Why second line of code below rises exception
StatusDlg statusDlg (CWnd::GetDesktopWindow());
statusDlg.ShowWindow(SW_SHOW);
and code below goes without problems
StatusDlg * statusDlg = new StatusDlg(NULL);
statusDlg->Create(StatusDlg::IDD,CWnd::GetDesktopWindow());
statusDlg->ShowWindow(SW_SHOW)
?
Because the first dosen't create the dialog's underlying window?
Related
I have the following wxDialog parent window:
I have created that parent window by the following code:
settingsFrm settingsWindow(this, "Settings");
settingsWindow.ShowModal();
I have tried to use FindWindowByName to get the value of the first text ctrl as follow:
wxLogMessage(dynamic_cast<wxTextCtrl*>(settingsWindow->FindWindowByName("keywords_txt"))->GetValue());
But unfortunately, it doesn't work and gives me a runtime error.
I don't know if that method suitable to do what I want.
How to get the value/other of a control through its parent window?
From your comments, it seems like you expect the function to find the control from the name of the variable in your code which is not how it works and would be pretty much impossible.
FindWindowByName() uses the window name (and, as a fallback, label, but this is irrelevant here because text controls don't have labels anyhow), so for it to work you need to set the window name when creating the control, using the corresponding parameter of its ctor. This is very rarely useful in C++ code, however, as it's simpler to just store a pointer to the control in some variable and use this instead.
FindWindowByName() can often be useful when creating controls from XRC, however. If you do this, then you should specify names for your controls in XRC and pass the same name to this function.
How did you create the TextCtrl instance? You should have something like wxTextCtrl m_textCtrl1 = new wxTextCtrl(/// arguments); Accessing the value should be very easy, as wxString text = m_textCtrl1->GetValue(); You definitely don't need FindWindowByName just for what you are trying to do here.
I'm writing an application in C++ using the Qt library. There is a central window (the parent) and all the children are launched when needed. Since a number of these windows can be open multiple times, but display different data, I'm declaring the objects with new. Here is an example of what I've got:
Home_Window.hpp
View_Window *SomeWindow;
Home_Window.cpp
void Home_Window::on_WindowButton_clicked()
{
SomeWindow = new View_Window();
SomeWindow->show();
}
What I want to do, is delete the object, when the window is closed to reduce the memory footprint of the application. I've already been able to delete all of the objects contained in the child window to reduce memory usage, but the core object still lingers, and if, through a single day a user opens and closes 1000's of windows, and each object holds onto 40-50KB of memory, the footprint of the application goes from a couple of MBs of memory to 100's of MBs of Memory.
I've not been able to find a guide online that would allow me to achieve this. I was considering a slot and signal pair, as I know that when a window is closed, it sends the QObject::destroyed() signal. Only issue, is I've not tried to setup a signal and slot pair like this.
Any suggestions are appreciated.
to delete the window when it is closed, you can set the WA_DeleteOnClose attribute on it. Your on_WindowButton_clicked() should look something like:
void Home_Window::on_WindowButton_clicked()
{
View_Window* w= new View_Window();
w->setAttribute(WA_DeleteOnClose);
w->show();
}
This way, you don't have to worry about destroying w yourself, it will get deleted automatically when it is closed.
You need to do two things:
The window's lifetime must be managed even if the window isn't closed.
You can give it a parent that you know will end its life at some point. Or you can use a QScopedPointer or std::unique_ptr.
The window must delete itself when it's closed.
void Home_Window::on_WindowButton_clicked()
{
// parent window flags
// vvvv vvvvvvvvvv
auto window = new View_Window(this, Qt::Dialog); /* 1. */
window->setAttribute(Qt::WA_DeleteOnClose); /* 2. */
window->show();
}
At the very least, you should set the Qt::Window flag. The Qt::Dialog includes the Qt::Window flag, and also declares the window to be a dialog box - that fact has platform-specific interpretation; read more about window flags here.
If your View_Window's API is broken, and it doesn't take the window flags as the 2nd argument to the constructor, you need to set them separately:
window->setWindowFlags(Qt::Dialog);
Every widget should be taking Qt::WindowFlags as the optional, 2nd argument to the constructor, with a default value reflecting the usual use of the window. That's the expectation set by all of Qt's widgets.
You can try to delete the pointer to ViewWindow by using: delete SomeWindow;
The below code, creating a Property Sheet, works without problem in an Application File.
.......
CProp_Sheet Pr_Sheet(_T("PS"));
CPr_Page_1 Pr_Page_1;
CPr_Page_2 Pr_Page_2;
Pr_Sheet.AddPage(&Pr_Page_1);
Pr_Sheet.AddPage(&Pr_Page_2);
m_pMainWnd = &Pr_Sheet;
int nResponse = Pr_Sheet.DoModal();
However, when I put the same code in a DLL, and call it from a menu item in another Application, m_pMainWnd cannot be used (the menu in the Application is to remain visible behind the Property Sheet).
I have tried to create a handle
CWnd* m_pWnd = &Pr_Sheet;
and use m_pWnd in the CProp_Sheet constructor, but although compiling correctly at run time failure always occurs at
CProp_Sheet::OnInitDialog().
Thanks in advance for any comments.
I'm developing a simple prototype with qt creator.
I have used designer in order to design my windows.
Say us that main window has a menu with an option called "Suspend". When this option is selected, it is called the method MainWindow::on_actionSuspend_triggered() whose simplified implementation could be resumed as follows:
void MainWindow::on_actionSuspend_triggered()
{
SuspendDialog suspend_dialog(this);
suspend_dialog.setModal(true);
auto status = suspend_dialog.exec();
return;
}
The SuspendDialog was specified with designer, it is derived from QDialog class and it is very simple (three push buttons a combo box and a spin box. This class does not allocate memory.
Now, when I run valgrind inside qtcreator for checking memory usage I get two issues of type Mismatched free() / delete / delete []. Some bizarrus is that the two issues refers the same line, which is at the end of destructor of SuspendDialog whose implementation is:
SuspendDialog::~SuspendDialog()
{
delete ui;
}
And that was automatically generated by qt designer.
My question is: is this a false positive of valgrind or am I doing some wrong?
Thanks in advance
By doing the below you are asking for trouble:
SuspendDialog suspend_dialog(this); // wrong! do not pass 'this' here
Passing pointer to 'this' in Qt implies that you pass the parent responsible for release of that widget. Or, the release will happen twice: first when the object on stack getting destroyed and next when the parent object getting destroyed.
If you execute the dialog with exec() you can still allocate the dialog widget on stack but do not pass this to it:
SuspendDialog suspend_dialog;
//
suspend_dialog.exec(); // exec() only
Or you can allocate the dialog widget in the heap and then you can pass this to it:
SuspendDialog* pSuspendDialog = new SuspendDialog(this);
//
pSuspendDialog->exec(); // or maybe show() depending on task
I have a Application mostly written with the owl-libary.
There I want open new vcl-windows out of the main owl-window.
This works great, though if a dialog-window is opened (even with ShowModal) and I focus another application, then the main-window get's into foreground but is blocked by the window behind it.
I guess the Problem is the missing parent-setting.
However, I can't convert owl's TWindow to vcl's TWinControl.
Is there a trick to set a vcl's parent setting to a owl's TWindow-Object?
Or could this be caused by something entirely different?
EDIT:
I'm using...
void(TWindow* parent){
Form=new TForm((HWND)parent->Handle);
Form->ParentWindow=parent->Handle;
Form->BorderIcons >> biMinimize >> biMaximize << biSystemMenu; //No minimize, no maximize, but close
Form->BorderStyle = bsSingle;
Form->Position = poMainFormCenter;
...
Form->ShowModal();
...now.
However, the new window is locked up and can not be clicked/closed/switched to.
Is there something I missed in using ParentWindow?
EDIT2:
I think it might be a Problem that the parent is a TDecoratedMDIFrame, which is a MDI-Container, so my dialog is treated like a mdi-child instead of a normal dialog...
TWinControl has a ParentWindow property for specifying a non-VCL parent window.
Also, in modern VCL versions, you can specify a ParentWnd when displaying a VCL dialog.