1 #ifndef DALI_TOOLKIT_ASYNC_IMAGE_LOADER_H
2 #define DALI_TOOLKIT_ASYNC_IMAGE_LOADER_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.
22 #include <dali/public-api/object/base-handle.h>
23 #include <dali/public-api/images/image-operations.h>
24 #include <dali/public-api/signals/dali-signal.h>
27 #include <dali-toolkit/public-api/dali-toolkit-common.h>
36 namespace Internal DALI_INTERNAL
38 class AsyncImageLoader;
42 * @brief The AsyncImageLoader is used to load pixel data from a URL asynchronously.
44 * The images are loaded in a worker thread to avoid blocking the main event thread.
46 * To keep track of the loading images, each load call is assigned an ID (which is returned by the Load() call).
47 * To know when the Load has completed, connect to the ImageLoadedSignal.
48 * This signal should be connected before Load is called (in case the signal is emitted immediately).
50 * Load errors can be detected by checking the PixelData object is valid from within the signal handler.
52 * Note: The PixelData object will automatically be destroyed when it leaves its scope.
57 * class MyClass : public ConnectionTracker
61 * MyCallback( uint32_t loadedTaskId, PixelData pixelData )
63 * // First check if the image loaded correctly.
66 * if( loadedTaskId == mId1 )
68 * // use the loaded pixel data from the first image
70 * else if( loadedTaskId == mId2 )
72 * // use the loaded pixel data from the second image
82 * AsyncImageLoader imageLoader = AsyncImageLoader::New();
84 * // Connect the signal here.
85 * imageLoader.ImageLoadedSignal().Connect( &myObject, &MyClass::MyCallback );
87 * // Invoke the load calls (must do this after connecting the signal to guarantee callbacks occur).
88 * myObject.mId1 = imageLoader.Load( "first_image_url.jpg" );
89 * myObject.mId2 = imageLoader.Load( "second_image_url.jpg" );
93 class DALI_TOOLKIT_API AsyncImageLoader : public BaseHandle
97 typedef Signal< void( uint32_t, PixelData ) > ImageLoadedSignalType; ///< Image loaded signal type @SINCE_1_2_14
102 * @brief Constructor which creates an empty AsyncImageLoader handle.
105 * Use AsyncImageLoader::New() to create an initialised object.
113 * This is non-virtual since derived Handle types must not contain data or virtual methods.
118 * @brief This copy constructor is required for (smart) pointer semantics.
121 * @param[in] handle A reference to the copied handle
123 AsyncImageLoader( const AsyncImageLoader& handle );
126 * @brief This assignment operator is required for (smart) pointer semantics.
129 * @param[in] handle A reference to the copied handle
130 * @return A reference to this
132 AsyncImageLoader& operator=( const AsyncImageLoader& handle );
135 * @brief Creates a new loader to load the image asynchronously in a worker thread.
138 * @return The image loader
140 static AsyncImageLoader New();
143 * @brief Downcasts a handle to AsyncImageLoader handle.
145 * If the handle points to an AsyncImageLoader object, the downcast produces a valid handle.
146 * If not, the returned handle is left uninitialized.
149 * @param[in] handle A handle to an object
150 * @return A handle to a AsyncImageLoader object or an uninitialized handle
152 static AsyncImageLoader DownCast( BaseHandle handle );
155 * @brief Starts an image loading task.
156 * Note: When using this method, the following defaults will be used:
157 * fittingMode = FittingMode::DEFAULT
158 * samplingMode = SamplingMode::BOX_THEN_LINEAR
159 * orientationCorrection = true
164 * @param[in] url The URL of the image file to load
165 * @return The loading task id
167 uint32_t Load( const std::string& url );
170 * @brief Starts an image loading task.
171 * Note: When using this method, the following defaults will be used:
172 * fittingMode = FittingMode::DEFAULT
173 * samplingMode = SamplingMode::BOX_THEN_LINEAR
174 * orientationCorrection = true
179 * @param[in] url The URL of the image file to load
180 * @param[in] dimensions The width and height to fit the loaded image to
181 * @return The loading task id
183 uint32_t Load( const std::string& url, ImageDimensions dimensions );
186 * @brief Starts an image loading task.
190 * @param[in] url The URL of the image file to load
191 * @param[in] dimensions The width and height to fit the loaded image to
192 * @param[in] fittingMode The method used to fit the shape of the image before loading to the shape defined by the size parameter
193 * @param[in] samplingMode The filtering method used when sampling pixels from the input image while fitting it to desired size
194 * @param[in] orientationCorrection Reorient the image to respect any orientation metadata in its header
195 * @return The loading task id
197 uint32_t Load( const std::string& url,
198 ImageDimensions dimensions,
199 FittingMode::Type fittingMode,
200 SamplingMode::Type samplingMode,
201 bool orientationCorrection );
204 * @brief Cancels an image loading task if it is still queueing in the work thread.
207 * @param[in] loadingTaskId The task id returned when invoking the load call.
208 * @return If true, the loading task is removed from the queue, otherwise the loading is already implemented and unable to cancel anymore
210 bool Cancel( uint32_t loadingTaskId );
213 * @brief Cancels all the loading tasks in the queue.
219 * @brief Signal emitted for connected callback functions to get access to the loaded pixel data.
221 * A callback of the following type may be connected:
223 * void YourCallbackName( uint32_t id, PixelData pixelData );
226 * @return A reference to a signal object to Connect() with
228 ImageLoadedSignalType& ImageLoadedSignal();
230 public: // Not intended for developer use
234 * @brief Allows the creation of a AsyncImageLoader handle from an internal pointer.
236 * @note Not intended for application developers
238 * @param[in] impl A pointer to the object
240 explicit DALI_INTERNAL AsyncImageLoader( Internal::AsyncImageLoader* impl );
245 } // namespace Toolkit
249 #endif // DALI_TOOLKIT_ASYNC_IMAGE_LOADER_H