Define safe comparisons for python bindings

* In particular this means that it's safe to compare a ResourceId or similar
  against None. It is always not-equal but it's useful to have the comparison
  work and return the expected result instead of throwing a null reference
  exception.

qrenderdoc/Code/pyrenderdoc/cosmetics.i

@@ -5,6 +5,35 @@
 %feature("python:nb_int") ResourceId "resid_int";
 %feature("python:tp_hash") ResourceId "resid_hash";
 
+%ignore ResourceId::operator <;
+
+%extend ResourceId {
+
+PyObject *__lt__(PyObject *other)
+{
+  bool result = false;
+  void *resptr = NULL;
+  ResourceId *id = NULL;
+
+  if(other && other != Py_None)
+  {
+    int res = SWIG_ConvertPtr(other, &resptr, SWIGTYPE_p_ResourceId, 0);
+    if (!SWIG_IsOK(res)) {
+      SWIG_exception_fail(SWIG_ArgError(res), "incorrect comparison type");
+    }
+
+    id = (ResourceId *)resptr;
+
+    result = (*$self < *id);
+  }
+
+  return PyBool_FromLong(result ? 1 : 0);
+fail:
+  return NULL;
+}
+
+} // %extend ResourceId
+
 %wrapper %{
 static PyObject *resid_str(PyObject *resid)
 {
@@ -59,4 +88,99 @@ static PyObject *resid_int(PyObject *resid)
 fail:
   return NULL;
 }
-%}
+%}
+
+// macro to define safe == and != operators for classes, that don't throw an exception comparing to
+// None
+
+%define DEFINE_SAFE_EQUALITY(Class)
+
+%ignore Class::operator ==;
+%ignore Class::operator !=;
+
+%extend Class {
+
+PyObject *__eq__(PyObject *other)
+{
+  bool result = false;
+  void *resptr = NULL;
+  Class *id = NULL;
+
+  if(other && other != Py_None)
+  {
+    int res = SWIG_ConvertPtr(other, &resptr, SWIGTYPE_p_##Class, 0);
+    if (!SWIG_IsOK(res)) {
+      SWIG_exception_fail(SWIG_ArgError(res), "incorrect comparison type");
+    }
+
+    id = (Class *)resptr;
+
+    result = (*$self == *id);
+  }
+  
+  return PyBool_FromLong(result ? 1 : 0);
+fail:
+  return NULL;
+}
+
+PyObject *__ne__(PyObject *other)
+{
+  bool result = true;
+  void *resptr = NULL;
+  Class *id = NULL;
+
+  if(other && other != Py_None)
+  {
+    int res = SWIG_ConvertPtr(other, &resptr, SWIGTYPE_p_##Class, 0);
+    if (!SWIG_IsOK(res)) {
+      SWIG_exception_fail(SWIG_ArgError(res), "incorrect comparison type");
+    }
+
+    id = (Class *)resptr;
+
+    result = !(*$self == *id);
+  }
+  
+  return PyBool_FromLong(result ? 1 : 0);
+fail:
+  return NULL;
+}
+
+} // %extend Class
+
+%enddef // %define DEFINE_SAFE_COMPARISONS
+
+DEFINE_SAFE_EQUALITY(DrawcallDescription)
+DEFINE_SAFE_EQUALITY(CounterResult)
+DEFINE_SAFE_EQUALITY(APIEvent)
+DEFINE_SAFE_EQUALITY(Bindpoint)
+DEFINE_SAFE_EQUALITY(BufferDescription)
+DEFINE_SAFE_EQUALITY(CaptureFileFormat)
+DEFINE_SAFE_EQUALITY(ConstantBlock)
+DEFINE_SAFE_EQUALITY(DebugMessage)
+DEFINE_SAFE_EQUALITY(EnvironmentModification)
+DEFINE_SAFE_EQUALITY(EventUsage)
+DEFINE_SAFE_EQUALITY(PathEntry)
+DEFINE_SAFE_EQUALITY(PixelModification)
+DEFINE_SAFE_EQUALITY(ResourceDescription)
+DEFINE_SAFE_EQUALITY(ResourceId)
+DEFINE_SAFE_EQUALITY(LineColumnInfo)
+DEFINE_SAFE_EQUALITY(ShaderCompileFlag)
+DEFINE_SAFE_EQUALITY(ShaderConstant)
+DEFINE_SAFE_EQUALITY(ShaderDebugState)
+DEFINE_SAFE_EQUALITY(ShaderResource)
+DEFINE_SAFE_EQUALITY(ShaderSampler)
+DEFINE_SAFE_EQUALITY(ShaderSourceFile)
+DEFINE_SAFE_EQUALITY(ShaderVariable)
+DEFINE_SAFE_EQUALITY(RegisterRange)
+DEFINE_SAFE_EQUALITY(LocalVariableMapping)
+DEFINE_SAFE_EQUALITY(SigParameter)
+DEFINE_SAFE_EQUALITY(TextureDescription)
+DEFINE_SAFE_EQUALITY(ShaderEntryPoint)
+DEFINE_SAFE_EQUALITY(Viewport)
+DEFINE_SAFE_EQUALITY(Scissor)
+DEFINE_SAFE_EQUALITY(ColorBlend)
+DEFINE_SAFE_EQUALITY(BoundVBuffer)
+DEFINE_SAFE_EQUALITY(VertexInputAttribute)
+DEFINE_SAFE_EQUALITY(BoundResource)
+DEFINE_SAFE_EQUALITY(BoundResourceArray)