I have a subclass of CComboBox that behaves differently in two different
contexts - both in native C++. In the working (test) context the top-level application was created
using VS2008. In the non-working case the application is greatly more complex
and was probably originally created by an earlier VS version.
In the failure case the control won't display a dropdown box, but responds to
up/down arrow key controls. Also in the failure case it always returns zero
when queried using GetMinVisible and always returns failure from
SetMinVisibleItems.
It appears that the problem is rooted in the definition of the COMBOBOX window
class. I have dumped the data returned from ::GetClassInfoEx in both cases.
Aside from the address of the wndProc, there are two differences. First, the working
case has style CS_GLOBALCLASS set while the failure case doesn't. Also the
working case specifies 4 bytes of extra window storage (cbWndExtra) while the
failure case specifies 8 bytes.
So my questions are: 1) What configuration properties might affect the definition of
the COMBOBOX window class?, and 2) How can I determine the correct wndProc to use if I make my own window class?
EDIT: The behavior of the dropdown box changes with the specification of the character set property in the General property tab. It works as expected if character set is unicode and fails when it's not set. The combo box subclass is in an ActiveX control, but the setting at the application level seems to affect the window class, which winds up messing up the combo box in ActiveX control. Interestingly there are other combo boxes, albeit in dialogs, elsewhere in the application that seem to behave just fine.
SetMinVisibleItems uses CB_SETMINVISIBLE and it requires comctl32 v6, this is your clue that this is a visual styles issue.
The older common controls version of the combobox actually uses the controls height as the size of the drop-down list so if you adjust that you might be able to fix it without adding a manifest.
Related
I am working on a Windows application using MFC and Visual Studio C++ 17.
I have multiple tabs in the application, one of which is currently implemented using CListBox and needs to be reimplemented using CCheckListBox.
CCheckListBox is a child class of CListBox.
I have a vector of unique CString's I want to display in the box.
To start simple, I tried making the tab with CListBox and by using CListBox::AddString(), this worked exactly as I wanted it to. It sorted the strings alphabetically, and automatically added a scroll bar on the side when the vector had too many CString's to display all at once in the list.
However, when swapping the CListBox variable to a CCheckListBox variable, I have come across the error when I press run along the lines of:
Debug Assertion Failed! ..... \mfc\winctrl3.cpp Line: 588
I found this GitHub link that has the winctrl3.cpp file and on line 588, there is a function called OnLButtonDblClk which is somewhat explained here.
The trouble is I am unsure of how to swap a variable from a parent class to a child class. Is it so different for Windows classes? In the courses and programs I have taken and written in the past, switching from a parent to child variable was straightforward but this is quite the opposite !
Any help is appreciated, thank you in advance ! :D
There is no assertion in line 588 of the source file in your link. That github upload dates back to 2014. Why not search the winctrl3.cpp source file in your own Visual Studio installation instead? In my own installation, it is in function PreSubclassWindow() and there is indeed an assertion there:
// CCheckListBoxes must be owner drawn
ASSERT(GetStyle() & (LBS_OWNERDRAWFIXED | LBS_OWNERDRAWVARIABLE));
That is the CCheckListBox must be owner-drawn. Find the CCheckListBox constructor code above, you will notice that it calls the CListBox (parent-class) constructor, applying either of the two owner-drawn styles. Instead, the CListBox constructor calls CWnd::Create() with the "LISTBOX" Windows Class-Name as a parameter. That is, it seems to be a MFC-implemented control, overriding the CListBox class, with an owner-drawn style. There is no mention of a native "Check-ListBox" class or style in the Win32 documentation either. Also the CCheckListBox documentation (in the link you posted) clearly states: CCheckListBox is only for owner-drawn controls because the list contains more than text strings.
Therefore:
If you are creating the control using a resource script, add an owner-drawn style (eg LBS_OWNERDRAWFIXED) to the control (or set the Owner-Drawn property in the property editor).
If you are creating the control programmatically make sure you are calling the CCheckListBox constructor, not the CListBox one.
Not sure what you mean about the scroll-bar (and why you mention it), doesn't the list-box display a scroll-bar automatically (WS_VSCROLL style - or property), do you have to do something on your own?
EDIT:
Forgot to mention, if you are creating the control using a resource script use the Class Wizard to add a member variable (of "Control" type, not "Value") to the dialog class. The new variable must be of type CCheckListBox (MFC class). This will subclass the control. If the old project already had a CListBox member variable change it to CCheckListBox.
Create a dialog-based application in Visual Studio 2019. Insert a new dialog in the resources. Place a control (or two) on that dialog that you will later (try to) hook up to a variable (e.g. an edit box to enter your name).
Prepare to add that control variable by creating a class for this second dialog. If you inherit from CDialogEx (or perhaps other classes too - not tested), you can go on to add a variable for the control you added - easy, normal.
But if you had the "tab control" context from the title above in your mind, and chose to inherit from CMFCPropertyPage instead, can you add a variable subsequently? No you cannot - the class added makes no reference to the ID of the dialog resource, and so the Add Variable process has no basis to find a class to add the variable to.
I think this is a bug in Visual Studio... but I'm not 100% sure because I have always found the documentation around property sheets and property pages somewhat confusing. Specifically:
Do the classes implementing the tabs contents on a tab control "contain" the controls "on" the tab... or is the tab control really just a way to provide visual cues to show/hide sets of controls, and all of those controls and associated variables reside in one class?
I believe it's intended to be the former, but I can imagine that one uses a tab control because there are strong similarities between tab contents, and therefore potential benefits in implementing all the control variables in one place so as to avoid duplication. I just wish it was stated explicitly somewhere what the intention was.
Wider context: I'm trying to implement a dialog-based app with a tab control dominating that dialog. MS documentation says to implement a tab control using CPropertySheet and CPropertyPage to implement the tabbed dialog and tab contents. However, there is no (direct) way to create a dialog-based application whose main dialog inherits from CPropertySheet. When you look for examples of tab controls at the application level, you readily find things that deviate from the documented path considerably - using neither CPropertySheet nor CPropertyPage and using the WM_LBUTTONDOWN event instead of TCN_SELCHANGE, both without obvious reasons.
Any tips on (a) how to repair the apparent Visual Studio bug and/or (b) how to inherit from CPropertySheet for my application dialog and/or (c) where to find a clearer and more conventional example of tab control use at the top level would be greatly appreciated.
Given that there appears to be no clear and consistent way of approaching this, if (like me) you think "how hard can it be?", you might naively set out to see if you can create a new dialog-based application based on CDialog and manually convert it to CPropertyPage. You might fare better; I quickly hit a weird problem with the app compiling but not running - it could not load the window caption from the resource ID, despite the caption literally being there in black and white. Due to the weirdness, this was a red flag, and so to my mind problem (b) seems to be not worth the effort.
Without a CPropertySheet at the top level, there is no point having any kind of CPropertyPage or CMFCPropertyPage involved, making problem (a) pointless. That said, if you manually convert from (default) CDialogEx to CPropertyPage for your tab classes, it seems to have no problem compiling and running - the tabs just don't have any functionality that integrates with the main dialog.
Instead, I can now recommend working through the details of the video example even though it does strange things at first glance. You can achieve the desired result in more or less the same way as follows:
Use plain CDialogEx throughout, and so provide all the tab switching/showing/hiding/control work yourself (which the example demonstrates).
Create your main dialog and all tabs in the resource editor, adding the CDialog-based classes from there.
If you create your tab dialog resources via Insert Dialog (generic) instead of Add Resource (uses specific templates) then you will have to manually set certain dialog properties for each tab:
Border: Thin (or I preferred None)
Style: Child
System Menu: false
Title Bar: false
You can simplify the repositioning of the tabs (see below; it barely justifies the separate SetRectangle() function)
You should (probably) drive the tab changing from the TCN_SELCHANGE event instead of WM_LBUTTONDOWN
As noted, repositioning the tabs can be simplified to something like:
CRect tabRect;
m_tabControl.GetWindowRect( &tabRect );
for ( int i = 0; i < m_totalTabs; i++ )
{
m_pTabPage[ i ]->SetWindowPos( &wndTop, tabRect.left, tabRect.top, 0, 0,
i == m_currentTab? SWP_NOSIZE|SWP_SHOWWINDOW : SWP_NOSIZE|SWP_HIDEWINDOW );
}
Additional calls to ShowWindow() for each tab shown in the example are redundant.
One time, I had made on application as such. I don't remember if I used the Visual Studio new project wizard. Most probably, I did. But I will assist you on how to do it if you can not reach how to do it via the assistant.
The essential things:
Define the main dialog in the resources and the respective class in its H and CPP files.
In the YourAppClass::InitInstance you will need to have something like:
YourMainDlgClass dlg;
m_pMainWnd = &dlg;
INT_PTR nResponse = dlg.DoModal();
if (nResponse == IDOK)
{
// TODO: Place code here to handle when the dialog is
// dismissed with OK
}
else if (nResponse == IDCANCEL)
{
// TODO: Place code here to handle when the dialog is
// dismissed with Cancel
}
else if (nResponse == -1)
{
TRACE(traceAppMsg, 0, "Warning: dialog creation failed, so application is terminating unexpectedly.\n");
TRACE(traceAppMsg, 0, "Warning: if you are using MFC controls on the dialog, you cannot #define _AFX_NO_MFC_CONTROLS_IN_DIALOGS.\n");
}
Insert a CMFCTabCtrl element in your dialog for tabs, instead of using a CPropertySheet.
We have an application that uses various system tray icons to communicate with users. Different icons indicate different internal states of the (otherwise windowless) application. We implemented our system tray stuff using code from this Code Guru project (the MFC version; this is not a new application by any means), and until recently, it has worked fine. However, recently we have tried to add another icon and have run into trouble.
Here's how it's supposed to work:
We have one main icon (call it 'A') that indicates that the application is running.
If a particular event occurs, we display icon 'B', over which the user can hover their mouse to get a tooltip with status regarding that event.
If a (recently added, internal, threaded) procedure starts, we display icon 'C', and again, the user can hover over that to see a tooltip that indicates the progress of that activity.
What's actually happening: if icon 'B' is visible when we (try to) display icon 'C', then icon 'B' either disappears entirely, never to return, or it stays there and icon 'C' never shows up, but the tooltip for icon 'B' is changed to what icon 'C' should have.
I've simplified the scenario a bit; we actually have a few other icons, but they're rarely used. However, we have never had any trouble displaying multiple icons until we added icon 'C' in the last couple of weeks.
Any ideas? Happy to clarify anything I haven't explained well.
You need to use a different uID for each icon. The documentation says:
The application-defined identifier of the taskbar icon. The Shell uses either (hWnd plus uID) or guidItem to identify which icon to operate on when Shell_NotifyIcon is invoked. You can have multiple icons associated with a single hWnd by assigning each a different uID. If guidItem is specified, uID is ignored.
In other words you need to pick a value for uID. This is how the shell knows which icon you are referring to each time you call Shell_NotifyIcon(). Clearly you must use a different value for each icon. So, use 0 for icon A, 1 for icon B etc.
I have an app with a customized frame (i.e., caption/titlebar, borders). I customized the frame by removing the WS_CAPTION style, and overriding OnNcCalcSize to reserve a custom-sized area for the caption, which the app paints in OnNcPaint.
A side effect is that the menu bar no longer displays, which is OK because I want to customize the appearance & location of the main menu. Unfortunately, I don't know how to do that. I would like the "File" menu to be further from the left edge than it is with the standard menu bar.
An acceptable alternative would be to remove the menu entirely, and use OnNcHitTest, OnNcPaint and OnNcMouseMove to manage a hand-coded replacement for the top-level menu.
I've never seen a way to modify the looks of the standard menu. You can remove it (remove the creation code from your InitInstance) and then code a replacement. I wouldn't do that in OnNcXXX though, rather make a new custom control that you position at the top. Or you could have a look at the MFC Next themed menus and write a custom UI renderer. It may be enough to override a few functions left and ride to set the alignment of the menu.
It's an MFC MDI app -- InitInstance is not where the menu is being created. I have tried to get rid of the menu (and succeeded, temporarily) but the MFC framework seems to be "putting it back" -- I think the MDI model has the child windows modify the menu, but the code that does that seems to be buried in the framework somewhere (or else I just haven't been able to find exactly where it happens in the application's code, but I suspect it's happening inside the MFC framework code). If I knew where, I might be able to override the methods(s) and take control... I think.
What would be the reason to write a custom control vs. handling OnNcMouseMove & OnNcLeftButtonDown, e.g.? I don't expect to need the functionality in any other app (a new app would be coded in C#, probably), so I'm looking for ease of implementation, not code reuse.
I'm creating a plugin framework, where my application loads a series of plugin DLL's, then creates a new window and pass this new window's handle to the plugin. The plugin can, then, use this handle to create their own GUI.
Everything seems to be working very well. The only problem is that when I press TAB on a plugin widget (An editbox, for example), it doen't jump to another widget. I figured out that some Windows messages are passed, and some others aren't. The WM_KEYDOWN is passed for other keys, because I can type on the editbox, but this message doesn't handle TAB key.
Hope somebody has a hint.
I'm using Borland VCL with CBuilder, but I think I could use any framework under WIN32 to create these plugins, since they never know how their parent windows were created.
It's very complex matter indeed.
When you hit TAB focus jumps to another control only when these controls belong to a Modal Dialog Box. In fact there are some buttons like ESC, LEFT, RIGHT, DOWN, UP, TAB which modal dialog message function treats in a special way. If you want these keys to behave in similar way with modeless dialog box or any other window you should change you message processing function and use IsDialogMessage inside. You'll find more information about IsDialogMessage function in MSDN also to better understand this stuff you may check as well Dialog Boxes section.
And, as was mentioned before, you should set WS_TABSTOP and WS_GROUP styles when needed.
Good luck!
I believe you'll have to take the following steps:
Subclass your edit controls (and other controls as needed).
Capture the WM_KEYDOWN message in your edit control's WndProc.
Check to see if the shift key is currently held down (using GetKeyState or similar).
Call GetWindow, passing in a handle to your edit control and either GW_HWNDPREV or GW_HWNDNEXT depending on whether shift is held down. This will give you the handle to the window that should receive focus.
Call SetFocus and pass in the window handle you got in step 4.
Make sure you handle the case where your edit controls are multiline, as you might want to have a real tab character appear instead of moving to the next control.
Hope that helps!
I believe you suffer from having a different instance of the VCL in each of your dlls and exes. Classes from the dll are not the same as the ones from your exe, even if they are called the same. Also global variables (Application, Screen) are not shared between them. Neither is the memory since they both have their own memory manager.
The solution is to have the dlls and the exe share the VCL library and the memory manager. I am not a BCB developer, but a Delphi developer. In Delphi we would just use the rtl and the vcl as runtime packages. Maybe you could do the BCB equivalent.
A DLL has its own TApplication object.
to provide uniform key handling. when the DLL Loads.
assign the DLL::TApplication to the EXE::TApplication
Be sure to do the reverse on exit.
--
Michael