Platform: make text input actually working on Emscripten.

The event handlers were still disabled and SDL_IsTexInputActive() needs
to be emulated.

src/Magnum/Platform/Sdl2Application.cpp

@@ -395,7 +395,6 @@ void Sdl2Application::mainLoop() {
                 break;
             }
 
-            #ifndef CORRADE_TARGET_EMSCRIPTEN
             case SDL_TEXTINPUT: {
                 TextInputEvent e{{event.text.text, std::strlen(event.text.text)}};
                 textInputEvent(e);
@@ -405,7 +404,6 @@ void Sdl2Application::mainLoop() {
                 TextEditingEvent e{{event.edit.text, std::strlen(event.text.text)}, event.edit.start, event.edit.length};
                 textEditingEvent(e);
             } break;
-            #endif
 
             case SDL_QUIT:
                 #ifndef CORRADE_TARGET_EMSCRIPTEN
@@ -462,12 +460,32 @@ void Sdl2Application::setMouseLocked(bool enabled) {
     #endif
 }
 
-#ifndef CORRADE_TARGET_EMSCRIPTEN
+bool Sdl2Application::isTextInputActive() {
+    #ifndef CORRADE_TARGET_EMSCRIPTEN
+    return SDL_IsTextInputActive();
+    #else
+    return _isTextInputActive;
+    #endif
+}
+
+void Sdl2Application::startTextInput() {
+    SDL_StartTextInput();
+    #ifdef CORRADE_TARGET_EMSCRIPTEN
+    _isTextInputActive = true;
+    #endif
+}
+
+void Sdl2Application::stopTextInput() {
+    SDL_StopTextInput();
+    #ifdef CORRADE_TARGET_EMSCRIPTEN
+    _isTextInputActive = false;
+    #endif
+}
+
 void Sdl2Application::setTextInputRect(const Range2Di& rect) {
     SDL_Rect r{rect.min().x(), rect.min().y(), rect.sizeX(), rect.sizeY()};
     SDL_SetTextInputRect(&r);
 }
-#endif
 
 void Sdl2Application::tickEvent() {
     /* If this got called, the tick event is not implemented by user and thus

src/Magnum/Platform/Sdl2Application.h

@@ -605,9 +605,12 @@ class Sdl2Application {
          *
          * If text input is active, text input events go to @ref textInputEvent()
          * and @ref textEditingEvent().
+         * @note Note that in @ref CORRADE_TARGET_EMSCRIPTEN "Emscripten" the
+         *      value is emulated and might not reflect external events like
+         *      closing on-screen keyboard.
          * @see @ref startTextInput(), @ref stopTextInput()
          */
-        bool isTextInputActive() { return SDL_IsTextInputActive(); }
+        bool isTextInputActive();
 
         /**
          * @brief Start text input
@@ -617,7 +620,7 @@ class Sdl2Application {
          * @see @ref stopTextInput(), @ref isTextInputActive(),
          *      @ref setTextInputRect()
          */
-        void startTextInput() { SDL_StartTextInput(); }
+        void startTextInput();
 
         /**
          * @brief Stop text input
@@ -625,7 +628,7 @@ class Sdl2Application {
          * @see @ref startTextInput(), @ref isTextInputActive(), @ref textInputEvent()
          *      @ref textEditingEvent()
          */
-        void stopTextInput() { SDL_StopTextInput(); }
+        void stopTextInput();
 
         /**
          * @brief Set text input rectangle
@@ -683,6 +686,7 @@ class Sdl2Application {
         UnsignedInt _minimalLoopPeriod;
         #else
         SDL_Surface* _glContext;
+        bool _isTextInputActive = false;
         #endif
 
         std::unique_ptr<Platform::Context> _context;