Platform: add missing EmscriptenApp::Config::{add,clear}WindowFlags().

All other apps have it.

doc/changelog.dox

@@ -226,6 +226,9 @@ See also:
     other context classes
 -   Undefining even more noise from `Xlib.h` (see
     [mosra/magnum#498](https://github.com/mosra/magnum/pull/498))
+-   Added @ref Platform::EmscriptenApplication::Configuration::addWindowFlags()
+    and @ref Platform::EmscriptenApplication::Configuration::clearWindowFlags()
+    for consistency with other application implementations
 
 @subsubsection changelog-latest-changes-shaders Shaders library
 

src/Magnum/Platform/EmscriptenApplication.h

@@ -1232,12 +1232,45 @@ class EmscriptenApplication::Configuration {
         /**
          * @brief Set window flags
          * @return Reference to self (for method chaining)
+         *
+         * Default are none. To avoid clearing default flags by accident,
+         * prefer to use @ref addWindowFlags() and @ref clearWindowFlags()
+         * instead.
          */
         Configuration& setWindowFlags(WindowFlags windowFlags) {
             _windowFlags = windowFlags;
             return *this;
         }
 
+        /**
+         * @brief Add window flags
+         * @return Reference to self (for method chaining)
+         * @m_since_latest
+         *
+         * Unlike @ref setWindowFlags(), ORs the flags with existing instead of
+         * replacing them. Useful for preserving the defaults.
+         * @see @ref clearWindowFlags()
+         */
+        Configuration& addWindowFlags(WindowFlags flags) {
+            _windowFlags |= flags;
+            return *this;
+        }
+
+        /**
+         * @brief Clear window flags
+         * @return Reference to self (for method chaining)
+         * @m_since_latest
+         *
+         * Unlike @ref setWindowFlags(), ANDs the inverse of @p flags with
+         * existing instead of replacing them. Useful for removing default
+         * flags.
+         * @see @ref addWindowFlags()
+         */
+        Configuration& clearWindowFlags(WindowFlags flags) {
+            _windowFlags &= ~flags;
+            return *this;
+        }
+
     private:
         Vector2i _size;
         Vector2 _dpiScaling;