Add canvas clear service boundary

src/app_layout.cpp

@@ -305,12 +305,31 @@ public:
         ActionManager::clear();
     }
 
-    void clear_canvas() override
+    void clear_canvas(const pp::app::DocumentCanvasClearPlan& plan) override
     {
-        if (!app_.canvas || !app_.canvas->m_canvas)
-            return;
+        class LegacyDocumentCanvasClearServices final : public pp::app::DocumentCanvasClearServices {
+        public:
+            explicit LegacyDocumentCanvasClearServices(App& app) noexcept
+                : app_(app)
+            {
+            }
 
-        app_.canvas->m_canvas->clear({ 0.0F, 0.0F, 0.0F, 0.0F });
+            void clear_current_canvas(float r, float g, float b, float a) override
+            {
+                if (!app_.canvas || !app_.canvas->m_canvas)
+                    return;
+
+                app_.canvas->m_canvas->clear({ r, g, b, a });
+            }
+
+        private:
+            App& app_;
+        };
+
+        LegacyDocumentCanvasClearServices services(app_);
+        const auto status = pp::app::execute_document_canvas_clear_plan(plan, services);
+        if (!status.ok())
+            LOG("Canvas clear failed: %s", status.message);
     }
 
     void show_message_box() override