1、引言

QT有众多图形绘制函数，包括x()、y()、frame()、pos()、geometry()、width()、height()、rect()、size()，它们对屏幕坐标的捕获是有区别的。

2、实验代码

代码出自Qt5开发及实例（第3版）

geometry.h

#pragma once

#include <QtWidgets/QDialog>
#include <QLabel>
#include <QGridLayout>

class geometry : public QDialog
{
    Q_OBJECT
public:
    geometry(QWidget *parent = nullptr);
    ~geometry();
    void updateLabel();
private:
    QLabel* xLabel;
    QLabel* xValueLabel;
    QLabel* yLabel;
	QLabel* yValueLabel;
	QLabel* FrmLabel;
	QLabel* FrmValueLabel;
	QLabel* posLabel;
	QLabel* posValueLabel;
	QLabel* geoLabel;
	QLabel* geoValueLabel;
	QLabel* widthLabel;
	QLabel* widthValueLabel;
	QLabel* heightLabel;
	QLabel* heightValueLabel;
	QLabel* rectLabel;
	QLabel* rectValueLabel;
	QLabel* sizeLabel;
	QLabel* sizeValueLabel;
	QGridLayout* mainLayout;
protected:
	void moveEvent(QMoveEvent*);
	void resizeEvent(QResizeEvent *);
};

geometry.cpp

#include "geometry.h"

geometry::geometry(QWidget *parent)
    : QDialog(parent)
{
	setWindowTitle(tr("CH601"));
    xLabel = new QLabel(tr("x():"));
    xValueLabel = new QLabel;
	yLabel = new QLabel(tr("y():"));
	yValueLabel = new QLabel;
	FrmLabel = new QLabel(tr("Frame():"));
	FrmValueLabel = new QLabel;
	posLabel = new QLabel(tr("pos():"));
	posValueLabel = new QLabel;
	geoLabel = new QLabel(tr("geometry():"));
	geoValueLabel = new QLabel;
	widthLabel = new QLabel(tr("width():"));
	widthValueLabel = new QLabel;
	heightLabel = new QLabel(tr("height():"));
	heightValueLabel = new QLabel;
	rectLabel = new QLabel(tr("rect():"));
	rectValueLabel = new QLabel;
	sizeLabel = new QLabel(tr("size():"));
	sizeValueLabel = new QLabel;
	mainLayout = new QGridLayout(this);
	mainLayout->addWidget(xLabel,0,0);
	mainLayout->addWidget(xValueLabel, 0, 1);
	mainLayout->addWidget(yLabel, 1, 0);
	mainLayout->addWidget(yValueLabel, 1, 1);
	mainLayout->addWidget(FrmLabel, 2, 0);
	mainLayout->addWidget(FrmValueLabel, 2, 1);
	mainLayout->addWidget(posLabel, 3, 0);
	mainLayout->addWidget(posValueLabel, 3, 1);
	mainLayout->addWidget(geoLabel, 4, 0);
	mainLayout->addWidget(geoValueLabel, 4, 1);
	mainLayout->addWidget(widthLabel, 5, 0);
	mainLayout->addWidget(widthValueLabel, 5, 1);
	mainLayout->addWidget(heightLabel, 6, 0);
	mainLayout->addWidget(heightValueLabel, 6, 1);
	mainLayout->addWidget(rectLabel, 7, 0);
	mainLayout->addWidget(rectValueLabel, 7, 1);
	mainLayout->addWidget(sizeLabel, 8, 0);
	mainLayout->addWidget(sizeValueLabel, 8, 1);
	//updateLabel();
}
geometry::~geometry()
{}

void geometry::updateLabel()
{
	QString xStr;
	xValueLabel->setText(xStr.setNum(x()));

	QString yStr;
	yValueLabel->setText(xStr.setNum(y()));

	QString frameStr;
	QString tempStr1, tempStr2, tempStr3, tempStr4;
	frameStr = tempStr1.setNum(frameGeometry().x()) + "," + tempStr2.setNum(frameGeometry().y())
		+ "," + tempStr3.setNum(frameGeometry().width()) + "," + tempStr4.setNum(frameGeometry().height());
	FrmValueLabel->setText(frameStr);

	QString positionStr;
	QString tempStr11, tempStr12;
	positionStr = tempStr11.setNum(pos().x()) + "," + tempStr12.setNum(pos().y());
	posValueLabel->setText(positionStr);

	QString geoStr;
	QString tempStr21, tempStr22, tempStr23, tempStr24;
	geoStr = tempStr21.setNum(geometry().x()) + "," + tempStr22.setNum(geometry().y())
		+ "," + tempStr23.setNum(geometry().width()) + "," + tempStr24.setNum(geometry().height());
	geoValueLabel->setText(geoStr);

	QString wStr, hStr;
	widthValueLabel->setText(wStr.setNum(width()));
	heightValueLabel->setText(wStr.setNum(height()));

	QString rectStr;
	QString tempSr31, tempStr32, tempStr33, tempStr34;
	rectStr = tempSr31.setNum(rect().x()) + "," + tempStr32.setNum(rect().y())+ ","
		+ tempStr33.setNum(/*rect().width()*/width()) + "," + tempStr34.setNum(/*rect().height()*/height());

	rectValueLabel->setText(rectStr);

	QString sizeStr;
	QString tempStr41, tempStr42;
	sizeStr = tempStr41.setNum(size().width()) + "," + tempStr42.setNum(size().height());
	sizeValueLabel->setText(sizeStr);
}

void geometry::moveEvent(QMoveEvent*)
{
	updateLabel();
}

void geometry::resizeEvent(QResizeEvent*)
{
	updateLabel();
}

实验结果：
结果1：

更改大小后得到结果2：

3、位置函数

3.1 x()

显示当前widget左上角坐标相对于主界面的x轴位置，x轴是向右计算。

3.2 y()

显示当前widget左上角坐标相对于主界面的y轴位置，y轴向下计算。

3.3 frame()

frame().x()和frame().y()和x()、y()相同，都表示左上角的坐标点，frame().width()表示当前整个程序框的宽度，frame().height()表示整个程序框的高度。

3.4 pos()

pos().x()和pos().y()都是相对于主界面来说的坐标点，与x()、y()相同。

3.5 geometry()

geometry().x()和geometry().y()返回当前主界面的坐标位置，同时geometry().width()和geometry().height()会返回主界面的大小，这里的Dialog属于是子窗口。

3.6 width()

width()返回当前窗口的宽度。

3.7 height()

height()返回当前窗口的高度。

3.8 rect()

rect().width()和rect().height()返回当前窗口的宽和高。

3.9 size()

size().width()和size().height()返回当前窗口的宽和高。