In the kernel extensions, there was setDeviceCanBeDefault() that I could hide and show audio devices. How I can achieve something similar in CoreAudio's HAL plugin? I want to hide and show my plugin, from sound devices, at runtime.
Implement the kAudioDevicePropertyIsHidden property and return (UInt32)1 from it in your device.
Don't forget to call PropertiesChanged() on the host when you modify this non IO-related property. Also keep in mind that hidden devices cannot become the default device.
Related
I have been trying to build a TV application, using an SD.
I have got features like image gallery, video player running,
However, I also wanted to add a virtual on-screen keyboard that works with up-down left-right arrow keys. Can somebody help me with how to get started?
When I wanted to do this with my Vestel (Polaroid Branded) smart TV, which uses "Opera for TV devices" as it's HbbTV browser, I found that I didn't need to.
I simply just used HTML text fields and input types where needed, and as soon as I clicked into them, the browser/OS kernel popped up an onscreen keyboard that was built in for me.
However, I did do some research to see if I needed it, and on some devices you do, whilst I never actually implemented it (My app was just for my own use) the "BBC Television Application Layer" (TAL for short) : https://github.com/bbc/tal had pretty good keyboard support.
Another one that might be worth looking at is "Mautilus SDK" : https://github.com/mautilus/sdk
Be aware though, both are horribly convoluted and use quite complex code where it's really not needed.
I am working on an open source project to add something in that i need. It uses an XInput system to get input from the keyboard and i cannot change that. However, for keypresses, i need to get the hardware scancodes, like those listed here. Is there a way to go from an XKeyPressedEvent to these KEY_* scan codes from input-event-codes.h, to know what key was pressed in a layout independent way?
I've got a bit of an interesting problem here. There are plenty of threads I've found where people are working to hide or get rid of a cursor on an embedded Qt GUI...but I'm trying to get a cursor to show up on an embedded Qt GUI.
I inherited a project that was 'finished' some time ago, and the person who did the most work on the project has moved on. Fast forward to today and there is a need to add a cursor to this functional touchscreen GUI. The system OS is Yocto Linux, and it is running a Qt 5.4 application on a framebuffer.
I've scoured the Qt code and there is nothing there that would hide a cursor. I've added in the appropriate QT_QPA_FB_HIDECURSOR=0 environment variable to my Qt startup script. I've experimented with adding a QCursor obejct to the GUI. Unfortunately none of these things are working. Using the QCusor I am sometimes able to get a cursor up on the screen, but isn't tied to the touch input (the cursor shows up at the position I programatically move it to, but it stays there when I interact with the GUI).
My touch input events are tied into Qt (via QT_QPA_GENERIC_PLUGINS=evdevtouch and QT_QPA_EVDEV_TOUCHSCREEN_PARAMETERS=/dev/input/event9:rotate=180), but for some reason that touch input cannot be tied to a cursor.
At this point I've spent a few days messing around with environment variables and startup script modifications, but nothing I've done has got the result I'm looking for.
Does anybody out there have some ideas on where to look for solutions to this problem?
Thanks!
Ian
So, now 3 months later I think my team and I just came up with a passable solution to this problem.
The path towards the solution started with the Qt Documentation on "Using libinput". The documentation boils down to a few important statements:
Parameters like the device node name can be set in the environment variables QT_QPA_EVDEV_MOUSE_PARAMETERS, QT_QPA_EVDEV_KEYBOARD_PARAMETERS and QT_QPA_EVDEV_TOUCHSCREEN_PARAMETERS
The mouse cursor shows up whenever QT_QPA_EGLFS_HIDECURSOR (for eglfs) or QT_QPA_FB_HIDECURSOR (for linuxfb) is not set and Qt's libudev-based device discovery reports that at least one mouse is available. When libudev support is not present, the mouse cursor always show up unless explicitly disabled via the environment variable.
The evdevtablet plugin provides basic support for Wacom and similar, pen-based tablets. It generates QTabletEvent events only. To enable it, pass QT_QPA_GENERIC_PLUGINS=evdevtablet in the environment or, alternatively, pass -plugin evdevtablet argument on the command-line. The plugin can take a device node parameter, for example QT_QPA_GENERIC_PLUGINS=evdevtablet:/dev/event1, in case the Qt's automatic device discovery (based either on libudev or a walkthrough of /dev/input/event*) is not functional or misbehaving.
So, in my system I have the device nodes: event0, event1, event2, event3, event4, event5, mice, and mouse0. Because I'm trying to get the mouse working, I made the assumption that I'd have to use the mouse0 node. This lead to me setting these environment variables:
QT_QPA_GENERIC_PLUGINS=evdevmouse
QT_QPA_EVDEV_MOUSE_PARAMETERS=/dev/input/mouse0
Much to my frustration these environment variables led to nothing. After some time my team and I figured out how to get debug output from Qt source on our system:
Modifying source code in the qtbase directory under our yocto build (roughly /yocto/poky/build/tmp/work/temp build directory/qtbase
Copying qtbase/plugins/generic/libqevdevmouseplugin.so to my hardware (roughly /usr/lib/qt5/plugins/generic)
Running Qt from the command line
We quickly discovered that the input events coming from mouse0 and mice were basically garbage data. On our system we did set up EVDEV in the kernel, so the mouse input was also tied to the device node event0. When we tried setting the Qt mouse parameter to event0 we started to see debug output that looked like real data.
QT_QPA_GENERIC_PLUGINS=evdevmouse
QT_QPA_EVDEV_MOUSE_PARAMETERS=/dev/input/event0
However, the problem of no-mouse-pointer still remained. After a while we looked back at the Qt Documentation, specifically at the 2nd paragraph listed above. As a last ditch attempt we tried adding in the QT_QPA_FB_HIDECURSOR environment variable...
QT_QPA_GENERIC_PLUGINS=evdevmouse
QT_QPA_EVDEV_MOUSE_PARAMETERS=/dev/input/event0
QT_QPA_FB_HIDECURSOR=0
And...voila! After countless hours of debugging and reading documentation, we finally got a mouse pointer.
I think the main crux of our issue was misinterpreting the Qt Documentation.
The mouse cursor shows up whenever ... QT_QPA_FB_HIDECURSOR (for linuxfb) is not set
By "not set", Qt means explicitly defined as FALSE...not simply "not set" at all.
This solution will work for us, but it does leave at least one thing to be desired. Along the way I stumbled across this thread answer on the Unix StackEx which points to the Kernel documentation of input/input.txt. In section "3.2.2 mousedev" you can see the line:
Each 'mouse' device is assigned to a single mouse or digitizer, except
the last one - 'mice'. This single character device is shared by all
mice and digitizers, and even if none are connected, the device is
present. This is useful for hotplugging USB mice, so that programs
can open the device even when no mice are present.
What this means for us is that while we can use event0 (which goes away when we unplug the mouse) for our mouse input event handling, we won't be able to support hot plugging without making some kernel/Qt-source modifications or figuring out how to get mice working as a Qt mouse input parameter.
So, the question of "why does event0 work and not mouse0/mice" still stands...but for now we've got a solution we can live with.
UPDATE: Now a little bit later we've figured out that udev was not working properly on our system. We added udev to the RDEPENDS in our package group for the Yocto build, and now we can set
QT_QPA_GENERIC_PLUGINS=evdevmouse
and we get a working mouse pointer with hotplug support.
I dont know if this applies to your problem (i dont use QT), but there is a
HAVE_TOUCHSCREEN=1 variable in the machconfig file. It is located normally in your BSP-layer in a recipes-bsp/formfactor/formfactor directory.
Setting this to 1 makes the cursor invisible.
Try setting it to 0
I have a barcode scanner works as HID device. Everytime a barcode scans it goes directly to windows keyboard, for example if I open notepad I can see the barcode typed there.
As far as I know programmatically is it possible to to read HID data from your HID devices.
But what happens if the user is already on a form with a text edit control? The scanned code will go inside the text box.
Can you block incoming text and make a background-only processing?
Can you explain the theory please?
See if your barcode scanner can emulate a serial port and just read the data directly from the the serial port into your app.
That is cleaner and less expensive then a global keyboard hook. When I was looking into this awhile ago I found that most USB barcode scanners can emulate a serial port, it's a cinch to read serial port data in most programming languages. I happened to be doing mine in Java, I posted an example in answer to this question actually.
You can set up your scanner to use USB-HID(POS) setting. Your datasheet of barcode settings for the scanner device should have it. I use this project to test my scanners. http://www.codeproject.com/Articles/18099/A-USB-HID-Component-for-C
Sure, just capture keypresses before they are handled by the control and suppress normal handling of the events. In VB.NET you might override the OnKeyPress method in your form and set KeyPreview to true, for example.
How (i.e. using which API) is the virtual keyboard opened on Symbian S60 5th edition? The documentation seems to lack information about this.
You are right, this should obviously be a published API and it should be highlighted in the documentation. No such luck.
If you are using one of the platform native controls, the virtual keyboard will automatically popup when the user accesses a text-editing control.
If you are making a custom control, you need to deal with its selection by adding your own version of the virtual keyboard: make a new text-editing, window-owning virtual keyboard look-alike custom control with the right buttons. Reuse it accross all your applications. One day, Nokia will realize they have made an obvious mistake and make the API publicly available.
If you are using direct screen access, well, you wouldn't exactly expect the very s60-looking virtual keyboard to popup out of nowwhere. Again, draw a nice image on the screen to let the user know where the virtual keys are and react to pointer events. This is going to be less reusable unless you build a good amount of customization (background, button edges...) into it.
EDIT: Nokia may be relying on Qt to fix this issue. I would expect the control to be part of the current 4.7 version of Qt.
Tinkering with focus on a QLineEdit inside custom coded kinetic scroll area, I've had a simmilar problem (how to open virtual keyboard manually). Then, I found it, this obviously works in Qt 4.6.3 on a C7 Symbian^3 phone:
// lineEdit is an instance of QLineEdit
QApplication::postEvent(lineEdit, new QEvent(QEvent::RequestSoftwareInputPanel));
Before that, I also had to post a QEvent::FocusIn event to that same lineedit, otherwise the QLineEdit did not update the content from virtual keyboard.
Hope this is helpful. I lost hours.
Thank you tihi, very useful tip! There's also the "close virtual keyboard" event that can be triggered:
QApplication::postEvent(lineEdit, new QEvent(QEvent::CloseSoftwareInputPanel));