The QStatusBar has just one line each time and I cannot track the history or save the history in a log file.
So I want to have a dock widget in my mainwindow that is able to display the messages I need in a multi-line way and auto-scrolling way and then automatically saved to a log file.
My question is how to do this in Qt?
If what you are looking for is something similar to the "Application Output" pane of QtCreator, then a simple QPlainTextEdit can do the job. You can call QPlainTextEdit::setReadOnly(true) if you don't want the user to be able to edit its content (i.e. only your application can write to it).
If you want auto-scrolling and automatically saving to a log file, you will need to subclass it though. Here's a little something to get you started:
#include <QCoreApplication>
class MyLogWindow : public QPlainTextEdit
{
Q_OBJECT
/* snip */
public:
void appendMessage(const QString& text);
private:
QFile m_logFile;
};
void MyLogWindow::appendMessage(const QString& text)
{
this->appendPlainText(text); // Adds the message to the widget
this->verticalScrollBar()->setValue(this->verticalScrollBar()->maximum()); // Scrolls to the bottom
m_logFile.write(text); // Logs to file
// optional if you want to see the changes
// after appendPlainText() immediately
// useful if you use this->appendMessage() in a loop
QCoreApplication::processEvents();
}
I leave it to you to deal with the boilerplate (opening and closing the file, dealing with newlines, etc.).
Now, simply put an instance of MyLogWindow in a dock in your QMainWindow, and call MyLogWindow::appendMessage() every time you need to log something to have it displayed, scrolled and saved automatically.
Related
i have a Qt project with mainwindow (GUI Application)
how can i communicate with my main via my form?
for example
increase variable (which there's in my main) while button a click in my form
i have make a project in C which its in console application. works fine, and now i make another project which contains ui form with same code. and i want to make communication between form and main function
You can use the Qt signal/slot functionality.
Example:
// on mainwindow.cpp. Delcare onButtonClicked as a slot() on the header
void onButtonClicked()
{
++myVar;
}
connect(myButton, SIGNAL(clicked()), this, SLOT(onButtonClicked());
Reference docs.
I have an Mfc application where I want to open a Qt modal window, while the Mfc application is still running behind.
To start a Qt application from an Mfc, I got the how to there. This page creates a Dll but my solution creates a static library instead.
As for creating a Qt modal window with main application running behind, it looks easy.
My problem is that it looks like that I cannot combined both solution.
The following code starts the Qt window, but I strongly suspect that I am blocking my main thread and main thread is not able to receive events.
void QtMfcFacade::startDevicesConfigurationWizard(HWND hWnd)
{
QWinWidget win( hWnd );
win.showCentered();
DevicesConfigurationWizard devicesConfigurationWizardUI(&win);
devicesConfigurationWizardUI.exec();
}
exec function is probably blocking main thread
Following solution should not block main thread, but the Qt windows appears only for few miliseconds and disappeared
void QtMfcFacade::startDevicesConfigurationWizard(HWND hWnd)
{
QWinWidget win( hWnd );
win.showCentered();
DevicesConfigurationWizard devicesConfigurationWizardUI(&win);
devicesConfigurationWizardUI.show();
}
So, the question is, is it possible to use show function instead of exec function?
(This works if I am creating a Dll and calling the Dll in a worker thread from my Mfc application, but I do prefer using static library)
I did not read enough the walkthough.
It is said : "Since we want the dialog to be modeless we cannot create the QWinWidget on the stack, since it would be deleted when it leaves the scope, and all its children, including the dialog, would be deleted as well. Instead we create QWinWidget on the heap, using operator new"
So, to make my window non modal while giving control back to main thread, I should do this :
void QtMfcFacade::startDevicesConfigurationWizard(HWND hWnd)
{
QWinWidget *win = new QWinWidget( hWnd );
win->showCentered();
DevicesConfigurationWizard devicesConfigurationWizardUI = new DevicesConfigurationWizard (win);
devicesConfigurationWizardUI->show();
}
I recreated the example of a webkit that displays the content of a textEdit containing HTML: http://qt-project.org/doc/qt-4.8/webkit-previewer.html
I changed it so rather than the webkit HTML being changed upon clicking the button, it's changed upon the text in the textEdit being changed:
// changed when button is click. Works fine.
void Previewer::on_previewButton_clicked()
{
// Update the contents in web viewer
QString text = htmlTextEdit->toPlainText();
webView->setHtml(text);
}
// change when text is changed. Crashes.
void Previewer::on_htmlTextEdit_textChanged()
{
// Update the contents in web viewer
QString text = "<html><body><h1>No crash!</h1></body></html>";
webView->setHtml(text);
}
This causes the program to crash as soon as it starts. I altered the program to run the function only a bit later (I thought maybe something needed to be initialized) but it still crashed once it reached the textChanged function. Why is it crashing? How can I fix this?
Your program is entering an infinite loop because, in the example, there's a connection between the webView's loadFinished(bool) signal and the text/html editor's updateTextEdit() slot.
Basically, editing the HTML causes the page to load again, which causes an update to the editor, which causes the page to load again, so on and so forth.
A quick way I solved this was to add a static bool flag to the updateTextEdit SLOT/function that only allows it to run once.
void MainWindow::updateTextEdit()
{
static bool once = false;
if (once) {
return;
}
once = true;
QWebFrame *mainFrame = centralWidget->webView->page()->mainFrame();
QString frameText = mainFrame->toHtml();
centralWidget->plainTextEdit->setPlainText(frameText);
}
Doing this worked for me, but your version might work differently than mine. I followed the example closely, but added an htmlchanged() slot to the previewer class, and made the connection like so:
connect(centralWidget->plainTextEdit, SIGNAL(textChanged()), centralWidget, SLOT(html_changed()));
Also, I'm no expert, but I'm pretty sure this is not the best way to get around this, and I assume that updateTextEdit() needs to run more than once. It'll work for the time being, though.
I am developing an application in Qt that rebuilds its menus very often. However, when we call clear(), and re-add the actions that we want in the menu, "Special Characters..." appears to remain in the menu. Is there any way to remove, or move this action to the bottom of the QMenu?
Here is the code that rebuilds the menu:
void MainWindow::initMenus(Tab* tab)
{
menuBar()->clear();
menuFile->clear();
menuEdit->clear();
menuSettings->clear();
menuHelp->clear();
ui_toolBar->clear();
menuBar()->addMenu(menuFile);
menuBar()->addMenu(menuEdit);
menuFile->addAction(actionNew);
menuFile->addAction(actionOpen);
if(tab) tab->addActionsFile(menuFile);
menuFile->addSeparator();
menuFile->addAction(actionNext);
menuFile->addAction(actionPrevious);
menuFile->addAction(actionClose);
menuFile->addSeparator();
menuFile->addAction(actionQuit);
if(tab) {
tab->addActionsEdit(menuEdit);
menuEdit->addSeparator();
tab->addActionsHelp(menuHelp);
menuHelp->addSeparator();
}
menuEdit->addAction(actionEditor_Settings);
menuHelp->addSeparator();
menuHelp->addAction(actionAbout);
if(tab) tab->addOtherActions(menuBar());
menuBar()->addMenu(menuHelp);
ui_toolBar->addAction(actionNew);
ui_toolBar->addAction(actionOpen);
if(tab) tab->addToolbarActions(ui_toolBar);
}
It is supplied a tab, which can add its own actions to the menu as well using those functions.
This is a feature of Mac OS X that isn't easily disabled. You'll notice that nearly every application on Mac OS has it. It's automatically added to the Edit menu by the OS to allow the input of international characters.
It seems from your question, but isn't quite clear, that when you initially create the Edit menu, the Special Characters... menu item is initially the last menu item, but becomes the first menu item once editMenu->clear() has been called. One route you could go is instead of clear()ing the menus, you can delete the menus and recreate them completely. Your edit menu looks pretty static, though. Maybe it doesn't have to be recreated at all.
Now, that said, if you're really sure you need to get rid of this menu item, there are a couple of ways to accomplish that.
The first, and least desirable one is to simply not have an "Edit" menu. If there's no menu titled "Edit", Mac OS will not add a "Special Characters" menu item.
The second method requires a little platform specific Objective-C code. Obviously, this should only be built into your project on Mac OS.
MenuDeleter.m:
#include <Foundation/NSUserDefaults.h>
void deleteSpecialCharacters()
{
[[NSUserDefaults standardUserDefaults]
setBool:YES forKey:#"NSDisabledCharacterPaletteMenuItem"];
}
MenuDeleter.h
#ifndef MENUDELETER_H_
#define MENUDELETER_H_
void deleteSpecialCharacters();
#endif
And finally, in main.cpp:
#include <QApplicaiton>
#include "MenuDeleter.h"
int main(int argc, char **argv)
{
#ifdef Q_OS_MAC
deleteSpecialCharacters();
#endif
QApplication app(argc, argv);
....
return app.exec();
}
So that's how to make it go away completely. But the question is, do you really want to prevent the user from being able to input special characters into your app?
This answer may be more applicable to a COCOA OSX app, but I was able to remove these menu items in Objective-C by getting an NSMenu handle to the Edit Menu itself in the applicationDidFinishLaunching function , looping through the NSMenuItems in the itemArray and removing them by calling removeItem.
I have a K* window, and within it, a widget which needs the events filtered.
For example I do not want the possibility of clicking it...
How can I do that?
Have I to use eventfilters? In this case, what's the best way?
but my problem is that I can't subclass my widget,because it's a TerminalInterface->widget(), not an object like others :\
Besides the setEnabled sledgehammer approach in the first answer, there are two other approaches, one of which is to use eventfilters.
The other is to subclass the widget, and then reimplement, say, the mouse* events. Simply leaving them empty will prevent any mouse interaction. So:
MyWidget : public QSomeWidget
{
Q_OBJECT
public:
MyWidget(QWidget *parent);
protected:
void mousePressEvent(QMouseEvent *) {}
.. etc ..
};
QWidget has an enabled property. Just call widget->setEnabled(false) and this will prevent it from accepting mouse clicks. It may also modify its appearance: for example a QPushButton will be grayed out.
Event Filters sound like overkill for what you want.
It looks like eventFilter() is what you want.
Here's the section of Qt docs that talk about it:
Event Filters
Basically you have to create a class that inherits QObject and then implement the virtual function eventFilter(). Then call the installEventFilter() method on the object that you want to filter with the filter as a parameter.