Platform: Sdl2Application::mainLoopIteration() now returns a bool.

To indicate when the app desires to exit.

doc/changelog.dox

@@ -500,6 +500,8 @@ See also:
     @ref Platform::GlfwApplication::exit() now have an optional parameter to
     specify the actual application return code (see
     [mosra/magnum#332](https://github.com/mosra/magnum/pull/332))
+-   @ref Platform::Sdl2Application::mainLoopIteration() now returns a
+    @cpp bool @ce to indicate if the application should exit
 -   @ref Platform::GlfwApplication and @ref Platform::EmscriptenApplication now
     implement @ref Platform::GlfwApplication::MouseMoveEvent::relativePosition()
     as well for better compatibility with @ref Platform::Sdl2Application. The

src/Magnum/Platform/Sdl2Application.cpp

@@ -692,7 +692,7 @@ Sdl2Application::~Sdl2Application() {
 
 int Sdl2Application::exec() {
     #ifndef CORRADE_TARGET_EMSCRIPTEN
-    while(!(_flags & Flag::Exit)) mainLoopIteration();
+    while(mainLoopIteration()) {}
     #else
     emscripten_set_main_loop_arg([](void* arg) {
         static_cast<Sdl2Application*>(arg)->mainLoopIteration();
@@ -701,16 +701,17 @@ int Sdl2Application::exec() {
     return _exitCode;
 }
 
-void Sdl2Application::exit(int exitCode) {
-    #ifndef CORRADE_TARGET_EMSCRIPTEN
+void Sdl2Application::exit(const int exitCode) {
+    /* On Emscripten this flag is used only to indicate a desire to exit from
+       mainLoopIteration() */
     _flags |= Flag::Exit;
-    #else
+    #ifdef CORRADE_TARGET_EMSCRIPTEN
     emscripten_cancel_main_loop();
     #endif
     _exitCode = exitCode;
 }
 
-void Sdl2Application::mainLoopIteration() {
+bool Sdl2Application::mainLoopIteration() {
     #ifndef CORRADE_TARGET_EMSCRIPTEN
     const UnsignedInt timeBefore = _minimalLoopPeriod ? SDL_GetTicks() : 0;
     #endif
@@ -828,12 +829,13 @@ void Sdl2Application::mainLoopIteration() {
                 ExitEvent e{event};
                 exitEvent(e);
                 if(e.isAccepted()) {
-                    #ifndef CORRADE_TARGET_EMSCRIPTEN
+                    /* On Emscripten this flag is used only to indicate a
+                       desire to exit from mainLoopIteration() */
                     _flags |= Flag::Exit;
-                    #else
+                    #ifdef CORRADE_TARGET_EMSCRIPTEN
                     emscripten_cancel_main_loop();
                     #endif
-                    return;
+                    return !(_flags & Flag::Exit);
                 }
             } break;
 
@@ -860,7 +862,7 @@ void Sdl2Application::mainLoopIteration() {
         }
         #endif
 
-        return;
+        return !(_flags & Flag::Exit);
     }
 
     #ifndef CORRADE_TARGET_EMSCRIPTEN
@@ -875,6 +877,7 @@ void Sdl2Application::mainLoopIteration() {
        indefinitely for next input event */
     if(_flags & Flag::NoTickEvent) SDL_WaitEvent(nullptr);
     #endif
+    return !(_flags & Flag::Exit);
 }
 
 void Sdl2Application::setMouseLocked(bool enabled) {

src/Magnum/Platform/Sdl2Application.h

@@ -504,13 +504,15 @@ class Sdl2Application {
 
         /**
          * @brief Run one iteration of application main loop
+         * @return @cpp false @ce if @ref exit() was called and the application
+         *      should exit, @cpp true @ce otherwise
          *
          * Called internally from @ref exec(). If you want to have better
          * control over how the main loop behaves, you can call this function
          * yourself from your own `main()` function instead of it being called
          * automatically from @ref exec() / @ref MAGNUM_SDL2APPLICATION_MAIN().
          */
-        void mainLoopIteration();
+        bool mainLoopIteration();
 
         #ifndef CORRADE_TARGET_EMSCRIPTEN
         /**
@@ -1003,9 +1005,7 @@ class Sdl2Application {
             VSyncEnabled = 1 << 1,
             NoTickEvent = 1 << 2,
             NoAnyEvent = 1 << 3,
-            #ifndef CORRADE_TARGET_EMSCRIPTEN
-            Exit = 1 << 4
-            #endif
+            Exit = 1 << 4,
             #ifdef CORRADE_TARGET_EMSCRIPTEN
             TextInputActive = 1 << 5,
             Resizable = 1 << 6