I'm trying to use QPainter::drawText() to render some Chinese characters. But in certain fonts, there is extra top spacing when drawing the text. Why is this happening to some characters only?
Tested on Qt version 6.6.3 & 5.15.2
Googled some info, but nothing really answers the question:
Meaning of top, ascent, baseline, descent, bottom, and leading in Android's FontMetrics
Qt Forum — Impossible to get true text hight with QFontMetrics/QFontMetricsF
As you can see below: green box is with metric height, while red is with bounding height. Sure, the bounding height does bound the entire text, but there is extra top and bottom spacing.
#include "mainwindow.h"#include "ui_mainwindow.h"#include <QPainter>#include <QFont>#include <QFontMetrics>MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent) , ui(new Ui::MainWindow){ ui->setupUi(this);}MainWindow::~MainWindow(){ delete ui;}void MainWindow::paintEvent(QPaintEvent* event){ // Call base class implementation first QMainWindow::paintEvent(event); // Obtain the QPainter object QPainter paint(this); QFont font; font.fromString("Apple LiGothic"); font.setPointSize(50); QFontMetrics metric(font); paint.setRenderHints(QPainter::TextAntialiasing | QPainter::Antialiasing, true); paint.setFont(font); paint.setPen(Qt::white); const int align = Qt::AlignLeft | Qt::AlignTop | Qt::TextWordWrap; QString text = "钳禾日当午"; QRect bound = metric.boundingRect(text); bound = QRect(0, 0, bound.width(), bound.height()); QRect metricBound(0, 0, bound.width(), metric.height()); paint.translate(10, 100); paint.setPen(Qt::red); paint.drawRect(bound); paint.setPen(Qt::green); paint.drawRect(metricBound/*.adjusted(0,10,0,10)*/); // hack adjustment paint.setPen(Qt::white); paint.drawText(0, 0, bound.width(), bound.height(), align, text); text = "汗滴禾下土"; bound = metric.boundingRect(text); bound = QRect(0, 0, bound.width(), bound.height()); metricBound = QRect(0, 0, bound.width(), metric.height()); paint.translate(0, 100); paint.setPen(Qt::red); paint.drawRect(bound); paint.setPen(Qt::green); paint.drawRect(metricBound); paint.setPen(Qt::white); paint.drawText(0, 0, bound.width(), bound.height(), align, text);}