I've been trying to build the Blink browser engine without any luck. Does anyone know how to create a simple window in Linux that opens an URL or renders an HTML file?
I'd suggest having a look at CEF library which enables just that - rendering content in window using, as a part of it, the Blink engine.
When it comes to running the engine itself it's tricky - mostly becase Blink can do little on its own, most of the functionality is provided by Chromium platform - this includes network I/O, fonts and images processing, rendering, user input handling and so on.
Related
Looking around at some SDL games and emulators I notice that each time there's an android version of it, same base code is used as the desktop versions.
For example in an atari 7800 emulator I've found on github, I don't really understand java and I'm trying to see how it's done there. I suppose that based on the line 991 it captures the display from the sdl2 process maybe by running it headless and rendering the sdlwindow in android?
No idea, trying to understand the code but I'm like looking at it like a cat looking at a calendar (a saying in my country).
What I'm trying to do is to somehow archive the same thing in QT5 since the platform I'm using uses it for the interface and anything app related to communicate with their APIs.
I am writing an application using Qt and want to try and deploy it as a web-application. I want user's to be able to use my application by accessing it through a web browser. I'm guessing that's what a web-application is? What kind of options do I have? I've never looked into doing anything like this but I'd like to learn something new.
EDIT: What if I deployed my application on a Linux server and had users access/run it through a terminal? I think writing web application is going to be more complicated than I had originally thought.
If all you have is a Qt application, then the best you can do is use Qt 5 and run it using a remote visualization package:
Use WebGL streaming, introduced in Qt 5.10. Qt exposes a browser-connectible interface directly, without need for third-party code.
For Qt 5.0-5.9, you can use the vnc platform plugin. Then connect using a web-browser based vnc client.
For many uses it might be sufficient, and certainly it's much less effort than coding up a web app.
You're looking for Wt which provides a different set of drawing routines for many Qt GUI elements, turning them from lines on screen to HTML controls.
http://www.webtoolkit.eu/wt
It also handles websocket calls to provide interactivity. It seems a great idea, let us know how it works in practice.
For the case of QML there is QmlWeb which is a JavaScript library that is able to parse QML-code and create a website out of it using normal HTML/DOM elements and absolute positions within CSS, translating the QML properties into CSS properties.
QmlWeb is a small project by Lauri Paimen that he’s already developing for a few years now. QmlWeb of course doesn’t yet support everything Qt’s implementation of QML does, but it already supports a quite usable subset of it. It supports nearly all of the most basic QML syntax. Moreover it has support for HTML input elements (Button, TextInput, TextArea are currently supported, more to come).
Well, QmlWeb is not finished. I hope Digia help with this project to make it ready with mature features.
Interestingly, it is possible to compile Qt applications to javascript using emscripten-qt. These run fairly fast with Firefox's asm.js interpreter:
http://vps2.etotheipiplusone.com:30176/redmine/projects/emscripten-qt/wiki
Try "Qt for Webassembly".
Webassembly allows the C/C++ code to be compiled and run natively inside majority of the browsers:
WebAssembly (Wasm, WA) is a web standard that defines a binary format and a corresponding assembly-like text format for executable code in Web pages. ... It is executed in a sandbox in the web browser after a verification step. Programs can be compiled from high-level languages into Wasm modules and loaded as libraries from within JavaScript applets ... Its initial aim is to support compilation from C and C++, though support for other source languages such as Rust and .NET languages is also emerging.
To run a Qt application unchanged over the web so users can operate it in a browser, you can compile it for Android using the x86 Android ABI, run it inside an Android emulator on a server and supply the Android Cast videostream to users' browsers. You'll also need to have JavaScript in place that records the keyboard and mouse events on the web clients and relays them back to the server.
I had previously tried Qt WebGL streaming and found it to be good over the local network but too slow over the Internet. A 10 s application startup time is acceptable, but 3 s to show a new screen is rather not. I had the exact same experience with the Qt VNC platform plugin. Compared with that, the Android Cast streaming based appetize.io solution (see below) was much faster, providing a well usable user experience even over my 8 Mbit/s connection.
Existing solutions
Here is an overview of commercial products and open source software components that I found that can help you with this approach:
appetize.io. This is a commercial product to run Android applications over the web for demo and testing purposes. I have just done this with a Qt QML based application and liked the outcome. When choosing an Android 9 / 10 device you can see that the "Screencast" setting is on; which is why I believe that this solution uses the Android Cast technology.
runthatapp.com. This is another commercial offer. Not as sophisticated (yet) as appetize.io, but providing a nice pay-as-you-go scheme.
ScreenStream. An open source Android app that provides a web server to view the screen of one Android device in a web browser, also relying on the Android Cast technology. That Android device could be an emulator running on a web server. And to make this multi-user capable you can employ a small load balancer similar to a technique that I developed for Qt WebGL streaming. The ScreenStream README shows that the application might consume up to 20 Mbit/s per client in short bursts.
Ideas for future improvements
Serving your Qt app as an interactive live video stream seems a promising idea to me, given that I found it already less sluggish than VNC and similar solutions. There are ways to make this even faster, such as using a hardware H.265 video encoder to create a video stream with very little delay. By operating multiple such encoders on a single server, the server could serve multiple clients and still keep its CPU load low. Maybe there are even better video formats for such a purpose, given that user interfaces of programs lend themselves well to lossless compression.
Some hints for appetize.io
Finally: since I used the appetize.io product for a Qt application over the last few days, here are some tips from that experience:
It is necessary to compile your Qt application for the x86 Android ABI. The default armeabi-v7a ABI will not work because most appetize.io devices are actually server-based Android emulators and the only ARM based device ("Nexus 5 Physical") failed to start any Qt application I tried to use with it.
The x86_64 ABI may also work, but you might then have to also compile Qt yourself for it, as not all versions of Qt come pre-compiled for that architecture.
All appetize.io links (both for standalone pages and embeddable iframes) support GET parameters to configure the app presentation format. Especially relevant here is screenOnly=true to show the app without a picture of a phone or tablet around it.
Features that rely on phone hardware (camera, position etc.) will not work or only show dummy data. But if you really wanted, you could create a hybrid application combined with client-side JavaScript. It would run device-dependent code in the user's browser, for example to take a photo with the webcam, and then provide the results to the Qt application via the appetize.io cross-document messaging protocol. The following message types seem suitable to build a simple communication protocol: pasteText(value), keypress(key, shiftKey) and openUrl(value).
In the default appetize.io standalone app demo pages, only the key events of ordinary letter keys are sent to the app, not keyboard shortcuts or function keys like F2 and Esc. This might be possible to fix with JavaScript on an own page embedding the appetize.io iframe, as their cross-document messaging protocol provides the keypress(key, shiftKey) message type.
Qt does not support writing browser based web applications. Unfortunately.
You need to use common web programming technologies for this. There are a lot of ways, but Qt is not one of them.
I have an application which plays a midi sound.
The application works fine without sandboxing, and plays the sound it is supposed to play, but I cannot here the sound when I enable sandboxing.
I need to upload the application to mac app store, but i cannot do it, because i cannot get sound.
I also cannot open the file dialog box, when I enable sandboxing.
Is there any way I can at least enable the sound in the app?
As Petesh said in above comments, I had to add some more entries in the entitlements file,
the link which was given by him above, contained following. You add them to your entitlement file, and everything will start working like a charm.
This one allows your application to access the microphone.
com.apple.security.device.microphone
This allows talking to the MIDI Server which coordinates all the Midi functionality across applications.
com.apple.security.temporary-exception.mach-lookup.global-name
This allows talking to audio components which are not itself sandboxed.
com.apple.security.temporary-exception.audio-unit-host
They worked for me.
I'm developing a C++ application which will run on a headless server and keep track of some statistics. The application will run in a terminal in a screen session so that I can login over SSH and check those statistics.
Now, what I want to do, is display plots of various data. For that I need pixel-per-pixel access of course, which is not possible with ncurses or S-Lang. I found out about DirectFB (and it's C++ wrappers DFB++ & ++DFB), but can't seem to find conclusive evidence if it is possible to draw graphics with it inside a terminal.
Is DirectFB the way to go? Will it work fine inside a screen session without creating extra windows? If not, is there any library out there that can achieve what I want?
Edit: Ideally, I would of course prefer a library that has some kind of widget support as well, so that I don't have to create tons of classes to emulate text fields/scrollbars/...
You could make your application have a web interface. You could use e.g. Wt or Onion to make your application an HTTP server (or you could make it a FastCgi application), and use SVG (perhaps with Javascript and Ajax tricks) to display vector graphics (or generate a pixel-based PNG or JPEG or GIF image; there are several libraries for that).
I don't think that DirectFB works with SSH, and I believe it is becoming deprecated (for example GTK3 don't support it anymore).
You might also generate Gnu Plot graphics (by generating the appropriate commands), but that is not very interactive.
I don't think that making graphics thru ssh without X make sense, unless you want only ASCII art (which I believe is not the right way for your needs).
This is NOT a question on plain old boring customization; I actually want to create an program, you know, with source code, etc...
I'm thinking about programming my own media centre interface, and I figured it'd look better if I coded my own splash screen for when the OS is loading.
Note: The media centre interface will be run in X, but this question is regarding what will happen before the X server loads.
Simply, I'd like to make a splash screen application to hide the linux kernel boot messages. Is there a way I can program some animation in to this like some sort of animated progress bar for example? I assume that I won't be able to code any 2D/3D graphics (as that'd require X to be running, right?), so how would I go about generating that?
I'd prefer to do this in C++, but C is also an option.
Note: I'm not looking to use any existing "themes" or anything like that, just interested in the programming side of things.
Update:
Some suggestions have been to use standard images (.bmp, .jpeg, etc), I am not interested in loading images in to an existing application. But obviously I may want to load images in to the boot screen application that I will make.
I'm not tied to a Linux distro, so this can be for anything, although Debian or a Debian-based distro would be nice.
I like the suggestion about loading the X server early and running a loading screen from there, however is there not a more direct approach? Surely you can make a program which hides the boot messages and shows a custom program? Obviously this would be very low level programming, but that's what I'm looking for...
Also, I'm not interested in altering the boot loader (LILO, GRUB, etc).
Update 2:
So far good suggestions have been looking at the source code for applications like splashy and fbsplash. Can anyone better this suggestion?
For the graphical output you can use the Linux framebuffer, for application development you can use gtk which support rendering directly to the framebuffer GtkFB.
For the video and such you can use mplayer which also support rendering to the framebuffer.
For the initialization you have to look around the system used, debian uses a sysv init style initialization http://www.debian-administration.org/articles/212, ubuntu uses upstart.
I'd look into splashy source code. But you will need to code in C.
If you have the skills, you can implement a software based 3D engine (like in the good old days). A simple rotating cube shouldn't be very hard to code and there are tons of tutorials.
The downside is that you will increase the boot time, something not very pleasant in a media center.
Here's the thing: there is a library/kernel patch, fbsplash, that has already been written to do exactly what it sounds like you want to do. It will display an image in place of the normal boot messages, and it can also incorporate a progress bar. When you're trying to do something for which a well-established open-source implementation already exists, there's really no better way to learn how to do it yourself than to look at the source code.
Even if you're looking for something more complicated (say if you want to create some fancier animation than a progress bar), you might be able to start with fbsplash and modify it to suit your needs.
There are several ways you could do this. You could have the X server load very early, and just write a program to display the splash screen. You could also use the framebuffer device. If you are using Intel hardware, or are willing to use the OSS AMD drivers, or Nouveau for Nvidia, you could use kernel mode setting. For this, I would look at Fedora's Plymouth. You could just write a Plymouth plugin to display your splash screen.
The splash screen is simply an image (.bmp, .jpg, etc.) and can be loaded by the boot loader. Since you haven't specified the distribution you're using, look into LILO, grub, or whichever one is appropriate. Check the /boot directory for clues that will direct your search.
If all you want to do is have a nice clean boot sequence with your own splash and absolutely no boot messaging you can do the following:
First, silence grub, boot messaging, and console cursor:
GRUB_CMDLINE_LINUX_DEFAULT = quiet fastboot splash vt.cur_default=1 loglevel=0
GRUB_TIMEOUT = 0
This will very quickly and silently (fade to black) bring you to your login screen, where you can place a splash. Your distro may show it's own splash briefly, which you can change if you like.
This yeilds a professional clean boot sequence, without all the usual linux warts and wrinkles. (Like OSX and Windows).
I personally use Ubunutu with LXDE, and have a clean splashy boot in under 3 seconds, even on older hardware.