1 #ifndef __DALI_HIT_TEST_ALGORITHM_H__
2 #define __DALI_HIT_TEST_ALGORITHM_H__
5 * Copyright (c) 2018 Samsung Electronics Co., Ltd.
7 * Licensed under the Apache License, Version 2.0 (the "License");
8 * you may not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
11 * http://www.apache.org/licenses/LICENSE-2.0
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
21 #include <dali/public-api/actors/actor.h>
22 #include <dali/public-api/common/stage.h>
23 #include <dali/integration-api/scene.h>
32 * @brief This namespace is provided for application developers to do hit-test for the actors.
34 * <h3>Hit Test Algorithm:</h3>
36 * Hit testing is dependent on the camera used, which is specific to each RenderTask. For each RenderTask,
37 * hit testing starts from the top-most layer and we go through all the layers until we have a hit or there
38 * are none left. Before we perform a hit test within a layer, we check if all the layer's parents meet the
39 * conditions defined by the function ((e.g. whether it is visible)). If they are not, we skip hit testing
40 * the actors in that layer altogether. Otherwise, we walk through the actor tree within a layer to check
41 * whether the actors within the actor tree should be hit-tested.
43 * The following pseudocode gives an example of what the function can typically check, which should normally
44 * be provided by the application code:
47 * HIT-TEST-FUNCTION( ACTOR, TRAVERSE-TYPE )
49 * if( TRAVERSE-TYPE == CHECK_ACTOR ) // Check whether current actor should be hit-tested
51 * if( ACTOR-IS-VISIBLE &&
52 * ACTOR-WORLD-COLOR-IS-NOT-TRANSPARENT )
57 * else if( TRAVERSE-TYPE == DESCEND_ACTOR_TREE ) ///< Check whether the actor tree should be descended to hit-test its children.
59 * if( ACTOR-IS-VISIBLE )
67 * The following pseudocode explains how the algorithm performs the hit-test with the above functor:
70 * HIT-TEST-WITHIN-LAYER( ACTOR )
72 * // Depth-first traversal within current layer, visiting parent first
74 * // Check whether current actor should be hit-tested
75 * IF ( HIT-TEST-FUNCTION( ACTOR, CHECK_ACTOR ) &&
76 * ACTOR-HAS-NON-ZERO-SIZE )
78 * // Hit-test current actor
81 * IF ( DISTANCE-TO-ACTOR < DISTANCE-TO-LAST-HIT-ACTOR )
83 * // The current actor is the closest actor that was underneath the touch
84 * LAST-HIT-ACTOR = CURRENT-ACTOR
89 * // Keep checking children, in case we hit something closer
90 * FOR-EACH CHILD (in order)
92 * IF ( HIT-TEST-FUNCTION( ACTOR, DESCEND_ACTOR_TREE ) &&
93 * ACTOR-IS-NOT-A-LAYER )
95 * // Continue traversal for this child's sub-tree
96 * HIT-TEST-WITHIN-LAYER ( CHILD )
98 * // else we skip the sub-tree with from this child
103 namespace HitTestAlgorithm
107 * @brief How the actor tree should be traversed.
111 CHECK_ACTOR, ///< Hit test the given actor.
112 DESCEND_ACTOR_TREE ///< Check whether the actor tree should be descended to hit-test its children.
116 * @brief Results structure containing the hit actor and where it was hit.
120 Actor actor; ///< The hit actor.
121 Vector2 actorCoordinates; ///< The actor coordinates.
125 * @brief Definition of a hit-test function to use in HitTest() method to check if the actor is hittable (e.g. touchable or focusable).
127 * @return true, if the actor is hittable, false otherwise.
129 typedef bool (*HitTestFunction)(Actor actor, TraverseType type);
132 * @brief Given screen coordinates, this method returns the hit actor & the local coordinates relative to
133 * the top-left (0.0f, 0.0f, 0.5f) of the actor.
135 * An actor is only hittable if the actor meets all the conditions
136 * defined by the given function (see HitTestAlgorithm).
138 * Typically, if an actor has a zero size or its world color is fully transparent, it should not be
139 * hittable; and if an actor's visibility flag is unset, its children should not be hittable either.
141 * @param[in] stage The stage.
142 * @param[in] screenCoordinates The screen coordinates.
143 * @param[out] results The results of the hit-test, only modified if something is hit
144 * @param[in] func The function to use in the hit-test algorithm.
145 * @return true if something was hit
147 DALI_CORE_API bool HitTest( Stage stage, const Vector2& screenCoordinates, Results& results, HitTestFunction func );
149 } // namespace HitTestAlgorithm
153 #endif // __DALI_HIT_TEST_ALGORITHM_H__