1 /* 2 * Copyright (C) 2023 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 * 16 */ 17 18 #ifndef _ANDROID_NATIVE_APP_GLUE_H 19 #define _ANDROID_NATIVE_APP_GLUE_H 20 21 #include <android/configuration.h> 22 #include <android/looper.h> 23 #include <android/native_activity.h> 24 #include <poll.h> 25 #include <pthread.h> 26 #include <sched.h> 27 28 #ifdef __cplusplus 29 extern "C" { 30 #endif 31 32 /** 33 * The native activity interface provided by <android/native_activity.h> 34 * is based on a set of application-provided callbacks that will be called 35 * by the Activity's main thread when certain events occur. 36 * 37 * This means that each one of this callbacks _should_ _not_ block, or they 38 * risk having the system force-close the application. This programming 39 * model is direct, lightweight, but constraining. 40 * 41 * The 'android_native_app_glue' static library is used to provide a different 42 * execution model where the application can implement its own main event 43 * loop in a different thread instead. Here's how it works: 44 * 45 * 1/ The application must provide a function named "android_main()" that 46 * will be called when the activity is created, in a new thread that is 47 * distinct from the activity's main thread. 48 * 49 * 2/ android_main() receives a pointer to a valid "android_app" structure 50 * that contains references to other important objects, e.g. the 51 * ANativeActivity object instance the application is running in. 52 * 53 * 3/ the "android_app" object holds an ALooper instance that already 54 * listens to two important things: 55 * 56 * - activity lifecycle events (e.g. "pause", "resume"). See APP_CMD_XXX 57 * declarations below. 58 * 59 * - input events coming from the AInputQueue attached to the activity. 60 * 61 * Each of these correspond to an ALooper identifier returned by 62 * ALooper_pollOnce with values of LOOPER_ID_MAIN and LOOPER_ID_INPUT, 63 * respectively. 64 * 65 * Your application can use the same ALooper to listen to additional 66 * file-descriptors. They can either be callback based, or with return 67 * identifiers starting with LOOPER_ID_USER. 68 * 69 * 4/ Whenever you receive a LOOPER_ID_MAIN or LOOPER_ID_INPUT event, 70 * the returned data will point to an android_poll_source structure. You 71 * can call the process() function on it, and fill in android_app->onAppCmd 72 * and android_app->onInputEvent to be called for your own processing 73 * of the event. 74 * 75 * Alternatively, you can call the low-level functions to read and process 76 * the data directly... look at the process_cmd() and process_input() 77 * implementations in the glue to see how to do this. 78 * 79 * See the sample named "native-activity" that comes with the NDK with a 80 * full usage example. Also look at the JavaDoc of NativeActivity. 81 */ 82 83 struct android_app; 84 85 /** 86 * Data associated with an ALooper fd that will be returned as the "outData" 87 * when that source has data ready. 88 */ 89 struct android_poll_source { 90 // The identifier of this source. May be LOOPER_ID_MAIN or 91 // LOOPER_ID_INPUT. 92 int32_t id; 93 94 // The android_app this ident is associated with. 95 struct android_app* app; 96 97 // Function to call to perform the standard processing of data from 98 // this source. 99 void (*process)(struct android_app* app, struct android_poll_source* source); 100 }; 101 102 /** 103 * This is the interface for the standard glue code of a threaded 104 * application. In this model, the application's code is running 105 * in its own thread separate from the main thread of the process. 106 * It is not required that this thread be associated with the Java 107 * VM, although it will need to be in order to make JNI calls any 108 * Java objects. 109 */ 110 struct android_app { 111 // The application can place a pointer to its own state object 112 // here if it likes. 113 void* userData; 114 115 // Fill this in with the function to process main app commands (APP_CMD_*) 116 void (*onAppCmd)(struct android_app* app, int32_t cmd); 117 118 // Fill this in with the function to process input events. At this point 119 // the event has already been pre-dispatched, and it will be finished upon 120 // return. Return 1 if you have handled the event, 0 for any default 121 // dispatching. 122 int32_t (*onInputEvent)(struct android_app* app, AInputEvent* event); 123 124 // The ANativeActivity object instance that this app is running in. 125 ANativeActivity* activity; 126 127 // The current configuration the app is running in. 128 AConfiguration* config; 129 130 // This is the last instance's saved state, as provided at creation time. 131 // It is NULL if there was no state. You can use this as you need; the 132 // memory will remain around until you call android_app_exec_cmd() for 133 // APP_CMD_RESUME, at which point it will be freed and savedState set to NULL. 134 // These variables should only be changed when processing a APP_CMD_SAVE_STATE, 135 // at which point they will be initialized to NULL and you can malloc your 136 // state and place the information here. In that case the memory will be 137 // freed for you later. 138 void* savedState; 139 size_t savedStateSize; 140 141 // The ALooper associated with the app's thread. 142 ALooper* looper; 143 144 // When non-NULL, this is the input queue from which the app will 145 // receive user input events. 146 AInputQueue* inputQueue; 147 148 // When non-NULL, this is the window surface that the app can draw in. 149 ANativeWindow* window; 150 151 // Current content rectangle of the window; this is the area where the 152 // window's content should be placed to be seen by the user. 153 ARect contentRect; 154 155 // Current state of the app's activity. May be either APP_CMD_START, 156 // APP_CMD_RESUME, APP_CMD_PAUSE, or APP_CMD_STOP; see below. 157 int activityState; 158 159 // This is non-zero when the application's NativeActivity is being 160 // destroyed and waiting for the app thread to complete. 161 int destroyRequested; 162 163 // ------------------------------------------------- 164 // Below are "private" implementation of the glue code. 165 166 pthread_mutex_t mutex; 167 pthread_cond_t cond; 168 169 int msgread; 170 int msgwrite; 171 172 pthread_t thread; 173 174 struct android_poll_source cmdPollSource; 175 struct android_poll_source inputPollSource; 176 177 int running; 178 int stateSaved; 179 int destroyed; 180 int redrawNeeded; 181 AInputQueue* pendingInputQueue; 182 ANativeWindow* pendingWindow; 183 ARect pendingContentRect; 184 }; 185 186 enum { 187 /** 188 * Looper data ID of commands coming from the app's main thread, which 189 * is returned as an identifier from ALooper_pollOnce(). The data for this 190 * identifier is a pointer to an android_poll_source structure. 191 * These can be retrieved and processed with android_app_read_cmd() 192 * and android_app_exec_cmd(). 193 */ 194 LOOPER_ID_MAIN = 1, 195 196 /** 197 * Looper data ID of events coming from the AInputQueue of the 198 * application's window, which is returned as an identifier from 199 * ALooper_pollOnce(). The data for this identifier is a pointer to an 200 * android_poll_source structure. These can be read via the inputQueue 201 * object of android_app. 202 */ 203 LOOPER_ID_INPUT = 2, 204 205 /** 206 * Start of user-defined ALooper identifiers. 207 */ 208 LOOPER_ID_USER = 3, 209 }; 210 211 enum { 212 /** 213 * Command from main thread: the AInputQueue has changed. Upon processing 214 * this command, android_app->inputQueue will be updated to the new queue 215 * (or NULL). 216 */ 217 APP_CMD_INPUT_CHANGED, 218 219 /** 220 * Command from main thread: a new ANativeWindow is ready for use. Upon 221 * receiving this command, android_app->window will contain the new window 222 * surface. 223 */ 224 APP_CMD_INIT_WINDOW, 225 226 /** 227 * Command from main thread: the existing ANativeWindow needs to be 228 * terminated. Upon receiving this command, android_app->window still 229 * contains the existing window; after calling android_app_exec_cmd 230 * it will be set to NULL. 231 */ 232 APP_CMD_TERM_WINDOW, 233 234 /** 235 * Command from main thread: the current ANativeWindow has been resized. 236 * Please redraw with its new size. 237 */ 238 APP_CMD_WINDOW_RESIZED, 239 240 /** 241 * Command from main thread: the system needs that the current ANativeWindow 242 * be redrawn. You should redraw the window before handing this to 243 * android_app_exec_cmd() in order to avoid transient drawing glitches. 244 */ 245 APP_CMD_WINDOW_REDRAW_NEEDED, 246 247 /** 248 * Command from main thread: the content area of the window has changed, 249 * such as from the soft input window being shown or hidden. You can 250 * find the new content rect in android_app::contentRect. 251 */ 252 APP_CMD_CONTENT_RECT_CHANGED, 253 254 /** 255 * Command from main thread: the app's activity window has gained 256 * input focus. 257 */ 258 APP_CMD_GAINED_FOCUS, 259 260 /** 261 * Command from main thread: the app's activity window has lost 262 * input focus. 263 */ 264 APP_CMD_LOST_FOCUS, 265 266 /** 267 * Command from main thread: the current device configuration has changed. 268 */ 269 APP_CMD_CONFIG_CHANGED, 270 271 /** 272 * Command from main thread: the system is running low on memory. 273 * Try to reduce your memory use. 274 */ 275 APP_CMD_LOW_MEMORY, 276 277 /** 278 * Command from main thread: the app's activity has been started. 279 */ 280 APP_CMD_START, 281 282 /** 283 * Command from main thread: the app's activity has been resumed. 284 */ 285 APP_CMD_RESUME, 286 287 /** 288 * Command from main thread: the app should generate a new saved state 289 * for itself, to restore from later if needed. If you have saved state, 290 * allocate it with malloc and place it in android_app.savedState with 291 * the size in android_app.savedStateSize. The will be freed for you 292 * later. 293 */ 294 APP_CMD_SAVE_STATE, 295 296 /** 297 * Command from main thread: the app's activity has been paused. 298 */ 299 APP_CMD_PAUSE, 300 301 /** 302 * Command from main thread: the app's activity has been stopped. 303 */ 304 APP_CMD_STOP, 305 306 /** 307 * Command from main thread: the app's activity is being destroyed, 308 * and waiting for the app thread to clean up and exit before proceeding. 309 */ 310 APP_CMD_DESTROY, 311 }; 312 313 /** 314 * Call when ALooper_pollAll() returns LOOPER_ID_MAIN, reading the next 315 * app command message. 316 */ 317 int8_t android_app_read_cmd(struct android_app* android_app); 318 319 /** 320 * Call with the command returned by android_app_read_cmd() to do the 321 * initial pre-processing of the given command. You can perform your own 322 * actions for the command after calling this function. 323 */ 324 void android_app_pre_exec_cmd(struct android_app* android_app, int8_t cmd); 325 326 /** 327 * Call with the command returned by android_app_read_cmd() to do the 328 * final post-processing of the given command. You must have done your own 329 * actions for the command before calling this function. 330 */ 331 void android_app_post_exec_cmd(struct android_app* android_app, int8_t cmd); 332 333 /** 334 * Placeholder function you can call to ensure glue code isn't stripped. 335 */ 336 void app_dummy(void); 337 338 /** 339 * This is the function that application code must implement, representing 340 * the main entry to the app. 341 */ 342 extern void android_main(struct android_app* app); 343 344 #ifdef __cplusplus 345 } 346 #endif 347 348 #endif /* _ANDROID_NATIVE_APP_GLUE_H */