Reland: Image Capture Linux/CrOs: wire some capabilities set/get

media/capture/video/linux/v4l2_capture_delegate.cc

Index: media/capture/video/linux/v4l2_capture_delegate.cc
diff --git a/media/capture/video/linux/v4l2_capture_delegate.cc b/media/capture/video/linux/v4l2_capture_delegate.cc
index d846e416b5153c3b0ffa8d326b8ac83d49b5b0bc..9d0275e0f7a2fb8e2a1be358c62c0c7b3c94a990 100644
--- a/media/capture/video/linux/v4l2_capture_delegate.cc
+++ b/media/capture/video/linux/v4l2_capture_delegate.cc
@@ -328,6 +328,86 @@ void V4L2CaptureDelegate::TakePhoto(
   take_photo_callbacks_.push(std::move(callback));
 }
 
+void V4L2CaptureDelegate::GetPhotoCapabilities(
+    VideoCaptureDevice::GetPhotoCapabilitiesCallback callback) {
+  DCHECK(v4l2_task_runner_->BelongsToCurrentThread());
+  if (!device_fd_.is_valid() || !is_capturing_)
+    return;

[chfremer, 2016/09/23 21:18:29]

This error case silently swallows the call and does not invoke the callback.
If it is an unexpected condition it should at least have a DCHECK(false).
If it is an expected condition it should report it back to the caller.

[mcasas, 2016/09/23 22:10:57]

The callback is not a simple thing, but a 
ScopedResultCallback [1]. which is correctly handled
when dropped, IOW, dropping it is the right
handling.

[1]
https://cs.chromium.org/chromium/src/media/capture/video/scoped_result_callba...

[chfremer, 2016/09/23 22:48:56]

Thanks. Now I remember you mentioned that to me before.
I like this mechanism. Only downside is that because of the typedef it is
somewhat non-obvious whether or not |callback| is a ScopedResultCallback or a
plain Callback.
I will look out for it next time.

+
+  mojom::PhotoCapabilitiesPtr photo_capabilities =
+      mojom::PhotoCapabilities::New();
+
+  photo_capabilities->zoom = mojom::Range::New();
+  v4l2_queryctrl zoom_range = {};
+  zoom_range.id = V4L2_CID_ZOOM_ABSOLUTE;
+  zoom_range.type = V4L2_CTRL_TYPE_INTEGER;
+  if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_QUERYCTRL, &zoom_range)) >=
+      0) {
+    photo_capabilities->zoom->max = zoom_range.maximum * 100;
+    photo_capabilities->zoom->min = zoom_range.minimum * 100;
+  }
+  v4l2_control zoom_current = {};
+  zoom_current.id = V4L2_CID_ZOOM_ABSOLUTE;
+  if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_G_CTRL, &zoom_current)) >= 0)
+    photo_capabilities->zoom->current = zoom_current.value * 100;
+
+  photo_capabilities->focus_mode = mojom::MeteringMode::NONE;
+  v4l2_control auto_focus_current = {};
+  auto_focus_current.id = V4L2_CID_FOCUS_AUTO;
+  if (HANDLE_EINTR(
+          ioctl(device_fd_.get(), VIDIOC_G_CTRL, &auto_focus_current)) >= 0) {
+    photo_capabilities->focus_mode = auto_focus_current.value
+                                         ? mojom::MeteringMode::CONTINUOUS
+                                         : mojom::MeteringMode::MANUAL;
+  }
+
+  photo_capabilities->exposure_mode = mojom::MeteringMode::NONE;
+  v4l2_control exposure_current = {};
+  exposure_current.id = V4L2_CID_EXPOSURE_AUTO;
+  if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_G_CTRL, &exposure_current)) >=
+      0) {
+    photo_capabilities->exposure_mode =
+        exposure_current.value == V4L2_EXPOSURE_MANUAL
+            ? mojom::MeteringMode::MANUAL
+            : mojom::MeteringMode::CONTINUOUS;
+  }
+
+  photo_capabilities->white_balance_mode = mojom::MeteringMode::NONE;
+  v4l2_control white_balance_current = {};
+  white_balance_current.id = V4L2_CID_AUTO_WHITE_BALANCE;
+  if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_G_CTRL,
+                         &white_balance_current)) >= 0) {
+    photo_capabilities->white_balance_mode =
+        white_balance_current.value ? mojom::MeteringMode::CONTINUOUS
+                                    : mojom::MeteringMode::MANUAL;
+  }
+
+  photo_capabilities->iso = mojom::Range::New();
+  photo_capabilities->height = mojom::Range::New();
+  photo_capabilities->width = mojom::Range::New();
+  photo_capabilities->exposure_compensation = mojom::Range::New();
+  photo_capabilities->fill_light_mode = mojom::FillLightMode::NONE;
+  photo_capabilities->red_eye_reduction = false;

[chfremer, 2016/09/23 21:18:29]

Does the spec allow these "empty ranges" as way of saying "not supported"?

[mcasas, 2016/09/23 22:10:57]

Yes, mojom::Range::New() essentially makes
all the fields 0, which will be interpreted
as min == max == current == 0.

+  callback.Run(std::move(photo_capabilities));
+}
+
+void V4L2CaptureDelegate::SetPhotoOptions(
+    mojom::PhotoSettingsPtr settings,
+    VideoCaptureDevice::SetPhotoOptionsCallback callback) {
+  DCHECK(v4l2_task_runner_->BelongsToCurrentThread());
+  if (!device_fd_.is_valid() || !is_capturing_)
+    return;

[chfremer, 2016/09/23 21:18:29]

Same as above.

[mcasas, 2016/09/23 22:10:57]

Acknowledged.

+
+  if (settings->has_zoom) {
+    v4l2_control zoom_current = {};
+    zoom_current.id = V4L2_CID_ZOOM_ABSOLUTE;
+    zoom_current.value = settings->zoom / 100;

[chfremer, 2016/09/23 21:18:29]

If the result of the division is a float, please write 100.0f (or 100.0 for
double), so that readers can understand without having to look up the type of
settings->zoom.

[mcasas, 2016/09/23 22:10:57]

Ridiculously enough, the setting (and the
underlying USB field) are integer, so throwing
away the decimals will happen either here or
inside the ioctl implementation.

[chfremer, 2016/09/23 22:48:56]

Seems I misinterpreted the value 100 by assuming the range of settings->zoom
would be [0:100] and the range of zoom_current.value would be [0,1]. 
In that case, could you please use a named constexpr instead of the magic number
to help me as a reader?

[mcasas, 2016/09/23 23:16:26]

|kZoomMultiplier| it is.

+    if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_S_CTRL, &zoom_current)) < 0)
+      DPLOG(ERROR) << "Error setting zoom value to " << (settings->zoom / 100);
+  }
+  callback.Run(true);
+}
+
 void V4L2CaptureDelegate::SetRotation(int rotation) {
   DCHECK(v4l2_task_runner_->BelongsToCurrentThread());
   DCHECK(rotation >= 0 && rotation < 360 && rotation % 90 == 0);