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Styler

Enables you to change a View's stylesheet based on a set of conditions.

Multiple conditional parts can be active, in which case they will be merged from first to last.

Example

#include <bdn/ui/Styler.h>
#include <bdn/ui/Button.h>

using namespace bdn;
using namespace bdn::ui;

auto styler = std::make_shared<Styler>();
auto button = std::make_shared<Button>();

styler->setCondition("os", std::make_shared<Styler::equals_condition>(BDN_TARGET));

// If 'os' equals 'ios' the button will get a 5px padding
// The margin will always be 5px
_styler->setStyleSheet(addButton,
    JsonStringify(
        [ 
            {
                "flex" : {"margin" : {"all" : 5}}
            },
            { 
                "if" : {"os" : "ios"}, 
                "flex" : {"padding" : {"all" : 5}}
            } 
        ]
    )
);

Declaration

namespace bdn::ui {
    class Styler
}

Layout

• void setStyleSheet(std::shared_ptr<View> view, json stylesheet)

  Sets the stylesheet for view. The stylesheet root must be an array.

• void setCondition(std::string name, std::shared_ptr<condition> condition)

  Adds a new condition named name that stylesheets can match against. If a condition with name already exists it will be overriden and all registered stylesheets will be updated accordingly.

Conditions

• condition

  Base class for conditions. Overload the bool operator() for your own custom conditions.

  struct condition
  {
      virtual ~condition() = default;
      virtual bool operator()(const json::value_type &) = 0;
  };
  

• equals_condition

  Returns true if the value is equal to the target value.

  struct equals_condition : public condition
  {
      equals_condition(json::value_type targetValue) 
          : _targetValue(targetValue) {}
      bool operator()(const json::value_type &value) override 
      { 
          return value == _targetValue; 
      }
      json::value_type _targetValue;
  };
  

• less_condition

  Returns true if the value is less than the target value.

  struct less_condition : public condition
  {
      less_condition(json::value_type targetValue) 
          : _targetValue(targetValue) {}
      bool operator()(const json::value_type &value) override 
      { 
          return value < _targetValue; 
      }
      json::value_type _targetValue;
  };
  

• greater_equal_condition

  Returns true if the value is greater or equal to the target value.

  struct greater_equal_condition : public condition
  {
      greater_equal_condition(json::value_type targetValue) 
          : _targetValue(targetValue) {}
      bool operator()(const json::value_type &value) override 
      { 
          return value >= _targetValue; 
      }
      json::value_type _targetValue;
  };
  

Source

Styler.h