Update for ImguiBackend

- Use RobotoMono-Regular.ttf instead of the default font
- Use delta-time instead of elapsed-time
- Fix for scissor/clipping rectangle

src/engine/engine.cc

@@ -45,7 +45,7 @@ Engine::Engine(Platform* platform)
   platform_->SetObserver(this);
 }
 
-Engine::~Engine() {
+Engine::~Engine() noexcept {
   LOG(0) << "Shutting down engine.";
 
   thread_pool_.CancelTasks();
@@ -157,12 +157,13 @@ void Engine::Draw(float frame_frac) {
   }
 
   if (stats_visible_) {
+    ImVec2 center = ImGui::GetMainViewport()->GetCenter();
+    ImGui::SetNextWindowPos(center, ImGuiCond_Appearing, ImVec2(0.5f, 0.5f));
     ImGuiWindowFlags window_flags =
         ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoTitleBar |
         ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoCollapse |
         ImGuiWindowFlags_NoNav | ImGuiWindowFlags_AlwaysAutoResize;
     ImGui::Begin("Stats", nullptr, window_flags);
-    ImGui::PushItemWidth(ImGui::GetFontSize() * -12);
     ImGui::Text("%s", renderer_->GetDebugName());
     ImGui::Text("%d fps", fps_);
     ImGui::End();

src/engine/imgui_backend.cc

@@ -6,6 +6,7 @@
 #include "engine/asset/shader_source.h"
 #include "engine/engine.h"
 #include "engine/input_event.h"
+#include "engine/platform/asset_file.h"
 #include "engine/renderer/renderer.h"
 #include "engine/renderer/shader.h"
 #include "engine/renderer/texture.h"
@@ -26,6 +27,22 @@ ImguiBackend::~ImguiBackend() = default;
 void ImguiBackend::Initialize() {
   IMGUI_CHECKVERSION();
   ImGui::CreateContext();
+
+  size_t buffer_size = 0;
+  auto buffer = AssetFile::ReadWholeFile("engine/RobotoMono-Regular.ttf",
+                                         Engine::Get().GetRootPath().c_str(),
+                                         &buffer_size);
+  if (buffer) {
+    ImFontConfig font_cfg = ImFontConfig();
+    font_cfg.FontDataOwnedByAtlas = false;
+    float size_pixels = Engine::Get().IsMobile() ? 64 : 32;
+    ImGui::GetIO().Fonts->AddFontFromMemoryTTF(buffer.get(), (int)buffer_size,
+                                               size_pixels, &font_cfg);
+    ImGui::GetIO().Fonts->Build();
+  } else {
+    LOG(0) << "Failed to read font file.";
+  }
+
   Engine::Get().SetImageSource(
       "imgui_atlas",
       []() -> std::unique_ptr<Image> {
@@ -33,7 +50,7 @@ void ImguiBackend::Initialize() {
         unsigned char* pixels;
         int width, height;
         ImGui::GetIO().Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);
-        LOG(0) << "imgui font width: " << width << " height: " << height;
+        LOG(0) << "Font atlas size: " << width << ", " << height;
         auto image = std::make_unique<Image>();
         image->Create(width, height);
         memcpy(image->GetBuffer(), pixels, width * height * 4);
@@ -98,7 +115,7 @@ void ImguiBackend::NewFrame() {
   ImGuiIO& io = ImGui::GetIO();
   io.DisplaySize = ImVec2((float)renderer_->GetScreenWidth(),
                           (float)renderer_->GetScreenHeight());
-  io.DeltaTime = timer_.Elapsed();
+  io.DeltaTime = timer_.Delta();
   ImGui::NewFrame();
 }
 
@@ -131,14 +148,14 @@ void ImguiBackend::Render() {
 
     for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.Size; cmd_i++) {
       const ImDrawCmd* pcmd = &cmd_list->CmdBuffer[cmd_i];
-      reinterpret_cast<Texture*>(pcmd->GetTexID())->Activate(0);
+      if (pcmd->ClipRect.z <= pcmd->ClipRect.x ||
+          pcmd->ClipRect.w <= pcmd->ClipRect.y)
+        continue;
 
-      if (pcmd->ClipRect.z > pcmd->ClipRect.x &&
-          pcmd->ClipRect.w > pcmd->ClipRect.y) {
+      reinterpret_cast<Texture*>(pcmd->GetTexID())->Activate(0);
       renderer_->SetScissor(int(pcmd->ClipRect.x), int(pcmd->ClipRect.y),
                             int(pcmd->ClipRect.z - pcmd->ClipRect.x),
                             int(pcmd->ClipRect.w - pcmd->ClipRect.y));
-      }
       renderer_->Draw(geometry_id, pcmd->ElemCount, pcmd->IdxOffset);
     }
     renderer_->DestroyGeometry(geometry_id);

src/engine/imgui_backend.h

@@ -29,7 +29,7 @@ class ImguiBackend {
  private:
   std::unique_ptr<Shader> shader_;
   Renderer* renderer_ = nullptr;
-  base::ElapsedTimer timer_;
+  base::DeltaTimer timer_;
 };
 
 }  // namespace eng

src/engine/renderer/opengl/renderer_opengl.cc

@@ -59,8 +59,6 @@ int RendererOpenGL::GetScreenHeight() const {
 }
 
 void RendererOpenGL::SetScissor(int x, int y, int width, int height) {
-  DCHECK(x >= 0 && y >= 0 && width >= 0 && height >= 0);
-  DCHECK(x + width <= GetScreenWidth() && y + height <= GetScreenHeight());
   glScissor(x, screen_height_ - y - height, width, height);
   glEnable(GL_SCISSOR_TEST);
 }

src/engine/renderer/vulkan/renderer_vulkan.cc

@@ -391,8 +391,14 @@ int RendererVulkan::GetScreenHeight() const {
 }
 
 void RendererVulkan::SetScissor(int x, int y, int width, int height) {
-  DCHECK(x >= 0 && y >= 0 && width >= 0 && height >= 0);
-  DCHECK(x + width <= GetScreenWidth() && y + height <= GetScreenHeight());
+  if (x < 0)
+    x = 0;
+  if (y < 0)
+    y = 0;
+  if (x + width > GetScreenWidth())
+    width = GetScreenWidth() - x;
+  if (y + height > GetScreenHeight())
+    height = GetScreenHeight() - y;
 
   VkRect2D scissor;
   scissor.offset.x = x;