experiment: providing a gateway for writing your own renderer through MirAL

debian/libmiral7.symbols

@@ -48,6 +48,8 @@ libmiral.so.7 libmiral7 #MINVER#
  (c++)"miral::CursorTheme::CursorTheme(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)@MIRAL_5.0" 5.0.0
  (c++)"miral::CursorTheme::operator()(mir::Server&) const@MIRAL_5.0" 5.0.0
  (c++)"miral::CursorTheme::~CursorTheme()@MIRAL_5.0" 5.0.0
+ (c++)"miral::CustomRenderer::CustomRenderer(std::function<std::unique_ptr<mir::renderer::Renderer, std::default_delete<mir::renderer::Renderer> > (std::unique_ptr<mir::graphics::gl::OutputSurface, std::default_delete<mir::graphics::gl::OutputSurface> >, std::shared_ptr<mir::graphics::GLRenderingProvider>)>&&)@MIRAL_5.0" 5.0.0
+ (c++)"miral::CustomRenderer::operator()(mir::Server&) const@MIRAL_5.0" 5.0.0
  (c++)"miral::DisplayConfiguration::DisplayConfiguration(miral::DisplayConfiguration const&)@MIRAL_5.0" 5.0.0
  (c++)"miral::DisplayConfiguration::DisplayConfiguration(miral::MirRunner const&)@MIRAL_5.0" 5.0.0
  (c++)"miral::DisplayConfiguration::add_output_attribute(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)@MIRAL_5.0" 5.0.0

include/miral/miral/custom_renderer.h

@@ -0,0 +1,59 @@
+/*
+ * Copyright © Canonical Ltd.
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 or 3 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef MIRAL_CUSTOM_RENDERER_H
+#define MIRAL_CUSTOM_RENDERER_H
+
+#include <memory>
+#include <functional>
+
+namespace mir
+{
+class Server;
+namespace graphics
+{
+class GLRenderingProvider;
+namespace gl
+{
+class OutputSurface;
+}
+}
+namespace renderer
+{
+class Renderer;
+}
+}
+
+namespace miral
+{
+
+class CustomRenderer
+{
+public:
+    using Builder = std::function<
+        std::unique_ptr<mir::renderer::Renderer>(
+        std::unique_ptr<mir::graphics::gl::OutputSurface>, std::shared_ptr<mir::graphics::GLRenderingProvider>)
+    >;
+
+    explicit CustomRenderer(Builder&& renderer);
+    void operator()(mir::Server& server) const;
+private:
+    struct Self;
+    std::shared_ptr<Self> self;
+};
+}
+
+#endif //MIRAL_CUSTOM_RENDERER_H

src/include/server/mir/server.h

@@ -67,6 +67,10 @@ namespace input
 {
 class SeatObserver;
 }
+namespace renderer
+{
+class RendererFactory;
+}
 
 class Fd;
 class MainLoop;
@@ -294,6 +298,9 @@ class Server
     /// Sets an override functor for creating the persistent_surface_store
     void override_the_persistent_surface_store(Builder<shell::PersistentSurfaceStore> const& persistent_surface_store);
 
+    /// Sets an override functor for the renderer_factory
+    void override_the_renderer_factory(Builder<renderer::RendererFactory> const& renderer_factory_builder);
+
     /// Each of the wrap functions takes a wrapper functor of the same form
     template<typename T> using Wrapper = std::function<std::shared_ptr<T>(std::shared_ptr<T> const&)>;
 
@@ -421,6 +428,9 @@ class Server
     auto the_session_lock() const ->
         std::shared_ptr<scene::SessionLock>;
 
+    auto the_renderer_factory() const ->
+        std::shared_ptr<renderer::RendererFactory>;
+
 /** @} */
 
 /** @name Client side support

src/miral/CMakeLists.txt

@@ -1,5 +1,6 @@
 include_directories(
   ${PROJECT_SOURCE_DIR}/src/include/server
+  ${PROJECT_SOURCE_DIR}/include/renderer
 )
 
 set(MIRAL_ABI 7)
@@ -54,6 +55,7 @@ add_library(miral SHARED
     configuration_option.cpp            ${miral_include}/miral/configuration_option.h
                                         ${miral_include}/miral/command_line_option.h
     cursor_theme.cpp                    ${miral_include}/miral/cursor_theme.h
+    custom_renderer.cpp                 ${miral_include}/miral/custom_renderer.h
     display_configuration.cpp           ${miral_include}/miral/display_configuration.h
     external_client.cpp                 ${miral_include}/miral/external_client.h
     keymap.cpp                          ${miral_include}/miral/keymap.h

src/miral/custom_renderer.cpp

@@ -0,0 +1,49 @@
+/*
+ * Copyright © Canonical Ltd.
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 or 3 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "miral/custom_renderer.h"
+#include <mir/server.h>
+#include <mir/renderer/renderer_factory.h>
+#include <mir/renderer/renderer.h>
+#include <mir/renderer/gl/gl_surface.h>
+
+struct miral::CustomRenderer::Self : public mir::renderer::RendererFactory
+{
+    explicit Self(Builder&& renderer)
+        : renderer(std::move(renderer))
+    {
+    }
+    [[nodiscard]] auto create_renderer_for(
+        std::unique_ptr<mir::graphics::gl::OutputSurface> output_surface,
+        std::shared_ptr<mir::graphics::GLRenderingProvider> gl_provider) const
+        -> std::unique_ptr<mir::renderer::Renderer> override
+    {
+        return renderer(std::move(output_surface), std::move(gl_provider));
+    }
+private:
+    miral::CustomRenderer::Builder const renderer;
+};
+
+miral::CustomRenderer::CustomRenderer(Builder&& renderer)
+    : self{std::make_shared<Self>(std::move(renderer))}
+{
+}
+
+void miral::CustomRenderer::operator()(mir::Server& server) const
+{
+    std::function<std::shared_ptr<mir::renderer::RendererFactory>()> builder = [self=self] { return self; };
+    server.override_the_renderer_factory(builder);
+}

src/miral/symbols.map

@@ -38,6 +38,9 @@ global:
     miral::CursorTheme::?CursorTheme*;
     miral::CursorTheme::CursorTheme*;
     miral::CursorTheme::operator*;
+    miral::CustomRenderer::?CustomRenderer*;
+    miral::CustomRenderer::CustomRenderer*;
+    miral::CustomRenderer::operator*;
     miral::DisplayConfiguration::?DisplayConfiguration*;
     miral::DisplayConfiguration::DisplayConfiguration*;
     miral::DisplayConfiguration::add_output_attribute*;
@@ -414,6 +417,7 @@ global:
     typeinfo?for?miral::CanonicalWindowManagerPolicy;
     typeinfo?for?miral::ConfigurationOption;
     typeinfo?for?miral::CursorTheme;
+    typeinfo?for?miral::CustomRenderer;
     typeinfo?for?miral::DisplayConfiguration;
     typeinfo?for?miral::ExternalClientLauncher;
     typeinfo?for?miral::FdHandle;

src/server/server.cpp

@@ -99,7 +99,8 @@ struct TemporaryCompositeEventFilter : public mi::CompositeEventFilter
     MACRO(session_listener)\
     MACRO(shell)\
     MACRO(application_not_responding_detector)\
-    MACRO(persistent_surface_store)
+    MACRO(persistent_surface_store)\
+    MACRO(renderer_factory)
 
 #define FOREACH_ACCESSOR(MACRO)\
     MACRO(the_buffer_stream_factory)\
@@ -131,7 +132,8 @@ struct TemporaryCompositeEventFilter : public mi::CompositeEventFilter
     MACRO(the_persistent_surface_store)\
     MACRO(the_display_configuration_observer_registrar)\
     MACRO(the_seat_observer_registrar)\
-    MACRO(the_session_lock)
+    MACRO(the_session_lock)\
+    MACRO(the_renderer_factory)
 
 #define MIR_SERVER_BUILDER(name)\
     std::function<std::invoke_result_t<decltype(&mir::DefaultServerConfiguration::the_##name),mir::DefaultServerConfiguration*>()> name##_builder;

src/server/symbols.map

@@ -143,6 +143,8 @@ MIR_SERVER_2.17 {
     mir::Server::override_the_session_listener*;
     mir::Server::override_the_shell*;
     mir::Server::override_the_window_manager_builder*;
+    mir::Server::the_renderer_factory*;
+    mir::Server::override_the_renderer_factory*;
     mir::Server::run*;
     mir::Server::set_command_line*;
     mir::Server::set_command_line_handler*;