PPAPI: implement GetSupportedPreviewSizes

ppapi/proxy/image_capture_resource.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ppapi/proxy/image_capture_resource.h"
+
+#include "ppapi/proxy/camera_capabilities_resource.h"
+#include "ppapi/proxy/plugin_resource_tracker.h"
+#include "ppapi/proxy/ppapi_messages.h"
+#include "ppapi/shared_impl/var.h"
+
+namespace ppapi {
+namespace proxy {
+
+ImageCaptureResource::ImageCaptureResource(Connection connection,
+                                           PP_Instance instance)
+    : PluginResource(connection, instance),
+      open_state_(BEFORE_OPEN) {
+  SendCreate(RENDERER, PpapiHostMsg_ImageCapture_Create());
+}
+
+ImageCaptureResource::~ImageCaptureResource() {
+}
+
+int32_t ImageCaptureResource::Open(
+    PP_Var device_id,
+    const scoped_refptr<TrackedCallback>& callback) {
+  if (open_state_ != BEFORE_OPEN)
+    return PP_ERROR_FAILED;
+
+  if (TrackedCallback::IsPending(open_callback_))
+    return PP_ERROR_INPROGRESS;
+
+  scoped_refptr<StringVar> source_string_var;
+  source_string_var = StringVar::FromPPVar(device_id);
+  if (!source_string_var || source_string_var->value().empty())
+    return PP_ERROR_BADARGUMENT;
+
+  open_callback_ = callback;
+
+  Call<PpapiPluginMsg_ImageCapture_OpenReply>(
+      RENDERER, PpapiHostMsg_ImageCapture_Open(source_string_var->value()),
+      base::Bind(&ImageCaptureResource::OnPluginMsgOpenReply,
+                 base::Unretained(this)));
+  return PP_OK_COMPLETIONPENDING;
+}
+
+void ImageCaptureResource::Close() {
+  if (open_state_ == CLOSED)
+    return;
+
+  if (TrackedCallback::IsPending(open_callback_)) {
+    open_callback_->PostAbort();
+    open_callback_ = NULL;
+  }
+

[Justin Chuang, 2015/02/10 17:56:38]

Note that it doesn't handle a race condition because I can no longer abort the
callback in Close().

1. Call ImageCaptureResource::GetCameraCapabilities()
2. Call ImageCaptureResource::Close()
3. OnPluginMsgGetPreviewSizesReply() is invoked, but this object is already
destroyed because I use Unretained() to this.

But I don't find reference code in ppapi/proxy handling it. Most seem to assume
the caller doesn't mess up.

Wonder if we should use WeakPtr to this in ::GetCameraCapabilities()

[dmichael (off chromium), 2015/02/10 18:12:32]

Oh, thanks for bringing that up. I wasn't thinking about Close() aborting the
callback. That's the behavior we would usually do for a "Close" method, so maybe
the callback really should be a member, just so that you can abort it at the
right time. Sorry about that.
Unretained is safe for reply handlers. This comment mentions it:
https://code.google.com/p/chromium/codesearch#chromium/src/ppapi/proxy/plugin...
...though I realize now it's not explained that well. Really, it's because the
reply message isn't dispatched to a deleted resource:
https://code.google.com/p/chromium/codesearch#chromium/src/ppapi/proxy/plugin...

[Justin Chuang, 2015/02/10 19:02:08]

Do you think it's worth the extra code to just for implementing the callback
abortion when Close()? 

I like the new method much more than the old one.  :)

If the abortion is recommended, I'll revert it back. 
Sounds great. Thanks for explanation.

[dmichael (off chromium), 2015/02/10 19:07:47]

Yes, I would recommend that. It's our convention for Close() methods on Pepper
resources. I'd prefer this class didn't have a Close that worked differently.

+  Post(RENDERER, PpapiHostMsg_ImageCapture_Close());
+
+  open_state_ = CLOSED;
+}
+
+int32_t ImageCaptureResource::GetCameraCapabilities(
+    PP_Resource* capabilities,
+    const scoped_refptr<TrackedCallback>& callback) {
+  if (!is_opened())
+    return PP_ERROR_FAILED;
+
+  if (camera_capabilities_.get()) {
+    *capabilities = camera_capabilities_->GetReference();
+    return PP_OK;
+  }
+
+  Call<PpapiPluginMsg_ImageCapture_GetSupportedPreviewSizesReply>(
+      RENDERER, PpapiHostMsg_ImageCapture_GetSupportedPreviewSizes(),
+      base::Bind(&ImageCaptureResource::OnPluginMsgGetPreviewSizesReply,
+                 base::Unretained(this), capabilities, callback));
+  return PP_OK_COMPLETIONPENDING;
+}
+
+void ImageCaptureResource::OnPluginMsgOpenReply(
+    const ResourceMessageReplyParams& params) {
+  if (open_state_ == BEFORE_OPEN && params.result() == PP_OK)
+    open_state_ = OPENED;
+
+  // The callback may have been aborted by Close().
+  if (TrackedCallback::IsPending(open_callback_))
+    open_callback_->Run(params.result());
+}
+
+void ImageCaptureResource::OnPluginMsgGetPreviewSizesReply(
+    PP_Resource* output_capabilities,
+    scoped_refptr<TrackedCallback> callback,
+    const ResourceMessageReplyParams& params,
+    const std::vector<PP_Size>& preview_sizes) {
+  int32_t result = params.result();
+  if (result == PP_OK) {
+    camera_capabilities_ =
+        new CameraCapabilitiesResource(pp_instance(), preview_sizes);
+    *output_capabilities = camera_capabilities_->GetReference();
+  }
+  callback->Run(result);
+}
+
+}  // namespace proxy
+}  // namespace ppapi