Dark UI Mode, compact commands

• Viewer commands now use std::variant, reducing wasted space for unused command data
• Added the glow::viewer::dark_ui configure tag, switching the UI theme to a dark version
  • No nesting, any single ViewerApp only has one UI mode (unspecified ordering if used more than once within the same main command queue)
  • Also has a glow::viewer::dark_ui(false) version
• Fixed a crash on the Shift + Esc global termination due to a missing AsyncTextureLoader shutdown
• The camera now rests in its initial position instead of smoothing to it on startup

viewer/glow-extras/viewer/detail/command_queue.cc

 #include "command_queue.hh"
 
+#include <glow/util/AsyncTextureLoader.hh>
+
 #include <glow-extras/viewer/ViewerApp.hh>
 #include <glow-extras/viewer/view.hh>
 
@@ -30,6 +32,8 @@ glow::viewer::detail::shared_command_queue createQueue()
 
 void poolQueue(glow::viewer::detail::shared_command_queue&& queue) { sUnusedCommandQueuePool.push_back(std::move(queue)); }
 
+bool sViewerImGuiDarkMode = false;
+
 } // anon namespace
 
 
@@ -51,7 +55,7 @@ void glow::viewer::detail::on_last_command()
         // Lazily init viewer globals
         global_init();
 
-        ViewerApp app(sCommandQueueStack.back());
+        ViewerApp app(sCommandQueueStack.back(), sViewerImGuiDarkMode);
 
         try
         {
@@ -60,11 +64,14 @@ void glow::viewer::detail::on_last_command()
         catch (ViewerApp::TerminateException&)
         {
             // Special Shift + ESC termination
+            glow::AsyncTextureLoader::shutdown();
             std::exit(0);
         }
 
         // Clear the entire command queue stack for subsequent viewer runs
         sCommandQueueStack.clear();
+        // Reset the viewer ImGui dark mode for subsequent viewer runs
+        sViewerImGuiDarkMode = false;
     }
     else
     {
@@ -84,21 +91,24 @@ bool glow::viewer::detail::is_interactive(const glow::viewer::detail::command_qu
 
 void glow::viewer::detail::create_layout_tree(glow::viewer::layout::tree_node& rootNode, const glow::viewer::detail::command_queue& commands, float deltaTime, bool allowInteractiveExecute)
 {
+    using cmd_t = detail::command;
+
     layout::tree_node* currentNode = nullptr;
     for (auto const& cmd : commands)
     {
-        if (cmd.instr == detail::command::instruction::AddRenderjob)
+        if (cmd.instr == cmd_t::instruction::AddRenderjob)
         {
             TG_ASSERT(currentNode != nullptr);
-            cmd.renderable->runLazyInit();
-            currentNode->scene.add(cmd.renderable);
+            auto& renderable = std::get<SharedRenderable>(cmd.data);
+            renderable->runLazyInit();
+            currentNode->scene.add(renderable);
         }
-        else if (cmd.instr == detail::command::instruction::ModifyScene)
+        else if (cmd.instr == cmd_t::instruction::ModifyScene)
         {
             TG_ASSERT(currentNode != nullptr);
-            cmd.sceneModifier(currentNode->scene);
+            std::get<cmd_t::scene_modifier_func_t>(cmd.data)(currentNode->scene);
         }
-        else if (cmd.instr == detail::command::instruction::BeginSubview)
+        else if (cmd.instr == cmd_t::instruction::BeginSubview)
         {
             // Begin a subview
             if (currentNode == nullptr)
@@ -115,7 +125,7 @@ void glow::viewer::detail::create_layout_tree(glow::viewer::layout::tree_node& r
                 continue;
             }
         }
-        else if (cmd.instr == detail::command::instruction::EndSubview)
+        else if (cmd.instr == cmd_t::instruction::EndSubview)
         {
             TG_ASSERT(currentNode != nullptr);
 
@@ -126,12 +136,12 @@ void glow::viewer::detail::create_layout_tree(glow::viewer::layout::tree_node& r
                 break;
             }
         }
-        else if (cmd.instr == detail::command::instruction::ModifyLayout)
+        else if (cmd.instr == cmd_t::instruction::ModifyLayout)
         {
             TG_ASSERT(currentNode != nullptr);
-            currentNode->layoutSettings = cmd.layout;
+            currentNode->layoutSettings = std::get<layout::settings>(cmd.data);
         }
-        else if (TG_LIKELY(cmd.instr == detail::command::instruction::InteractiveSubview && allowInteractiveExecute))
+        else if (TG_LIKELY(cmd.instr == cmd_t::instruction::InteractiveSubview && allowInteractiveExecute))
         {
             // Interactive subviews still use Begin/End as usual
             TG_ASSERT(currentNode != nullptr);
@@ -142,7 +152,7 @@ void glow::viewer::detail::create_layout_tree(glow::viewer::layout::tree_node& r
             // Run the interactive lambda to fill innerCommandQueue
             {
                 sCommandQueueStack.push_back(innerCommandQueue);
-                cmd.interactiveLambda(deltaTime);
+                std::get<cmd_t::interactive_func_t>(cmd.data)(deltaTime);
                 sCommandQueueStack.pop_back();
             }
 
@@ -153,3 +163,8 @@ void glow::viewer::detail::create_layout_tree(glow::viewer::layout::tree_node& r
         }
     }
 }
+
+void glow::viewer::detail::set_ui_darkmode(bool active)
+{
+    sViewerImGuiDarkMode = active;
+}