I'm attempting to create a window class that supports fading in and out, even for child windows. Basically it adds the WS_EX_LAYERED style to the window, and then it calls SetLayeredWindowAttributes on a timer, gradually changing the alpha value.
That approach is okay, but of course the fading will become temporarily interrupted if there are higher priority messages that come through the thread's message queue. So, for example, if there's some resize event going on somewhere, the fading will slow or temporarily stop.
I'm wondering if there's a strategy to somehow avoid this. So far my only solution is to create the fadable window on its own thread, so the timer messages don't get interrupted by anything. That solution is feasible, but it does add some additional threading complexity, so I was hoping to avoid it if possible. Thanks for any input.
Related
I have a problem handling GLFW poll events. As far as I know, all user input events are handled via callbacks or via constantly checking keyboard / mouse states. The latter is not so efficient an can even result in missing some input (e. g. when button pressed and then released between checking state). What is more, some events like window resizing cannot be handled without callbacks.
So, the problem is that whenever user starts resizing window (presses mouse button but doesn't move mouse), the app seems to freeze. This is, assuming resize callback is enabled and defined validly (even when copied right from GLFW API). And the problem is not that window doesn't redraw. Redraw on callback can be done with creating and calling own render() function in callback function.
The actual problem is that even when I handle resize event properly and redraw on callback, there is still some lag. This lag is after mouse press on decorated window border and when mouse is not moving. Here's a demonstration (button click is highlighted green):
Sorry for messed up GIF. All callbacks listed in GLFW API are enabled and handled (window-, input-, joystick- and monitor-callbacks) and redraw is called in each one. It seems that I'm missing some of the callbacks or GLFW just works like that.
According to this answer, this can't be done without threading:
That only works when the user moves the mouse while holding - just holding left-click on the resize window part still stalls. To fix that, you need to render in a separate thread in addition to this. (No, you can't do that without threading. Sorry, this is how GLFW works, no one except them can change it.)
So, the questions are:
How can I fix this issue without threading? If I can't, I guess I can emulate resizing with different cursors shapes and resizing zones or smth like that...
If this is still impossible to solve in GLFW, do other GLFW alternatives have this issue?
Are there any problems with GLFW similar to this one?
GLFW is not at fault here. It's how the operating system handles certain user input events like mouse down on the decorator resize handles of a window or moving the whole window.
See this answer for a more elaborate detail: Win32: My Application freezes while the user resizes the window
GLFW uses the standard Windows PeekMessage -> TranslateMessage/DispatchMessage loop which you will find in any GUI Windows application. This will get invoked when you call glfwPollEvents() and it processes all Window event messages that the OS has accumulated so far for all windows in this process. After all messages so far have been processed, the call to glfwPollEvents() will return and will allow your own window/game loop to continue.
What happens is that once the user clicks down the window decoration's resize handles, effectively the call to glfwPollEvents() will block within the OS itself in order for the OS / window-manager to intercept the mouse and keyboard messages to do its window resizing/reshaping thing.
I'm afraid that even though Windows will inform the process about the start of a window resize or move action (after which the OS will have control of the window message processing) and GLFW already handling these events internally, right now GLFW will not notify the client application about this. It would be possible though for GLFW to provide an appropriate event callback to the application, so that the application can start a timer or thread only for as long as the window resize/move action happens (as is also mentioned in the linked other Stackoverflow answer).
So, the only thing that you can do in order to keep rendering while the user holds onto the resize handles or while the user moves the window around, is to render in a separate thread.
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.
In a display application we do use a large Window painting area. The display application gets so many updates for painting realtime data that all CPU time of the PC is used for painting. We do use InvalidateRect() and then paint the items in WM_PAINT message.
So we decided to use a dirty flag for each item to paint for reducing painting it.
How to know when the application can paint the items so that not all CPU time is consumed. Is there anything telling us that we can do our paint stuff now ?
If the data is updating so fast that painting each update is too much, you can use a timer. Every (say) quarter second, the timer fires, and if any items are dirty, the timer handler calls InvalidateRect(). Updating the data no longer invalidates; only the timer handler does that.
Edit: You could query Windows for the CPU load and if it's low, do the Invalidate immediately; see How to get system cpu/ram usage in c++ on Windows
One method I've used is to make sure that only one paint event is on the event queue at a time. You can use a boolean flag to mark when you begin updating and then reset the flag at the end of the WM_PAINT message (the end of the update process). Of course, if you try to update the window again and the flag is already set, then don't do anything. This will keep extra events from being piled into the queue, which can bog down your system. It looks like you may have thought of this, but do this with the entire update in addition to the individual items. Keep in mind that I'm only thinking of the updating of the windows themselves and not any underlying data.
One other thing I had to do was to "pump" (or process) the message queue during my (application) updates because updating a window (in my case) took several messages, ending with the WM_PAINT.
Another thing to watch out for is to not use idle messages for updating your interface. This is a quick and dirty way of having the update happen automatically, but ends up being a really bad idea because the idling only happens when there are no other events on the message queue. Of course, any time you move the mouse or press keys those events are placed onto the event queue and causes a "stall" of the update process. The idle events can end up coming so fast that it causes your application to use most of the CPU processing power just for displaying data that hasn't even changed. It's better to have your GUI only update when the underlying data it displays actually updates.
I had data coming in at 60Hz and updating lots of lists with columns of data as well as 3D stuff going on. I finally had to prioritize the updates and just not update the lists for each cycle, but DO update the 3D data each cycle. Updaing the lists at about 1-5 Hz was good enough for me and when combined with the techniques above resulted in a much improved and responsive system.
I have a problem with a progress bar that is implemented through adding a D2D object in MFC library.
I set up a message map to my function that keeps redrawing the progress bar based on some calculations:
BEGIN_MESSAGE_MAP(CProgressControl, CStatic)
ON_WM_PAINT()
ON_REGISTERED_MESSAGE(AFX_WM_DRAW2D, &CProgressControl::OnDraw2D)
END_MESSAGE_MAP()
My problem is that when the user locks out of the computer and the screen is asleep my drawing function does not seem to be called. It seems that the D2D notification message AFX_WM_DRAW2D is never sent to redraw when the screen is asleep.
I have tried to search for information on this online but did not find anything good about what might happen differently when the screen is asleep. I would appreciate any insight anyone might have on this.
Seems to me like this could be a normal behavior. Do you get any messages when your app is minimized or the computer is locked? I suspect that not.
Anyways, why should this bother you? Obviously your progress bar is invisible at the time, so why bother with the panting? You should be happy - Windows has an optimization for your program.
However if you do anything else besides painting in the painting messages, then I'd advise moving it elsewhere, as it is not that right place for it anyway. Paint message handlers should ONLY contain paint logic, and be prepared to be called at any time (or not at all).
Search the MFC sources for AFX_WM_DRAW2D and you'll see in wincore.cpp that the message is sent from a method called CWnd::DoD2DPaint() inbetween the render target's BeginDraw and EndDraw calls.
Therefore call DoD2DPaint to force a repaint. I did this on the sample CMFCD2DWalkthroughView (http://msdn.microsoft.com/en-us/library/gg482848.aspx) in the OnSize method to ensure that the gradient is updated and painted when the window is resized instead of the size/paint being out of sync.
I'm using SetTimer to create a timer in my application with an interval of 50ms, this timer is going to be used to draw an object, and move it around.
Now I don't want the object to move when the window is out of focus, but I still need it to be painted.
And having it paint every 50ms, seems unnecessary. And performance is extremely important in this project.
So I need a way to pause the timer, but still draw the object, but preferably only when needed.
When you get WM_ACTIVATE, decide whether to call KillTimer or SetTimer.
Just a note aside to you initial problem.
I would not rely on Windows Timer with such low resolution. It's a low priority message and if you have lots of heavy duty things going on in you program, the timer might be invoked at higher intervals that you expect.