I am working on an application using Qt5 in which you can free hand draw arbitrary shapes in vector graphics, move them and and partially remove parts (just like an eraser in Microsoft paint).
I draw the shapes in QGraphicsScene by adding QGraphicsPathItem and move them using the QGraphicsItem::ItemIsMovable flag. The question of the eraser remains.
Has anyone faced the task of partial removal of QGraphicsPathItem? Especially in a situation when we divide the figure into two (or more) parts with an eraser and these should become separate new QGraphicsPathItem ? Is it possible to implement it?
Thanks for any help!
Coincidentally, I am making a similar application. My app only involves d0freehand drawing. I am using mouse events to add or erase. I started with this and modified it alot. I am keeping a using a selection buffer to select an object and using matrices to move them.
To answer your question, for partially erasing :
Divide previous item two items
Delete the previous item.
Redraw the new items.
Related
I am having trouble getting my simple JavaFX Maze Game to work. I just wanted to do this to test how much I knew, and I have gotten almost to the end.
All I want to do now is see if there is a way for me to combine all of the Rectangle2D Boundaries into a single bounding shape for me to do collision detection with.
Right now, I have maze walls set up like
this, and I have to check for collision against every single one of the wall objects, which I have contained in a list.
What I want to know is there anyway of turning that into a single shape that I can check collision against. That would make my job so much easier when it comes to finishing my game.
EDIT 1: The red boxes in the image are just there to represent the Rectangle2D bounding boxes. They will not actually be there in the final product.
EDIT 2: All of these have been created using a simple black square sprite, and all of the bounding Rectangle2D boxes are using the javafx.geometry package, not the javafx.scene.shape package.
Any help would be appreciated. Thanks in advance!
Do you mean union many shapes into one?
Thanks to the help of the comment thread on Powercoder's answer, I was able to get it figured out. Instead of using javafx.geometry classes, I was able to switch to javafx.scene.shape classes, which allowed me to finish everything I was trying to do.
Here is my old code: https://pastebin.com/1DBXuq79
and here is my new code: https://pastebin.com/uXTrcsZ2
For anybody who wants to compare and figure out how I changed it.
I am learning Qt5 using PyQt.
My goal is to create a UI with several goals (I will base my need on the screenshot below).
So here are my goals:
My need
Add directories to a list of directories to be scanned (I know how to use QFileDialog.getExistingDirectory for that). For this I'd like to have a "+" button.
When pressed the QFileDialog would open and a new row would be added.
Then I would scan the directory to look for files. It won't be my first implementation but I'd like to have a circular progress bar being displayed during the scan (at the place of the classic progress bar).
When the scan is done, the UI would display the number of files found during the scan. And the progress bar would be replaced by a tick mark icon (not shown on the screenshot...).
At the beginning of each row, I'd like to have a "-" button to delete the row.
My goal is to learn
This is important, I know I am not the first one to have the idea of such a UI.
So I not looking for a third party lib on top of Qt.
My goal is to learn Qt5 (with PyQt) with this example.
But if its unrealistic, please tell me!
My knowledge
Mode View: I implemented some basic model view widgets to display strings, and I understand how to extend the idea to tables or trees.
In this case the number of rows in the table would be handled automatically.
But is it possible to created a table that would display not only strings but also widgets?
Widget Mapper: I read that another methodology is the QDataWidgetMapper. In this case, I would have to deal with creation of news rows by myself, and then I would map data onto them.
But it seems to be a hard and long job.
So, is it a good idea?
So finally could someone tell what is the best direction for that?
I am not looking for code, but since it takes a lots of time to learn new concepts, I'd like to learn and use the correct one before starting coding.
Thank you for your help :)!
After so more searches, I found that I need to use the delegate methodology.
In Qt5 it's QStyledItemDelegate and in Qt4 it's QItemDelegate.
I could find a nice tutorial at the moment, but I started coded it.
I have a lot of 2D, time-variant data (aka a movie) that I'd like to visualise inside a Qt interface. The idea is that the results can be viewed as a movie, browsed using a time-slider and then individual data points should be selectable to get more information about that point. (The data being shown is generated from simulations, and then converted to RGB through some colormap, so I'm not really looking for a component that plays mp4)
I have some experience using a QGraphicsScene, which makes it easy to get the cursor location & react to mouse events. But is it suitable for video? Or am I better off with some kind of QImage directly on a widget?
Ok, so it works well in PyQt, not so well in PySide.
I'm using a QPixmap wrapped in a QPixmapItem that gets added to the scene. To update the frame, I change the contents of the pixmap object and call update() on the scene.
Performance is good enough for video (although I don't need high frame rates for this project).
In PySide I ran into weird issues when I used more than 1 pixmap item, in PyQt it works just fine.
I want to use Qt to draw lines in chalk style, as you typically see on a blackboard. Here is an example of what I have in mind:
What is the best way to achieve this rendering style? Do I need to draw a lot of little lines with a special brush, or is there a better way to get the "curvy" style you see in the sample image?
And where is the best place to integrate this? Theoretically it would be ideal to get this underneath QPainter, e.g. in a custom QPaintEngine, so that e.g. all the various QPainter::drawLine calls end up using the chalk style. However, it seems while the QPaintEngine interface looks perfect for this, the class itself isn't meant to be used for this purpose...
Thanks in advance for any help.
Greetings,
Fabian
I have solved the problem in a different way. Using textured brushes didn't provide good results (maybe my fault). QGraphicsEffect was unfortunately not an option since my rendering is not based on QGraphicsView.
What I have done in the end:
Derived an own class from QPainter (i.e. ChalkPainter)
Added a new drawChalkLine() method to ChalkPainter. This method takes the passed line, splits it into smaller chunks and renders these chunks as bezier curves via QPainter::drawPath. For each bezier curve chunk I randomly shift the control point orthogonal to the line.
Next I added additional rendering methods to the ChalkPainter class, such as drawChalkRect(), all internally using the drawChalkLine() method.
This is not the most elegant method since I can't use the QPainter methods directly, but it provides good results for my purpose. Here is an example:
I would start looking in QGraphicsEffect's way.. I think it should be possible to develop such a filter which will produce similar effect..
I'll update in here answer on your comment.
No, QGraphicsEffect can be applied 'per graphics item'. If you have a look on QGraphicsItem you will see that there is a setGraphicsEffect method, so you can design an effect which works on QGraphicsLineItem for example and set it only on lines you want to look chalky..
Important thing is that you don't have to operate on pre-drawn image, you can either make it completely owner-draw item with graphicsEffect (for example make an assumption that effect is only applicable on QGraphicsLineItem) pre-draw it using drawSource() and then modify OR draw it completely from scratch..
I would love to help you with some coding, probably will do it somewhere around next week, since I will need similar thing for project I am working on now.. but physically don't have time next few days..
I'll update an answer with sources link as soon as it's done.
Custom brush also looks really promising..
What is the best starting point for a Qt4 widget for entering Latitude/Longitude in DD:MM:SS format (degrees, minutes, seconds)? Customize a QLineEdit? A series of spin boxes?
There are some variants:
QLineEdit with Validator - wasn't good enough for us, we couldn't achieve usable editing and proper view (with ', '' and degree symbols in place and ability to forbid incorrect values and still allow semi-correct states, and the target behaviour is not to mark errors and force user to fix them, but to allow user to enter only valid values).
Three spin edits in a line with the proper symbols between them grouped as a single widget and some code to move keyboard input from one no next when needed etc. Looks good enough in some cases, and you can find the variant of realization in the famous Marble project.
Still, my boss said that this approach is almost as ugly as first, so here is another approach: subclass QAbstractSpinBox, as Trolltech did in their QDateTimeEditor. In fact, behaviour of such a widget is near similar to one, implemented in QDateTimeEditor.
I, myself didn't do it yet, cause of task priorities, but will have to do.
I would use a QValidator, attaching it to a QLineEdit using QLineEdit::setValidator().
You'll need to subclass so you can implement the validate() function and possibly the fixup() function for your particular case, since the two validators included with Qt only cover integers and doubles.
It's a bit friendlier, in my opinion, to provide a single input box for this rather than three separate spin boxes (which could look cluttered and isn't as nice to type in).
[Edit: One other alternative is to set a "validation input mask" on your QLineEdit using QLineEdit::setInputMask(). You might want a line edit with symbols already in place and placeholders for other characters, for example, and this approach will give you something similar to that. The QtDemo app has an example of this which you can check out by choosing Widgets->Line Edits (Widgets is on the second page).]