From ca75f6128964dd49e8a6e2656cbbff54206a4d9f Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <rreverser@google.com>
Date: Fri, 23 Jul 2021 20:04:32 +0000
Subject: [PATCH] Check for pending events before updating the config

Small optimisation that significantly reduces number of config updates.
---
 api.cpp     | 13 ++++++++++++-
 ui/index.js |  7 ++++++-
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/api.cpp b/api.cpp
index 9294e80..a0f585e 100644
--- a/api.cpp
+++ b/api.cpp
@@ -60,6 +60,16 @@ class Context {
     });
   }
 
+  bool hasPendingEvent() {
+    return gpp_rethrow([=]() {
+      CameraEventType event_type = GP_EVENT_UNKNOWN;
+      gpp_unique_ptr<void, free> event_data(GPP_CALL(
+          void *, gp_camera_wait_for_event(camera.get(), 0, &event_type, _,
+                                           context.get())));
+      return event_type != GP_EVENT_TIMEOUT;
+    });
+  }
+
   val configToJS() {
     return gpp_rethrow([=]() {
       GPPWidget config(
@@ -277,5 +287,6 @@ EMSCRIPTEN_BINDINGS(gphoto2_js_api) {
       .function("configToJS", &Context::configToJS)
       .function("setConfigValue", &Context::setConfigValue)
       .function("capturePreviewAsBlob", &Context::capturePreviewAsBlob)
-      .function("captureImageAsFile", &Context::captureImageAsFile);
+      .function("captureImageAsFile", &Context::captureImageAsFile)
+      .function("hasPendingEvent", &Context::hasPendingEvent);
 }
diff --git a/ui/index.js b/ui/index.js
index 737610e..1a7b78e 100644
--- a/ui/index.js
+++ b/ui/index.js
@@ -79,7 +79,12 @@ class App extends Component {
         type: 'Config',
         config
       });
-      await new Promise(resolve => setTimeout(resolve, 100));
+      do {
+        await new Promise(resolve => setTimeout(resolve, 100));
+      } while (
+        !(await this.connection.schedule(context => context.hasPendingEvent()))
+      );
+      console.log('Event!');
     }
   }