WebHID followup IDL changes

This modifies the WebHID IDL to address comments in a previous CL:

https://chromium-review.googlesource.com/c/chromium/src/+/1559344

In the prior commit, HIDReportItem held raw indices into the USB
string table (|stringMinimum| and |stringMaximum|). These members
are removed in favor of a new |strings| member which will return
the actual device data.

|designatorMinimum| and |designatorMaximum|, which held indices
into the physical descriptor table, are removed.

HIDReportItem held a |unit| member which described the unit factors
that make up the unit definition. The member was a 32-bit value composed
of 7 4-bit values and 4 reserved bits. These nibbles have been split
into separate members for the unit system and unit factor exponents.

In HIDCollectionInfo, the |reportIds| member is removed as its utility
is duplicated by the report information.

BUG=890096

Change-Id: I8403f9b7e275d97e58bb6c9ad73c2e2654f9d3d5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1583427Reviewed-by: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Matt Reynolds <mattreynolds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#659157}

third_party/blink/renderer/modules/hid/hid_collection_info.cc

@@ -41,10 +41,6 @@ const HeapVector<Member<HIDReportInfo>>& HIDCollectionInfo::featureReports()
   return feature_reports_;
 }
 
-const Vector<uint8_t>& HIDCollectionInfo::reportIds() const {
-  return report_ids_;
-}
-
 uint32_t HIDCollectionInfo::collectionType() const {
   return 0;
 }

third_party/blink/renderer/modules/hid/hid_collection_info.h

@@ -27,7 +27,6 @@ class HIDCollectionInfo : public ScriptWrappable {
   const HeapVector<Member<HIDReportInfo>>& inputReports() const;
   const HeapVector<Member<HIDReportInfo>>& outputReports() const;
   const HeapVector<Member<HIDReportInfo>>& featureReports() const;
-  const Vector<uint8_t>& reportIds() const;
   uint32_t collectionType() const;
 
   void Trace(blink::Visitor* visitor) override;
@@ -37,7 +36,6 @@ class HIDCollectionInfo : public ScriptWrappable {
   HeapVector<Member<HIDReportInfo>> input_reports_;
   HeapVector<Member<HIDReportInfo>> output_reports_;
   HeapVector<Member<HIDReportInfo>> feature_reports_;
-  Vector<uint8_t> report_ids_;
 };
 
 }  // namespace blink

third_party/blink/renderer/modules/hid/hid_collection_info.idl

@@ -25,8 +25,4 @@
     readonly attribute FrozenArray<HIDReportInfo> inputReports;
     readonly attribute FrozenArray<HIDReportInfo> outputReports;
     readonly attribute FrozenArray<HIDReportInfo> featureReports;
-
-    // The 8-bit report IDs associated with this collection, in the order they
-    // were encountered in the report descriptor.
-    readonly attribute FrozenArray<octet> reportIds;
 };

third_party/blink/renderer/modules/hid/hid_report_item.cc

@@ -10,8 +10,4 @@ HIDReportItem::HIDReportItem(const device::mojom::blink::HidReportItem& item) {}
 
 HIDReportItem::~HIDReportItem() {}
 
-void HIDReportItem::Trace(blink::Visitor* visitor) {
-  ScriptWrappable::Trace(visitor);
-}
-
 }  // namespace blink

third_party/blink/renderer/modules/hid/hid_report_item.h

@@ -7,6 +7,10 @@
 
 #include "services/device/public/mojom/hid.mojom-blink.h"
 #include "third_party/blink/renderer/platform/bindings/script_wrappable.h"
+#include "third_party/blink/renderer/platform/heap/heap_allocator.h"
+#include "third_party/blink/renderer/platform/heap/member.h"
+#include "third_party/blink/renderer/platform/wtf/text/wtf_string.h"
+#include "third_party/blink/renderer/platform/wtf/vector.h"
 
 namespace blink {
 
@@ -24,23 +28,25 @@ class HIDReportItem : public ScriptWrappable {
   const Vector<uint32_t>& usages() const { return usages_; }
   uint32_t usageMinimum() const { return 0; }
   uint32_t usageMaximum() const { return 0; }
-  uint32_t designatorMinimum() const { return 0; }
-  uint32_t designatorMaximum() const { return 0; }
-  uint32_t stringMinimum() const { return 0; }
-  uint32_t stringMaximum() const { return 0; }
+  const Vector<String>& strings() const { return strings_; }
   uint16_t reportSize() const { return 0; }
   uint16_t reportCount() const { return 0; }
   uint32_t unitExponent() const { return 0; }
-  uint32_t unit() const { return 0; }
+  String unitSystem() const { return String(); }
+  int8_t unitFactorLengthExponent() const { return 0; }
+  int8_t unitFactorMassExponent() const { return 0; }
+  int8_t unitFactorTimeExponent() const { return 0; }
+  int8_t unitFactorTemperatureExponent() const { return 0; }
+  int8_t unitFactorCurrentExponent() const { return 0; }
+  int8_t unitFactorLuminousIntensityExponent() const { return 0; }
   int32_t logicalMinimum() const { return 0; }
   int32_t logicalMaximum() const { return 0; }
   int32_t physicalMinimum() const { return 0; }
   int32_t physicalMaximum() const { return 0; }
 
-  void Trace(blink::Visitor* visitor) override;
-
  private:
   Vector<uint32_t> usages_;
+  Vector<String> strings_;
 };
 
 }  // namespace blink

third_party/blink/renderer/modules/hid/hid_report_item.idl

@@ -6,6 +6,28 @@
 // the report.
 // https://wicg.github.io/webhid/index.html#report-descriptor
 
+// The HID specification allows a device to specify units in one of four
+// standard unit systems. A device may also specify it is not using units, or is
+// using a vendor-defined unit system. Each unit system corresponds to a set of
+// units for length, mass, time, temperature, current, and luminous intensity.
+// See the units table in section 6.2.2.7 of the Device Class Definition for
+// HID, v1.11.
+// https://www.usb.org/document-library/device-class-definition-hid-111
+enum HIDUnitSystem {
+    // No unit system in use.
+    "none",
+    // Centimeter, gram, seconds, kelvin, ampere, candela.
+    "si-linear",
+    // Radians, gram, seconds, kelvin, ampere, candela.
+    "si-rotation",
+    // Inch, slug, seconds, Fahrenheit, ampere, candela.
+    "english-linear",
+    // Degrees, slug, seconds, Fahrenheit, ampere, candela.
+    "english-rotation",
+    "vendor-defined",
+    "reserved",
+};
+
 [
     Exposed(Window WebHID),
     SecureContext
@@ -39,18 +61,6 @@
     readonly attribute unsigned long usageMinimum;
     readonly attribute unsigned long usageMaximum;
 
-    // The minimum and maximum designator indices associated with this item. If
-    // there are no designators, both are set to zero.
-    // TODO(mattreynolds): Expose the designators instead of the indices.
-    readonly attribute unsigned long designatorMinimum;
-    readonly attribute unsigned long designatorMaximum;
-
-    // The minimum and maximum string indices associated with this item. If
-    // there are no designators, both are set to zero.
-    // TODO(mattreynolds): Expose the strings instead of the indices.
-    readonly attribute unsigned long stringMinimum;
-    readonly attribute unsigned long stringMaximum;
-
     // The size of a single field described by this item, in bits.
     readonly attribute unsigned short reportSize;
 
@@ -62,12 +72,21 @@
     // kilograms |unitExponent| would be 3 and for micrograms it would be -6.
     readonly attribute unsigned long unitExponent;
 
-    // A value that specifies the unit factors that make up the units for this
-    // report item. See the units table in section 6.2.2.7 of the Device Class
-    // Definition for HID, v1.11.
-    // https://www.usb.org/document-library/device-class-definition-hid-111
-    // TODO(mattreynolds): Split this into its component nibbles.
-    readonly attribute unsigned long unit;
+    // The unit system determines which units are used for length, mass, time,
+    // temperature, current, and luminous intensity. May be "none" if the values
+    // for this report item are unitless.
+    readonly attribute HIDUnitSystem unitSystem;
+
+    // The following members determine the exponents for each factor of the
+    // unit definition. For instance, for acceleration all factors would have
+    // an exponent of 0 except |unitFactorLengthExponent| which would be 1 and
+    // |unitFactorTimeExponent| which would be -2.
+    readonly attribute byte unitFactorLengthExponent;
+    readonly attribute byte unitFactorMassExponent;
+    readonly attribute byte unitFactorTimeExponent;
+    readonly attribute byte unitFactorTemperatureExponent;
+    readonly attribute byte unitFactorCurrentExponent;
+    readonly attribute byte unitFactorLuminousIntensityExponent;
 
     // The minimum and maximum values that may be represented by this input. A
     // device with |hasNull| may report a value outside this range to indicate
@@ -79,4 +98,7 @@
     // and |unitExponent|.
     readonly attribute long physicalMinimum;
     readonly attribute long physicalMaximum;
+
+    // The strings associated with this item.
+    readonly attribute FrozenArray<DOMString> strings;
 };

third_party/blink/web_tests/webexposed/global-interface-listing-expected.txt

@@ -2369,7 +2369,6 @@ interface HIDCollectionInfo
     getter featureReports
     getter inputReports
     getter outputReports
-    getter reportIds
     getter usage
     getter usagePage
     method constructor
@@ -2405,8 +2404,6 @@ interface HIDReportInfo
     method constructor
 interface HIDReportItem
     attribute @@toStringTag
-    getter designatorMaximum
-    getter designatorMinimum
     getter hasNull
     getter isAbsolute
     getter isArray
@@ -2417,10 +2414,15 @@ interface HIDReportItem
     getter physicalMinimum
     getter reportCount
     getter reportSize
-    getter stringMaximum
-    getter stringMinimum
-    getter unit
+    getter strings
     getter unitExponent
+    getter unitFactorCurrentExponent
+    getter unitFactorLengthExponent
+    getter unitFactorLuminousIntensityExponent
+    getter unitFactorMassExponent
+    getter unitFactorTemperatureExponent
+    getter unitFactorTimeExponent
+    getter unitSystem
     getter usageMaximum
     getter usageMinimum
     getter usages