// Button style
 GUIStyle toggleStyle = new GUIStyle("Button");
 toggleStyle.fixedWidth = buttonSize;
 toggleStyle.fixedHeight = buttonSize;
 toggleStyle.fontSize = 8;

// Grid layout
private void DrawGuiContentGrid(string label, IEnumerable<GridButton> gridButtons, GUIStyle toggleStyle)
{
    GUILayout.Label(label, EditorStyles.boldLabel);

    if (gridButtons == null || gridButtons.Count() == 0)
    {
        GUILayout.Label("No objects found");
    }
    else
    {
        const int padding = 40;
        int columns = Mathf.Max(1, Mathf.FloorToInt((EditorGUIUtility.currentViewWidth - padding) / buttonSize));
        int c = 0;
        GUILayout.BeginHorizontal();
        int i = 0;
        foreach (GridButton gridButton in gridButtons)
        {
            if (gridButton.Content == null)
            {
                continue;
            }

            bool wasSelected = gridButton == selectedGridButton;
            bool selected = GUILayout.Toggle(gridButton == selectedGridButton, gridButton.Content, toggleStyle);
            if (selected && !wasSelected)
            {
                gridButton.OnClick();
            }
            i++;
            c++;

            if (c >= columns)
            {
                GUILayout.EndHorizontal();
                GUILayout.BeginHorizontal();
                c = 0;
            }
        }
        GUILayout.EndHorizontal();
    }
}