qt4

问题 I have a QImage that I built from a pixmap something like the following: QPixmap fullPmap = topItem->pixmap(); fullPmap = fullPmap.copy(isec.toRect()); QImage chip = fullPmap.toImage(); This is basically intersecting with a rectangle on screen to crop the image to a chipped size. I now need to get the character array representing that data back from chip. How can I do this? I tried something like this: unsigned char * data = chip.bits(); And when I display "data" I get a completely distorted

问题 I am working on a GUI developed via PyQt and Qt4. Within my GUI I have a QTextEdit that has various data written to. Is there a way in which I can manipulate the color of one word within the QTextEdit? For example redText = "I want this text red" self.myTextEdit.write(redText) blackText = "And this text black" self.myTextEdit.append(blackText) Is this possible? If so, how could I do this? Regards, sudo!! 回答1: You should provide a rich text for it. It can be done by creating a <span> tag and

问题 I'm new to GUI programming and multithreading. I am in the process of creating a real-time app that receives information from my car and renders it in some meaningful way. My app is layed out as 3 threads, the GUI (main thread), the rendering thread and the hardware comm thread. Inbetwen the the render and the hardware threads is a shared ring buffer. In the render I have created a timer so that it draws the new interface 20 times a second. I would like the thread to notify the main thread

问题 I have noticed, Qt (4.8) changes the behaviour of sscanf() . Without Qt sscanf() works as usual, but with, it takes only localized strings. Here's a minimized example: Without Qt (plain C++) int main(int argc, char *argv[]) { float f; sscanf("0.83", "%f", &f); std::cout << f << "\t-->\t" << typeid("0.83").name() << std::endl; return 0; } Output: 0.83 --> A5_c (given string is a 5x char -array, result correct) With Qt int main(int argc, char *argv[]) { /* * This breaks sscanf() for the whole (

问题 Using MinGW 4.7.2 every compiled Qt 4 application crashes - even programs that ran before. MinGW: 4.7.2 QT: 4.8.3 Used Libs: QtCore4.dll QtCored4.dll QtGui4.dll (used if gui) QtGuid4.dll (used if gui) Simple Program as an example: #include <QtGui/QApplication> int main(int argc, char *argv[]) { QApplication app(argc, argv); /* Crash here */ return app.exec(); } Crash: Signal received: SIGSEGV (Segmentation fault) Call Stack: ZN23QCoreApplicationPrivate27processCommandLineArgumentsEv+68: mov (

问题 We've compiled QT 4.6 and QWT 5.2.0 for VS2005. We're trying to derive a class from QwtDial, and the derived class has slots. So, we need to add the Q_OBJECT macro. However, when we do that, the linker chokes out this error: error LNK2001: unresolved external symbol "public: static struct QMetaObject const QwtDial::staticMetaObject" (?staticMetaObject@QwtDial@@2UQMetaObject@@B) I've looked at the Qwt.dll with depends, and it has that function. Looking at the .lib file with a hex editor shows

问题 Yes, I know that you cannot use GUI things from non-GUI threads. However, it seems reasonable to be able to create a QWidget object, send it to the GUI thread, and then send signals to it. However, when I try to do so, I get errors that widgets cannot be moved. However, this seems to works: #include <iostream> #include <QApplication> #include <QtConcurrentRun> #include <QDialog> class BasicViewer : public QDialog { Q_OBJECT public: void Function(const float a) { std::cout << a << std::endl; }

问题 You must first delete the existing layout manager (returned by layout()) before you can call setLayout() with the new layout. from http://doc.qt.io/qt-5.9/qwidget.html#setLayout Which function is used for deleting the previous layout? 回答1: You just use delete layout; like you would with any other pointer you created using new . 回答2: Chris Wilson's answer is correct, but I've found the layout does not delete sublayouts and qwidgets beneath it. It's best to do it manually if you have

问题 I am trying to embed a 3D plot in a Qt4 GUI (has other buttons), is this possible using matplotlib's mplot3d? I am aware that 2d plots are possible using "matplotlib.backends.backend_qt4agg", and i have done this. If yes, please quote an example. If no, what is the favorite option? VTK? Thanks! 回答1: While not the cleanest thing you're going to see. I've noticed that is it not as fast as the tkinter backend. Then again it works. Have fun: import os import sys from PyQt4 import QtCore, QtGui

问题 Thanks to this thread, I'm able to add widgets to 2nd or later column of QAbstractItemView (in my example QTreeView) of top level items of a view . But is it possible to add widgets to the children items? Here's what I've tried which partly went well: #!/usr/bin/env python import os from PyQt4.QtCore import QModelIndex, Qt from PyQt4.QtGui import QApplication, QItemSelectionModel, \ QPushButton, QStandardItem, \ QStandardItemModel, QTreeView from PyQt4.uic import loadUi class PrvTreeviewNest