Re-enable display scale observing for msd::BasicManager and

`miral::DecorationBasicManager`.

examples/miral-shell/decoration/decoration.cpp

@@ -50,16 +50,7 @@ auto UserDecoration::InputManager::buttons() const -> std::vector<std::shared_pt
 
 void UserDecoration::render_titlebar(Renderer::Buffer const& titlebar_buffer)
 {
-    fill_solid_color(titlebar_buffer, current_titlebar_color);
-
-    auto const draw_button =
-        [&]( geometry::Rectangle button_rect, Renderer::Pixel color)
-    {
-        auto start = button_rect.top_left;
-        auto end = button_rect.bottom_right();
-        for (auto y = start.y; y < end.y; y += geometry::DeltaY{1})
-            Renderer::render_row(titlebar_buffer, {start.x, y}, geometry::as_width(end.x - start.x), color);
-    };
+    Renderer::fill_solid_color(titlebar_buffer, current_titlebar_color);
 
     auto buttons = input_manager.buttons();
     for (auto const& button : buttons)
@@ -85,15 +76,11 @@ void UserDecoration::render_titlebar(Renderer::Buffer const& titlebar_buffer)
         if (should_highlight)
             color += 0x00444444;
 
-        draw_button(button_rect, color);
-    }
-}
-
-void UserDecoration::fill_solid_color(Renderer::Buffer const& left_border_buffer, Renderer::Pixel color)
-{
-    for (geometry::Y y{0}; y < as_y(left_border_buffer.size().height); y += geometry::DeltaY{1})
-    {
-        Renderer::render_row(left_border_buffer, {0, y}, left_border_buffer.size().width, color);
+        // The buffers are automatically scaled with different display scales.
+        // `fill_solid_color` and `render_rect` use the scaled size to properly fill the buffer.
+        //
+        // Anything you draw yourself should be properly scaled with size.
+        Renderer::render_rect_scaled(titlebar_buffer, button_rect, scale, color);
     }
 }
 
@@ -370,6 +357,11 @@ void UserDecoration::focused()
     current_titlebar_color = focused_titlebar_color;
 }
 
+void UserDecoration::scale_changed(float new_scale)
+{
+    scale = new_scale;
+}
+
 auto UserDecoration::create_manager(mir::Server& server)
     -> std::shared_ptr<miral::DecorationManagerAdapter>
 {
@@ -398,15 +390,15 @@ auto UserDecoration::create_manager(mir::Server& server)
                        },
                        [decoration](auto const& left_border_buffer)
                        {
-                            decoration->fill_solid_color(left_border_buffer, decoration->current_titlebar_color);
+                       Renderer::fill_solid_color(left_border_buffer, decoration->current_titlebar_color);
                        },
                        [decoration](auto const& right_border_buffer)
                        {
-                            decoration->fill_solid_color(right_border_buffer, decoration->current_titlebar_color);
+                           Renderer::fill_solid_color(right_border_buffer, decoration->current_titlebar_color);
                        },
                        [decoration](auto const& bottom_border_buffer)
                        {
-                            decoration->fill_solid_color(bottom_border_buffer, decoration->current_titlebar_color);
+                           Renderer::fill_solid_color(bottom_border_buffer, decoration->current_titlebar_color);
                        },
                        [decoration](auto... args)
                        {
@@ -467,6 +459,11 @@ auto UserDecoration::create_manager(mir::Server& server)
                        {
                            decoration->redraw_notifier()->notify();
                        },
+                       [decoration](auto new_scale)
+                       {
+                           decoration->scale_changed(new_scale);
+                           decoration->redraw_notifier()->notify();
+                       },
                        [decoration](auto window_state)
                        {
                            decoration->input_manager.update_window_state(*window_state);

examples/miral-shell/decoration/decoration.h

@@ -49,7 +49,6 @@ class UserDecoration : public miral::Decoration
 
     using Renderer = miral::decoration::Renderer;
     void render_titlebar(Renderer::Buffer const& titlebar_buffer);
-    void fill_solid_color(Renderer::Buffer const& left_border_buffer, Renderer::Pixel color);
 
     static auto create_manager(mir::Server&)
         -> std::shared_ptr<miral::DecorationManagerAdapter>;
@@ -129,12 +128,11 @@ class UserDecoration : public miral::Decoration
     void focused();
     void unfocused();
 
-    void minimized();
-    void maximized();
-    void normal();
+    void scale_changed(float new_scale);
 
     InputManager input_manager;
     static Renderer::Pixel const focused_titlebar_color = 0xFF323232;
     static Renderer::Pixel const unfocused_titlebar_color = 0xFF525252;
     Renderer::Pixel current_titlebar_color = focused_titlebar_color;
+    float scale = 1.0;
 };

include/miral/miral/decoration_adapter.h

@@ -87,6 +87,7 @@ using OnWindowResized =
     std::function<void(ms::Surface const* window_surface, mir::geometry::Size const& /*window_size*/)>;
 using OnWindowRenamed = std::function<void(ms::Surface const* window_surface, std::string const& name)>;
 using OnWindowStateUpdated = std::function<void(std::shared_ptr<miral::decoration::WindowState>)>;
+using OnScaleChanged = std::function<void(float)>;
 
 struct InputContext
 {
@@ -167,16 +168,26 @@ class Renderer
         Renderer::RenderingCallback render_right_border,
         Renderer::RenderingCallback render_bottom_border);
 
-    static void render_row(Buffer const& buffer, geometry::Point left, geometry::Width length, uint32_t color);
+    static void fill_solid_color(Renderer::Buffer const& left_border_buffer, Renderer::Pixel color);
+
+    // Renders in display-scale-space, takes into account the display scale
+    static void render_rect_scaled(Buffer const& buffer, geometry::Rectangle unscaled_rect, float scale, Pixel color);
 
     void update_state(miral::decoration::WindowState const& window_state);
     auto streams_to_spec(std::shared_ptr<miral::decoration::WindowState> const& window_state) const
         -> msh::SurfaceSpecification;
     void update_render_submit(std::shared_ptr<miral::decoration::WindowState> const& window_state);
 
+    void scale_changed(float new_scale);
+    auto scale() const -> float;
+
 private:
     auto make_graphics_buffer(Buffer const&) -> std::optional<std::shared_ptr<mg::Buffer>>;
 
+    // Renders in buffer pixel-scale-space, independent of the actual display scale
+    static void render_row_unscaled(Buffer const& buffer, geometry::Point left, geometry::Width length, uint32_t color);
+
+
     std::shared_ptr<ms::Session> const session;
     std::shared_ptr<mg::GraphicBufferAllocator> const buffer_allocator;
 
@@ -189,26 +200,39 @@ class Renderer
     RenderingCallback const render_left_border;
     RenderingCallback const render_right_border;
     RenderingCallback const render_bottom_border;
+
+    float scale_ = 1.0;
 };
 
 struct DecorationAdapter
 {
     DecorationAdapter(
+        // Notifies Mir that decorations should be redrawn
         std::shared_ptr<DecorationRedrawNotifier> const& redraw_notifier,
+
+        // Called by user code in response to input events
         Renderer::RenderingCallback render_titlebar,
         Renderer::RenderingCallback render_left_border,
         Renderer::RenderingCallback render_right_border,
         Renderer::RenderingCallback render_bottom_border,
 
+        // Called by Mir to inform user code of input events
         OnProcessEnter process_enter,
         OnProcessLeave process_leave,
         OnProcessDown process_down,
         OnProcessUp process_up,
         OnProcessMove process_move,
         OnProcessDrag process_drag,
+
+        // Called by Mir to inform user code of changes to the window being decorated
         OnWindowAttribChanged attrib_changed,
         OnWindowResized window_resized_to,
         OnWindowRenamed window_renamed,
+
+        // Called by Mir to inform user code that the display scale changed
+        OnScaleChanged scale_changed,
+
+        // Called whenever the internal WindowState is updated
         OnWindowStateUpdated update_decoration_window_state);
 
     void set_custom_geometry(std::shared_ptr<miral::decoration::StaticGeometry> geometry);

src/include/server/mir/shell/decoration/basic_manager.h

@@ -52,7 +52,7 @@ class BasicManager :
         std::shared_ptr<scene::Surface> const& surface)>;
 
     BasicManager(
-        /* mir::ObserverRegistrar<mir::graphics::DisplayConfigurationObserver>& display_configuration_observers, */
+        mir::ObserverRegistrar<mir::graphics::DisplayConfigurationObserver>& display_configuration_observers,
         DecorationBuilder&& decoration_builder);
     ~BasicManager();
 

src/miral/decoration_adapter.cpp

@@ -233,7 +233,7 @@ auto md::Renderer::Buffer::stream() const -> std::shared_ptr<mc::BufferStream>
     return stream_;
 }
 
-void md::Renderer::render_row(Buffer const& buffer, geometry::Point left, geometry::Width length, uint32_t color)
+void md::Renderer::render_row_unscaled(Buffer const& buffer, geometry::Point left, geometry::Width length, uint32_t color)
 {
     auto buf_size = buffer.size();
     if (left.y < geometry::Y{} || left.y >= as_y(buf_size.height))
@@ -246,6 +246,26 @@ void md::Renderer::render_row(Buffer const& buffer, geometry::Point left, geomet
         *i = color;
 }
 
+void md::Renderer::fill_solid_color(Renderer::Buffer const& left_border_buffer, Renderer::Pixel color)
+{
+    for (geometry::Y y{0}; y < as_y(left_border_buffer.size().height); y += geometry::DeltaY{1})
+    {
+        Renderer::render_row_unscaled(left_border_buffer, {0, y}, left_border_buffer.size().width, color);
+    }
+}
+
+void md::Renderer::render_rect_scaled(Buffer const& buffer, geometry::Rectangle unscaled_rect, float scale, Pixel color)
+{
+    auto tl = unscaled_rect.top_left;
+    auto start = mir::geometry::Point{tl.x.as_value() * scale, tl.y.as_value() * scale};
+
+    auto br = unscaled_rect.bottom_right();
+    auto end = mir::geometry::Point{br.x.as_value() * scale, br.y.as_value() * scale};
+
+    for (auto y = start.y; y < end.y; y += geometry::DeltaY{1})
+        Renderer::render_row_unscaled(buffer, {start.x, y}, geometry::as_width(end.x - start.x), color);
+}
+
 auto md::Renderer::make_graphics_buffer(Buffer const& buffer)
     -> std::optional<std::shared_ptr<mg::Buffer>>
 {
@@ -274,10 +294,11 @@ auto md::Renderer::make_graphics_buffer(Buffer const& buffer)
 void md::Renderer::update_state(md::WindowState const& window_state)
 {
     auto const conditional_resize =
-        [](auto& buffer, auto const& rect)
+        [scale = this->scale_](auto& buffer, auto const& rect)
     {
-        if (rect.size != buffer.size())
-            buffer.resize(rect.size);
+        auto scaled_rect_size = rect.size * scale;
+        if (scaled_rect_size != buffer.size())
+            buffer.resize(scaled_rect_size);
     };
 
     conditional_resize(titlebar_buffer, window_state.titlebar_rect());
@@ -356,7 +377,7 @@ void md::Renderer::update_render_submit(std::shared_ptr<md::WindowState> const&
         break;
     }
 
-    float inv_scale = 1.0f; // 1.0f / window_state->scale();
+    float inv_scale =  1.0f / scale_;
     for (auto const& [stream, buffer_opt] : new_buffers)
     {
         if (buffer_opt)
@@ -367,6 +388,16 @@ void md::Renderer::update_render_submit(std::shared_ptr<md::WindowState> const&
     }
 }
 
+void md::Renderer::scale_changed(float new_scale)
+{
+    scale_ = new_scale;
+}
+
+auto md::Renderer::scale() const -> float
+{
+    return scale_;
+}
+
 class WindowSurfaceObserver : public ms::NullSurfaceObserver
 {
 public:
@@ -437,6 +468,7 @@ struct md::DecorationAdapter::Impl : public msd::Decoration
         OnWindowAttribChanged attrib_changed,
         OnWindowResized window_resized_to,
         OnWindowRenamed window_renamed,
+        OnScaleChanged scale_changed,
         OnWindowStateUpdated update_decoration_window_state) :
         redraw_notifier_{redraw_notifier},
         render_titlebar{render_titlebar},
@@ -468,6 +500,7 @@ struct md::DecorationAdapter::Impl : public msd::Decoration
                               window_renamed(args...);
                               on_update_decoration_window_state(window_state);
                           }},
+        on_scale_changed{scale_changed},
         geometry{std::make_shared<md::StaticGeometry>(default_geometry)}
     {
     }
@@ -487,7 +520,7 @@ struct md::DecorationAdapter::Impl : public msd::Decoration
 
     auto redraw_notifier() { return redraw_notifier_; }
 
-    void set_scale(float) override {}
+    void set_scale(float new_scale) override;
 
     ~Impl();
 
@@ -519,6 +552,7 @@ struct md::DecorationAdapter::Impl : public msd::Decoration
     OnWindowAttribChanged on_attrib_changed;
     OnWindowResized on_window_resized_to;
     OnWindowRenamed on_window_renamed;
+    OnScaleChanged on_scale_changed;
 
     std::shared_ptr<md::StaticGeometry> geometry;
 };
@@ -538,6 +572,7 @@ md::DecorationAdapter::DecorationAdapter(
     OnWindowAttribChanged attrib_changed,
     OnWindowResized window_resized_to,
     OnWindowRenamed window_renamed,
+    OnScaleChanged scale_changed,
     OnWindowStateUpdated update_decoration_window_state) :
     impl{std::make_shared<Impl>(
         redraw_notifier,
@@ -554,6 +589,7 @@ md::DecorationAdapter::DecorationAdapter(
         attrib_changed,
         window_resized_to,
         window_renamed,
+        scale_changed,
         update_decoration_window_state)}
 {
 }
@@ -677,6 +713,15 @@ void md::DecorationAdapter::Impl::window_state_updated(std::shared_ptr<ms::Surfa
     window_state = std::make_shared<md::WindowState>(geometry, window_surface.get());
 }
 
+void md::DecorationAdapter::Impl::set_scale(float new_scale)
+{
+    if(new_scale == renderer->scale())
+        return;
+
+    renderer->scale_changed(new_scale);
+    on_scale_changed(new_scale);
+}
+
 md::DecorationAdapter::DecorationAdapter::Impl::~Impl()
 {
     window_surface->unregister_interest(*window_surface_observer);

src/miral/decoration_basic_manager.cpp

@@ -61,7 +61,8 @@ struct miral::DecorationBasicManager::Self : public mir::shell::decoration::Basi
 {
     Self(mir::Server& server, Decoration::DecorationBuilder&& decoration_builder) :
         mir::shell::decoration::BasicManager(
-            [&server,decoration_builder](auto shell, auto window_surface)
+            *server.the_display_configuration_observer_registrar(),
+            [&server, decoration_builder](auto shell, auto window_surface)
             {
                 auto session = window_surface->session().lock();
                 auto decoration_surface = create_surface(window_surface, shell);

src/miral/symbols.map

@@ -576,7 +576,12 @@ global:
     miral::decoration::Renderer::area*;
     miral::decoration::Renderer::buffer_format*;
     miral::decoration::Renderer::bytes_per_pixel*;
+    miral::decoration::Renderer::fill_solid_color*;
+    miral::decoration::Renderer::render_rect_scaled*;
     miral::decoration::Renderer::render_row*;
+    miral::decoration::Renderer::render_row_unscaled*;
+    miral::decoration::Renderer::scale*;
+    miral::decoration::Renderer::scale_changed*;
     miral::decoration::Renderer::streams_to_spec*;
     miral::decoration::Renderer::update_render_submit*;
     miral::decoration::Renderer::update_state*;
@@ -590,6 +595,7 @@ global:
     miral::decoration::WindowState::left_border_rect*;
     miral::decoration::WindowState::resize_corner_input_size*;
     miral::decoration::WindowState::right_border_rect*;
+    miral::decoration::WindowState::scale*;
     miral::decoration::WindowState::side_border_height*;
     miral::decoration::WindowState::side_border_width*;
     miral::decoration::WindowState::titlebar_height*;