Is there a way to check for dead keys in the current layout? I am currently capturing the users input for a project I am doing. I created a map of all keys on the keyboard, but there seems to be no flag or whatsoever defining a key as dead or not. I use libxkb in my current code.
The layout is retrieved using
KeySym * keysyms = XGetKeyboardMapping(display_, keycode_low, keycode_high - keycode_low + 1, &num_keysym);
I understand you need to know which key will not directly produce a character, maybe because you are writing a game and do not want to have it use keys as input that would require another key to be pressed to produce some output (if so, please mention in the question)
Not through standard Xlib calls, to my knowledge, and definitely not without actually pressing the respective key. Composing is entirely done within Xlib, and transparent to the front end. (For its original purpose, it should be as transparent as possible to work properly, after all)
You could, however, do the same thing that Xlib does and parse through the various Compose configuration files starting with $HOME/.Xcompose. But that could be a tedious process.
On second thought, I am definitely not proposing the following:
You could, for each key you are looking for information, create a synthetic keypress event and feed it into XLookupString. Hand in an emptied XComposeStatus structure as well. If the structure returns modified, this could be a strong hint you have found a compose key. But it could also mean the server modifies it without any need..... If I were very desparate, I'd probably try.
Related
I'm currently working on a notes app because I really dislike any notes app that I could find on the app store because the lists you can create are either:
only text
only checkboxes
lines of text followed by checkboxes or vice versa
But by now I found no app (except for Samsung's proprietary Samsung Notes app which only works on Samsung smartphones as it seems) that allows alternating use of lines text and checkboxes.
When thinking about how to implement this properly I had some issues coming up with a proper way of identifying when there is a checkbox and when there should be a line of text. For obvious reasons, just storing text and specifying an identifier like <chkbox> (or something along those lines) is not a good solution because checkboxes should only be placeable by clicking the respective icon. The user should neither be restricted to use the term <chkbox> (because for whatever reason he might want to use it) nor should injections like this be possible.
The best thing that came to my mind up until now was to store each line individually (identified by \n) in a list with dynamic datatype and for each line either store it as text object or string or as checkbox item. Finally, I could simply store the list as one single object in the database. However, I'm unsure whether that's good practice as I could imagine that it makes changes to the list quite cumbersome (e.g. for changing the ticked-value of one single checkbox we would need to store the entire datastructure again instead of just changing one boolean in the database)?
I'm working in Flutter and use Firebase Firestore as my backend/database. Although I'm mostly looking for a general approach/solution to this, with the chosen technologies in mind, is there any solution that would work better than what my recent thoughts are, or is there any serious flaws or drawbacks that I overlooked? Thanks in advance for any constructive input.
I have worked a great deal with the text system in Objective-C for macOS/iOS (e.g. NSTextView, NSTextStorage, etc.) I am now experimenting with GTK3 to see how well I can translate my project for use on Linux, etc.
I am brand new to using GTK, but after a few days of Google time and experimenting, I have a working text editor prototype with my custom code plugged in.
The problem is this -- I need to be able to detect when a user highlights a section of text, and then replaces it with other text (e.g. a keystroke). This is distinct from highlighting a section of text, hitting the delete key, and then typing the new text. A specific use example would be highlighting a word, then typing a double quote character in order to wrap the word in quotes (e.g. foo becomes "foo").
In Cocoa, one would receive replaceCharactersInRange: that indicates the range originally selected, as well as the new string to replace it with. I can then detect the presumed intent of the user based on the information received.
In GTK, it seems that we receive a delete-range signal, followed by a separate insert-text signal. Because of this separation, the code in the "insert" section has no way of knowing that the user intended to replace text, not insert new text.
I used the following to receive the signals above:
g_signal_connect(buffer, "insert-text", G_CALLBACK(insert_text_cb), NULL);
g_signal_connect(buffer, "delete-range", G_CALLBACK(delete_range_cb), NULL);
Is there something else I can do in order to tell that there is a delete, followed by an insert as part of the same user action?
Thanks for any pointers offered!
Instead of trying to correlate the delete and insert events, I would suggest creating a GAction for your desired action (e.g. toggle quotes around the selected text) and setting its shortcut key to " using gtk_application_set_accels_for_action().
For more information, check out this HowDoI wiki page.
No answers over the last month, so I kept brainstorming and digging around. I finally came up with this, which works, but is not quite as elegant as I had hoped.
Handle delete-range signal as before, but keep track of the the deleted text for later (e.g. in char * deletedText).
Handle the insert-text signal as before, but if we have a string in deletedText then change the behavior to perform a replacement instead of an insertion. In my case, this actually meant inserting the deleted text back in, and then performing the replacement.
Add a callback for the end-user-action signal, which indicates that all delete/inserts associated with a particular action are complete. In this callback, free deletedText from above and set to NULL (to indicate that everything has been handled).
Again -- this works, but feels a bit inelegant. And depending on how complex your delete/insert routines are, it may slow the performance slightly since some steps have to be duplicated. A better solution would be to detect during the delete-range callback that there is a pending insert-text callback and handle both steps at once. I have thus far not been able to do that.
I'm trying to make a small game using (free)GLUT. I know that it's old and there are better alternatives, but currently I prefer to stick with it and use it as much as possible. I program with C.
I'm currently trying to make GLUT detect properly all the keys I press.
I use glutKeyboardFunc, glutKeyboardUpFunc, glutSpecialFunc and glutSpecialUpFunc to detect pressed keys and I store their state in a short array I created (I currently have only 5 usable keys, so I just created a specific array for them).
However, while everything works fine for 2 keys or less, the game doesn't detect properly 3 keys or more. While for some keys it detect the combination properly (that actually happens for only 1 specific combination), for others the functions simply don't detect the third key that I press.
I checked my code a few times, and there is nothing special about the combination that does work.
I also made glutKeyboardFunc and glutSpecialFunc directly print every key-press that they receive, and it seems they simply stop working after I press more then 2 keys.
Is it a known issue with GLUT or something? I googled a lot and didn't find anyone with a similar issue.
I am not very into GLUT but as I know, but you should make sure, that your keyboard supports more than 2 input keys at once. This feature is called n-key rollover. This page says, that 2-key rollover may be a common value for some keyboards, but you dont need to trust this source.
I'll clarify a point: The glutKeyBoardFunc is a callback i.e., it is invoked for every key pressed and re-executed over and over again and all the if-else (or switch-case) statements for various key combinations are executed. What it means is this - if you were to press 'A', '->' (right arrow) and 'D' all at once, depending on which key-press event was received first the callback will be executed accordingly. Sometimes with a delay and sometimes the on screen animation may stop momentarily.
GLUT is purely for educational/learning purposes but not good for full blown applications since that's not what it was designed for. You land up using OS specific libs or other languages (e.g., Qt) to embed OpenGL "window" within them and execute the keyboard events etc., The event handling in those (and/or OS specific frameworks) is radically different (and better) than GLUT.
You may want to keep your simultaneous key presses to a minimum. You may augment it with the mouse to get rid of the jerky response/processing...
I encountered a bug that has me beat. Fortunately, I found a work around here (not necessary reading to answer this q) -
http://lists.apple.com/archives/quartz-dev/2009/Oct/msg00088.html
The problem is, I don't understand all of it. I am ok with the event taps etc, but I am supposed to 'set up a thread-safe queue) using MPQueue, add events to it pull them back off later.
Can anyone tell me what an MPQueue is, and how I create one - also how to add items and read/remove items? Google hasn't helped at all.
It's one of the Multiprocessing Services APIs.
… [A] message queue… can be used to notify (that is, send) and wait for (that is, receive) messages consisting of three pointer-sized values in a preemptively safe manner.
I'm using a WPF InkCanvas control to capture signatures in a Tablet PC application.
One of my requirements is to validate whether or not the application has really been "signed". Right now I'm doing this by checking the Strokes collection of the InkCanvas - if there are 0 strokes, then I know the user has not "signed".
However, if the user enters a single slash, or even a single dot, this counts as a stroke and my validation test will pass, even though the signature isn't really valid.
Any ideas about how to build a better test for this? Granted, the use case for what is and is not a valid signature is pretty fuzzy, but I want to try to eliminate obviously bad signatures.
Or is this simply unsolvable in any straightforward way?
I know there are algorithms to test if a signature is a valid match for an existing signature, like the one outlined here. However, finding out if something is a signature in the first place seems to be much more complex.
From Wikipedia:
On legal documents, an illiterate signatory can make a "mark" (often an "X" but occasionally a personalized symbol)
...
Several cultures whose languages use writing systems other than alphabets do not share the Western notion of signatures per se: the "signing" of one's name results in a written product no different from the result of "writing" one's name in the standard way. For these languages, to write or to sign involves the same written characters. Three such examples are Chinese, Japanese, and Korean.
While this could be approached using Intelligent Character Recognition, I also know that my signature rarely looks like it has any characters in it. It's even worse if I am using one of those UPS or FedEx package singing pads. Next time a package arrives though I will try signing with just a dash and a dot and see if it allows it (Which I think it will allow since it's already close enough to that).
Because a signature may not match any recognizable words or characters, trying to 'validate' it any further then you currently are could actually be discarding some valid signatures. If for some reason you do still need to know if there is something more then a dot, take a look at validating instead that the signature fills a certain sized rectangle. That still may invalidate results that shouldn't be, so if you do attempt to add any validation to it make sure to document fully the expectations of a valid signature.