Add kTimeSinceStrokeEndInSeconds brush behavior source

This allows for one-shot whole-stroke animations that occur after input is finished.

PiperOrigin-RevId: 872922797

Author: Ink Open Source

ink/brush/brush_behavior.cc

@@ -61,6 +61,7 @@ bool IsValidBehaviorSource(BrushBehavior::Source source) {
     case BrushBehavior::Source::kPredictedTimeElapsedInSeconds:
     case BrushBehavior::Source::kDistanceRemainingInMultiplesOfBrushSize:
     case BrushBehavior::Source::kTimeSinceInputInSeconds:
+    case BrushBehavior::Source::kTimeSinceStrokeEndInSeconds:
     case BrushBehavior::Source::
         kAccelerationInMultiplesOfBrushSizePerSecondSquared:
     case BrushBehavior::Source::
@@ -95,9 +96,10 @@ absl::Status ValidateSourceAndOutOfRangeCombination(
     BrushBehavior::Source source, BrushBehavior::OutOfRange out_of_range) {
   switch (source) {
     case BrushBehavior::Source::kTimeSinceInputInSeconds:
+    case BrushBehavior::Source::kTimeSinceStrokeEndInSeconds:
       if (out_of_range != BrushBehavior::OutOfRange::kClamp) {
         return absl::InvalidArgumentError(
-            "`Source::kTimeSinceInputInSeconds` must only be used with "
+            "`kTimeSince*` sources can only be used with a "
             "`source_out_of_range_behavior` of `kClamp`.");
       }
       break;
@@ -514,6 +516,8 @@ std::string ToFormattedString(BrushBehavior::Source source) {
       return "kDistanceRemainingInMultiplesOfBrushSize";
     case BrushBehavior::Source::kTimeSinceInputInSeconds:
       return "kTimeSinceInputInSeconds";
+    case BrushBehavior::Source::kTimeSinceStrokeEndInSeconds:
+      return "kTimeSinceStrokeEndInSeconds";
     case BrushBehavior::Source::
         kAccelerationInMultiplesOfBrushSizePerSecondSquared:
       return "kAccelerationInMultiplesOfBrushSizePerSecondSquared";

ink/brush/brush_behavior.h

@@ -107,8 +107,7 @@ struct BrushBehavior {
   // List of input properties along with their units that can act as sources for
   // a `BrushBehavior`.
   //
-  // This should match the enum in BrushBehavior.kt and
-  // BrushFamilyExtensions.kt.
+  // This should match the enum in BrushBehavior.kt.
   //
   // Behaviors that consider properties of the stroke input do not consider
   // alterations to the visible position of that point in the stroke by brush
@@ -180,10 +179,16 @@ struct BrushBehavior {
     kDistanceRemainingInMultiplesOfBrushSize,
     // Time elapsed since the modeled stroke input. This continues to increase
     // even after all stroke inputs have completed, and can be used to drive
-    // stroke animations. These enumerators are only compatible with a
+    // wet-layer stroke animations. This source is only compatible with a
     // `source_out_of_range_behavior` of `kClamp`, to ensure that the animation
     // will eventually end.
     kTimeSinceInputInSeconds,
+    // Time elapsed since the final input of the stroke, or zero if the final
+    // input hasn't arrived yet. This can be used to drive wet-layer stroke
+    // animations that should occur after the final input. This source is only
+    // compatible with a `source_out_of_range_behavior` of `kClamp`, to ensure
+    // that the animation will eventually end.
+    kTimeSinceStrokeEndInSeconds,
     // Absolute acceleration of the modeled stroke input in multiples of the
     // brush size per second squared. Note that this value doesn't take into
     // account brush behaviors that offset the position of that visible point in
@@ -247,8 +252,7 @@ struct BrushBehavior {
 
   // List of tip properties that can be modified by a `BrushBehavior`.
   //
-  // This should match the enums in BrushBehavior.kt and
-  // BrushFamilyExtensions.kt.
+  // This should match the enum in BrushBehavior.kt.
   enum class Target : int8_t {
     // `kWidthMultiplier` and `kHeightMultiplier` scale the brush-tip size along
     // one dimension, starting from the values calculated using
@@ -324,8 +328,7 @@ struct BrushBehavior {
 
   // List of vector tip properties that can be modified by a `BrushBehavior`.
   //
-  // This should match the enums in BrushBehavior.kt and
-  // BrushFamilyExtensions.kt.
+  // This should match the enum in BrushBehavior.kt.
   enum class PolarTarget : int8_t {
     // Adds the vector to the brush tip's absolute x/y position in stroke space,
     // where the angle input is measured in radians and the magnitude input is
@@ -349,8 +352,7 @@ struct BrushBehavior {
   // The desired behavior when an input value is outside the bounds of
   // `source_value_range`.
   //
-  // This should match the enum in BrushBehavior.kt and
-  // BrushFamilyExtensions.kt.
+  // This should match the enum in BrushBehavior.kt.
   enum class OutOfRange : int8_t {
     // Values outside the range will be clamped to not exceed the bounds.
     kClamp,
@@ -387,8 +389,7 @@ struct BrushBehavior {
 
   // List of input properties that might not be reported by `StrokeInput`.
   //
-  // This should match the enums in BrushBehavior.kt and
-  // BrushFamilyExtensions.kt.
+  // This should match the enum in BrushBehavior.kt.
   enum OptionalInputProperty : int8_t {
     kPressure,
     kTilt,

ink/brush/brush_behavior_test.cc

@@ -80,6 +80,8 @@ TEST(BrushBehaviorTest, StringifySource) {
       "kDistanceRemainingInMultiplesOfBrushSize");
   EXPECT_EQ(absl::StrCat(BrushBehavior::Source::kTimeSinceInputInSeconds),
             "kTimeSinceInputInSeconds");
+  EXPECT_EQ(absl::StrCat(BrushBehavior::Source::kTimeSinceStrokeEndInSeconds),
+            "kTimeSinceStrokeEndInSeconds");
   EXPECT_EQ(
       absl::StrCat(BrushBehavior::Source::
                        kAccelerationInMultiplesOfBrushSizePerSecondSquared),
@@ -729,8 +731,18 @@ TEST(BrushBehaviorTest, ValidateSourceNode) {
   });
   EXPECT_EQ(status.code(), absl::StatusCode::kInvalidArgument);
   EXPECT_THAT(status.message(),
-              HasSubstr("kTimeSinceInputInSeconds` must only be used with "
-                        "`source_out_of_range_behavior` of `kClamp"));
+              HasSubstr("`kTimeSince*` sources can only be used with a "
+                        "`source_out_of_range_behavior` of `kClamp`"));
+
+  status = brush_internal::ValidateBrushBehaviorNode(BrushBehavior::SourceNode{
+      .source = BrushBehavior::Source::kTimeSinceStrokeEndInSeconds,
+      .source_out_of_range_behavior = BrushBehavior::OutOfRange::kMirror,
+      .source_value_range = {0, 2},
+  });
+  EXPECT_EQ(status.code(), absl::StatusCode::kInvalidArgument);
+  EXPECT_THAT(status.message(),
+              HasSubstr("`kTimeSince*` sources can only be used with a "
+                        "`source_out_of_range_behavior` of `kClamp`"));
 
   status = brush_internal::ValidateBrushBehaviorNode(BrushBehavior::SourceNode{
       .source = BrushBehavior::Source::kInputDistanceTraveledInCentimeters,

ink/brush/brush_family_test.cc

@@ -522,6 +522,9 @@ TEST(BrushFamilyTest, CreateWithInvalidBehaviorSourceAndOutOfRangeBehavior) {
   BrushTip brush_tip = {
       .behaviors = {BrushBehavior{{
           BrushBehavior::SourceNode{
+              .source = BrushBehavior::Source::kTimeSinceInputInSeconds,
+              .source_out_of_range_behavior =
+                  BrushBehavior::OutOfRange::kRepeat,
               .source_value_range = {0, 1},
           },
           BrushBehavior::TargetNode{
@@ -530,17 +533,11 @@ TEST(BrushFamilyTest, CreateWithInvalidBehaviorSourceAndOutOfRangeBehavior) {
           },
       }}},
   };
-  BrushBehavior::SourceNode* source_node =
-      &std::get<BrushBehavior::SourceNode>(brush_tip.behaviors[0].nodes[0]);
-
-  source_node->source = BrushBehavior::Source::kTimeSinceInputInSeconds;
-  source_node->source_out_of_range_behavior =
-      BrushBehavior::OutOfRange::kRepeat;
-  absl::Status status = BrushFamily::Create(brush_tip, BrushPaint{}).status();
-  EXPECT_EQ(status.code(), kInvalidArgument);
-  EXPECT_THAT(status.message(),
-              HasSubstr("kTimeSinceInputInSeconds` must only be used with "
-                        "`source_out_of_range_behavior` of `kClamp"));
+  EXPECT_THAT(
+      BrushFamily::Create(brush_tip, BrushPaint{}).status(),
+      StatusIs(kInvalidArgument,
+               HasSubstr("`kTimeSince*` sources can only be used with a "
+                         "`source_out_of_range_behavior` of `kClamp`")));
 }
 
 TEST(BrushFamilyTest, CreateWithInvalidBehaviorTargetModifierRange) {

ink/brush/fuzz_domains.cc

@@ -177,6 +177,7 @@ Domain<BrushBehavior::OutOfRange> ValidBrushBehaviorOutOfRangeForSource(
     BrushBehavior::Source source) {
   switch (source) {
     case BrushBehavior::Source::kTimeSinceInputInSeconds:
+    case BrushBehavior::Source::kTimeSinceStrokeEndInSeconds:
       return Just(BrushBehavior::OutOfRange::kClamp);
     default:
       return ArbitraryBrushBehaviorOutOfRange();
@@ -206,6 +207,7 @@ Domain<BrushBehavior::Source> ArbitraryBrushBehaviorSource() {
       BrushBehavior::Source::kPredictedTimeElapsedInSeconds,
       BrushBehavior::Source::kDistanceRemainingInMultiplesOfBrushSize,
       BrushBehavior::Source::kTimeSinceInputInSeconds,
+      BrushBehavior::Source::kTimeSinceStrokeEndInSeconds,
       BrushBehavior::Source::
           kAccelerationInMultiplesOfBrushSizePerSecondSquared,
       BrushBehavior::Source::

ink/storage/brush.cc

@@ -187,6 +187,8 @@ proto::BrushBehavior::Source EncodeBrushBehaviorSource(
           SOURCE_DISTANCE_REMAINING_IN_MULTIPLES_OF_BRUSH_SIZE;
     case BrushBehavior::Source::kTimeSinceInputInSeconds:
       return proto::BrushBehavior::SOURCE_TIME_SINCE_INPUT_IN_SECONDS;
+    case BrushBehavior::Source::kTimeSinceStrokeEndInSeconds:
+      return proto::BrushBehavior::SOURCE_TIME_SINCE_STROKE_END_IN_SECONDS;
     case BrushBehavior::Source::
         kAccelerationInMultiplesOfBrushSizePerSecondSquared:
       return proto::BrushBehavior::
@@ -372,6 +374,8 @@ absl::StatusOr<BrushBehavior::Source> DecodeBrushBehaviorSource(
     case proto::BrushBehavior::
         SOURCE_DISTANCE_REMAINING_AS_FRACTION_OF_STROKE_LENGTH:
       return BrushBehavior::Source::kDistanceRemainingAsFractionOfStrokeLength;
+    case proto::BrushBehavior::SOURCE_TIME_SINCE_STROKE_END_IN_SECONDS:
+      return BrushBehavior::Source::kTimeSinceStrokeEndInSeconds;
     default:
       return absl::InvalidArgumentError(absl::StrCat(
           "invalid ink.proto.BrushBehavior.Source value: ", source_proto));

ink/storage/proto/brush_family.proto

@@ -651,8 +651,8 @@ message BrushBehavior {
 
     // Time elapsed (in seconds) since the modeled stroke input. This continues
     // to increase even after all stroke inputs have completed, and can be used
-    // to drive stroke animations. These enumerators are only compatible with a
-    // `source_out_of_range_behavior` of `OUT_OF_RANGE_CLAMP`, to ensure that
+    // to drive wet-layer stroke animations. This source is only compatible with
+    // a `source_out_of_range_behavior` of `OUT_OF_RANGE_CLAMP`, to ensure that
     // the animation will eventually end.
     SOURCE_TIME_SINCE_INPUT_IN_SECONDS = 19;
 
@@ -755,6 +755,13 @@ message BrushBehavior {
     // the input path, as a fraction of the current total length of the stroke.
     // This value changes for each input as inputs are added.
     SOURCE_DISTANCE_REMAINING_AS_FRACTION_OF_STROKE_LENGTH = 39;
+
+    // Time elapsed (in seconds) since the final input of the stroke, or zero if
+    // the final input hasn't arrived yet. This can be used to drive wet-layer
+    // stroke animations that should occur after the final input. This source is
+    // only compatible with a `source_out_of_range_behavior` of
+    // `OUT_OF_RANGE_CLAMP`, to ensure that the animation will eventually end.
+    SOURCE_TIME_SINCE_STROKE_END_IN_SECONDS = 40;
   }
   // LINT.ThenChange(../../brush/brush_behavior.h:source)
 

ink/strokes/in_progress_stroke.cc

@@ -165,6 +165,9 @@ absl::Status InProgressStroke::UpdateShape(Duration32 current_elapsed_time) {
 
   input_modeler_.ExtendStroke(queued_real_inputs_, queued_predicted_inputs_,
                               current_elapsed_time);
+  if (inputs_are_finished_) {
+    input_modeler_.FinishStrokeInputs();
+  }
   uint32_t num_coats = BrushCoatCount();
   for (uint32_t i = 0; i < num_coats; ++i) {
     StrokeShapeUpdate update = shape_builders_[i].ExtendStroke(input_modeler_);

ink/strokes/internal/BUILD.bazel

@@ -151,6 +151,7 @@ cc_test(
         "//ink/types:type_matchers",
         "@com_google_absl//absl/log:absl_check",
         "@com_google_absl//absl/status:status_matchers",
+        "@com_google_absl//absl/status:statusor",
         "@com_google_fuzztest//fuzztest",
         "@com_google_googletest//:gtest_main",
     ],
@@ -239,6 +240,7 @@ cc_library(
         ":brush_tip_state",
         ":easing_implementation",
         ":modeled_stroke_input",
+        ":noise_generator",
         "//ink/brush:brush_behavior",
         "//ink/brush:brush_tip",
         "//ink/geometry:angle",
@@ -591,12 +593,14 @@ cc_test(
         ":stroke_shape_builder",
         ":stroke_shape_update",
         ":stroke_vertex",
+        "//ink/brush:brush_behavior",
         "//ink/brush:brush_coat",
         "//ink/brush:brush_family",
         "//ink/brush:brush_paint",
         "//ink/brush:brush_tip",
         "//ink/geometry:envelope",
         "//ink/geometry:mutable_mesh",
+        "//ink/geometry:rect",
         "//ink/geometry:type_matchers",
         "//ink/geometry/internal:algorithms",
         "//ink/strokes/input:stroke_input_batch",

ink/strokes/internal/brush_tip_extruder.cc

@@ -62,20 +62,8 @@ void BrushTipExtruder::StartStroke(float brush_epsilon, bool is_particle_brush,
   max_chord_height_ = GetMaxChordHeight(brush_epsilon);
   simplification_threshold_ = GetSimplificationThreshold(brush_epsilon);
   is_particle_brush_ = is_particle_brush;
-  extrusions_.clear();
-  saved_extrusion_data_count_ = 0;
-  deleted_save_point_extrusions_.clear();
   geometry_.Reset(MutableMeshView(mesh));
-  bounds_ = {};
-  // Pre-allocate the first outline.
-  num_outlines_ = 1;
-  if (outlines_.empty()) {
-    outlines_.resize(1);
-  }
-  // Clear all the outlines from the previous stroke.
-  for (StrokeOutline& outline : outlines_) {
-    outline.TruncateIndices({0, 0});
-  }
+  RestartStroke();
 }
 
 namespace {
@@ -137,6 +125,24 @@ StrokeShapeUpdate BrushTipExtruder::ExtendStroke(
                          vertex_count_before_update);
 }
 
+void BrushTipExtruder::RestartStroke() {
+  ABSL_CHECK_GT(brush_epsilon_, 0) << "`StartStroke()` has not been called";
+  extrusions_.clear();
+  saved_extrusion_data_count_ = 0;
+  deleted_save_point_extrusions_.clear();
+  geometry_.Reset(geometry_.GetMeshView());
+  bounds_ = {};
+  // Pre-allocate the first outline.
+  num_outlines_ = 1;
+  if (outlines_.empty()) {
+    outlines_.resize(1);
+  }
+  // Clear all the outlines from the previous stroke.
+  for (StrokeOutline& outline : outlines_) {
+    outline.TruncateIndices({0, 0});
+  }
+}
+
 void BrushTipExtruder::ClearCachedPartialBounds() {
   bounds_.cached_partial_bounds.Reset();
   bounds_.cached_partial_bounds_left_index_count = 0;