I am working on drawing in the sliceViewers, which contains a RenderWindow. But if I enlarge or diminish the window, or change the layout of my module, the drawings become not fit. In other words, the drawing is misplaced when the sliceViewer size is changed.
And what I want is to monitor the size of the sliceViewer in realtime. Once it is changed in any scenrios, I rerender the drawing with the saved data.
I have searched something like observer of vtk or QtObject::connect(), but don't know whether they are really useful or not. Can they help or there is other method?
Thanks in advanced.
Related
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'm thinking like text fade in and slide effects. I imagine implementing this would be rather trivial and plan to do so myself, but wanted to make sure I'm not reinventing the wheel first. If it doesn't exist then I'm looking on advice on the best way to implement these.
The 2 things I'm looking to do are fade in text and have the window slide down when resizing, eg if I show a label that was previously hidden it would slide down ~20 pixels instead of just instantly growing 20 pixels larger.
The way I was thinking to implement the first one is, assuming it's possible, get the window/bg color and start it at that and transition it to the font color, if there's alpha channel support that would be even simpler to do (I'm not sure if there is since I haven't messed with colors yet). To do this I'd just choose a transition time period and process it with a for loop or something once the color increments have been determined.
Similarly to do the window transitions I would get the height of the change (not sure how to do that yet), determine the increments of change based on the transition time and in a for loop gradually adjust the size. Sorry if I didn't explain those very clear, I'm trying to get this in before I go to work and figure most of you will know what I'm trying to explain. As always thanks for the help!
For window resize transition effect, QPropertyAnimation may be the easiest to do since height is a widget property. Fading text might work the same way if the foreground color can be coerced into a property.
I have a QGraphicsView for a very wide QGraphicsScene. I need to draw the background in drawBackground() and the background is a bit complicated (long loop) although it doesn't need to be repainted constantly. I store it in a static QPixmap (I tried QImage too) inside the function drawBackground() and that pixmap is what I draw onto the painter of the view. Only when needed is the QPixmap painted on again.
If I didn't use a static pixmap, the complicated background would be generated every time I scroll sideways for example. The problem is that apparently there is a maximum width for pixmaps on Windows, on my computer it's 32770. I could store a list of pixmaps and draw them side by side but it would make the code uglier and I also don't know what the maximum width of a pixmap is for every Windows machine. Since this might be a well-known problem I was wondering if anyone has a better solution.
Thanks.
You can probably avoid the windows limit by using unaccelerated raster paint device, but 32770*1024 is 100MiB of pixmap; you probably don't want to do that even if Windows would let you.
You've already thought of the usual answer (tile it in more reasonably-sized chunks and load/generate them on demand). The other piece of the usual solution is to use something like QPixmapCache to keep the recently-used tiles so you don't regenerate them too often (only when the user scrolls a long way).
You didn't say how complex your complex background is, but you might also want to look at the Mandelbrot set example for how to do piecewise rendering of an (infinitely) large background pixmap on-demand, without blocking the UI.
This is the common use case for the tiling pattern. Basically you split the background into small images.
I'm not sure why you think "it would make the code uglier". It is certainly not a one-liner. Depending whether you have fixed size background image or not, the tiling code is usually pretty straightforward.
Im trying to do a screen-flashing application that flashes the screen depending on the audio(like an audio visualizer, but instead of a visualization like bars or something like that, just flash the screen).
I already made the music player and know how to make the widget get full screen and change color(which will flash), but I dont know how to detect the (I think it's audio-card)buffer is full, because when it is full I would change the color of the widget, and this would be really super fast, so the screen flashes super quickly.
Any ideas on how to detect if the buffer is full, or any other approach I might pursue to achieve my goal?
Thanks beforehand.
Have you checked the SoundMixer Class computeSpectrum method? It doesn't give you a buffer info rather it returns info about the sound being played that you can use in order to represent the sound graphically.
I subclassed QGraphicsItem and reimplemented paint.
In paint I wrote something like this for labeling the item:
painter->drawText("Test",10,40);
After some time I think It may be useful to handle labeling with seperate item. So I wrote something like this.
QGraphicsTextItem *label = new QGraphicsTextItem("TEST",this);
setPos(10,40);
But two "TEST" drawing do not appear in the same place on screen. I guess difference may be related with item coordinates - scene coordinates. I tried all mapFrom... and mapTo... combinations inside QGraphicsItem interface but no progress. I want to drawings to appear in the same place on screen.
What I miss?
I assume that you are using the same font size and type in both cases. If the difference in position is very small the reason can be the QGraphicTextItem is using some padding for the text it contains. I would try to use QGraphicsSimpleTextItem that is not going to add fancy stuff internally and see if you still have the same problem. The coordinates system is the same one if you use painter or setPost so that is not the problem. If this doesn't help I will suggest to specify the same rect for both to avoid Qt adding it owns separation spaces.