How to auto indent a C++ class with 4 spaces using clang-format?

Question

I got the next .clang-format file in my project's root directory:

---
AlignTrailingComments: true
AllowShortFunctionsOnASingleLine: false
AllowShortIfStatementsOnASingleLine: true
AllowShortLoopsOnASingleLine: true
BreakBeforeBinaryOperators: false
IndentWidth: 4
SortIncludes: false
NamespaceIndentation: All
...

Problem comes when I run clang-format on my c++ headers, the classes become autoindented like this:

As you can see, labels public & private are indented only with 2 spaces. But what I'm trying to achieve is the below output (indentation was manually tweaked):

That way code-collapsing becomes something really pleasant to do.

How could I tweak my .clang-format to achieve this effect? If not possible, how would you patch clang-format source code to achieve this desired behaviour?

EDIT:

I've tried using unsuccessfully AccessModifierOffset, I've used values {-2,0,2,4} example below:

As you can see the statement inside the public block won't be indented properly.

EDIT2:

I've tried the @Henrique Jung solution and that's definitely not what I'm asking for, if using that combination the result would be something like this one:

And as you can see, the content inside the functions are indented 8 spaces instead 4, which is not good.

EDIT3:

I gave a bounty few months ago so I'm going to try again as this one is definitely interesting. If I got enough knowledge about clang-format source code I'd give it a shot, unfortunately I don't.

Answer 1

As near as I can tell, clang-format offers no option for indenting function contents differently from non-access-modifier class contents. That is, consider the following code:

class A {
  public:
    void foo() {}
}

void bar() {
    int a;
}

In this code, the line "void foo() {}" will always be indented the same amount as "int a;" by clang-format.

The closest thing to the style you seem to want that is available would come from not indenting the access modifiers, e.g.:

class A {
public:
    void foo() {}
}

void bar() {
    int a;
}

This is done, for example, by the WebKit, Mozilla, and LLVM styles. It's achieved by setting:

IndentWidth: 4
AccessModifierOffset: -4