Replace ALooper_pollAll with ALooper_pollOnce (#477)

This commit is sourced from a downstream patch.

The incoming NDK r27 removes `ALooper_pollAll` as it can't be called
safely.

See android/ndk#2020 for more context.

While this change strives to introduce as little behavior change as
possible, Some behavior changes might be happening.
1. We are failing more explicitly when `ALooper_pollOnce` returns
`ALOOPER_POLL_ERROR`. When this error is returned, there is no point in
retrying polling in the current thread.
2. Compared with `ALooper_pollAll`, `ALooper_pollOnce` can return more
frequently with `ALOOPER_POLL_CALLBACK`. This can lead to "on_idle"
logic being executed more frequently.

Signed-off-by: Nathan Gauër <brioche@google.com>
Co-authored-by: google-yfyang <yfyang@google.com>

src/android/main.cpp

@@ -1,6 +1,7 @@
 #include "ppx/profiler.h"
 
 #include <android_native_app_glue.h>
+#include <android/looper.h>
 #include <jni.h>
 #include <string>
 #include <vector>
@@ -101,15 +102,18 @@ void WaitForNonIdleState(struct android_app* pApp)
     pApp->userData     = nullptr;
 
     while (gApplicationState == READY) {
-        int                  events;
-        android_poll_source* pSource;
-        if (ALooper_pollAll(/* timeoutMillis= */ 0,
-                            /* outFd= */ nullptr,
-                            /* outEvents= */ &events,
-                            /* outData= */ (void**)&pSource) >= 0) {
-            if (pSource) {
-                pSource->process(pApp, pSource);
-            }
+        android_poll_source* pSource = nullptr;
+        auto                 result  = ALooper_pollOnce(
+            /* timeoutMillis= */ 0,
+            /* outFd= */ nullptr,
+            /* outEvents= */ nullptr,
+            /* outData= */ (void**)&pSource);
+        if (result == ALOOPER_POLL_ERROR) {
+            PPX_ASSERT_MSG(false, "ALooper_pollOnce returned an error.");
+            return;
+        }
+        if (pSource) {
+            pSource->process(pApp, pSource);
         }
     }
 }

src/ppx/window_android.cpp

@@ -18,6 +18,7 @@
 #include "ppx/window.h"
 #include "ppx/grfx/grfx_swapchain.h"
 
+#include <android/looper.h>
 #include <android_native_app_glue.h>
 
 #include "backends/imgui_impl_android.h"
@@ -115,12 +116,18 @@ bool WindowImplAndroid::IsRunning() const
 
 void WindowImplAndroid::ProcessEvent()
 {
-    int                  events;
-    android_poll_source* pSource;
-    if (ALooper_pollAll(0, nullptr, &events, (void**)&pSource) >= 0) {
-        if (pSource) {
-            pSource->process(mAndroidApp, pSource);
-        }
+    android_poll_source* pSource = nullptr;
+    auto                 result  = ALooper_pollOnce(
+        /* timeoutMillis= */ 0,
+        /* outFd= */ nullptr,
+        /* outEvents= */ nullptr,
+        /* outData= */ (void**)&pSource);
+    if (result == ALOOPER_POLL_ERROR) {
+        PPX_ASSERT_MSG(false, "ALooper_pollOnce returned an error.");
+        return;
+    }
+    if (pSource) {
+        pSource->process(mAndroidApp, pSource);
     }
 }