QT notes - unpolish() and polish() of QT dynamic attributes

Changing styles dynamically Dynamic attributes , For example, clicking the button can change the style of the button ： From red -> Blue -> green
Let's take a look at this function ：

bool QObject::setProperty(const char *name, const QVariant &value)

What does this function do ？
For one based on QObject For controls , Can pass setProperty To set properties

What are its parameters ？
const char *name： That is, the custom attribute name , Be careful not to have the same name as the default property of the control
const QVariant &value： The value of this attribute

See this link for details ：QT property Application of attributes

How to use it for this article ？
Our needs ： Dynamically change the style of the button , Then it will play a great role

1. We need to create a new class , stay ui Put one in it pushButton, Then set the style for the button

Right click on our pushButton Click style sheet , The content is ：
The first line is the initial color ,PropertyTest The new class name for us ,borderColor For the properties we need to set ,“=” The following is the value of the attribute ,btn For us pushButton Of ObjectName

#btn{
      border:4px solid blue;}
PropertyTest[borderColor="red"] #btn{
    border:4px solid red;}
PropertyTest[borderColor="green"] #btn{
    border:4px solid green;}
PropertyTest[borderColor="blue"] #btn{
    border:4px solid blue;}

2, Declare the slot function that clicks the button

private slots:
	void changeBorderColor();	// Change the color of the attribute 
private：
	int m_iTest;				// The number of hits 

3. Connect our slot function

connect(ui.btn, &QPushButton::clicked, this, &PropertyTest::changeBorderColor);

4. Define the contents of our slot function

void PropertyTest::changeBorderColor()
{
    
	if (m_iTest % 3 == 0)
	{
    
		setProperty("borderColor", "red");
	}
	else if (m_iTest % 3 == 1)
	{
    
		setProperty("borderColor", "green");
	}
	else
	{
    
		setProperty("borderColor", "blue");
	}
	// There are two ways to update styles manually   The first one is 
	//ui.btn->style()->unpolish(ui.btn); // Clean up the previous style 
	//ui.btn->style()->polish(ui.btn); // Used to add new styles 
	//ui.btn->update();
	// The second kind 
	ui.btn->setStyle(QApplication::style());
	m_iTest++;
}

effect ：


The second method ：
1. The first step of the same method
2. We need to add inheritance from QObject Used in Q_PROPERTY Macro instructions

What does this macro do ？
Look at this example ：

Q_PROPERTY(QString borderColor READ getBorderColor WRITE setBorderColor)

basis Q_PROPERTY( Parameter type Parameter name READ Get attribute value function WRITE Set attribute value function )
Parameter type ：QString
Parameter name ：borderColor
Get attribute value function ：getBorderColor
Set attribute value function ：setBorderColor

See specific macro links ：Q_PROPERTY Introduce
3. Define the read-write member functions we write in macros and Save the set color

public:
      void setBorderColor(const QString& strBorderColor) {
     m_strBorderColor = strBorderColor; }
      QString getBorderColor() {
     return m_strBorderColor; }
private：
      QString m_strBorderColor;
	  int m_iTest; 

4. The third step of the same method
5. Define our slot function

void PropertyTest::changeBorderColor()
{
    
	if (m_iTest % 3 == 0)
	{
    
		setBorderColor("red");
	}
	else if (m_iTest % 3 == 1)
	{
    
		setBorderColor("green");
	}
	else
	{
    
		setBorderColor("blue");
	}
	// Update styles manually 
	//ui.btn->style()->unpolish(ui.btn);
	//ui.btn->style()->polish(ui.btn);
	//ui.btn->update();
	ui.btn->setStyle(QApplication::style());
	m_iTest++;
}

The effect is the same as the first

Complete code ：
PropertyTest.h

#pragma once
#include <QtWidgets/QWidget>
#include "ui_PropertyTest.h"
#include <QStyle>
#include <QDebug>
class PropertyTest : public QWidget
{
    
	Q_OBJECT
	//Q_PROPERTY(QString borderColor READ getBorderColor WRITE setBorderColor)
public:
	PropertyTest(QWidget *parent = Q_NULLPTR);
	~PropertyTest();
	//void setBorderColor(const QString& strBorderColor) { m_strBorderColor = strBorderColor; }
	//QString getBorderColor() { return m_strBorderColor; }
private slots:
	void changeBorderColor();
private:
	Ui::PropertyTestClass ui;

	QString m_strBorderColor;
	int m_iTest;
};

PropertyTest.cpp

#include "PropertyTest.h"

PropertyTest::PropertyTest(QWidget *parent)
	: QWidget(parent), m_iTest(0)
{
    
	ui.setupUi(this);
	connect(ui.btn, &QPushButton::clicked, this, &PropertyTest::changeBorderColor);
}

PropertyTest::~PropertyTest()
{
    

}
void PropertyTest::changeBorderColor()
{
    
	if (m_iTest % 3 == 0)
	{
    
		setProperty("borderColor", "red");
		//setBorderColor("red");
	}
	else if (m_iTest % 3 == 1)
	{
    
		setProperty("borderColor", "green");
		//setBorderColor("green");
	}
	else
	{
    
		setProperty("borderColor", "blue");
		//setBorderColor("blue");
	}
	// Update styles manually 
	//ui.btn->style()->unpolish(ui.btn);
	//ui.btn->style()->polish(ui.btn);
	//ui.btn->update();
	ui.btn->setStyle(QApplication::style());
	m_iTest++;
}

Reference blog ：
Qt Dynamic properties of unpolish() and polish()
QT property Application of attributes
Q_PROPERTY Introduce