How can I replce Qpainter::drawText with a more effecient way to draw text in a table cell
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UPDATE:
After tested with a simpler QWidget subclass, I realized may be it's not adrawTextproblem.
I've removed the colorful gifs, but keep the last two gray or white gifs to better demonstrate the problem.the original post:
I try to implement a simple table drawing widget by overriding the QWidget:PaintEvent method.
Now I find that, before the text and color shows up, the window is about 1 second visible blank.
This is the gif that shows the blank.
Using VS2019 Perfomance Profiling Tools， We can see drawText occupies about 30% ~ 50% cpu work. And if I removed all the text
drawing， the visible blank disappears.
Here is my code.
main.cpp#include <QtWidgets/QApplication> #include "QPlainStyleTable.h" int main(int argc, char *argv[]) { QApplication a(argc, argv); auto _m_pTable = new QPlainStyleTable(); _m_pTable->SetHeaderColor(Qt::red, Qt::green); _m_pTable->SetContentColor(Qt::gray, Qt::yellow, Qt::blue); _m_pTable->SetBorderColor(Qt::white); _m_pTable->SetFont(QFont("微软雅黑"), QFont("微软雅黑")); _m_pTable->SetDimension(8, 6); _m_pTable->SetTitle({ "姓名", "年龄", "性别", "学历", "籍贯" }); _m_pTable->AddData({ "小红", "28", "女", "大学", "山东" }); _m_pTable->AddData({ "姓名", "年龄", "性别", "学历", "籍贯" }); _m_pTable->AddData({ "姓名", "年龄", "性别", "学历", "籍贯" }); _m_pTable->AddData({ "姓名", "年龄", "性别", "学历", "籍贯" }); _m_pTable->show(); return a.exec(); }QPlainStyleTable.h
#pragma once #include <vector> #include <string> #include <functional> #include <map> #include <memory> #include <QWidget> #include <QPixmap> #include <QColor> #include <QFont> #include <QMenu> //返回true即不再可编辑 using CellEditCallBack = std::function<void(int mouseX, int mouseY)>; class QPlainStyleTable : public QWidget { Q_OBJECT public: QPlainStyleTable(QWidget *parent = nullptr); ~QPlainStyleTable(); void SetHeaderColor(const QColor& bkColor, const QColor& txtColor); void SetContentColor(const QColor& evenBkColor, const QColor& oddBkColor, const QColor& txtColor); void SetBorderColor(const QColor& color); void SetFont(const QFont& headerFont, const QFont& contentFont); void SetDimension(int row, int col); void SetTitle(const std::vector<std::string>& title); void AddData(const std::vector<std::string>& row); void ClearContent(); void SetCellEditCallBack(int row, int col, CellEditCallBack callback); void SetUnEditable(int row, int col); void UpdateContent(int row, int col, const std::string& content); protected: virtual void paintEvent(QPaintEvent *event) override; virtual bool eventFilter(QObject *watched, QEvent *event) override; private: //缓存背景 QPixmap bkCache; void DrawBk(); bool BkSizeIsSame(); //行列 int row; int col; //单元格大小, 在画背景时计算出 int headerH; int tailW; int cellH; int cellW; QColor headerBkColor; QColor headerTxtColor; QColor contentTxtColor; QColor evenBkColor; QColor oddBkColor; QColor borderColor; QFont headerFont; QFont contentFont; // headerText std::vector<std::string> title; // contentText std::vector<std::vector<std::string>> contents; struct EditableCell { int row; int col; bool operator<(const EditableCell& rhs) const { if (row == rhs.row) { return col < rhs.col; } else if (col == rhs.col) { return row < rhs.row; } return false; } }; std::map<EditableCell, CellEditCallBack> callbacks; CellEditCallBack IsEditable(int row, int col); };QPlainStyleTable.cpp
#include <algorithm> #include <QEvent> #include <QMouseEvent> #include <QPainter> #include "QPlainStyleTable.h" QPlainStyleTable::QPlainStyleTable(QWidget *parent) : QWidget(parent), row(0), col(0), cellW(0), cellH(0) { installEventFilter(this); } QPlainStyleTable::~QPlainStyleTable() { } void QPlainStyleTable::SetHeaderColor(const QColor& bkColor, const QColor& txtColor) { headerBkColor = bkColor; headerTxtColor = txtColor; } void QPlainStyleTable::SetContentColor(const QColor& evenBkColor, const QColor& oddBkColor, const QColor& txtColor) { this->evenBkColor = evenBkColor; this->oddBkColor = oddBkColor; this->contentTxtColor = txtColor; } void QPlainStyleTable::SetBorderColor(const QColor& color) { this->borderColor = color; } void QPlainStyleTable::SetFont(const QFont& headerFont, const QFont& contentFont) { this->headerFont = headerFont; this->contentFont = contentFont; } void QPlainStyleTable::SetDimension(int row, int col) { this->row = row; this->col = col; } void QPlainStyleTable::SetTitle(const std::vector<std::string>& title) { this->title = title; } void QPlainStyleTable::AddData(const std::vector<std::string>& row) { this->contents.push_back(row); update(); } void QPlainStyleTable::ClearContent() { this->contents.clear(); this->callbacks.clear(); update(); } void QPlainStyleTable::SetCellEditCallBack(int row, int col, CellEditCallBack callback) { callbacks[EditableCell{ row, col}] = callback; } void QPlainStyleTable::paintEvent(QPaintEvent *event) { if (bkCache.isNull()) { DrawBk(); } else { if (!BkSizeIsSame()) { DrawBk(); } } QPainter painter(this); painter.drawPixmap(rect(), bkCache); // DrawContentTxt painter.setFont(contentFont); painter.setPen(contentTxtColor); auto showRows = std::min((int)contents.size(), row); for (int idx = 0; idx < showRows; ++idx) { auto& oneRow = contents[idx]; auto showCols = std::min((int)oneRow.size(), col); for (int idy = 0; idy < showCols; ++idy) { auto& txt = oneRow[idy]; //painter.setPen(contentTxtColor); painter.setClipping(true); painter.drawText(idy * cellW, idx* cellH + headerH, cellW, cellH, Qt::AlignCenter | Qt::TextSingleLine | Qt::TextDontClip | Qt::TextWordWrap , QString::fromLocal8Bit(txt.c_str())); if (IsEditable(idx, idy)) { painter.setPen(Qt::red); painter.setRenderHint(QPainter::Antialiasing); painter.drawRoundedRect(idy * cellW, idx * cellH + headerH, cellW, cellH , 2, 2); } } } } bool QPlainStyleTable::eventFilter(QObject *watched, QEvent *event) { if (watched == this && event->type() == QEvent::MouseButtonDblClick) { auto theEvent = (QMouseEvent*)event; auto x = theEvent->x(); auto y = theEvent->y(); auto clickRow = y < headerH ? -1 : (y - headerH) / cellH; auto clickCol = x / cellW; auto callback = IsEditable(clickRow, clickCol); if (callback) { auto globalPos = theEvent->globalPos(); callback(globalPos.x(), globalPos.y()); } return true; } return QWidget::eventFilter(watched, event); } void QPlainStyleTable::DrawBk() { QPixmap bk(width(), height()); auto thisW = bk.width(); auto thisH = bk.height(); cellH = thisH / (row + 1); cellW = thisW / col; headerH = thisH - (cellH * row); tailW = thisW - (cellW * col); QPainter painter(&bk); painter.setPen(Qt::NoPen); // header painter.setBrush(headerBkColor); painter.drawRect(0, 0, thisW - 1, headerH - 1); headerFont.setHintingPreference(QFont::PreferNoHinting); painter.setFont(headerFont); painter.setPen(headerTxtColor); painter.setRenderHint(QPainter::TextAntialiasing); auto min = std::min(col, (int)title.size()); for (int idx = 0; idx < min; ++idx) { auto txt = title[idx]; painter.drawText(idx * cellW, 0, cellW, headerH , Qt::AlignCenter | Qt::TextSingleLine | Qt::TextDontClip | Qt::TextWordWrap , QString::fromLocal8Bit(txt.c_str())); } // content auto isEven = [](int n) { return n % 2 == 0; }; for (int idx = 0; idx < row; ++idx) { int upperY = headerH + idx * cellH; painter.setPen(Qt::NoPen); painter.setBrush(isEven(idx) ? evenBkColor : oddBkColor); painter.drawRect(0, upperY, thisW - 1, headerH - 1); painter.setPen(borderColor); painter.setBrush(Qt::NoBrush); painter.drawLine(0, upperY - 1, thisW - 1, upperY - 1); } // border painter.setPen(borderColor); painter.setBrush(Qt::NoBrush); painter.drawRect(0, 0, thisW - 1, thisH - 1); bkCache.swap(bk); } bool QPlainStyleTable::BkSizeIsSame() { return bkCache.size() == size(); } CellEditCallBack QPlainStyleTable::IsEditable(int row, int col) { for (auto& p: callbacks) { if (p.first.row == row && p.first.col == col) { return p.second; } } return nullptr; } void QPlainStyleTable::SetUnEditable(int row, int col) { callbacks.erase(EditableCell{row, col}); } void QPlainStyleTable::UpdateContent(int row, int col, const std::string& content) { bool found{ false }; for (int idx =0 ; idx < contents.size(); ++idx) { auto& oneRow = contents[idx]; for (int idy = 0; idy < oneRow.size(); ++idy) { if (idx == row && idy == col) { found = true; auto& old = oneRow[idy]; old = content; break; } } } if (found) { update(); } } -
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@jsulm
I use VS2019 IDE, with multibyte charset and need show some chinese characters.I just tried QString::(txt.c_str()), still has the problem.
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@xce1 There is no need for txt.c_str() at all! txt is already a QString which is UTF-16 and can handle Chinese.
@jsulm
Thanks for your attention, but txt is really a std::string.
The other parts of the program uses c++ std lib mostly, so here I usedstd::vector<std::vector<std::string>> contents;to store cell strings.I just upload the gif, which shows what I described as
drawTextis slow.
Would you help me with that?Best regards.
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@jsulm
Thanks for your attention, but txt is really a std::string.
The other parts of the program uses c++ std lib mostly, so here I usedstd::vector<std::vector<std::string>> contents;to store cell strings.I just upload the gif, which shows what I described as
drawTextis slow.
Would you help me with that?Best regards.
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I've replaced all std::strings to QString, and change VS2019 charset to utf, and only use ASCII chars in string.
Still there is a visible blank before the custom tables shows.Even there is only one column， one row.
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I've tested it with a single drawText call in paintEvent, the problem still exists.
But if I put a label on widget, the problem disappears!
main.cpp#include <QtWidgets/QApplication> #include "QPlainStyleTable.h" #include "QtClass.h" int main(int argc, char *argv[]) { QApplication a(argc, argv); // auto _m_pTable = new QPlainStyleTable(); // _m_pTable->SetHeaderColor(Qt::red, Qt::green); // _m_pTable->SetContentColor(Qt::gray, Qt::yellow, Qt::blue); // _m_pTable->SetBorderColor(Qt::white); // //_m_pTable->SetFont(QFont(u8"微软雅黑"), QFont(u8"微软雅黑")); // // _m_pTable->SetDimension(1, 1); // // _m_pTable->SetTitle({ "a", "b", "c", "d", "e" }); // _m_pTable->AddData({ "a1", "b1", "c1", "d1", "e1`" }); // _m_pTable->AddData({ "a2", "b2", "c2", "d2", "e2" }); // _m_pTable->AddData({ "a3", "b3", "c3", "d3", "e3" }); // _m_pTable->AddData({ "a4", "b4", "c4", "d4", "e4" }); // // _m_pTable->show(); auto _m_pQClass = new QtClass(nullptr); _m_pQClass->setFixedSize(500, 400); _m_pQClass->show(); return a.exec(); }QtClass.h
#pragma once #include <QWidget> class QtClass : public QWidget { Q_OBJECT public: QtClass(QWidget *parent); ~QtClass(); void paintEvent(QPaintEvent* e) override; };QtClass.cpp with QLabel commented out.
#include "QtClass.h" #include <QPainter> #include <QLabel> QtClass::QtClass(QWidget *parent) : QWidget(parent) { // auto _pLabel = new QLabel(this); // _pLabel->setText("HELLO WORLD!"); // _pLabel->move(200, 300); } QtClass::~QtClass() { } void QtClass::paintEvent(QPaintEvent* e) { QPainter painter(this); painter.drawText(0, 0, 100, 200, Qt::AlignCenter | Qt::TextSingleLine | Qt::TextDontClip | Qt::TextWordWrap, QString("Hello World!")); }
QtClass.cpp with QLabel .
#include "QtClass.h" #include <QPainter> #include <QLabel> QtClass::QtClass(QWidget *parent) : QWidget(parent) { auto _pLabel = new QLabel(this); _pLabel->setText("HELLO WORLD!"); _pLabel->move(200, 300); } QtClass::~QtClass() { } void QtClass::paintEvent(QPaintEvent* e) { QPainter painter(this); painter.drawText(0, 0, 100, 200, Qt::AlignCenter | Qt::TextSingleLine | Qt::TextDontClip | Qt::TextWordWrap, QString("Hello World!")); }
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Hi,
Something just came to mind: maybe QStaticText might be of interest.
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Hi,
Something just came to mind: maybe QStaticText might be of interest.
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I've no performance problem with your code on linux and windows7 (both in a VM, 64bit, Qt5.15.x)
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I've tested it with a single drawText call in paintEvent, the problem still exists.
But if I put a label on widget, the problem disappears!
main.cpp#include <QtWidgets/QApplication> #include "QPlainStyleTable.h" #include "QtClass.h" int main(int argc, char *argv[]) { QApplication a(argc, argv); // auto _m_pTable = new QPlainStyleTable(); // _m_pTable->SetHeaderColor(Qt::red, Qt::green); // _m_pTable->SetContentColor(Qt::gray, Qt::yellow, Qt::blue); // _m_pTable->SetBorderColor(Qt::white); // //_m_pTable->SetFont(QFont(u8"微软雅黑"), QFont(u8"微软雅黑")); // // _m_pTable->SetDimension(1, 1); // // _m_pTable->SetTitle({ "a", "b", "c", "d", "e" }); // _m_pTable->AddData({ "a1", "b1", "c1", "d1", "e1`" }); // _m_pTable->AddData({ "a2", "b2", "c2", "d2", "e2" }); // _m_pTable->AddData({ "a3", "b3", "c3", "d3", "e3" }); // _m_pTable->AddData({ "a4", "b4", "c4", "d4", "e4" }); // // _m_pTable->show(); auto _m_pQClass = new QtClass(nullptr); _m_pQClass->setFixedSize(500, 400); _m_pQClass->show(); return a.exec(); }QtClass.h
#pragma once #include <QWidget> class QtClass : public QWidget { Q_OBJECT public: QtClass(QWidget *parent); ~QtClass(); void paintEvent(QPaintEvent* e) override; };QtClass.cpp with QLabel commented out.
#include "QtClass.h" #include <QPainter> #include <QLabel> QtClass::QtClass(QWidget *parent) : QWidget(parent) { // auto _pLabel = new QLabel(this); // _pLabel->setText("HELLO WORLD!"); // _pLabel->move(200, 300); } QtClass::~QtClass() { } void QtClass::paintEvent(QPaintEvent* e) { QPainter painter(this); painter.drawText(0, 0, 100, 200, Qt::AlignCenter | Qt::TextSingleLine | Qt::TextDontClip | Qt::TextWordWrap, QString("Hello World!")); }QtClass.cpp with QLabel .
#include "QtClass.h" #include <QPainter> #include <QLabel> QtClass::QtClass(QWidget *parent) : QWidget(parent) { auto _pLabel = new QLabel(this); _pLabel->setText("HELLO WORLD!"); _pLabel->move(200, 300); } QtClass::~QtClass() { } void QtClass::paintEvent(QPaintEvent* e) { QPainter painter(this); painter.drawText(0, 0, 100, 200, Qt::AlignCenter | Qt::TextSingleLine | Qt::TextDontClip | Qt::TextWordWrap, QString("Hello World!")); } -
I've no performance problem with your code on linux and windows7 (both in a VM, 64bit, Qt5.15.x)
Hi, Thank you for your attention.
Would you please take a look at the situation below ?
@xce1 said in How can I replce Qpainter::drawText with a more effecient way to draw text in a table cell:
I've tested it with a single drawText call in paintEvent, the problem still exists.
But if I put a label on widget, the problem disappears!
main.cpp#include <QtWidgets/QApplication> #include "QPlainStyleTable.h" #include "QtClass.h" int main(int argc, char *argv[]) { QApplication a(argc, argv); // auto _m_pTable = new QPlainStyleTable(); // _m_pTable->SetHeaderColor(Qt::red, Qt::green); // _m_pTable->SetContentColor(Qt::gray, Qt::yellow, Qt::blue); // _m_pTable->SetBorderColor(Qt::white); // //_m_pTable->SetFont(QFont(u8"微软雅黑"), QFont(u8"微软雅黑")); // // _m_pTable->SetDimension(1, 1); // // _m_pTable->SetTitle({ "a", "b", "c", "d", "e" }); // _m_pTable->AddData({ "a1", "b1", "c1", "d1", "e1`" }); // _m_pTable->AddData({ "a2", "b2", "c2", "d2", "e2" }); // _m_pTable->AddData({ "a3", "b3", "c3", "d3", "e3" }); // _m_pTable->AddData({ "a4", "b4", "c4", "d4", "e4" }); // // _m_pTable->show(); auto _m_pQClass = new QtClass(nullptr); _m_pQClass->setFixedSize(500, 400); _m_pQClass->show(); return a.exec(); }QtClass.h
#pragma once #include <QWidget> class QtClass : public QWidget { Q_OBJECT public: QtClass(QWidget *parent); ~QtClass(); void paintEvent(QPaintEvent* e) override; };QtClass.cpp with QLabel commented out.
#include "QtClass.h" #include <QPainter> #include <QLabel> QtClass::QtClass(QWidget *parent) : QWidget(parent) { // auto _pLabel = new QLabel(this); // _pLabel->setText("HELLO WORLD!"); // _pLabel->move(200, 300); } QtClass::~QtClass() { } void QtClass::paintEvent(QPaintEvent* e) { QPainter painter(this); painter.drawText(0, 0, 100, 200, Qt::AlignCenter | Qt::TextSingleLine | Qt::TextDontClip | Qt::TextWordWrap, QString("Hello World!")); }QtClass.cpp with QLabel .
#include "QtClass.h" #include <QPainter> #include <QLabel> QtClass::QtClass(QWidget *parent) : QWidget(parent) { auto _pLabel = new QLabel(this); _pLabel->setText("HELLO WORLD!"); _pLabel->move(200, 300); } QtClass::~QtClass() { } void QtClass::paintEvent(QPaintEvent* e) { QPainter painter(this); painter.drawText(0, 0, 100, 200, Qt::AlignCenter | Qt::TextSingleLine | Qt::TextDontClip | Qt::TextWordWrap, QString("Hello World!")); } -
@xce1 said in How can I replce Qpainter::drawText with a more effecient way to draw text in a table cell:
Would you please take a look at the situation below ?
That's the same code as above.
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@xce1 said in How can I replce Qpainter::drawText with a more effecient way to draw text in a table cell:
Would you please take a look at the situation below ?
That's the same code as above.
@Christian-Ehrlicher
Yes. It is. I thought maybe you missed the last post. Sorry about that.I used Qt5.14.2 on Win10 VS2019.
Since no one else has the same problem. I'm about to just put a
QLabelor other Qt widget to bypass it.Thank you anyway.
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@Christian-Ehrlicher
Yes. It is. I thought maybe you missed the last post. Sorry about that.I used Qt5.14.2 on Win10 VS2019.
Since no one else has the same problem. I'm about to just put a
QLabelor other Qt widget to bypass it.Thank you anyway.
