In: C++\Win32 application (not in fullscreen)\DX9
How can i redraw window content during resize fast and nice enough? Resize == user drag window border.
Different approaches:
Reset device on each WM_SIZE\WM_PAINT. Adequate resolution, but black stripes appears on fast upscale.
Reset device on WM_EXITSIZEMOVE and pause rendering on WM_ENTERSIZEMOVE. Best speed, but to ugly ~ black stripes during resize.
Can't find out how to use dx9's swapchain in this case
Keep rendering and swapping buffers during resize; reset on WM_EXITSIZEMOVE. Exactly what occurs in official demos from 2010 SDK. Looks fast and acceptable nice. But [suddenly] on slow computer black stripes reappeared. Thin and rare, but real. Actually, thats very strange: synchronous rendering and Present(,,,) on every WM_SIZE and\or WM_PAINT excludes that at first glance. And at the second. Perhaps i dont understand something important?
So, when last method failed i decided to ask here. Is that possible somehow make dx9 surface securely glued to window border. No black stripes. Prefer to slow scale speed down, but sync it somehow with DX.
I allocate a backbuffer large enough for the maximum client size of the window, and set a viewport that matches the current window client size on WM_SIZE. Then I render to resp. present from that viewport only. This way no device reset is required.
Related
My OpenGL screen consists of 2 triangles and 1 texture, nothing else. I'd like to update the screen as little as possible, to save power and limit CPU/GPU usage. Unfortunately, when my draw_scene routine returns early without drawing anything, the OpenGL screen goes black-- even if I never call glutSwapBuffers. My background color is not black by the way. It seems that if I do not draw, the OpenGL window loses its contents. How can I minimize the amount of drawing that is done?
Modern graphics systems assume, that when a redraw is initiated, that the whole contents are redrawn. Furthermore, if you get a redraw event from the graphics system, then that's usually because the contents of the window have become undefined and need to be recreated, so you must redraw in that situation.
To save power you have to disable the idle loop (or just pass over everything that does and immediately yield back to the OS scheduler) and don't have timers create events.
I have a wxWidgets application that has a number of child opengl windows. I'm using my own GL canvas class, not the wx one. The windows share their OpenGL context.
I don't think the fact it is wxwidgets is really relevant here.
The opengl windows are children of a windows that are siblings of one another, contained within a tab control. Kind of an MDI style interface, but it is not an MDI window.. Each one can be individually resized. All works lovely unless Aero is enabled and the DWM is active.
Resizing any window (not even the opengl ones) causes all of the opengl windows to flicker occasionally with a stale backing-store view that contains whatever rubbish has been on the screen at that point that is not opengl. This ONLY happens with Aero enabled.
I'm pretty certain that this is the DWM not actually having the opengl contents on its drawing surface backing store and the window not being repainted at the right moment.
I've tried so many things to get round this, I do have a solution but it is not very nice and involves reading the framebuffer with glReadPixels into a DIB and then blitting it to the paint DC in my onPaint routine. This workaround is only enabled if DWM is active but I'd rather not have to do this at all as it hurts performance slightly (but not too bad on a capable system - the scenes are relatively simple 3d graphs). Also mixing GDI and opengl is not recommended but this approach works, surprisingly. I can live with it for now but I'd rather not have to. I still have to do this in WM_PRINT if I want to take a screenshot of the child window anyway, I don't see a way around that.
Does anyone know of a better solution to this?
Before anyone asks I definitely do the following:
Window class has CS_OWNDC
WM_ERASEBACKGROUND does nothing and returns TRUE.
Double Buffering is enabled.
Windows have the WS_CLIPSIBLINGS and WS_CLIPCHILDREN window styles.
In my resize event handler I immediately repaint the window.
I've tried:
Setting PFD_SUPPORT_COMPOSITION in the pixel format descriptor.
Not using a wxPaintDC in the paint handler and calling
::ValidateRect(hwnd, NULL) instead.
Handling WM_NCPAINT and excluding the client area
Disabling NC paint via the DWM API
Excluding the client area in the paint event
Calling glFlush and/or glFinish before and after the buffer swap.
Invalidating the window at every paint event (as a test!) - still
flickers!
Not using a shared GL context.
Disabling double buffering.
Writing to GL_FRONT_AND_BACK
Disabling DWM is not an option.
And as far as I am aware this is even a problem if you are using Direct3D instead on OpenGL, though I have not tested this as it represents a lot of work.
This is a longshot, but I just solved exactly this same problem myself.
The longshot part comes in because we're doing owner draw of the outline of a captionless group box that surrounds our OpenGL window (i.e., to make a nice little border), and that may not describe your case.
What we found caused the problem was this:
We had been using a RoundRect() call (with a HOLLOW_BRUSH) to draw the outline of the group box. Changing it to a MoveToEx() and LineTo() calls to ensure JUST the lines are drawn and nothing gets done inside the group box kept the GDI from trying to unexpectedly repaint the whole content of the control. It's possible there's a difference in invalidation logic (or we had a bug somehow in loading the intended hollow brush). We're still investigating.
-Noel
My app has only a single OpenGL window (the main window) but I ran into some nasty DWM tearing issues on window resize and I wonder if one of the solutions may work for you.
First of all, I found that during window resize there are at least two different bad guys who want to "help" you by modifying your client area before you have a chance to update the window yourself, creating flicker.
The first bad guy dates back to a XP/Vista/7 BitBlt inside the SetWindowPos() that Windows does internally during window resize, and can be eliminated with a trick involving intercepting WM_NCCALCSIZE or another trick involving intercepting WM_WINDOWPOSCHANGING.
In Windows 8/10 we still have that problem but we have a new bad guy, the Aero DWM.exe window manager, who will do his own different kind of BitBlt when he thinks you are "behind" updating the screen.
I suspect that the rubbish pixels you are seeing might actually be an intentional and very very poor attempt by DWM to fill in something "acceptable" while it waits for you to draw. I discovered that DWM extends the edge pixels of old client area data when it blits the new client area, which is insane.
Unfortunately, I don't know of any 100% solution to prevent DWM from doing this, but I do have a timing hack that greatly reduces the frequency of it.
For source code to the WM_NCCALCSIZE/WM_WINDOWPOSCHANGING hack as well as the DWM timing hack, please see:
How to smooth ugly jitter/flicker/jumping when resizing windows, especially dragging left/top border (Win 7-10; bg, bitblt and DWM)?
Hmm, maybe you have ran into the same issue: if you are using "new" MFC
it will create and application with Tabs and Window Spliter.
The splitter has some logic (I am guessing somewhere around transparent window and drawing XOR
lines for the split) that causes this behavior. Remove the splitter to confirm it resolve
your issue. If you need split functionality -- put in a different splitter.
Also Tabs allow docking and again splitting the windows that has the same issue -- remove/replace.
Good luck,
Igor
I am haveing trouble understanding the concept of the UpdateLayaredWindow api, how it works and how to implement it. Say for example I want to override CFrameWnd and draw a custom, alpha blended frame with UpdateLayeredWindow, as I understand it, the only way to draw child controls is to either: Blend them to the frame's Bitmap buffer (Created with CreateCompatibleBitmap) and redraw the whole frame, or create another window that sits ontop of the layered frame and draws child controls regularly (which defeats the whole idea of layered windows, because the window region wouldn't update anyway).
If I use the first method, the whole frame is redrawn - surely this is inpractical for a large application..? Or is it that the frame is constantly updated anyway so modifying the bitmap buffer wouldn't cause extra redrawing.
An example of a window similar to what I would like to achieve is the Skype notification box/incoming call box. A translucent frame/window with child contorls sitting ontop, that you can move around the screen.
In a practical, commercial world, how do I do it? Please don't refer me to the documentation, I know what it says; I need someone to explain practical methods of the infrastructure I should use to implement this.
Thanks.
It is very unclear exactly what aspect of layered windows gives you a problem, I'll just noodle on about how they are implemented and explaining their limitations from that.
Layered windows are implemented by using a hardware feature of the video adapter called "layers". The adapter has the basic ability to combine the pixels from distinct chunks of video memory, mixing them before sending them to the monitor. Obvious examples of that are the mouse cursor, it gets super-imposed on the pixels of the desktop frame buffer so it doesn't take a lot of effort to animate it when you move the mouse. Or the overlay used to display a video, the video stream decoder writes the video pixels directly to a separate frame buffer. Or the shadow cast by the frame of a toplevel window on top of the windows behind it.
The video adapter allows a few simple logical operations on the two pixel values when combining their values. The first one is an obvious one, the mixing operation that lets some of the pixel value overlap the background pixel. That effect provides opacity, you can see the background partially behind the window.
The second one is color-keying, the kind of effect you see used when the weather man on TV stands in front of a weather map. He actually stands in front of a green screen, the camera mixing panel filters out the green and replaces it with the pixels from the weather map. That effect provides pure transparency.
You see this back in the arguments passed to UpdateLayeredWindow(), the function you must call in your code to setup the layered window. The dwFlags argument select the basic operations supported by the video hardware, ULW_ALPHA flag enables the opacity effect, the ULW_COLORKEY flag enables the transparency effect. The transparency effect requires the color key, that's specified with the crKey argument value. The opacity effect is controlled with the pblend argument. This one is built for future expansion, one that hasn't happened yet. The only interesting field in the BLENDFUNCTION struct is SourceConstantAlpha, it controls the amount of opacity.
So a basic effect available for a layered window is opacity, overlapping the background windows and leaving the partially visible. One restriction to that the entire window is partially opaque, including the border and the title bar. That doesn't look good, you typically want to create a borderless window and take on the burden of creating your own window frame. Requires a bunch of code btw.
And a basic effect is transparency, completely hiding parts of a window. You often want to combine the two effects and that requires two layered windows. One that provides the partial opacity, another on top and owned by the bottom one that displays the parts of the window that are opaque, like the controls. Using the color key to make its background transparent and make the the bottom window visible.
Beyond this, another important feature for custom windows is enabled by SetWindowRgn(). It lets you give the window a shape other than a rectangle. Again it is important to omit the border and title bar, they don't work on a shaped window. The programming effort is to combine these features in a tasteful way that isn't too grossly different from the look-and-feel of windows created by other applications and write the code that paints the replacement window parts and still makes the window functional like a regular window. Things like resizing and moving the window for example, you typically do so by custom handling the WM_NCHITTEST message.
I want to create my own tiny windowless GUI system, for that I am using GDI+. I cannot post code here because it got huge(c++) but bellow is the main steps I am following...
Create a bitmap of size equal to the application window.
For all mouse and keyboard events update the custom control states (eg. if mouse is currently held over a particular control e.t.c.)
For WM_PAINT event paint the background to offscreen bitmap and then paint all the updated controls on top of it and finally copy entire offscreen image to the front buffer via Graphics::DrawImage(..) call.
For WM_SIZE/WM_SIZING delete the previous offscreen bitmap and create another one with new window size.
Also there are some checks to prevent repeated drawing of controls i.e. controls are drawn only when it needs repainting in other words when the state of a control is changed only then it is painted e.t.c.
The system is working fine but only with one exception...when window is being resizing something sort of tearing effect appears. Now what I mean by tearing effect I shall try to explain ...
On the sizing edge/border there is a flickering gap as I drag the border.It is as if my DrawImage() function returns immediately and while one swap operation is half done another image drawing starts up.
Now you may think that it is common artifact that happens in many other application for the fact that resizing backbuffer is not always as fast as resizing window are but in other applications I noticed in other applications that although there is a leg between window size and client area size as window grows in size nothing flickers near the edge (its usually just white background that shows up as thin uniform strips along the border).
Also the dynamic controls which move with window resize acts jerky during sizing.
At first it seemed to me that using a constant fullscreen size offscreen surface could minimize the artifact but when I tried it results are not that satisfactory. I also tried to call Sleep() during sizing so that the flipping is done completely before another flip starts but strangely even that won't worked for me!
I have heard that GDI on vista is not hardware accelerated, could that might be the problem?
Also I wonder how frameworks such as Qt renders windowless GUI so smoothly, even if you size a complex Qt GUI window very fast negligibly little artifact appears. As far as I know Qt can use opengl for GUI rendering but that is second option.
If I use directx then real time resizing is even harder, opengl on the other hand seems to be nice for resizing without any problem but I will loose all the 2d drawing capability of GDI+.
If any of you have done anything like this before please guide me. Also if you have any pointer that I should consider for custom user interface design then provide me the links.
Thanks!
I always wished to design interfaces like windows media player 11 but can someone tell me that there is a straight forward solution for a c++ programmer (I want to know how rather than use some existing framework etc.)? Subclassing, owner drawing, custom drawing nothing seems to give you such level of control, I dont know a way to draw semitransparent control with common controls, so I think this question deserves some special attention . Thanks again.
Could it be a WM_ERASEBKGND message that's causing it?
see this question: GDI+ double buffering in C++
Also, if you need fast response from your GUI I would advise against GDI+.
I have a top-level Qt widget with the FramelessWindowHint flag and the WA_TranslucentBackground attribute set. It has several children, each of which draws an image on it. They are not in a layout. Instead, I simply move them around when something changes (it is not user-resizable).
There are two states to the window - a big state and a small state. When I switch between them, I resize the window and reposition the children. The problem is that as the window resizes, a black box is briefly flashed on the top-level window before the images are painted over it.
The problem goes away if I disable Aero. I found brief mention of this problem being fixed in an article describing a new release of Qt (this release is long past), but it still doesn't work.
Any ideas why?
Thanks!
I don't have experience with Qt specifically, but I have worked with other windowing toolkits. Typically you see this kind of flashing when you are drawing updates directly to the screen. The fix is to instead use Double buffering, which basically means that you render your updates into an offscreen buffer (a bitmap of some sort, in the purest sense of the word), and then copy the entire updated image to screen in a single, fast operation.
The reason you only see the flickering sometimes is simply an artifact of how quickly your screen refreshes versus how quickly the updates are drawn. If you get "lucky" then all the updates occur between screen refreshes and you may not see any flicker.