[Impeller] Add OpenGL debugging utilities.

impeller/renderer/backend/gles/proc_table_gles.cc

@@ -9,6 +9,7 @@
 #include "fml/closure.h"
 #include "impeller/base/allocation.h"
 #include "impeller/base/comparable.h"
+#include "impeller/base/strings.h"
 #include "impeller/base/validation.h"
 #include "impeller/renderer/backend/gles/capabilities_gles.h"
 #include "impeller/renderer/capabilities.h"
@@ -241,24 +242,24 @@ static const char* AttachmentTypeString(GLint type) {
 
 static std::string DescribeFramebufferAttachment(const ProcTableGLES& gl,
                                                  GLenum attachment) {
-  GLint param = GL_NONE;
+  GLint type = GL_NONE;
   gl.GetFramebufferAttachmentParameteriv(
       GL_FRAMEBUFFER,                         // target
       attachment,                             // attachment
       GL_FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE,  // parameter name
-      &param                                  // parameter
+      &type                                   // parameter
   );
 
-  if (param != GL_NONE) {
-    param = GL_NONE;
+  if (type != GL_NONE) {
+    GLint object = GL_NONE;
     gl.GetFramebufferAttachmentParameteriv(
         GL_FRAMEBUFFER,                         // target
         attachment,                             // attachment
         GL_FRAMEBUFFER_ATTACHMENT_OBJECT_NAME,  // parameter name
-        &param                                  // parameter
+        &object                                 // parameter
     );
     std::stringstream stream;
-    stream << AttachmentTypeString(param) << "(" << param << ")";
+    stream << AttachmentTypeString(type) << "(" << object << ")";
     return stream.str();
   }
 
@@ -268,11 +269,15 @@ static std::string DescribeFramebufferAttachment(const ProcTableGLES& gl,
 std::string ProcTableGLES::DescribeCurrentFramebuffer() const {
   GLint framebuffer = GL_NONE;
   GetIntegerv(GL_FRAMEBUFFER_BINDING, &framebuffer);
+  if (framebuffer == GL_NONE) {
+    return "The default framebuffer (FBO0) was bound.";
+  }
   if (IsFramebuffer(framebuffer) == GL_FALSE) {
-    return "No framebuffer or the default window framebuffer is bound.";
+    return SPrintF("The framebuffer binding (%d) was not a valid framebuffer.",
+                   framebuffer);
   }
 
-  GLenum status = CheckFramebufferStatus(framebuffer);
+  GLenum status = CheckFramebufferStatus(GL_FRAMEBUFFER);
   std::stringstream stream;
   stream << "FBO "
          << ((framebuffer == GL_NONE) ? "(Default)"
@@ -287,10 +292,10 @@ std::string ProcTableGLES::DescribeCurrentFramebuffer() const {
   stream << "Color Attachment: "
          << DescribeFramebufferAttachment(*this, GL_COLOR_ATTACHMENT0)
          << std::endl;
-  stream << "Color Attachment: "
+  stream << "Depth Attachment: "
          << DescribeFramebufferAttachment(*this, GL_DEPTH_ATTACHMENT)
          << std::endl;
-  stream << "Color Attachment: "
+  stream << "Stencil Attachment: "
          << DescribeFramebufferAttachment(*this, GL_STENCIL_ATTACHMENT)
          << std::endl;
   return stream.str();
@@ -303,7 +308,7 @@ bool ProcTableGLES::IsCurrentFramebufferComplete() const {
     // The default framebuffer is always complete.
     return true;
   }
-  GLenum status = CheckFramebufferStatus(framebuffer);
+  GLenum status = CheckFramebufferStatus(GL_FRAMEBUFFER);
   return status == GL_FRAMEBUFFER_COMPLETE;
 }
 

impeller/renderer/backend/gles/proc_table_gles.h

@@ -45,6 +45,31 @@ struct AutoErrorCheck {
   }
 };
 
+template <class Type>
+void BuildGLArgumentsStream(std::stringstream& stream, Type arg) {
+  stream << arg;
+}
+
+constexpr void BuildGLArgumentsStream(std::stringstream& stream) {}
+
+template <class Type, class... Rest>
+void BuildGLArgumentsStream(std::stringstream& stream,
+                            Type arg,
+                            Rest... other_args) {
+  BuildGLArgumentsStream(stream, arg);
+  stream << ", ";
+  BuildGLArgumentsStream(stream, other_args...);
+}
+
+template <class... Type>
+[[nodiscard]] std::string BuildGLArguments(Type... args) {
+  std::stringstream stream;
+  stream << "(";
+  BuildGLArgumentsStream(stream, args...);
+  stream << ")";
+  return stream.str();
+}
+
 template <class T>
 struct GLProc {
   using GLFunctionType = T;
@@ -66,6 +91,14 @@ struct GLProc {
   ///
   PFNGLGETERRORPROC error_fn = nullptr;
 
+  //----------------------------------------------------------------------------
+  /// Whether the OpenGL call and its arguments should be logged.
+  ///
+  /// Only works in IMPELLER_DEBUG and for environments where traditional
+  /// tracing is hard. Expect log spam and only use during development.
+  ///
+  bool log_calls = false;
+
   //----------------------------------------------------------------------------
   /// @brief      Call the GL function with the appropriate parameters. Lookup
   ///             the documentation for the GL function being called to
@@ -81,6 +114,10 @@ struct GLProc {
     // validation log will at least give us a hint as to what's going on.
     FML_CHECK(IsAvailable()) << "GL function " << name << " is not available. "
                              << "This is likely due to a missing extension.";
+    if (log_calls) {
+      FML_LOG(IMPORTANT) << name
+                         << BuildGLArguments(std::forward<Args>(args)...);
+    }
 #endif  // defined(IMPELLER_DEBUG) && !defined(NDEBUG)
     return function(std::forward<Args>(args)...);
   }