONDARY_TOUCHES = 32;
+    private static final java.util.ArrayDeque<String> secondaryTouches =
+        new java.util.ArrayDeque<>();
 
     @Keep
     public static void setSecondaryEnabled(final boolean on) {
@@ -1377,6 +1380,7 @@ public class GameActivity extends SDLActivity {
     private static void teardownSecondaryDisplay() {
         SecondaryPresentation p = secondaryPresentation;
         secondaryPresentation = null;
+        synchronized (secondaryTouches) { secondaryTouches.clear(); }
         if (p != null) {
             try { p.dismiss(); } catch (Throwable t) {}
         }
@@ -1395,6 +1399,13 @@ public class GameActivity extends SDLActivity {
         }
     }
 
+    @Keep
+    public static String pollSecondaryDisplayTouch() {
+        synchronized (secondaryTouches) {
+            return secondaryTouches.pollFirst();
+        }
+    }
+
     private static class SecondaryPresentation extends android.app.Presentation {
         private final FrameView frameView;
 
@@ -1461,6 +1472,7 @@ public class GameActivity extends SDLActivity {
         private final android.graphics.Paint paint = new android.graphics.Paint();
         private final Object lock = new Object();
         private int fw, fh;
+        private int activePointer = -1;
 
         FrameView(Context context) {
             super(context);
@@ -1482,6 +1494,52 @@ public class GameActivity extends SDLActivity {
             postInvalidate();
         }
 
+        private void enqueueTouch(String event) {
+            synchronized (secondaryTouches) {
+                if (secondaryTouches.size() >= MAX_SECONDARY_TOUCHES) {
+                    secondaryTouches.clear();
+                    secondaryTouches.addLast("cancel,0,0");
+                } else {
+                    secondaryTouches.addLast(event);
+                }
+            }
+        }
+
+        private int logicalX(float x) {
+            return Math.min(fw - 1, Math.max(0,
+                (int) ((x - dst.left) * fw / dst.width())));
+        }
+
+        private int logicalY(float y) {
+            return Math.min(fh - 1, Math.max(0,
+                (int) ((y - dst.top) * fh / dst.height())));
+        }
+
+        @Override
+        public boolean onTouchEvent(android.view.MotionEvent event) {
+            synchronized (lock) {
+                int action = event.getActionMasked();
+                if (action == android.view.MotionEvent.ACTION_DOWN && fw > 0
+                        && dst.contains((int) event.getX(), (int) event.getY())) {
+                    activePointer = event.getPointerId(0);
+                    enqueueTouch("down," + logicalX(event.getX()) + ","
+                        + logicalY(event.getY()));
+                } else if (action == android.view.MotionEvent.ACTION_UP
+                        && activePointer >= 0) {
+                    int index = event.findPointerIndex(activePointer);
+                    if (index >= 0 && fw > 0) {
+                        enqueueTouch("up," + logicalX(event.getX(index)) + ","
+                            + logicalY(event.getY(index)));
+                    }
+                    activePointer = -1;
+                } else if (action == android.view.MotionEvent.ACTION_CANCEL) {
+                    activePointer = -1;
+                    enqueueTouch("cancel,0,0");
+                }
+            }
+            return true;
+        }
+
         @Override
         protected void onDraw(android.graphics.Canvas canvas) {
             synchronized (lock) {

src/render/SecondScreen.lua

@@ -5,13 +5,15 @@
 
 local SecondScreen = {}
 local C = nil
+local ffi = nil
 
 local function log(msg)
   pcall(function() require("src.core.Logger").info("SecondScreen: %s", msg) end)
 end
 
 do
-  local ok, ffi = pcall(require, "ffi")
+  local ok
+  ok, ffi = pcall(require, "ffi")
   if not (ok and ffi) then
     log("ffi unavailable (not LuaJIT); second display disabled")
   else
@@ -19,6 +21,7 @@ do
       int love_android_secondary_ready();
       void love_android_push_secondary(const void *rgba, int w, int h);
       void love_android_secondary_enable(int on);
+      const char *love_android_poll_secondary_touch();
     ]])
     local okLib, lib = pcall(ffi.load, "love")
     if okLib and lib and pcall(function() return lib.love_android_secondary_ready end) then
@@ -51,6 +54,17 @@ function SecondScreen.push(imageData, w, h)
   end)
 end
 
+-- Returns the oldest queued secondary-display event as "action,x,y", where
+-- coordinates are in the submitted frame's pixel space.
+function SecondScreen.pollTouch()
+  if not C then return nil end
+  local ok, event = pcall(function()
+    return C.love_android_poll_secondary_touch()
+  end)
+  if not ok or event == nil or event == ffi.NULL then return nil end
+  return ffi.string(event)
+end
+
 function SecondScreen.setEnabled(on)
   if not C then return end
   pcall(function() C.love_android_secondary_enable(on and 1 or 0) end)

tests/engine/second_screen_touch_test.lua

@@ -0,0 +1,42 @@
+package.path = "./?.lua;./?/init.lua;" .. package.path
+
+local T = require("tests.harness")
+local name = "src.render.SecondScreen"
+local oldModule = package.loaded[name]
+local oldFfi = package.loaded.ffi
+local oldPreload = package.preload.ffi
+local null = {}
+local calls = 0
+local C = {
+  love_android_secondary_ready = function() return 1 end,
+  love_android_push_secondary = function() end,
+  love_android_secondary_enable = function() end,
+  love_android_poll_secondary_touch = function()
+    calls = calls + 1
+    return calls == 1 and "down,12,34" or null
+  end,
+}
+local fakeFfi = {
+  C = C,
+  NULL = null,
+  cdef = function() end,
+  load = function() return C end,
+  string = function(value) return value end,
+}
+
+package.loaded[name] = nil
+package.loaded.ffi = nil
+package.preload.ffi = function() return fakeFfi end
+
+local SecondScreen = require(name)
+T.eq(SecondScreen.pollTouch(), "down,12,34",
+  "secondary touch reaches the Lua facade")
+T.eq(SecondScreen.pollTouch(), nil, "an empty native touch queue returns nil")
+C.love_android_poll_secondary_touch = nil
+T.eq(SecondScreen.pollTouch(), nil, "an older native bridge remains safe")
+
+package.loaded[name] = oldModule
+package.loaded.ffi = oldFfi
+package.preload.ffi = oldPreload
+
+T.finish("second-screen touch facade")