I am trying to implement a TreeView where the item texts have a colored background and a frame. I do not want to put the frame around the whole item, but only around the text. Please have a look at this mock-up:
https://www.dropbox.com/s/irl8hedyxy520yy/screenshot.jpg
(a) looks like what I would like to achieve.
I understand that I have at least the following options:
(a) Replace the items of qtreeview with qLabel widgets.This is possible, but I believe that creating a widget for each and every item is a bad idea. I read somewhere else that an item delegate should be used in this case, and only the visible items should be widgets. That is going to be complicated.
(b) Use a stylesheet.It seems very simple and elegant, but I do not manage to frame only the text, and not the item which fills the whole column (see screenshot)
(c) Use a qStyledItemDelegate and paint the boxes and texts as I wish.Certainly possible, but requires a lot of code and complexity.
What would be the most elegant way to solve this?
I am using ruby, qtbindings, and Qt4.8, but my question is about Qt in general, not about the implementation with ruby.
Thanks for any help,
Bogl
Related
I'm writing a messenger, and there is a message feed there. As you all know message feeds usually look like lists and go from bottom to top, the keep the scrolling positions anchored to the bottom when a new element is added, they grow upwards when resized and all kinds of fancy behavior like that.
So, I wanted to use QListView to make the feed, I have a model written elsewhere, it's absolutely under my control. But it doesn't seem like QListView supports this mode. There is a trick of how to do it with QML, but I don't have QML used anywhere else in my project and I'm not sure of how to interact with it, like how to set there my model, how to listen for signals or if it's going to behave well in my QGridLayout where I want it to place.
I can't believe no one ever faced the same situation. I'm trying to find the most standard solution, involving as little of my rookie code as possible, keeping in mind that Qt guys are much more experienced in layouting elements in list view and handling all corner cases. If I'm correct my options are
Use QML for the feed
Try to rotate QListView with QGraphicScene tricks
Reimplement QListView
Which of those you think is a better solution? Or, may be, someone knows some better way to do it?
This is a follow-up question of Making an editable flowchart in Qt/C++.
I want to add a QGraphicsItem to a QGraphicsGridLayout in a way that the item takes up its own spot in the grid and then automatically centers in its 'cell'.
I am using QGraphicsView and QGraphicsScene, and drag-and-drop to any location works, but it's looking messy, and could prove to be problematic in future development.
What do I have to do so the item snaps to the grid and centers in its cell?
PS: I have taken a look at http://qt-project.org/doc/qt-4.8/graphicsview-basicgraphicslayouts.html as an example but this didn't help me to solve my problem.
Also, it'd be ideal to have this layout and its data be savable to a text file, etc. I'm assuming a 2D array would be the best way to do this. Should I somehow make the QGraphicsGridLayout based on that array, or is there a better solution?
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.
Is there a way to get a resize effect between two widgets? Like say I have two QTextEdit boxes next to eachother, I want to get a handle between them so I can move it back and forth. Sort of in the same way that the textarea I'm writing in now has a handle at the bottom for making it larger.
I'm using QT Creator and I can't seem to figure this out. I got something similar to what I want by using a QDockWidget, but that really doesn't seem like the purpose for which it was intended.
What you need is a QSplitter.
I have a custom Qt widget which I used to display disassembly and I am looking to add syntax coloring to it.
Currently, I simply set the QPen to a solid color, construct the text I want to display, and render it to the QPainter at the appropriate coordinates.
The question is, what is the best approach to adding syntax coloring? I've thought of a few:
I could simply divide the coloring into logical blocks, each preceded by setting the QPen to the desired color.
I could have special escape characters which represent a change in the color palette, and render 1 character at a time.
I could do a modification of #1 and create a list of std::pair<QColor, QString>, then I could simply iterate the list setting the color and drawing the text as I pop items off the front of the list.
Something entirely different?
I know that each of the 3 approaches I've listed will technically work, but I'm looking for a very efficient solution. This code will be called a lot. And since this is an interactive debugger, if this code is slow, someone rapidly stepping or tracing will see a visible slowdown.
EDIT: I'm aware of QSyntaxHighlighter and QTextDocument. The main issue is that these don't generally suite my purposes very well. I have several columns which all have dividers and can be slid back and forth. To give you an idea, Here's a link to a screenshot of my debugger. As you can see it isn't really like a text document at all. In fact it is closer to a list or table. But there is already a bunch of custom drawing going on making a normal QTextDocument somewhat impractical.
EDIT: I was incorrect, It seems that QTextDocument can render directly to a QPainter. Looks like what I need!
EDIT: It is unclear how to control where and how QTextDocument or QTextLayout will draw on a QPainter. I've attempted to use them to no avail. So if someone could provide a rudimentary example, that would be very helpful.
EDIT: I was eventually able to get what I wanted using something like this:
painter.setPen(default_color);
QTextDocument doc;
doc.setDefaultFont(font());
doc.setDocumentMargin(0);
doc.setPlainText(text);
highlighter_->setDocument(&doc);
painter.save();
painter.translate(x, y);
QAbstractTextDocumentLayout::PaintContext context;
context.palette.setColor(QPalette::Text, painter.pen().color());
doc.draw(&painter, context);
painter.restore();
Qt provides a QSyntaxHighlighter that is probably exactly what you want. QSyntaxHighlighter uses a QTextDocument to mark each block of code with a specific state which can be associated with a specific presentation format.
The documentation on QSyntaxHighlighter provides a sample demonstrating how this may be accomplished and does some nice things:
Separates the model from presentation
Separates the formatting into different reusable classes (if implemented as such)
Supports the State design pattern if useful to your language
I'd use either QTextEdit or directlay its underlining engine QTextDocument.