Platform: improve {Glfw,Sdl2}Application.

Two new methods, setMinWindowSize() and setMaxWindowSize(), were added.
They use the underlying library's API to achieve their purpose.

src/Magnum/Platform/GlfwApplication.cpp

@@ -534,6 +534,20 @@ Vector2i GlfwApplication::windowSize() const {
     return size;
 }
 
+void GlfwApplication::setMinWindowSize(const Vector2i& size) {
+    CORRADE_ASSERT(_window, "Platform::GlfwApplication::setMinWindowSize(): no window opened", );
+
+    glfwSetWindowSizeLimits(_window, size.x(), size.y(), _maxWindowSize.x(), _maxWindowSize.y());
+    _minWindowSize = size;
+}
+
+void GlfwApplication::setMaxWindowSize(const Vector2i& size) {
+    CORRADE_ASSERT(_window, "Platform::GlfwApplication::setMaxWindowSize(): no window opened", );
+
+    glfwSetWindowSizeLimits(_window, _minWindowSize.x(), _minWindowSize.y(), size.x(), size.y());
+    _maxWindowSize = size;
+}
+
 #ifdef MAGNUM_TARGET_GL
 Vector2i GlfwApplication::framebufferSize() const {
     CORRADE_ASSERT(_window, "Platform::GlfwApplication::framebufferSize(): no window opened", {});

src/Magnum/Platform/GlfwApplication.h

@@ -336,6 +336,22 @@ class GlfwApplication {
          */
         Vector2i windowSize() const;
 
+        /**
+         * @brief Set window minimum size
+         * @param size    The minimum size, in screen coordinates.
+         * 
+         * If a value is set to -1, it will disable/remove the corresponding limit.
+         */
+        void setMinWindowSize(const Vector2i& size = {-1, -1});
+        
+        /**
+         * @brief Set window maximum size
+         * @param size    The maximum size, in screen coordinates.
+         * 
+         * If a value is set to -1, it will disable/remove the corresponding limit.
+         */
+        void setMaxWindowSize(const Vector2i& size = {-1, -1});
+
         #if defined(MAGNUM_TARGET_GL) || defined(DOXYGEN_GENERATING_OUTPUT)
         /**
          * @brief Framebuffer size
@@ -552,6 +568,9 @@ class GlfwApplication {
         Containers::Pointer<Platform::GLContext> _context;
         #endif
         int _exitCode;
+        
+        Vector2i _minWindowSize;
+        Vector2i _maxWindowSize;
 };
 
 CORRADE_ENUMSET_OPERATORS(GlfwApplication::Flags)

src/Magnum/Platform/Sdl2Application.cpp

@@ -550,6 +550,18 @@ Vector2i Sdl2Application::windowSize() const {
     return size;
 }
 
+#ifndef CORRADE_TARGET_EMSCRIPTEN
+void Sdl2Application::setMinWindowSize(const Vector2i& size) {
+    CORRADE_ASSERT(_window, "Platform::Sdl2Application::setMinWindowSize(): no window opened", );
+    SDL_SetWindowMinimumSize(_window, size.x(), size.y());
+}
+
+void Sdl2Application::setMaxWindowSize(const Vector2i& size) {
+    CORRADE_ASSERT(_window, "Platform::Sdl2Application::setMaxWindowSize(): no window opened", );
+    SDL_SetWindowMaximumSize(_window, size.x(), size.y());
+}
+#endif
+
 #ifdef MAGNUM_TARGET_GL
 Vector2i Sdl2Application::framebufferSize() const {
     Vector2i size;

src/Magnum/Platform/Sdl2Application.h

@@ -639,6 +639,24 @@ class Sdl2Application {
          */
         Vector2i windowSize() const;
 
+        #if !defined(CORRADE_TARGET_EMSCRIPTEN) || defined(DOXYGEN_GENERATING_OUTPUT)
+        /**
+         * @brief Set minimum window size
+         * @param size    The minimum size for the window, in screen coordinates.
+         * 
+         * Note that SDL2 doesn't have a way to disable/remove a size limit.
+         */
+        void setMinWindowSize(const Vector2i& size);
+
+        /**
+         * @brief Set maximal window size
+         * @param size    The maximum size for the window, in screen coordinates.
+         * 
+         * Note that SDL2 doesn't have a way to disable/remove a size limit.
+         */
+        void setMaxWindowSize(const Vector2i& size);
+        #endif
+
         #if defined(MAGNUM_TARGET_GL) || defined(DOXYGEN_GENERATING_OUTPUT)
         /**
          * @brief Framebuffer size