supercell-wx/scwx-qt/source/scwx/qt/map/draw_layer.cpp

#include <scwx/qt/manager/font_manager.hpp>
#include <scwx/qt/map/draw_layer.hpp>
#include <scwx/qt/model/imgui_context_model.hpp>
#include <scwx/qt/gl/shader_program.hpp>
#include <scwx/util/logger.hpp>

#include <backends/imgui_impl_opengl3.h>
#include <backends/imgui_impl_qt.hpp>
#include <fmt/format.h>
#include <imgui.h>

namespace scwx
{
namespace qt
{
namespace map
{

static const std::string logPrefix_ = "scwx::qt::map::draw_layer";
static const auto        logger_    = scwx::util::Logger::Create(logPrefix_);

class DrawLayerImpl
{
public:
   explicit DrawLayerImpl(std::shared_ptr<MapContext> context) :
       context_ {context},
       drawList_ {},
       textureAtlas_ {GL_INVALID_INDEX},
       imGuiRendererInitialized_ {false}
   {
      static size_t currentMapId_ {0u};
      imGuiContextName_ = fmt::format("Layer {}", ++currentMapId_);
      imGuiContext_ = 
         model::ImGuiContextModel::Instance().CreateContext(imGuiContextName_);

      // Initialize ImGui Qt backend
      ImGui_ImplQt_Init();
   }
   ~DrawLayerImpl()
   {
      // Set ImGui Context
      ImGui::SetCurrentContext(imGuiContext_);

      // Shutdown ImGui Context
      if (imGuiRendererInitialized_)
      {
         ImGui_ImplOpenGL3_Shutdown();
      }
      ImGui_ImplQt_Shutdown();

      // Destroy ImGui Context
      model::ImGuiContextModel::Instance().DestroyContext(imGuiContextName_);
   }

   void ImGuiCheckFonts();

   std::shared_ptr<MapContext>                      context_;
   std::vector<std::shared_ptr<gl::draw::DrawItem>> drawList_;
   GLuint                                           textureAtlas_;

   std::uint64_t textureAtlasBuildCount_ {};

   std::string imGuiContextName_;
   ImGuiContext* imGuiContext_;
   bool          imGuiRendererInitialized_;
   std::uint64_t imGuiFontsBuildCount_ {};
};

void DrawLayerImpl::ImGuiCheckFonts()
{
   // Update ImGui Fonts if required
   std::uint64_t currentImGuiFontsBuildCount =
      manager::FontManager::Instance().imgui_fonts_build_count();

   if (imGuiFontsBuildCount_ != currentImGuiFontsBuildCount ||
       !model::ImGuiContextModel::Instance().font_atlas()->IsBuilt())
   {
      ImGui_ImplOpenGL3_DestroyFontsTexture();
      ImGui_ImplOpenGL3_CreateFontsTexture();
   }

   imGuiFontsBuildCount_ = currentImGuiFontsBuildCount;
}

DrawLayer::DrawLayer(const std::shared_ptr<MapContext>& context) :
    GenericLayer(context), p(std::make_unique<DrawLayerImpl>(context))
{
}
DrawLayer::~DrawLayer() = default;

void DrawLayer::Initialize()
{
   p->textureAtlas_ = p->context_->GetTextureAtlas();

   for (auto& item : p->drawList_)
   {
      item->Initialize();
   }

   ImGuiInitialize();
}

void DrawLayer::StartImGuiFrame()
{
   auto defaultFont = manager::FontManager::Instance().GetImGuiFont(
      types::FontCategory::Default);

   // Setup ImGui Frame
   ImGui::SetCurrentContext(p->imGuiContext_);

   // Start ImGui Frame
   ImGui_ImplQt_NewFrame(p->context_->widget());
   ImGui_ImplOpenGL3_NewFrame();
   p->ImGuiCheckFonts();
   ImGui::NewFrame();
   ImGui::PushFont(defaultFont->font());
}

void DrawLayer::EndImGuiFrame()
{
   // Pop default font
   ImGui::PopFont();

   // Render ImGui Frame
   ImGui::Render();
   ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
}

void DrawLayer::ImGuiInitialize()
{
   ImGui::SetCurrentContext(p->imGuiContext_);
   ImGui_ImplQt_RegisterWidget(p->context_->widget());
   ImGui_ImplOpenGL3_Init();
   p->imGuiFontsBuildCount_ =
      manager::FontManager::Instance().imgui_fonts_build_count();
   p->imGuiRendererInitialized_ = true;
}

void DrawLayer::RenderWithoutImGui(
   const QMapLibre::CustomLayerRenderParameters& params)
{
   gl::OpenGLFunctions& gl = p->context_->gl();
   p->textureAtlas_        = p->context_->GetTextureAtlas();

   // Determine if the texture atlas changed since last render
   std::uint64_t newTextureAtlasBuildCount =
      p->context_->texture_buffer_count();
   bool textureAtlasChanged =
      newTextureAtlasBuildCount != p->textureAtlasBuildCount_;

   // Set OpenGL blend mode for transparency
   gl.glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

   gl.glActiveTexture(GL_TEXTURE0);
   gl.glBindTexture(GL_TEXTURE_2D_ARRAY, p->textureAtlas_);

   for (auto& item : p->drawList_)
   {
      item->Render(params, textureAtlasChanged);
   }

   p->textureAtlasBuildCount_ = newTextureAtlasBuildCount;
}

   void DrawLayer::Render(const QMapLibre::CustomLayerRenderParameters& params)
{
   StartImGuiFrame();
   RenderWithoutImGui(params);
   EndImGuiFrame();
}

void DrawLayer::Deinitialize()
{
   p->textureAtlas_ = GL_INVALID_INDEX;

   for (auto& item : p->drawList_)
   {
      item->Deinitialize();
   }
}

bool DrawLayer::RunMousePicking(
   const QMapLibre::CustomLayerRenderParameters& params,
   const QPointF&                                mouseLocalPos,
   const QPointF&                                mouseGlobalPos,
   const glm::vec2&                              mouseCoords,
   const common::Coordinate&                     mouseGeoCoords,
   std::shared_ptr<types::EventHandler>&         eventHandler)
{
   bool itemPicked = false;

   // For each draw item in the draw list in reverse
   for (auto it = p->drawList_.rbegin(); it != p->drawList_.rend(); ++it)
   {
      // Run mouse picking on each draw item
      if ((*it)->RunMousePicking(params,
                                 mouseLocalPos,
                                 mouseGlobalPos,
                                 mouseCoords,
                                 mouseGeoCoords,
                                 eventHandler))
      {
         // If a draw item was picked, don't process additional items
         itemPicked = true;
         break;
      }
   }

   return itemPicked;
}

void DrawLayer::AddDrawItem(const std::shared_ptr<gl::draw::DrawItem>& drawItem)
{
   p->drawList_.push_back(drawItem);
}

} // namespace map
} // namespace qt
} // namespace scwx