Platform: fix SDL2/GLFW viewportEvent() on Retina-aware {i,mac}OS apps.

doc/changelog.dox

@@ -325,6 +325,9 @@ See also:
 -   Properly zero-initializing the UTF-8 buffer in
     @ref Platform::GlfwApplication::textInputEvent() (see
     [mosra/magnum#324](https://github.com/mosra/magnum/pull/324))
+-   @ref Platform::Sdl2Application::viewportEvent() and
+    @ref Platform::GlfwApplication::viewportEvent() is fixed to behave
+    correctly with @ref platforms-macos-hidpi "Retina-aware" apps on macOS/iOS
 -   @ref Text::AbstractFontConverter::exportFontToFile() and
     @ref Text::AbstractFontConverter::exportGlyphCacheToFile() now properly
     returns failure when the underlying data export function returns an empty

src/Magnum/Platform/GlfwApplication.cpp

@@ -470,15 +470,19 @@ void GlfwApplication::setupCallbacks() {
         /* Properly redraw after the window is restored from minimized state */
         static_cast<GlfwApplication*>(glfwGetWindowUserPointer(window))->drawEvent();
     });
+    #ifdef MAGNUM_TARGET_GL
     glfwSetFramebufferSizeCallback(_window, [](GLFWwindow* const window, const int w, const int h) {
         auto& app = *static_cast<GlfwApplication*>(glfwGetWindowUserPointer(window));
-        ViewportEvent e{{w, h}
-            #ifdef MAGNUM_TARGET_GL
-            , app.framebufferSize()
-            #endif
-            , app.dpiScaling()};
-        static_cast<GlfwApplication*>(glfwGetWindowUserPointer(window))->viewportEvent(e);
+        ViewportEvent e{app.windowSize(), {w, h}, app.dpiScaling()};
+        app.viewportEvent(e);
     });
+    #else
+    glfwSetWindowSizeCallback(_window, [](GLFWwindow* const window, const int w, const int h) {
+        auto& app = *static_cast<GlfwApplication*>(glfwGetWindowUserPointer(window));
+        ViewportEvent e{{w, h}, app.dpiScaling()};
+        app.viewportEvent(e);
+    });
+    #endif
     glfwSetKeyCallback(_window, [](GLFWwindow* const window, const int key, int, const int action, const int mods) {
         auto& app = *static_cast<GlfwApplication*>(glfwGetWindowUserPointer(window));
 

src/Magnum/Platform/Sdl2Application.cpp

@@ -693,7 +693,11 @@ void Sdl2Application::mainLoopIteration() {
                            https://github.com/kripken/emscripten/issues/1731 */
                         CORRADE_ASSERT_UNREACHABLE();
                         #else
-                        ViewportEvent e{event, {event.window.data1, event.window.data2},
+                        /* {event.window.data1, event.window.data2} seems to be
+                           framebuffer size and not window size on macOS, which
+                           is weird. Query the values directly instead to be
+                           really sure. */
+                        ViewportEvent e{event, windowSize(),
                             #ifdef MAGNUM_TARGET_GL
                             framebufferSize(),
                             #endif