I have a styled QScrollBar on my table which uses an image for the handle of the scroll bar. The handle is rounded at the edges (with transparency in the image around the edges, of course). Now the problem is that i can't seem to make it re-size nicely.
It's a vertical scroll-bar, so the only way I found to work so far is to set:
background-image: url(:/res/img/scrollbar-vhandle.png);
background-repeat: repeat-y;
in my stylesheet. Which does what it's supposed to, only my scroll bar looks ugly, especially because of the rounded corners.
The image could be 'stretched' nicely by repeating a 1px high line from it's y-center. But even y-stretching should be ok. I just can't find a good way to do it.
Something like a QPushButton, where 9 images can be used for 1 button in order to scale would work, but unfortunately doesn't seem like it does.
So, if anyone can let me know if it's a way to do it through stylesheets (or deriving from QScrollBar, and repainting the handle) i'd appreciate it very much.
If you need more info, please let me know.
Well, as you say, you could inherit from the scrollbar and overload the paintEvent function. Therein you can pretty much to whatever you want, for example compute your new pixmap by repeating that one line and painting it. There are actually a couple of functions in QPixmap that should make this relatively easy.
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I'm making my own UI from scratch using OpenGL that is why I'm asking this and please don't make any discouragement as this is just a hobby project.
Currently, I'm stuck implementing how this scrollbars really work. In my current implementation, the content scrolls at the wrong step value as well as the thumb, meaning, I set the value manually like 1px step for each of them.
The structure of my scrollbar implementation is describe as follows:
I draw scrollbars i.e the main rectangle where the 3 button lies.
Those 3 buttons are, thumb, buttonBack and buttonNext.
All of them do the basic logic of scrollbars i.e when I click each one of them, they moved. But the whole part(scrollbar) don't know how to scroll contents
So what I did is: I make another object and I call it scrollarea
It has two scrollbars, vertical and horizontal scrollbar.
I made a function called scrollToX and scrollToY which
does what I named to them.
But the step values I set to them are
manually set up.
I try to google some scrollbar, scrollarea, scrollview or whatever you call to that scrollable rectangle thing, but all I see are implementation and I cannot find any guides how to build your own. I have no choice but to look at their implementation. I try my best to comprehend what they did but their implementation of how their whole UI structure is very different to mine, and I cannot find anything useful there.
So I ask again here if anybody can explain me well how to make a properly functional scrollbar.
Most specific things I'm really concerned of are:
How do I determine the thumb step value?
How do I determine the content step value?
All of these depend on your content -
Is it just an image ? If so, you only need to change the offset depending on the size of the image.
Is it a list of values like in Windows explorer ? Then you need to create a data structure first that contains all of it, and shows the content that fits within the window as it scrolls.
OpenGL does not fit into this discussion.
I'm having all sorts of size problems with Qt. I am creating my own widgets and using different layouts (generally, I need my own to make them work properly without spending hours on the "powerful" default layouts... which don't lay things out as intended.)
Once I'm done with a widget and its layout though, it doesn't work right. The size is never getting set properly unless I call widget->resize(1, 1); which finally forces a "resize" and makes the widget look correct (i.e. recompute the geometry.) Even the updateGeometry() call has no effect.
This is a dreadful problem when the resize() needs to be called on the parent widget (yuck!) and from what I'm reading should not be necessary were the layouts properly programmed.
Is there a sample that works and is not several thousand of lines long, or does Qt require several thousand lines to make anything work perfectly, even the simplest widget?
What are the minimal functions to be called to make a widget & its layout work at once?
Thank you.
Alexis
P.S. I tried to implement the sizeHint(), minimumSize(), maximumSize(), others that I'm missing? I was hoping that would be enough. Obviously, I also implement the setGeometry() on the layout to resize the children appropriately.
--- addition 1
There is a sample image with a layout that clearly isn't available as is in Qt. The positioning, functions, and colors of the different keys is XML driven and works for any keyboard in the world.
(note, this sample doesn't show the Enter key displayed on two rows and wider below than at the top; more or less, not doable at all with the regular layouts; of course, it works with my version.)
--- clarification
I'm not too sure how to describe the problem better. I was thinking to write a test widget next to see how I can reproduce the problem and then post that and eventually fix it. 8-)
The default layout function that the internal Qt layouts make use of require a lot of coding. I would like to avoid having to copy/paste all of that because for maintenance, it makes it close to impossible.
--- today's findings
As I needed to tweak one of the widgets, I decided to add a VBoxLayout and make it work.
I actually found the problem... One of the widgets in my tree is a QScrollArea and that sizeHint() returns (-1, -1). Not exactly what I'd expect but... whatever you put inside that widget has better know how to compute its width and height or else... it fails.
Looking at the code closely, I could actually compute the width by using the widest width found. Once I used that, the widget would appear (and it actually resizes itself as things change in the list, kinda cool.)
This being said, my earlier comment about having a tree of widgets that auto-resize themselves stands. From the root up to the parents of the leaves in your tree, all of those widgets will need a valid layout. Once I added one in the top widget it resized itself and its children properly (well... in my case up to the QScrollArea, the rest required a bottom to top resizing. Funny how that works!)
--- ah! ha! moment (or: what you find reading the implementation code!)
Today I bumped in another problem which just needed the correct call... I just couldn't find anything worth it in the documentation.
All the objects have a layout now, but a certain parent would not resize properly. Plain simple.
I had a call to the parent as following:
// changes to the children are changing the geometry
parentWidget()->updateGeometry();
Yeah. The docs says that's what you have to do. Nothing happens at all with that call. No idea what it's supposed to do, I did not look at that function. It never did anything for me anyway.
So... I looked at the layout to try to understand how it would send the info up/down. I did not see much except for one interesting comment:
// will trigger resize
This is said of the SetFixedSize mode. To reach that function you need to make the layout for update. Ah! Yes... the layout, not the parent widget... let's try that instead:
parentWidget()->layout()->update();
And voila! It resizes correctly in all cases I have. Quite incredible that the widget updateGeometry() doesn't trigger the same effect...
Although it's possible to do what you want it sounds like the problems you are having are because you're using Qt in a way that it's not meant to be used. Why do you need separate widgets for each key represented on the keyboard?
I see two options, both of which are better in some way:
Use QGraphicsScene and QGraphicsView.
A single custom widget that uses custom drawing to display the keyboard (and likely uses hover for hints).
The first option is probably better. Your keys could then be represented by QGraphicsSimpleTextItem's or even a QGraphicsSvgItem. It also provides a number of standard layouts or you could choose to write your own layout. By default you can use the keyPressEvent or mouseReleaseEvent to respond to user interactions.
I'd highly recommend you take a look at the QGraphicsView examples to get an idea what you can do.
If you go the second route you'll need to record the different key locations so you can respond accordingly as the user moves the mouse around, clicks, etc.
This won't help you with your immediate issue but I wanted to show you a keyboard I made using standard layouts and buttons. It's not perfect and it still won't help you with an enter key that spans two rows but it's not bad. It's resizable too by resizing the window, although I'm not sure if that will be apparent from the images below as SO may be scaling them. (you can view the actual images by opening them in their own tab)
Anyway, this was done using only Qt Designer with no manual coding. It consists of a top level vertical layout with 5 horizontal layouts in it. The buttons are then inserted into one of the 5 horizontal layouts. The size of the keys can be controlled by setting the horizontal and vertical size policies to "ignored" for most of the buttons and then horizontal "minimum" for buttons that you want to be wider. Things can be tweaked by setting min and max size restrictions to buttons. When resized, the buttons will not maintain their relative proportions though, that would probably take some custom programming.
The styling in your example could be approximated pretty well using css style sheets and background images. Still not a minor effort but you should be able to get most of the way there without custom layouts and buttons.
I've been using label to display images. I'd like to be able to click and create a bounding box then be able to drag the cursor to move around in the image. What would I need to do this? Thanks.
I'm not 100% sure I understand what you are trying to do, but I think the QGraphicsScene is what you are looking for. You can (among many other things):
Render images (QGraphicsPixmapItem, for example)
Change the zoom level when rendering the scene on a QGraphicsView.
Select things using a "rubber band"
Move items around with the mouse (see QGraphicsItem::ItemIsMovable)
etc.
You may need to get familiar with Qt's graphics view framework.
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.