I'm asking this question ahead of time, since I haven't gotten around to attempting an actual, real implementation yet. Win32 (C++) is turning out to be a colossal pain to program. But, my question is this:
I want to make my application's window become fully transparent with a dotted perimeter when resizing the window. How would I accomplish this? Think of what happens in Windows 3/3.1 (I believe it was this version) when resizing a window. Everything goes transparent, with a dotted-outline where the mouse is moving, then it repaints the entire contents. That's what I'm trying to achieve.
A while ago, I tried handling the WM_(ENTER/EXIT)SIZEMOVE messages and make use of SetWindowLong() to set the WS_EX_TRANSPARENT extended style, but my window became (indefinitely) pass-through, and when the window's focus was killed, it could never again regain focus.
Do I need to handle other messages like WM_NCLBUTTON(DOWN/UP)? I have a boolean flag to tell me when to halt drawing during resizing, and the logic for determining when I'm resizing works perfectly, but I cannot get the visuals to work. I'm not sure which parts of the Win32 API to actually use. I've done some research, and uxtheme.lib/.h seems promising, but I'm not sure how that would work with WM_NCPAINT, which I have been using with (some) luck.
EDIT
I need to clarify something, in case anyone was confused or unsure of what I meant. What I meant by the Windows 3.1/3 resizing scenario is that once WM_ENTERSIZEMOVE has occurred, the window (controls, caption, frame) should be made entirely invisible, and the window's nonclient-region's perimeter should display a dotted-outline of sorts. Then, only until the resize has been finished, when WM_EXITSIZEMOVE has occurred should the entire window (controls, caption, frame) be fully redrawn, updated, and returned to its normal, functional state. Sorry for any miscommunication!
I found the answer... After so long, finally found it. Here's where I found it! http://www.catch22.net/tuts/win32/docking-toolbars-part-2# - Hope it helps anyone else possibly in my shoes!
And it turns out that the solution was rather simple. In fact, the core concept of what is explained is near-completely what I was thinking, yet I just had no idea how to implement it. The solution involves overriding the default WM_NCLBUTTONDOWN, WM_MOUSEMOVE, WM_LBUTTONUP (specifically when initiating a window movement) messages, and drawing a patterned rectangle which follows the position of the cursor. Then, afterwards, calling SetWindowPos or some other similar function to relocate the window.
Basically, block Windows from attempting to display anything graphics related until the resizing has been finished. Then, and only then, make Windows move the entire window in one huge, foul swoop.
Based on Remy's comment, there is a global option and corresponding registry setting for this, so perhaps try setting the registry setting when the move starts and restoring it when the move finishes.
Unfortunately this doesn't work as Windows appears only to pick up the setting on restart, broadcasting WM_SETTINGCHANGE also doesn't trigger it, which is a pity as doing something yourself that the OS already has an implementation of do is rather a poor state of affairs.
I am trying to deploy a cross platform Qt application written in c++. It works fine on my Ubuntu Linux but when I run it on Windows the application's main window's position gets set on the very top left point of the screen with the upper frame (that holds the minimize, maximize, close buttons) missing.
That is it until i resize the main window (in this case making the width smaller from the right). When this happens the upper frame and the control buttons appear as in the visualization I provided.
Note: I've removed all widgets on the app so they do not аppear as a distraction.
Note2: It appears the maximize button is disabled, which is not the case inside Ubuntu. I have not set any window flags.
How do i visualize the upper frame at the very start of the application without the need to resize the window. I understand its an OS specific behaviour. Setting the main window's geometry with a starting point with a higher y value does NOT help. It still pops at the very top left of the screen.
try to use QWidget::move to set the Window position after setGeometry.
If the widget is a window, the position is that of the widget on the
desktop, including its frame.
You ask a question about cross-platform UI code, and then you don't show the full code. Please show the full code.
The one line of code you do show does something in the wrong way: if you want to maximize a window, call the appropriate function, instead of setting its absolute size that you think shows the window maximized. Windows, their decorations and their placement are very very platform specific, and you should prefer their cross-platform abstractions over trying to do them yourself.
Concretely: the window positioning handles the decorations (title bar) differently on Windows and on Ubuntu. There is absolutely nothing you can do about it except not position your windows absolutely like this.
In the MainWindow constructor at the end this->setGeometry(0, 0, 1336, 600);
That's the problem. setGeometry deals with the geometry of the client area. This is well documented. You should use move to change the position of the widget frame. To set the size of the frame requires the knowledge of the frame's incremental width and height:
bool setWidgetFrameGeometry(QWidget *w, const QRect &r) {
auto frame = w->frameGeometry().size();
auto client = w->size();
auto delta = frame - client;
auto maxDelta = 128;
if (delta.width() > 0 && delta.width() < maxDelta
&& delta.height() > 0 && delta.height() < maxDelta) {
w->move(r.topLeft());
w->resize(r.size() - delta);
return true;
}
return false;
}
The call may need to be deferred to when the event loop had a chance to run:
auto setter = [this]{ return setWidgetFrameGeometry(this, {0,0,1336,600}); };
if (!setter())
QTimer::singleShot(0, this, setter);
Is there a good way for preventing a window from being moved in gtkmm?
At first I tried to do this by overloading on_configure_event (forcibly move window to fixed position), but this caused some strange graphical glitches and huge slowdowns during a resize of window.
Window position is usually a responsibility of the Window Manager, not of the application. You are fighting the system, and hence the glitches.
My advice is: just don't do it. The user should be able to move the window.
If you really need this, the best thing is to tell the Window Manager not to manage your window, and then do the managing tasks you still need yourself (resizing the window, for example).
For details, see the function gtk_window_set_decorated() and the GTK_WINDOW_POPUP argument to gtk_window_new().
I need to clear any mouse clicks which has happened before the end of an animation.Only mouse clicks afterwards have to be considered.
I tried enabling my mouse function after the animation,but any clicks that happened during the animation was considered.
To my understanding there is a buffer where mouseclicks are stored and during any mouse callback , it takes the co-ordinates and any other info of the first click stored in that buffer.so i need to know how to clear this.
I used fflush(stdin) but it doesnt clear keyboard or the mouse buffer.
Am using windowsxp and programming in visualsudio2008 in c language.i also use glut.h
i also use glut.h
Then you can't. If you're doing an animation, it's up to you to process (or choose not to process) any messages.
You should not be animating something by looping within your display method. Instead, you should set up a timer callback or something that will call glutPostRedisplay that will constantly call your drawing method. During this time, you should ignore any messages if you don't want to process them.
When the user grabs a corner of a resizable window, and then moves it, windows first moves the contents of the window around, then issues a WM_SIZE to the window being resized.
Thus, in a dialog where I want to control the movement of various child controls, and I want to eliminate flickering, the user first sees what windows OS thinks the window will look like (because, AFAICT, the OS uses a bitblt approach to moving things around inside the window before sending the WM_SIZE) - and only then does my dialog get to handle moving its child controls around, or resize them, etc., after which it must force things to repaint, which now causes flicker (at the very least).
My main question is: Is there a way to force windows NOT to do this stupid bitblt thing? Its definitely going to be wrong in the case of a window with controls that move as the window is resized, or that resize themselves as their parent is resized. Either way, having the OS do a pre-paint just screws the works.
I thought for a time that it might be related to CS_HREDRAW and CSVREDRAW class flags. However, the reality is that I don't want the OS to ask me to erase the window - I just want to do the repainting myself without the OS first changing the contents of my window (i.e. I want the display to be what it was before the user started resizing - without any bitblit'ing from the OS). And I don't want the OS to tell every control that it needs to be redrawn either (unless it happened to be one that was in fact obscured or revealed by the resize.
What I really want:
To move & resize child controls before anything gets updated onscreen.
Draw all of the moved or resized child controls completely so that they appear without artifacts at their new size & location.
Draw the spaces inbetween the child controls without impacting the child controls themselves.
NOTE: Steps 2 and 3 could be reversed.
The above three things appear to happen correctly when I use DeferSetWindowPos() in combination with the dialog resource marked as WS_CLIPCHILDREN.
I'd get an additional small benefit if I could do the above to a memory DC, and then only do a single bitblt at the end of the WM_SIZE handler.
I have played with this for a while now, and I cannot escape two things:
I still am unable to suppress Windows from doing a 'predictive bitblt'. Answer: See below for a solution that overrides WM_NCCALCSIZE to disable this behavior.
I cannot see how one can build a dialog where its child controls draw to a double buffer. Answer: See John's answer (marked as answer) below for how to ask Windows OS to double buffer your dialog (note: this disallows any GetDC() in-between paint operations, according to the docs).
My Final Solution (Thank you everyone who contributed, esp. John K.):
After much sweat and tears, I have found that the following technique works flawlessly, both in Aero and in XP or with Aero disabled. Flicking is non-existent(1).
Hook the dialog proc.
Override WM_NCCALCSIZE to force Windows to validate the entire client area, and not bitblt anything.
Override WM_SIZE to do all of your moves & resizes using BeginDeferWindowPos/DeferWindowPos/EndDeferWindowPos for all visible windows.
Ensure that the dialog window has the WS_CLIPCHILDREN style.
Do NOT use CS_HREDRAW|CS_VREDRAW (dialogs don't, so generally not an issue).
The layout code is up to you - its easy enough to find examples on CodeGuru or CodeProject of layout managers, or to roll your own.
Here are some code excerpts that should get you most of the way:
LRESULT ResizeManager::WinProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
{
switch (msg)
{
case WM_ENTERSIZEMOVE:
m_bResizeOrMove = true;
break;
case WM_NCCALCSIZE:
// The WM_NCCALCSIZE idea was given to me by John Knoeller:
// see: http://stackoverflow.com/questions/2165759/how-do-i-force-windows-not-to-redraw-anything-in-my-dialog-when-the-user-is-resiz
//
// The default implementation is to simply return zero (0).
//
// The MSDN docs indicate that this causes Windows to automatically move all of the child controls to follow the client's origin
// and experience shows that it bitblts the window's contents before we get a WM_SIZE.
// Hence, our child controls have been moved, everything has been painted at its new position, then we get a WM_SIZE.
//
// Instead, we calculate the correct client rect for our new size or position, and simply tell windows to preserve this (don't repaint it)
// and then we execute a new layout of our child controls during the WM_SIZE handler, using DeferWindowPos to ensure that everything
// is moved, sized, and drawn in one go, minimizing any potential flicker (it has to be drawn once, over the top at its new layout, at a minimum).
//
// It is important to note that we must move all controls. We short-circuit the normal Windows logic that moves our child controls for us.
//
// Other notes:
// Simply zeroing out the source and destination client rectangles (rgrc[1] and rgrc[2]) simply causes Windows
// to invalidate the entire client area, exacerbating the flicker problem.
//
// If we return anything but zero (0), we absolutely must have set up rgrc[0] to be the correct client rect for the new size / location
// otherwise Windows sees our client rect as being equal to our proposed window rect, and from that point forward we're missing our non-client frame
// only override this if we're handling a resize or move (I am currently unaware of how to distinguish between them)
// though it may be adequate to test for wparam != 0, as we are
if (bool bCalcValidRects = wparam && m_bResizeOrMove)
{
NCCALCSIZE_PARAMS * nccs_params = (NCCALCSIZE_PARAMS *)lparam;
// ask the base implementation to compute the client coordinates from the window coordinates (destination rect)
m_ResizeHook.BaseProc(hwnd, msg, FALSE, (LPARAM)&nccs_params->rgrc[0]);
// make the source & target the same (don't bitblt anything)
// NOTE: we need the target to be the entire new client rectangle, because we want windows to perceive it as being valid (not in need of painting)
nccs_params->rgrc[1] = nccs_params->rgrc[2];
// we need to ensure that we tell windows to preserve the client area we specified
// if I read the docs correctly, then no bitblt should occur (at the very least, its a benign bitblt since it is from/to the same place)
return WVR_ALIGNLEFT|WVR_ALIGNTOP;
}
break;
case WM_SIZE:
ASSERT(m_bResizeOrMove);
Resize(hwnd, LOWORD(lparam), HIWORD(lparam));
break;
case WM_EXITSIZEMOVE:
m_bResizeOrMove = false;
break;
}
return m_ResizeHook.BaseProc(hwnd, msg, wparam, lparam);
}
The resizing is really done by the Resize() member, like so:
// execute the resizing of all controls
void ResizeManager::Resize(HWND hwnd, long cx, long cy)
{
// defer the moves & resizes for all visible controls
HDWP hdwp = BeginDeferWindowPos(m_resizables.size());
ASSERT(hdwp);
// reposition everything without doing any drawing!
for (ResizeAgentVector::const_iterator it = m_resizables.begin(), end = m_resizables.end(); it != end; ++it)
VERIFY(hdwp == it->Reposition(hdwp, cx, cy));
// now, do all of the moves & resizes at once
VERIFY(EndDeferWindowPos(hdwp));
}
And perhaps the final tricky bit can be seen in the ResizeAgent's Reposition() handler:
HDWP ResizeManager::ResizeAgent::Reposition(HDWP hdwp, long cx, long cy) const
{
// can't very well move things that no longer exist
if (!IsWindow(hwndControl))
return hdwp;
// calculate our new rect
const long left = IsFloatLeft() ? cx - offset.left : offset.left;
const long right = IsFloatRight() ? cx - offset.right : offset.right;
const long top = IsFloatTop() ? cy - offset.top : offset.top;
const long bottom = IsFloatBottom() ? cy - offset.bottom : offset.bottom;
// compute height & width
const long width = right - left;
const long height = bottom - top;
// we can defer it only if it is visible
if (IsWindowVisible(hwndControl))
return ::DeferWindowPos(hdwp, hwndControl, NULL, left, top, width, height, SWP_NOZORDER|SWP_NOACTIVATE);
// do it immediately for an invisible window
MoveWindow(hwndControl, left, top, width, height, FALSE);
// indicate that the defer operation should still be valid
return hdwp;
}
The 'tricky' being that we avoid trying to mess with any windows that have been destroyed, and we don't try to defer a SetWindowPos against a window that is not visible (as this is documented as "will fail".
I've tested the above in a real project that hides some controls, and makes use of fairly complex layouts with excellent success. There is zero flickering(1) even without Aero, even when you resize using the upper left corner of the dialog window (most resizable windows will show the most flickering and problems when you grab that handle - IE, FireFox, etc.).
If there is interest enough, I could be persuaded to edit my findings with a real example implementation for CodeProject.com or somewhere similar. Message me.
(1) Please note that it is impossible to avoid one draw over the top of whatever used to be there. For every part of the dialog that has not changed, the user can see nothing (no flicker whatsoever). But where things have changed, there is a change visible to the user - this is impossible to avoid, and is a 100% solution.
You can't prevent painting during resizing, but you can (with care) prevent repainting which is where flicker comes from. first, the bitblt.
There a two ways to stop the bitblt thing.
If you own the class of the top level window, then just register it with the CS_HREDRAW | CS_VREDRAW styles. This will cause a resize of your window to invalidate the entire client area, rather than trying to guess which bits are not going to change and bitblting.
If you don't own the class, but do have the ability to control message handling (true for most dialog boxes). The default processing of WM_NCCALCSIZE is where the class styles CS_HREDRAW and CS_VREDRAW are handled, The default behavior is to return WVR_HREDRAW | WVR_VREDRAW from processing WM_NCCALCSIZE when the class has CS_HREDRAW | CS_VREDRAW.
So if you can intercept WM_NCCALCSIZE, you can force the return of these values after calling DefWindowProc to do the other normal processing.
You can listen to WM_ENTERSIZEMOVE and WM_EXITSIZEMOVE to know when resizing of your window starts and stops, and use that to temporarily disable or modify the way your drawing and/or layout code works to minimize the flashing. What exactly you want to do to modify this code will depend on what your normal code normally does in WM_SIZE WM_PAINT and WM_ERASEBKGND.
When you paint the background of your dialog box, you need to not paint behind any of the child windows. making sure that the dialog has WS_CLIPCHILDREN solves this, so you have this handled already.
When you do move the child windows, Make sure that you use BeginDeferWindowPos / EndDefwindowPos so that all of the repainting happens at once. Otherwise you will get a bunch of flashing as each window redraws their nonclient area on each SetWindowPos call.
If I understood the question properly, it's exactly the question Raymond addressed today.
Here's a 2018 update, since I just ran through the very same gauntlet as you.
The "final solution" in your question, and the related answers, that mention tricks with WM_NCCALCSIZE and CS_HREDRAW|CS_VREDRAW are good for preventing Windows XP/Vista/7 from doing the BitBlt that molests your client area during resizing. It might even be useful to mention a similar trick: you can intercept WM_WINDOWPOSCHANGING (first passing it onto DefWindowProc) and set WINDOWPOS.flags |= SWP_NOCOPYBITS, which disables the BitBlt inside the internal call to SetWindowPos() that Windows makes during window resizing. This has the same eventual effect of skipping the BitBlt.
And some people mentioned that your WM_NCCALCSIZE trick no longer works in Windows 10. I think that might be because the code you wrote returns WVR_ALIGNLEFT|WVR_ALIGNTOP when it should be returning WVR_VALIDRECTS in order for the two rectangles you constructed (nccs_params->rgrc[1] and nccs_params->rgrc[2]) to be used by Windows, at least according to the very skimpy dox in the MSDN pages for WM_NCCALCSIZE and NCCALCSIZE_PARAMS. It's possible that Windows 10 is more strict about that return value; I would try it out.
However, even if we assume that we can convince Windows 10 not to do BitBlt inside SetWindowPos(), it turns out there's a new problem...
Windows 10 (and possibly also Windows 8) adds another layer of client area molestation on top of the old legacy molestation from XP/Vista/7.
Under Windows 10, apps do not draw directly to the framebuffer, but instead draw into offscreen buffers that the Aero Window manager (DWM.exe) composites.
It turns out that DWM will sometimes decide to "help" you by drawing its own content over your client area (sort of like a BitBlt but even more perverse and even further out of your control).
So in order to be free of client area molestation, we still need to get WM_NCCALCSIZE under control but we also need to prevent DWM from messing with your pixels.
I was fighting with exactly the same problem and created a roundup Question/Answer which brings together 10 years of posts on this topic and offers some new insights (too long to paste the content here in this question). The BitBlt mentioned above is no longer the only problem, as of Windows Vista. Enjoy:
How to smooth ugly jitter/flicker/jumping when resizing windows, especially dragging left/top border (Win 7-10; bg, bitblt and DWM)?
For some controls, you can use WM_PRINT message to make the control draw into a DC. But that doesn't really solve your primary problem, which is that you want Windows to NOT draw anything during resize, but to let you do it all.
And the answer is that you just can't do what you want as long as you have child windows.
The way I ended up solving this eventually in my own code is to switch to using Windowless Controls. Since they have no window of their own, they always draw at the same time (and into the same DC) as their parent window. This allows me to use simple double buffering to completely remove flicker. I can even trivially suppress painting of the children when I need to just by not calling their draw routine inside the parent's draw routine.
This is the only way I know of to completely get rid of flicker and tearing during resize operations.
If you can find a place to plug it in, CWnd::LockWindowUpdates() will prevent any drawing from occuring until after you unlock the updates.
But keep in mind this is a hack, and a fairly ugly one at that. Your window will look terrible during resizes. If the problem you are having is flickering during resizes, then the best thing to do is diagnose the flickering, rather than hiding the flickering by blocking paints.
One thing to look for are redraw commands that get called too often during the resize. If you r window's controls are calling RedrawWindow() with the RDW_UPDATENOW flag specified, it is going to repaint then and there. But you can strip out that flag and specify RDW_INVALIDATE instead, which tells the control to invalidate the window without repainting. It will repaint at idle time, keeping the display fresh without spazzing out.
There are various approaches, but I found the only one that can be used generally is double buffering: draw to an offscreen buffer, then blit the entire buffer to screen.
That comes for free in Vista Aero and above, so your pain might be shortlived.
I am not aware of a general double-buffering implementation for windows and system controls under XP, However, here are some things to explore:
Keith Rule's CMemDC for double-buffering anything you draw yourself with GDI
WS_EX_COMPOSITED Window style (see the remarks section, and something here on stackoverflow)
there is only one way to effectively diagnose repainting problems - remote debugging.
Get a 2nd PC. Install MSVSMON on it. Add a post build step or utility project that copies your build products to the remote PC.
Now you should be able to place breakpoints in WM_PAINT handlers, WM_SIZE handlers and so on and actually trace through your dialog code as it performs the size and redraw. If you download symbols from the MS symbol servers you will be able to see full call stacks.
Some well placed breakpoints - in your WM_PAINT, WM_ERAGEBKGND handlers and you should have a good idea of why your window is being synchronously repainted early during the WM_SIZE cycle.
There are a LOT of windows in the system that consist of a parent window with layered child controls - explorer windows are massivly complicated with listviews, treeviews preview panels etc. Explorer does not have a flicker problem on resizing, so It is celarly possible to get flicker free resizing of parent windows :- what you need to do is catch the repaints, figure out what caused them, and, well, ensure that the cause is removed.
What appears to work:
Use the WS_CLIPCHILDREN on the parent dialog (can be set in WM_INITDIALOG)
During WM_SIZE, loop through the child controls moving and resizing them using DeferSetWindowPos().
This is very close to perfect, in my testing under Windows 7 with Aero.