I need to put a "back-tab" into a bar code. I'm assuming I cannot do this, since there is no ASCII equivalent character associated with it, unlike "tab" with is ascii character 0x09
I have a form that I want to fill in by scanning a QR barcode. There is a field on the form that when using the keyboard to fill in - you would select "shift-tab" on your keyboard to go back to the field, and then tab to move onto the next field.
Any idea how I can accomplish this?
Yes there's no "back tab" character.
You can certainly encode byte value 9 in a QR code, and it is entirely valid in QR code byte mode, where bytes are interpreted as ISO-8859-1.
However it's up to the reader as to what's done with the data. Even if there were such a character, it would not necessarily do something specific like enter a form field and be interpreted as a control rather than text.
So no you can't do this, but you could read a QR code and then write custom code to do whatever you need to do based on its content.
Related
I would like to ask for some help with firstly how to define the windows keys "Alt+Tab" and "Enter" key when using an online barcode generator like https://barcode.tec-it.com/en. Alternatively, if there isn't a way to define the keyboard commands, is there a place that I can find these commands in the form of Barcodes? Code-128 is preferred.
Thank you
Barcodes simply contain ASCII (or with more modern 2d symbols) UTF-8 character codes. So standard keyboard values such as Enter and Tab that correspond to ASCII values can be encoded in a barcode.
On the other hand, dedicated barcode scanners that attach via USB are essentially keyboard emulators. And those can be programmed to create Alt and Ctrl key sequences.
Unfortunately, I do not know of any scanner makers that support Alt-Tab. Most programmable scanners can create Alt-A ... Alt-Z but not Alt-Tab.
Additionally, most barcode scanners allow you to define prefix and suffix key codes to send when a barcode is scanned. The most common configuration is to send Enter or Tab after each scanned barcode. This is done by programming the scanner, not in the barcode.
Can someone help? I've googled it a lot and couldn't find an answer. Is there a way to show/hide non-printable characters on the CKEditor, like there is on word? I couldn't find any plugin for it :/
In short, there is no way to do it or at least it is not easy.
Now the longer version. If you are talking about the Pilcrow character then it is possible to show it in CKEditor by using HTML entities ¶ or ¶ but please note this character is NOT non-printable by any means and in order to make it non-printable you would need to write a code which handles it and this is not easy. First of all you would need write a code (can be done as CKEditor plugin) which inserts Pilcrows on Enter and removes them wherever data is sent to server. So far so good but since this is a normal character (from CKEditor content area POV) you would need to handle all situations in which this character can be removed while typing, styling and modifying entered text and this is next to impossible.
As an alternative you could try having a code which inserts e.g. spans with PilcRow as a background image. While it would be easier to handle spans than plain character you would still need to handle all situations in which this span should or should not be removed while typing, deleting text, styling etc. and again this is very hard to do.
I am using CK editor 4.4.6.
It seem on the first instance of pressing shift + enter, the editor inserts an invisible character. Upon submission, the character saves as a question mark. I can't see the character in the form submission when viewing the debug in the browser or the source code in the WYSIWYG editor itself. I do however notice when I press the right arrow that the cursor pauses at this character even though I can't see it. The page is being served in UTF-8.
This character is zero-width-space and is used by CKEditor to workaround Safari's and Blink's problems with placing selection inside empty inline tags or around them or in couple of other positions.
However, this character should never end up in data. It's used only internally and it is removed when getting data from editor. So, if you can find it in your database it means that you either get data from editor incorrectly, or you encounter some bug in the mechanism I described. In the latter is true please report a bug on http://dev.ckeditor.com, but please also describe how you reproduce it.
Looks like the editor is inserting character 8203.
What's HTML character code 8203?
I don't want to mess with the editor script at the moment so I'm just stripping out that character in the future on form/ajax post.
Years ago, I was messing around with Visual Basic and I discovered a bug with the MsgBox function. I tried searching for it, but nobody had ever said anything about it. It's not just with Visual Basic though; it's with anything that uses the standard Windows MessageBox API call.
The bug is triggered when the title text has more than one character, and the first character is a lowercase 'y' with an umlaut ('ÿ'). What's so special about this character? It almost definitely not the character itself, but rather its ASCII value that's special. 'ÿ' is character 255 (0xFF), meaning it's the highest value that can be stored in an unsigned byte, and all its bits are set to 1.
What does this bug do? Well, there are two different possibilities, which depend on the number of characters in the title text. If there are an even number of characters (unless it's 2) in the title text, no message box appears, and you just hear the alert sound. If there are two characters in the title text, or any odd number other than 1 (in which case the bug wouldn't be triggered)...then this happens:
And that's not all--the message will also be truncated to one line. It seems like the kind of bug that would occur in at least one semi-high-profile incident, considering how often this API call is used. Are there any reports of this on the Internet, or anything showing what could cause it? Maybe it's a Unicode-related glitch, like that "bush hid the facts" glitch in Notepad?
I made a program in case you want to play around with this; download it here.
Alternatively, copy the following into Notepad, save it with a .vbs extension, and double-click it to display the dialog box seen above:
MsgBox "Windows 3.1 font, anyone?", 0, "ÿ ODD NUMBER!"
Or for a different font:
MsgBox "I CAN HAS CHEEZBURGER?", 0, "ÿ HImpact"
EDIT: It seems that if the first four characters are ÿ's, it doesn't ever display the message, even if there's an odd number of characters.
This is a bug with dialog templates generally. It is not a message box bug as such.
For example, in Visual Studio create the default win32 application. In the .rc file, change the caption in the template for the about box from
CAPTION "About sampleapp"
to
CAPTION "ÿT"
and the bug will manifest itself when you display the about box.
In the DLGTEMPLATEEX documentation note that the menu and class name have type sz_Or_Ord which means either a null-terminated string or 0xFFFF followed by a single word resource identifier.
Windows incorrectly applies a similar scheme to the dialog title: if the first character is 0xFF then it treats the title as being two WORDs long, but only when it is trying to locate the font information. When it is displaying the title it correctly treats the title as a string.
In other words, Windows is looking for the font information inside the title string. In most case this won't specify a valid font, so Windows defaults to the system font.
To prove this, I constructed a dialog template in memory (based on this). Once this was working I deleted the code that writes the font information to the template and used the dialog title "ÿa\xd\x200\x21SimSun". This displays the dialog in italic SimSun because windows is reading the font information from the title string.
This bug is likely a hangover from 16-bit Windows, where (I guess) 0xFF was used as the resource ID marker.
A strange bug. I suspect the symptoms are the result of the way the MessageBox() actually displays the dialog.
Internally, MessageBox() builds a dialog template dynamically. If you look at the description of a DLGTEMPLATE structure you'll find the following nugget of information:
In a standard template for a dialog box, the DLGTEMPLATE structure is
always immediately followed by three variable-length arrays that
specify the menu, class, and title for the dialog box. When the
DS_SETFONT style is specified, these arrays are also followed by a
16-bit value specifying point size and another variable-length array
specifying a typeface name.
So, the in-memory layout of a dialog template has the font specification immediately following the dialog box title.
Visual Basic does not use Unicode and so the function you're calling is actually MessageBoxA(). This is simply a thunk that converts the passed-in strings from multibyte to Unicode and then calls MessageBoxW().
I believe what's happening is that, for some reason, the conversion of that string from multibyte to Unicode is either going wrong, or returning a spurious length value. This has the knock-on effect, when the dialog template is built in memory, of corrupting the memory immediately following the title string - which, as we know, is the font specification.
I was going thru some content about control characters especially newline character(will focus on this).After going thru
http://en.wikipedia.org/wiki/Control_characters, got to know that \n is the line character in unix
while it is \r\n in windows. Now i got the question how OS comes into picture when iterpreting
ASCII Codes becoz i was under impression when we type any given character on keyboard, any OS send the same
bits and editor interprets that bit and display the corresponding character. Looks like this understanding is
wrong, Because different bit is sent in case of unix(\n) and windows(\r\n) when we press ENTER(new line terminator).As per
new understanding if we press ENTER on diff OS(say unix and windows),different bits are sent to editor and its
responsibilty of text editor to show the typed stuff in new line keeping the underlying OS in picture.Please let me
know if my understanding is correct as this will help me to understand other basics also?
Next question is if above is correct, what can be the reason different OS treat some control characters differently
when they treat all other characters equally? Is it becoz specific bits are already reserved in specific OS?
How an application treats keyboard input varies a bit, actually. When you press return the application is under no obligation to actually generate LF or CR+LF anywhere. E.g. it might decide to just end the current paragraph object and start a new one (e.g. in a word processor). If it's a Windows text editor then it will probably just write CR+LF into the file, while on Unix it just writes an LF.
They keyboard itself is very, very far removed from things you see on the screen or even on the disk. This goes through scan codes, keyboard layouts and other transformations before it ends up as text or markup somewhere.