Macro-based constraints

third_party/WebKit/Source/modules/mediastream/MediaConstraintsImpl.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 495 matching lines @@
     if (blinkForm.hasIdeal()) {
         webForm.setIdeal(blinkForm.ideal());
     }
     if (blinkForm.hasExact()) {
         webForm.setExact(blinkForm.exact());
     }
 }
 
 void copyConstraints(const MediaTrackConstraintSet& constraintsIn, WebMediaTrackConstraintSet& constraintBuffer)
 {
-    if (constraintsIn.hasWidth()) {
-        copyLongConstraint(constraintsIn.width(), constraintBuffer.width);
+
+#define CONSTRAINT_ITEM(lowercase, uppercase, datatype) \
+    if (constraintsIn.has##uppercase()) { \

[tommi (sloooow) - chröme, 2016/05/01 17:52:16]

crazy question.  Instead of all of these type specific getters and setters,
would it be easier if the type was always base::Value? (see src/base/values.h)

[hta - Chromium, 2016/05/02 08:22:00]

two problems with that:

- the constraints types aren't simple types, they're max/min/exact/ideal or
multivalues (ConstrainXXX rather than just XXX)
- the chief API I'm struggling with is the API generated by the WebIDL compiler.
I've tried to not go into changing that.

some of the #datatype# calls can be eliminated by templating. But not the
data-declaration one; that has to have the type because that's what tells C++
which type each constraint has.

[tommi (sloooow) - chröme, 2016/05/03 16:49:34]

What I'm wondering is if it would make more sense to do something similar to the
stats value type in webrtc:
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/webrtc...

Then add to that the 'has' and 'get' methods.

+        copy##datatype##Constraint(constraintsIn.lowercase(), constraintBuffer.lowercase); \
     }
-    if (constraintsIn.hasHeight()) {
-        copyLongConstraint(constraintsIn.height(), constraintBuffer.height);
-    }
-    if (constraintsIn.hasAspectRatio()) {
-        copyDoubleConstraint(constraintsIn.aspectRatio(), constraintBuffer.aspectRatio);
-    }
-    if (constraintsIn.hasFrameRate()) {
-        copyDoubleConstraint(constraintsIn.frameRate(), constraintBuffer.frameRate);
-    }
-    if (constraintsIn.hasFacingMode()) {
-        copyStringConstraint(constraintsIn.facingMode(), constraintBuffer.facingMode);
-    }
-    if (constraintsIn.hasVolume()) {
-        copyDoubleConstraint(constraintsIn.volume(), constraintBuffer.volume);
-    }
-    if (constraintsIn.hasSampleRate()) {
-        copyLongConstraint(constraintsIn.sampleRate(), constraintBuffer.sampleRate);
-    }
-    if (constraintsIn.hasSampleSize()) {
-        copyLongConstraint(constraintsIn.sampleSize(), constraintBuffer.sampleSize);
-    }
-    if (constraintsIn.hasEchoCancellation()) {
-        copyBooleanConstraint(constraintsIn.echoCancellation(), constraintBuffer.echoCancellation);
-    }
-    if (constraintsIn.hasLatency()) {
-        copyDoubleConstraint(constraintsIn.latency(), constraintBuffer.latency);
-    }
-    if (constraintsIn.hasChannelCount()) {
-        copyLongConstraint(constraintsIn.channelCount(), constraintBuffer.channelCount);
-    }
-    if (constraintsIn.hasDeviceId()) {
-        copyStringConstraint(constraintsIn.deviceId(), constraintBuffer.deviceId);
-    }
-    if (constraintsIn.hasGroupId()) {
-        copyStringConstraint(constraintsIn.groupId(), constraintBuffer.groupId);
-    }
+
+    CONSTRAINT_LIST
+
+#undef CONSTRAINT_ITEM
 }
 
 WebMediaConstraints create(ExecutionContext* context, const MediaTrackConstraints& constraintsIn, MediaErrorState& errorState)
 {
     WebMediaConstraints constraints;
     WebMediaTrackConstraintSet constraintBuffer;
     Vector<WebMediaTrackConstraintSet> advancedBuffer;
     copyConstraints(constraintsIn, constraintBuffer);
     if (constraintsIn.hasAdvanced()) {
         for (const auto& element : constraintsIn.advanced()) {
@@ skipping 25 matching lines @@
 
 WebMediaConstraints create()
 {
     WebMediaConstraints constraints;
     constraints.initialize();
     return constraints;
 }
 
 } // namespace MediaConstraintsImpl
 } // namespace blink