From fef3c597d0870219b72e8d0afb5a400d087005bd Mon Sep 17 00:00:00 2001
From: Dan Paulat <dpaulat@gmail.com>
Date: Sat, 26 Nov 2022 21:46:57 -0600
Subject: [PATCH] ImGui unique contexts

---
 .../scwx/qt/manager/resource_manager.cpp      |  4 +-
 scwx-qt/source/scwx/qt/map/map_widget.cpp     | 39 ++++++++++++--
 .../source/scwx/qt/ui/imgui_debug_dialog.ui   |  4 +-
 .../source/scwx/qt/ui/imgui_debug_widget.cpp  | 52 +++++++++++++++++--
 4 files changed, 89 insertions(+), 10 deletions(-)

diff --git a/scwx-qt/source/scwx/qt/manager/resource_manager.cpp b/scwx-qt/source/scwx/qt/manager/resource_manager.cpp
index ad299533..c5eff320 100644
--- a/scwx-qt/source/scwx/qt/manager/resource_manager.cpp
+++ b/scwx-qt/source/scwx/qt/manager/resource_manager.cpp
@@ -27,6 +27,7 @@ static void LoadTextures();
 static void ShutdownImGui();
 
 static std::unique_ptr<QOffscreenSurface> surface_ {};
+static ImGuiContext*                      imGuiContext_ {};
 
 void Initialize()
 {
@@ -53,7 +54,7 @@ static void InitializeImGui()
    }
 
    // Initialize ImGui
-   ImGui::CreateContext();
+   imGuiContext_ = ImGui::CreateContext();
    ImGui_ImplQt_Init();
    ImGui_ImplOpenGL3_Init();
    QOpenGLContext::globalShareContext()->doneCurrent();
@@ -89,6 +90,7 @@ static void LoadTextures()
 static void ShutdownImGui()
 {
    QOpenGLContext::globalShareContext()->makeCurrent(surface_.get());
+   ImGui::SetCurrentContext(imGuiContext_);
    ImGui_ImplOpenGL3_Shutdown();
    ImGui_ImplQt_Shutdown();
    ImGui::DestroyContext();
diff --git a/scwx-qt/source/scwx/qt/map/map_widget.cpp b/scwx-qt/source/scwx/qt/map/map_widget.cpp
index 581d6199..30eca271 100644
--- a/scwx-qt/source/scwx/qt/map/map_widget.cpp
+++ b/scwx-qt/source/scwx/qt/map/map_widget.cpp
@@ -14,6 +14,7 @@
 #include <scwx/util/time.hpp>
 
 #include <backends/imgui_impl_opengl3.h>
+#include <backends/imgui_impl_qt.hpp>
 #include <imgui.h>
 #include <QApplication>
 #include <QColor>
@@ -60,6 +61,7 @@ public:
        settings_(settings),
        map_(),
        layerList_ {},
+       imGuiContext_ {ImGui::CreateContext()},
        radarProductManager_ {nullptr},
        radarProductLayer_ {nullptr},
        alertLayer_ {std::make_shared<AlertLayer>(context_)},
@@ -79,8 +81,31 @@ public:
    {
       SetRadarSite(scwx::qt::manager::SettingsManager::general_settings()
                       ->default_radar_site());
+
+      // Set ImGui Context
+      ImGui::SetCurrentContext(imGuiContext_);
+
+      // ImGui Configuration
+      auto& io = ImGui::GetIO();
+
+      // Disable automatic configuration loading/saving
+      io.IniFilename = nullptr;
+
+      // Initialize ImGui Qt backend
+      ImGui_ImplQt_Init();
+      ImGui_ImplQt_RegisterWidget(widget_);
+   }
+
+   ~MapWidgetImpl()
+   {
+      // Set ImGui Context
+      ImGui::SetCurrentContext(imGuiContext_);
+
+      // Shutdown ImGui Context
+      ImGui_ImplOpenGL3_Shutdown();
+      ImGui_ImplQt_Shutdown();
+      ImGui::DestroyContext(imGuiContext_);
    }
-   ~MapWidgetImpl() = default;
 
    void AddLayer(const std::string&            id,
                  std::shared_ptr<GenericLayer> layer,
@@ -103,6 +128,8 @@ public:
    std::shared_ptr<QMapLibreGL::Map> map_;
    std::list<std::string>            layerList_;
 
+   ImGuiContext* imGuiContext_;
+
    std::shared_ptr<manager::RadarProductManager> radarProductManager_;
 
    std::shared_ptr<common::ColorTable> colorTable_;
@@ -136,6 +163,8 @@ MapWidget::MapWidget(const QMapLibreGL::Settings& settings) :
     p(std::make_unique<MapWidgetImpl>(this, settings))
 {
    setFocusPolicy(Qt::StrongFocus);
+
+   ImGui_ImplQt_RegisterWidget(this);
 }
 
 MapWidget::~MapWidget()
@@ -644,6 +673,10 @@ void MapWidget::initializeGL()
    makeCurrent();
    p->context_->gl().initializeOpenGLFunctions();
 
+   // Initialize ImGui OpenGL3 backend
+   ImGui::SetCurrentContext(p->imGuiContext_);
+   ImGui_ImplOpenGL3_Init();
+
    p->map_.reset(
       new QMapLibreGL::Map(nullptr, p->settings_, size(), pixelRatio()));
    p->context_->set_map(p->map_);
@@ -686,10 +719,10 @@ void MapWidget::paintGL()
    p->frameDraws_++;
 
    // Setup ImGui Frame
-   ImGui::GetIO().DisplaySize = {static_cast<float>(size().width()),
-                                 static_cast<float>(size().height())};
+   ImGui::SetCurrentContext(p->imGuiContext_);
 
    // Start ImGui Frame
+   ImGui_ImplQt_NewFrame(this);
    ImGui_ImplOpenGL3_NewFrame();
    ImGui::NewFrame();
 
diff --git a/scwx-qt/source/scwx/qt/ui/imgui_debug_dialog.ui b/scwx-qt/source/scwx/qt/ui/imgui_debug_dialog.ui
index a2790a62..5752a7c1 100644
--- a/scwx-qt/source/scwx/qt/ui/imgui_debug_dialog.ui
+++ b/scwx-qt/source/scwx/qt/ui/imgui_debug_dialog.ui
@@ -6,8 +6,8 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>570</width>
-    <height>760</height>
+    <width>592</width>
+    <height>754</height>
    </rect>
   </property>
   <property name="windowTitle">
diff --git a/scwx-qt/source/scwx/qt/ui/imgui_debug_widget.cpp b/scwx-qt/source/scwx/qt/ui/imgui_debug_widget.cpp
index 63998602..0764cf62 100644
--- a/scwx-qt/source/scwx/qt/ui/imgui_debug_widget.cpp
+++ b/scwx-qt/source/scwx/qt/ui/imgui_debug_widget.cpp
@@ -16,33 +16,77 @@ static const std::string logPrefix_ = "scwx::qt::ui::imgui_debug_widget";
 class ImGuiDebugWidgetImpl
 {
 public:
-   explicit ImGuiDebugWidgetImpl(ImGuiDebugWidget* self) : self_ {self}
+   explicit ImGuiDebugWidgetImpl(ImGuiDebugWidget* self) :
+       self_ {self}, context_ {ImGui::CreateContext()}
    {
+      // Set ImGui Context
+      ImGui::SetCurrentContext(context_);
+
       // ImGui Configuration
       auto& io = ImGui::GetIO();
 
-      // Initialize Qt backend
+      // Disable automatic configuration loading/saving
+      io.IniFilename = nullptr;
+
+      // Initialize ImGui Qt backend
+      ImGui_ImplQt_Init();
       ImGui_ImplQt_RegisterWidget(self_);
    }
-   ~ImGuiDebugWidgetImpl() {}
+
+   ~ImGuiDebugWidgetImpl()
+   {
+      // Set ImGui Context
+      ImGui::SetCurrentContext(context_);
+
+      // Shutdown ImGui Context
+      ImGui_ImplOpenGL3_Shutdown();
+      ImGui_ImplQt_Shutdown();
+      ImGui::DestroyContext(context_);
+   }
 
    ImGuiDebugWidget* self_;
+   ImGuiContext*     context_;
+
+   bool firstRender_ {true};
 };
 
 ImGuiDebugWidget::ImGuiDebugWidget(QWidget* parent) :
     QOpenGLWidget(parent), p {std::make_unique<ImGuiDebugWidgetImpl>(this)}
 {
+   // Accept focus for keyboard events
+   setFocusPolicy(Qt::StrongFocus);
 }
 
-void ImGuiDebugWidget::initializeGL() {}
+void ImGuiDebugWidget::initializeGL()
+{
+   makeCurrent();
+
+   // Initialize ImGui OpenGL3 backend
+   ImGui::SetCurrentContext(p->context_);
+   ImGui_ImplOpenGL3_Init();
+}
 
 void ImGuiDebugWidget::paintGL()
 {
+   ImGui::SetCurrentContext(p->context_);
+
    ImGui_ImplQt_NewFrame(this);
    ImGui_ImplOpenGL3_NewFrame();
 
    ImGui::NewFrame();
 
+   if (p->firstRender_)
+   {
+      // Set initial position of demo window
+      ImGui::SetNextWindowPos(ImVec2 {width() / 2.0f, height() / 2.0f},
+                              ImGuiCond_FirstUseEver,
+                              ImVec2 {0.5f, 0.5f});
+      ImGui::Begin("Dear ImGui Demo");
+      ImGui::End();
+
+      p->firstRender_ = false;
+   }
+
    ImGui::ShowDemoWindow();
 
    ImGui::Render();