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+.. default-domain:: cpp
+.. highlight:: cpp
+.. namespace:: pugl
+
+###############
+Creating a View
+###############
+
+A `view` is a drawable region that receives events.
+You may think of it as a window,
+though it may be embedded and not represent a top-level system window. [#f1]_
+
+Pugl communicates with views by dispatching events.
+For flexibility, the event handler can be a different object than the view.
+This allows using :class:`View` along with a separate event handler class.
+Alternatively, a view class can inherit from :class:`View` and set itself as its event handler,
+for a more object-oriented style.
+
+This documentation will use the latter approach,
+so we will define a class for our view that contains everything needed:
+
+.. code-block:: cpp
+
+ class MyView : public pugl::View
+ {
+ public:
+ explicit MyView(pugl::World& world)
+ : pugl::View{world}
+ {
+ setEventHandler(*this);
+ }
+
+ pugl::Status onEvent(const pugl::ConfigureEvent& event) noexcept;
+ pugl::Status onEvent(const pugl::ExposeEvent& event) noexcept;
+
+ // With other handlers here as needed...
+
+ // Fallback handler for all other events
+ template<PuglEventType t, class Base>
+ pugl::Status onEvent(const pugl::Event<t, Base>&) noexcept
+ {
+ return pugl::Status::success;
+ }
+
+ private:
+ // Some data...
+ };
+
+Pugl will call an ``onEvent`` method of the event handler (the view in this case) for every event.
+
+Note that Pugl uses a static dispatching mechanism rather than virtual functions to minimize overhead.
+It is therefore necessary for the final class to define a handler for every event type.
+A terse way to do this without writing every implementation is to define a fallback handler as a template,
+as in the example above.
+Alternatively, you can define an explicit handler for each event that simply returns :enumerator:`Status::success`.
+This way, it will be a compile error if any event is not explicitly handled.
+
+*********************
+Configuring the Frame
+*********************
+
+Before display,
+the necessary :doc:`frame <api/frame>` and :doc:`window <api/window>` attributes should be set.
+These allow the window system (or plugin host) to arrange the view properly.
+
+Derived classes can configure themselves during construction,
+but we assume here that configuration is being done outside the view.
+For example:
+
+.. code-block:: cpp
+
+ const double defaultWidth = 1920.0;
+ const double defaultHeight = 1080.0;
+
+ view.setWindowTitle("My Window");
+ view.setDefaultSize(defaultWidth, defaultHeight);
+ view.setMinSize(defaultWidth / 4.0, defaultHeight / 4.0);
+ view.setAspectRatio(1, 1, 16, 9);
+
+There are also several :type:`hints <PuglViewHint>` for basic attributes that can be set:
+
+.. code-block:: cpp
+
+ view.setHint(pugl::ViewHint::resizable, true);
+ view.setHint(pugl::ViewHint::ignoreKeyRepeat, true);
+
+*********
+Embedding
+*********
+
+To embed the view in another window,
+you will need to somehow get the :type:`native view handle <pugl::NativeView>` for the parent,
+then set it with :func:`View::setParentWindow`.
+If the parent is a Pugl view,
+the native handle can be accessed with :func:`View::nativeWindow`.
+For example:
+
+.. code-block:: cpp
+
+ view.setParentWindow(view, parent.getNativeWindow());
+
+*****************
+Setting a Backend
+*****************
+
+Before being realized, the view must have a backend set with :func:`View::setBackend`.
+
+The backend manages the graphics API that will be used for drawing.
+Pugl includes backends and supporting API for
+:doc:`Cairo <api/cairo>`, :doc:`OpenGL <api/gl>`, and :doc:`Vulkan <api/vulkan>`.
+
+Using Cairo
+===========
+
+Cairo-specific API is declared in the ``cairo.hpp`` header:
+
+.. code-block:: cpp
+
+ #include <pugl/cairo.hpp>
+
+The Cairo backend is provided by :func:`cairoBackend()`:
+
+.. code-block:: cpp
+
+ view.setBackend(pugl::cairoBackend());
+
+No additional configuration is required for Cairo.
+To draw when handling an expose event,
+the `Cairo context <https://www.cairographics.org/manual/cairo-cairo-t.html>`_ can be accessed with :func:`View::context`:
+
+.. code-block:: cpp
+
+ cairo_t* cr = static_cast<cairo_t*>(view.context());
+
+Using OpenGL
+============
+
+OpenGL-specific API is declared in the ``gl.hpp`` header:
+
+.. code-block:: cpp
+
+ #include <pugl/gl.hpp>
+
+The OpenGL backend is provided by :func:`glBackend()`:
+
+.. code-block:: cpp
+
+ view.setBackend(pugl::glBackend());
+
+Some hints must also be set so that the context can be set up correctly.
+For example, to use OpenGL 3.3 Core Profile:
+
+.. code-block:: cpp
+
+ view.setHint(pugl::ViewHint::useCompatProfile, false);
+ view.setHint(pugl::ViewHint::contextVersionMajor, 3);
+ view.setHint(pugl::ViewHint::contextVersionMinor, 3);
+
+If you need to perform some setup using the OpenGL API,
+there are two ways to do so.
+
+The OpenGL context is active when
+:type:`CreateEvent` and
+:type:`DestroyEvent`
+events are dispatched,
+so things like creating and destroying shaders and textures can be done then.
+
+Alternatively, if it is cumbersome to set up and tear down OpenGL in the event handler,
+:func:`enterContext` and :func:`leaveContext` can be used to manually activate the OpenGL context during application setup.
+Note, however, that unlike many other APIs, these functions must not be used for drawing.
+It is only valid to use the OpenGL API for configuration in a manually entered context,
+rendering will not work.
+For example:
+
+.. code-block:: cpp
+
+ pugl::enterContext(view);
+ myApp.setupOpenGL();
+ pugl::leaveContext(view);
+
+ while (!myApp.quit()) {
+ world.update(0.0);
+ }
+
+ pugl::enterContext(view);
+ myApp.teardownOpenGL();
+ pugl::leaveContext(view);
+
+Using Vulkan
+============
+
+Vulkan-specific API is declared in the ``vulkan.hpp`` header.
+This header includes Vulkan headers,
+so if you are dynamically loading Vulkan at runtime,
+you should define ``VK_NO_PROTOTYPES`` before including it.
+
+.. code-block:: cpp
+
+ #define VK_NO_PROTOTYPES
+
+ #include <pugl/vulkan.hpp>
+
+The Vulkan backend is provided by :func:`vulkanBackend()`:
+
+.. code-block:: cpp
+
+ view.setBackend(pugl::vulkanBackend());
+
+Unlike OpenGL, almost all Vulkan configuration is done using the Vulkan API directly.
+Pugl only provides a portable mechanism to load the Vulkan library and get the functions used to load the rest of the Vulkan API.
+
+Loading Vulkan
+--------------
+
+For maximum compatibility,
+it is best to not link to Vulkan at compile-time,
+but instead load the Vulkan API at run-time.
+To do so, first create a :class:`VulkanLoader`:
+
+.. code-block:: cpp
+
+ pugl::VulkanLoader loader{world};
+
+The loader manages the dynamically loaded Vulkan library,
+so it must be kept alive for as long as the application is using Vulkan.
+You can get the function used to load Vulkan functions with :func:`VulkanLoader::getInstanceProcAddrFunc`:
+
+.. code-block:: cpp
+
+ auto vkGetInstanceProcAddr = loader.getInstanceProcAddrFunc();
+
+It is best to use this function to load everything at run time,
+rather than link to the Vulkan library at run time.
+You can, for example, pass this to get the ``vkCreateInstance`` function using this,
+then use that to create your Vulkan instance.
+In practice, you will want to use some loader or wrapper API since there are many Vulkan functions.
+
+It is not necessary to use :class:`VulkanLoader`,
+you can, for example, use the ``DynamicLoader`` from ``vulkan.hpp`` in the Vulkan SDK instead.
+
+The details of using Vulkan are far beyond the scope of this documentation,
+but Pugl provides a portable function, :func:`createSurface`,
+to get the Vulkan surface for a view.
+Assuming you have somehow created your ``VkInstance``,
+you can get the surface for a view using :func:`createSurface`:
+
+.. code-block:: cpp
+
+ VkSurfaceKHR* surface = nullptr;
+ puglCreateSurface(loader.getDeviceProcAddrFunc(),
+ view,
+ vulkanInstance,
+ nullptr,
+ &surface);
+
+Pugl does not provide API that uses ``vulkan.hpp`` to avoid the onerous dependency,
+but if you are using it with exceptions and unique handles,
+it is straightforward to wrap the surface handle yourself.
+
+****************
+Showing the View
+****************
+
+Once the view is configured, it can be "realized" with :func:`View::realize`.
+This creates a "real" system view, for example:
+
+.. code-block:: cpp
+
+ pugl::Status status = view.realize();
+ if (status != pugl::Status::success) {
+ std::cerr << "Error realizing view: " << pugl::strerror(status) << "\n";
+ }
+
+Note that realizing a view can fail for many reasons,
+so the return code should always be checked.
+This is generally the case for any function that interacts with the window system.
+Most functions also return a :enum:`Status`,
+but these checks are omitted for brevity in the rest of this documentation.
+
+A realized view is not initially visible,
+but can be shown with :func:`View::show`:
+
+.. code-block:: cpp
+
+ view.show();
+
+To create an initially visible view,
+it is also possible to simply call :func:`View::show()` right away.
+The view will be automatically realized if necessary.
+
+.. rubric:: Footnotes
+
+.. [#f1] MacOS has a strong distinction between
+ `views <https://developer.apple.com/documentation/appkit/nsview>`_,
+ which may be nested, and
+ `windows <https://developer.apple.com/documentation/appkit/nswindow>`_,
+ which may not.
+ On Windows and X11, everything is a nestable window,
+ but top-level windows are configured differently.