Emulate bad vertex attribute casts on GL in mesh viewer

* On GL you can specify a vertex attribute that's stored as int but gets
  converted to float with glVertexAttribFormat instead of glVertexAttribIFormat.
  However if the shader accepts an int this is invalid and the value is
  undefined - we emulate this as the float bits being read as int directly, but
  that's not guaranteed behaviour.
* Normally we don't emulate this kind of mis-cast behaviour and just display the
  type of data passed to the shader, but in this case GL lets you specify three
  types (stored as int, cast to float, read as int) so our normal behaviour of
  just showing the input can be more misleading than normal.

qrenderdoc/Windows/BufferViewer.cpp

@@ -455,6 +455,7 @@ struct BufferElementProperties
   int buffer = 0;
   ShaderBuiltin systemValue = ShaderBuiltin::Undefined;
   bool perinstance = false;
+  bool floatCastWrong = false;
   int instancerate = 1;
 };
 
@@ -733,7 +734,14 @@ static QString interpretVariant(const QVariant &v, const ShaderConstant &el,
   }
   else if(vt == QMetaType::UInt || vt == QMetaType::UShort || vt == QMetaType::UChar)
   {
-    uint u = v.toUInt();
+    uint32_t u = v.toUInt();
+
+    if(prop.floatCastWrong)
+    {
+      float f = (float)u;
+      memcpy(&u, &f, sizeof(f));
+    }
+
     if(el.type.descriptor.displayAsHex && prop.format.type == ResourceFormatType::Regular)
       ret = Formatter::HexFormat(u, prop.format.compByteWidth);
     else
@@ -741,7 +749,14 @@ static QString interpretVariant(const QVariant &v, const ShaderConstant &el,
   }
   else if(vt == QMetaType::Int || vt == QMetaType::Short || vt == QMetaType::SChar)
   {
-    int i = v.toInt();
+    int32_t i = v.toInt();
+
+    if(prop.floatCastWrong)
+    {
+      float f = (float)i;
+      memcpy(&i, &f, sizeof(f));
+    }
+
     if(i >= 0)
       ret = lit(" ") + Formatter::Format(i);
     else
@@ -1533,6 +1548,7 @@ static void ConfigureMeshColumns(ICaptureContext &ctx, PopulateBufferData *bufda
     p.buffer = a.vertexBuffer;
     p.perinstance = a.perInstance;
     p.instancerate = a.instanceRate;
+    p.floatCastWrong = a.floatCastWrong;
     p.format = a.format;
 
     bufdata->vsinConfig.genericsEnabled[bufdata->vsinConfig.columns.count()] = false;