1 #ifndef __DALI_HIT_TEST_ALGORITHM_H__
2 #define __DALI_HIT_TEST_ALGORITHM_H__
5 * Copyright (c) 2014 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>
31 * @brief This namespace is provided for application developers to do hit-test for the actors.
33 * <h3>Hit Test Algorithm:</h3>
35 * Hit testing is dependent on the camera used, which is specific to each RenderTask. For each RenderTask,
36 * hit testing starts from the top-most layer and we go through all the layers until we have a hit or there
37 * are none left. Before we perform a hit test within a layer, we check if all the layer's parents meet the
38 * conditions defined by the function ((e.g. whether it is visible)). If they are not, we skip hit testing
39 * the actors in that layer altogether. Otherwise, we walk through the actor tree within a layer to check
40 * whether the actors within the actor tree should be hit-tested.
42 * The following pseudocode gives an example of what the function can typically check, which should normally
43 * be provided by the application code:
46 * HIT-TEST-FUNCTION( ACTOR, TRAVERSE-TYPE )
48 * if( TRAVERSE-TYPE == CHECK_ACTOR ) // Check whether current actor should be hit-tested
50 * if( ACTOR-IS-VISIBLE &&
51 * ACTOR-WORLD-COLOR-IS-NOT-TRANSPARENT )
56 * else if( TRAVERSE-TYPE == DESCEND_ACTOR_TREE ) ///< Check whether the actor tree should be descended to hit-test its children.
58 * if( ACTOR-IS-VISIBLE )
66 * The following pseudocode explains how the algorithm performs the hit-test with the above functor:
69 * HIT-TEST-WITHIN-LAYER( ACTOR )
71 * // Depth-first traversal within current layer, visiting parent first
73 * // Check whether current actor should be hit-tested
74 * IF ( HIT-TEST-FUNCTION( ACTOR, CHECK_ACTOR ) &&
75 * ACTOR-HAS-NON-ZERO-SIZE )
77 * // Hit-test current actor
80 * IF ( DISTANCE-TO-ACTOR < DISTANCE-TO-LAST-HIT-ACTOR )
82 * // The current actor is the closest actor that was underneath the touch
83 * LAST-HIT-ACTOR = CURRENT-ACTOR
88 * // Keep checking children, in case we hit something closer
89 * FOR-EACH CHILD (in order)
91 * IF ( HIT-TEST-FUNCTION( ACTOR, DESCEND_ACTOR_TREE ) &&
92 * ACTOR-IS-NOT-A-LAYER )
94 * // Continue traversal for this child's sub-tree
95 * HIT-TEST-WITHIN-LAYER ( CHILD )
97 * // else we skip the sub-tree with from this child
102 namespace HitTestAlgorithm
106 * @brief How the actor tree should be traversed.
110 CHECK_ACTOR, ///< Hit test the given actor.
111 DESCEND_ACTOR_TREE ///< Check whether the actor tree should be descended to hit-test its children.
115 * @brief Results structure containing the hit actor and where it was hit.
119 Actor actor; ///< The hit actor.
120 Vector2 actorCoordinates; ///< The actor coordinates.
124 * @brief Definition of a hit-test function to use in HitTest() method to check if the actor is hittable (e.g. touchable or focusable).
126 * @return true, if the actor is hittable, false otherwise.
128 typedef bool (*HitTestFunction)(Actor actor, TraverseType type);
131 * @brief Given screen coordinates, this method returns the hit actor & the local coordinates relative to
132 * the top-left (0.0f, 0.0f, 0.5f) of the actor.
134 * An actor is only hittable if the actor meets all the conditions
135 * defined by the given function (see HitTestAlgorithm).
137 * Typically, if an actor has a zero size or its world color is fully transparent, it should not be
138 * hittable; and if an actor's visibility flag is unset, its children should not be hittable either.
140 * @param[in] stage The stage.
141 * @param[in] screenCoordinates The screen coordinates.
142 * @param[out] results The results of the hit-test, only modified if something is hit
143 * @param[in] func The function to use in the hit-test algorithm.
144 * @return true if something was hit
146 DALI_IMPORT_API bool HitTest( Stage stage, const Vector2& screenCoordinates, Results& results, HitTestFunction func );
149 * @brief Hit test specific to a given RenderTask.
151 * @param[in] renderTask The render task for hit test
152 * @param[in] screenCoordinates The screen coordinates.
153 * @param[out] results The results of the hit-test, only modified if something is hit
154 * @param[in] func The function to use in the hit-test algorithm.
155 * @return true if something was hit
157 DALI_IMPORT_API bool HitTest( RenderTask& renderTask, const Vector2& screenCoordinates, Results& results, HitTestFunction func );
159 } // namespace HitTestAlgorithm
163 #endif // __DALI_HIT_TEST_ALGORITHM_H__