Dose the ListBox in MFC framework have limited item length? If so, what is the limit?
There is a limit. For an owner draw one it's probably related to the limits of the GDI coordinate system.
However, long before you reach the ListBox limit, you reach the limit of good UI. Wide horizontally scrollable listboxes aren't easy to use. If you have very wide data to expose, consider another UI abstraction, like a tree or multicolumn list, and consider what kind of data your user actually needs to see.
Martyn
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I'm writing a GUI in python, and using tkinter. I'm having trouble settling on an approach and need guidance.
Background: there's a server (not a webserver) that wants to present a lot of information to users, and let them edit some of it. It needs to send down information that a (relatvely) dumb python client uses to fill the window. Read only fields are Labels. The fields are generally single line Entry widgets, but some are multiline Text. There are some buttons, checkboxes and dropdowns. Asynchronously, the server can also update widgets, add them and remove them. In some cases, there are tables presented, to which the user needs to be able to add and remove rows.
The real problem is, the layout is dense and chaotic. The first row might contain 3 dropdown fields. The next might be 20 short Labels. The next might be a single long Entry field, and then I might want two tables (of different lengths) side by side,and then etc.. Based on user input of external factors, widgets, rows or entire tables might have to be dyamically added, or vanish.
I considered Grid, but it's unusable. A row with a single, long entry widgit in it, makes the first column wide and thereby pushes 12 of the 13 columns in the next row right off the window.
I considered Place, but this app will run on 3 different operating systems and users will be able to select their own fonts, so I'll never get the positions right. If there was some way to ask a widget how big it was, I'd happily use that to compute my own layouts in pixels, but it's apparently impossible to ask the size of a widget until AFTER it's been laid out by a geometry manager, which of course is too late.
So what I think I'm left with is Pack, where each row is its own frame, and some of those rows have tables (grids) in them. But I'm concerned that that means lots and lots of frames to render, and some of the users are on old, slow hardware. Plus... it looks just plain complex.
Am I missing a better way? Grid would be fine if I could convince it to stop trying to make columns line up. Place would be crunchy, but ok, if I could get the size of each widget in advance. Is placing within a lot of frames really the best I have?
Short answer, there's no better way; and the frame count isn't high enough to cause performance problems; so generating a frame per row is what works.
My PyQt application pulls data from third party API calls. The dataset returned usually contains in the neighborhood of hundreds of items. On occasion, the dataset returned contains in the tens of thousands of items. On those occasions, the interface is painfully slow to display - too slow to be useful.
To speed things up, I would like to load less of the data during the initial load. I would like to be able to populate the interface based on the scrollbar handle position. I would prefer that the scrollbar have the correct range as soon as the widget is displayed, but as the user scrolls, the data that they should be seeing is populated into the widget (a QTreeWidget in this case). This is to say that I'd rather the user didn't have to scroll to the bottom of the widget to load more data at the bottom & therefore change the range of the scroll bar.
I believe QSqlTable behaves this way out of the box, but because I'm not relying on sql queries (and because some of the columns' data is calculated by the GUI), I don't believe I can use that module. Is this possible with QTreeWidget and w/o direct sql calls?
There is built-in functionality for this in Qt model-view framework. See QAbstractItemModel.canFetchMore() and QAbstractItemModel.fetchMore() here
Oh, I've just realised you aren't using MVF but stand-alone QTreeWidget instead. If you are dealing with large data and require such a functionality, a switch to MVF may be a right thing to do.
I want create a tree elements. For example, as this is figure
Can I use treeview, expandableview or NSOutlineView in monotouch?
Is there a tree of objects in monotouh?
There is no built-in or default control to represent a tree on iOS and frankly, you shouldn't really need one and most cases it should probably be avoided.
It's hard to fit a tree like control we have on our desktops in the touch world where you have huge fingers (so huge nodes) and with the nodes offset to show depth, there isn't much space left over. Adding it to the iOS environment would create a weird UX flow so you should re-think your design.
The common solution is to use tables with a detail accessory indicator and show a new controller the data (either a table or something else).
If you absolutely need one, you will need to roll your own. Check this for reference http://dotnet.kapenilattex.com/?p=566
I would like to implement a GUI handling a huge number of rows and I need to use GTK in Linux.
I started having a look at GTKTreeView with lists but I don't think that adding millions of lines directly to that widget will help in having a GUI that doesn't slow the application.
Do you know whether there is a GTK widget already in place for this problem or do I have to handle my self the window frame that that must display those lines? Eventually I would write the data directly using GtkDrawingArea (essentially writing a new widget).
Any suggestion about any GTK topic or project I can look as starting point for my research?
As suggested in the comments, you can use the Cell Data Func, and get the displayed data under contro. But I have another idea: Millions of lines are much much more than any amount of information a human user can see and understand. So maybe a better, more usable and user-friendly solution, is to diaplay the data in a way the users can more easily navigate in it.
Imagine opening a huge hierarchy, scrolling down, and forgetting what were the top-level items you opened.
Example for a possible solution: Have a combo box which allows to choose some filter or category, and this can reduce the amount of data to a reasonable amount the user can more easily navigate and make a mental model of it if necessary.
NOTE: As far as I know, GtkTreeView doesn't support sorting/filtering and drag-n-drop at the same time, so if you want to use both features, I suggest you use the existing drag-n-drop functionality (otherwise very complicated to implement by hand) and implement your own sorting/filtering.
Apologies if there is a thread for this already, I couldn't find one that I could get my teeth into.
Anyway, I'm new to WPF and want to create a custom control that will be a sort of graphic control. The graphic will always consist of a circle, containing a matrix of several squares (from several hundred to several thousand actually) The squares need to respond to mouse click and mouse over events (and ideally be possible to navigate/select via keyboard.) Each square will represent an object I've coded.
In the past I've used a grid control to display the coloured squares (with VCL in CBuilder) but I would like to make a graphical version. (Actually, another question I'd like to ask is, is there a WPF grid control where I can set the colours of individual cells?)
The question is, where to start? Do I start with a canvas and draw on it? Do I derive from an existing object? I'm just a little lacking on ideas on implementation so any pointers or advice you can offer will be greatly received.
BBz
First off I would suggest getting a decent handle on WPF and how it approaches the problem set. It is vastly different from previous .NET Desktop technologies such as WinForms. Once you have a decent understanding in regards to the separation of logic from UI and how WPF approaches the problem then you can dive in and begin making the right decisions based upon what you encounter.
The problem you mention can be solved in multiple ways. In regards to your question about making use of a Grid, that could be done as that is a layout type. It is vastly superior to the Canvas in terms of arranging your visual structure. The defined rows/columns are nothing more then containers which can hold varying UI objects. Therefore pushing a Rectangle into the Grid and coloring as desired would give you the effect you are looking for. This Rectangle could then become a custom control which would allow you to define varying properties on, as well as specific triggers for mouse overs, etc...
At a higher level you will want to encapsulate this logic as a UserControl which will also hold your custom control. Perhaps the UserControl contains the Grid which will make use of your custom control.
Hopefully this gives you some ideas around how to get started, however getting a better understanding of WPF will help you immensely in achieving your goal.