[Impeller] Press to toggle wireframe (#40001)

Author: bdero

impeller/aiks/aiks_context.cc

@@ -32,7 +32,7 @@ std::shared_ptr<Context> AiksContext::GetContext() const {
   return context_;
 }
 
-const ContentContext& AiksContext::GetContentContext() const {
+ContentContext& AiksContext::GetContentContext() const {
   return *content_context_;
 }
 

impeller/aiks/aiks_context.h

@@ -26,7 +26,7 @@ class AiksContext {
 
   std::shared_ptr<Context> GetContext() const;
 
-  const ContentContext& GetContentContext() const;
+  ContentContext& GetContentContext() const;
 
   bool Render(const Picture& picture, RenderTarget& render_target);
 

impeller/aiks/aiks_playground.cc

@@ -6,6 +6,8 @@
 
 #include "impeller/aiks/aiks_context.h"
 
+#include "third_party/imgui/imgui.h"
+
 namespace impeller {
 
 AiksPlayground::AiksPlayground() = default;
@@ -32,6 +34,11 @@ bool AiksPlayground::OpenPlaygroundHere(AiksPlaygroundCallback callback) {
 
   return Playground::OpenPlaygroundHere(
       [&renderer, &callback](RenderTarget& render_target) -> bool {
+        static bool wireframe = false;
+        if (ImGui::IsKeyPressed(ImGuiKey_Z)) {
+          wireframe = !wireframe;
+          renderer.GetContentContext().SetWireframe(wireframe);
+        }
         return callback(renderer, render_target);
       });
 }

impeller/entity/contents/content_context.cc

@@ -142,6 +142,8 @@ void ContentContextOptions::ApplyToPipelineDescriptor(
   }
 
   desc.SetPrimitiveType(primitive_type);
+
+  desc.SetPolygonMode(wireframe ? PolygonMode::kLine : PolygonMode::kFill);
 }
 
 template <typename PipelineT>
@@ -379,4 +381,8 @@ const IDeviceCapabilities& ContentContext::GetDeviceCapabilities() const {
   return context_->GetDeviceCapabilities();
 }
 
+void ContentContext::SetWireframe(bool wireframe) {
+  wireframe_ = wireframe;
+}
+
 }  // namespace impeller

impeller/entity/contents/content_context.h

@@ -269,13 +269,14 @@ struct ContentContextOptions {
   PrimitiveType primitive_type = PrimitiveType::kTriangle;
   std::optional<PixelFormat> color_attachment_pixel_format;
   bool has_stencil_attachment = true;
+  bool wireframe = false;
 
   struct Hash {
     constexpr std::size_t operator()(const ContentContextOptions& o) const {
       return fml::HashCombine(o.sample_count, o.blend_mode, o.stencil_compare,
                               o.stencil_operation, o.primitive_type,
                               o.color_attachment_pixel_format,
-                              o.has_stencil_attachment);
+                              o.has_stencil_attachment, o.wireframe);
     }
   };
 
@@ -289,7 +290,8 @@ struct ContentContextOptions {
              lhs.primitive_type == rhs.primitive_type &&
              lhs.color_attachment_pixel_format ==
                  rhs.color_attachment_pixel_format &&
-             lhs.has_stencil_attachment == rhs.has_stencil_attachment;
+             lhs.has_stencil_attachment == rhs.has_stencil_attachment &&
+             lhs.wireframe == rhs.wireframe;
     }
   };
 
@@ -598,6 +600,8 @@ class ContentContext {
 
   const IDeviceCapabilities& GetDeviceCapabilities() const;
 
+  void SetWireframe(bool wireframe);
+
   using SubpassCallback =
       std::function<bool(const ContentContext&, RenderPass&)>;
 
@@ -706,6 +710,10 @@ class ContentContext {
       return nullptr;
     }
 
+    if (wireframe_) {
+      opts.wireframe = true;
+    }
+
     if (auto found = container.find(opts); found != container.end()) {
       return found->second->WaitAndGet();
     }
@@ -731,6 +739,7 @@ class ContentContext {
   std::shared_ptr<Tessellator> tessellator_;
   std::shared_ptr<GlyphAtlasContext> glyph_atlas_context_;
   std::shared_ptr<scene::SceneContext> scene_context_;
+  bool wireframe_ = false;
 
   FML_DISALLOW_COPY_AND_ASSIGN(ContentContext);
 };

impeller/entity/entity_playground.cc

@@ -6,6 +6,8 @@
 
 #include "impeller/entity/contents/content_context.h"
 
+#include "third_party/imgui/imgui.h"
+
 namespace impeller {
 
 EntityPlayground::EntityPlayground() = default;
@@ -37,6 +39,11 @@ bool EntityPlayground::OpenPlaygroundHere(EntityPlaygroundCallback callback) {
     return false;
   }
   SinglePassCallback pass_callback = [&](RenderPass& pass) -> bool {
+    static bool wireframe = false;
+    if (ImGui::IsKeyPressed(ImGuiKey_Z)) {
+      wireframe = !wireframe;
+      content_context.SetWireframe(wireframe);
+    }
     return callback(content_context, pass);
   };
   return Playground::OpenPlaygroundHere(pass_callback);