https://bugs.kde.org/show_bug.cgi?id=359662
--- Comment #6 from Oleg Girko <ol+...@infoserver.ru> --- I've spent several days trying to understand what's going on, but my knowledge of layout mechanics in Qt is not sufficient to find out the root cause. I'll try to summarise my findings here in hope that it will be helpful for somebody more knowledgeable than me to solve this bug. # My setup I have konsole5-18.12.3-2.fc30.x86_64 package installed in Fedora 30. My laptop's screen size is 3200x1800 pixels (295x167 millimeters). DPI is explicitly set to 192 in KDE settings. Font in Konsole profile is set to Consolas, size 7 (yes, this is small). Menu and tabbar in Konsole are disabled. I've added tons of debug prints to konsole5 source code, but except of debug print statements (using qWarning()), the source code and build procedure is identical to this Fedora package: https://koji.fedoraproject.org/koji/buildinfo?buildID=1247868 I've set "Use current window size on next startup" to false, and Terminal Size in my only profile to 80x24. # What's going on Everything is happening in Application::newInstance() method. 1. MainWindow is created. Then MainWindow::createSession() is called that in turn calls ViewManager::createView(Session *) that creates TabbedViewContainer. Constructor of TabbedViewContainer calls TabbedViewContainer::konsoleConfigChanged() that calls tabBar()->setVisible(false); 2. Later in ViewManager::createView(Session *) another overload with the same name is called: ViewManager::createView(Session *, TabbedViewContainer *, int) that creates TerminalDisplay. Then it calls TerminalDisplay::setSize(80, 24) on newly created TerminalDisplay. I have the following before TerminalDisplay::setSize(80, 24): ViewSplitter: - isVisible() = false - contentsRect() = QRect(0,0 640x480) - sizeHint() = QSize(8, 8) - size() = QSize(640, 480) - geometry() = QRect(0,0 640x480) TabbedViewContainer: - isVisible() = false - contentsRect() = QRect(0,0 640x480) - sizeHint() = QSize(8, 8) - size() = QSize(640, 480) - geometry() = QRect(0,0 640x480) QTabBar: - isVisible() = false - contentsRect() = QRect(0,0 0x0) - sizeHint() = QSize(0, 0) - size() = QSize(0, 0) - geometry() = QRect(0,0 0x0) TerminalDisplay: - isVisible() = false - contentsRect() = QRect(0,0 640x480) - sizeHint() = QSize(-1, -1) - size() = QSize(640, 480) - geometry() = QRect(0,0 640x480) As you see, these values are just placeholders, nothing interesting. I have the following after TerminalDisplay::setSize(80, 24): ViewSplitter: - isVisible() = false - contentsRect() = QRect(0,0 640x480) - sizeHint() = QSize(8, 8) - size() = QSize(640, 480) - geometry() = QRect(0,0 640x480) TabbedViewContainer: - isVisible() = false - contentsRect() = QRect(0,0 640x480) - sizeHint() = QSize(8, 8) - size() = QSize(640, 480) - geometry() = QRect(0,0 640x480) QTabBar: - isVisible() = false - contentsRect() = QRect(0,0 0x0) - sizeHint() = QSize(0, 0) - size() = QSize(0, 0) - geometry() = QRect(0,0 0x0) TerminalDisplay: - isVisible() = false - contentsRect() = QRect(0,0 640x480) - sizeHint() = QSize(819, 482) - size() = QSize(640, 480) - geometry() = QRect(0,0 640x480) What changed here is TerminalDisplay::sizeHint() changed to something that makes sense for 80x24 display. 3. Later in ViewManager::createView(Session *, TabbedViewContainer *, int), container->addView() is called. TabbedViewContainer::addView() method just calls QTabWidget::addTab() method with newly created TerminalDisplay as its first argument, but it causes geometry of widgets to be recalculated dramatically. This is what I have after this: ViewSplitter: - isVisible() = false - contentsRect() = QRect(0,0 640x480) - sizeHint() = QSize(827, 535) - size() = QSize(640, 480) - geometry() = QRect(0,0 640x480) TabbedViewContainer: - isVisible() = false - contentsRect() = QRect(0,0 640x480) - sizeHint() = QSize(827, 535) - size() = QSize(640, 480) - geometry() = QRect(0,0 640x480) QTabBar: - isVisible() = false - contentsRect() = QRect(0,0 0x0) - sizeHint() = QSize(129, 45) - size() = QSize(0, 0) - geometry() = QRect(0,0 0x0) TerminalDisplay: - isVisible() = false - contentsRect() = QRect(0,0 640x480) - sizeHint() = QSize(819, 482) - size() = QSize(640, 480) - geometry() = QRect(0,0 640x480) Look at sizeHint() of TabbedViewContainer and ViewSplitter that encloses it. 827x535 is way bigger than 819x482 of TerminalDisplay. Height of 535 is even 8 pixels higher that 482 (height of TerminalDisplay) + 45 (height of QTabBar). I think, the key question to understand the cause of the problem is what happened here. How sizeHint() of TabbedViewContainer (that is essentially QTabWidget) became significantly bigger than one of TerminalDisplay that was just added to it, despite its tabBar() being hidden? Remember this size: 827x535, it is what will cause problems later. 4. In the end of Application::newInstance(), Application::finalizeNewMainWindow(MainWindow *) is called. First, it calls: window->resize(window->sizeHint()); Essentially, it resizes the main window to that problematic size of 827x535 that was miscalculated in the previous step. 5. Then, Application::finalizeNewMainWindow(MainWindow *) calls: window->show(); This triggers the following chain of events: TerminalDisplay::resizeEvent() and TerminalDisplay::showEvent(). 6. TerminalDisplay::resizeEvent() does not detect yet that TerminalDisplay is resized to the wrong size. However, its contentsRect() gets changed somewhere deep inside call stack when layout recalculation is triggered by some innocently looking function. The stack trace leading to this recalculation is following. I've omited internal details of signal handling and internal Qt methods to simplify it. Also, I've omited line numbers because they mean nothing in code heavily edited with debug prints. Also, I've removed Konsole namespace from method names and added some comments to this stack trace. QWidget::setGeometry(const QRect & = (0, 0, 826, 534)) # this has TerminalDisplay type QLayoutPrivate::doResize(const QSize & = (827, 535)) QWidget::setGeometry(const QRect & = (0, 0, 826, 534)) # this has QStackedWidget type QTabWidget::setUpLayout(false) # this has TabbedViewContainer type QTabWidget::setTabText(...) # this has TabbedViewContainer type TabbedViewContainer::updateTitle(ViewProperties *) emit ViewProperties::titleChanged(...) ViewProperties::setTitle(const QString &) # this has SessionController type SessionController::sessionAttributeChanged() emit sessionAttributeChanged() Session::setTitle(TitleRole, const QString &) SessionController::snapshot() emit started() Session::run() emit imageSizeInitialized() Emulation::setImageSize(24, 80) Konsole::Session::updateTerminalSize() emit TerminalDisplay::changedContentSizeSignal(480, 800) TerminalDisplay::updateImageSize() TerminalDisplay::resizeEvent(QResizeEvent *event) # event->size() = QSize(819, 482) QWidget::setVisible(...) # this has QStackedWidget type QWidget::setVisible(...) # this has TabbedViewContainer type QWidget::setVisible(...) # this has ViewSplitter type QWidget::setVisible(...) # this has MainWindow type Application::finalizeNewMainWindow(MainWindow *) # calls window->show() Application::newInstance() kdemain() As tou see, TerminalDisplay::resizeEvent() receives QResizeEvent with a good size. Deeper in call stack it calls TerminalDisplay::changedContentSizeSignal(), also with the right size. Deeper Emulation::setImageSize() is called with right args and emits imageSizeInitialized() signal. However, deeper in call stack TabbedViewContainer::updateTitle(ViewProperties *) calls QTabWidget::setTabText() method on TabbedViewController that in turn triggers QTabWidget::setUpLayout(false). This resizes TerminalDIsplay to 826x534 (1x1 pixel smaller than the size miscalculated above). 7. The final act of this tragedy happens in TerminalDisplay::showEvent() method that is also triggered by the same window->show(); in Application::finalizeNewMainWindow(MainWindow *) method. Here TerminalDisplay notices that its contentsRect() changed to QRect(0,0 827x535) and recalculates its size in TerminalDisplay::calcGeometry(). Essentially, it has the same effect as if the window was resized to 827x535. Even a tooltip showing terminal's new size (80x26) is shown. That's all I've discovered so far. I hope it will be useful to find out what happened and fix this bug. -- You are receiving this mail because: You are watching all bug changes.
