[BUG] <title>关于GS等控制字符的显示

[layfolk233]

Is there an existing issue for this?

• I have searched the existing issues

Description of the Issue

First of all, in a Windows computer, you can output ASCII codes through the alt+ keypad, for example, press and hold alt + 6 + 5 + to release alt=A and alt+2+9=GS (control character).

Secondly, notepad++ software can directly output ASCII code through menu-edit-character panel.as shown in Figure 1.

The GS characters output through the character panel, both my computer and the client's computer are in the form of white characters on a black background, which is no problem, as shown in Figure 2.

At present, in the notepad++ software of my computer, the GS characters output through alt+2+9 are also in the form of white characters on a black background (as are most computers in the company).

However, the GS character output by the client's computer (win11 system Russian) through alt+2+9 is a double arrow symbol ‘�’(UTF-8=0x1D), as shown in Figure 3.

The question now is, how to set the gs characters that the other party wants to output through alt, and want to be in the form of white characters on a black background instead of double arrows?

My computer can't reproduce his situation. I tested Chinese (I) Russian (customer) of Win10 Win11 system, and tried the old version, the new version and the intermediate version of notepad, as shown in Figure 4.

The attempt to modify the menu-view-display symbol is invalid, as shown in Figure 5.

Menu-Settings-Preferences-Edit 2- Related Settings also failed, as shown in Figure 6.

Steps To Reproduce

Press and hold alt + 2 + 9 + to release alt = GS (control character).

Current Behavior

Output a double arrow symbol ‘�’

Expected Behavior

The GS characters output through alt+2+9 are in the form of white characters on a black background

Debug Information

Notepad++ v8.8.5   (32-bit)
Build time: Aug 14 2025 - 00:17:53
Scintilla/Lexilla included: 5.5.7/5.4.5
Boost Regex included: 1_85
Path: E:\Program Files\Notepad++\notepad++.exe
Command Line: 
Admin mode: OFF
Local Conf mode: OFF
Cloud Config: OFF
Periodic Backup: ON
Placeholders: OFF
Scintilla Rendering Mode: SC_TECHNOLOGY_DIRECTWRITE (1)
Multi-instance Mode: monoInst
asNotepad: OFF
File Status Auto-Detection: cdEnabledNew (for current file/tab only)
Dark Mode: OFF
Display Info:
    primary monitor: 1920x1080, scaling 100%
    visible monitors count: 2
    installed Display Class adapters: 
        0000: Description - NVIDIA GeForce GT 730
        0000: DriverVersion - 27.21.14.5638
        0001: Description - NVIDIA GeForce GT 730
        0001: DriverVersion - 27.21.14.5671
        0002: Description - OrayIddDriver Device
        0002: DriverVersion - 17.1.58.818
OS Name: Windows 10 Enterprise (64-bit)
OS Version: 22H2
OS Build: 19045.5965
Current ANSI codepage: 936
Plugins: 
    mimeTools (3.1)
    NppConverter (4.6)
    NppExport (0.4)

Anything else?

[layfolk233]

Sorry, I uploaded the pictures out of order. I hope it won't affect your reading.

[pryrt]

Alt Codes are a feature of the operating system, not the application (Notepad++). As per the wiki article, there are two variants of the numeric-keypad-only alt-codes: in the "old form", you use Alt+## or Alt+### to get the character from the current OEM codepage. In the second, you use Alt+0## or Alt+0### to force it to be from the "ANSI codepage" instead. With my setup, Alt+29 does the ↔, whereas Alt+029 does the GS. By default in the US, the old OEM codepage is 437, and the CP437 character set has the ↔ at index 29 (0x1D) -- and the western european CP850 is similar. So this is what you should get without the 0 prefix in the alt-code. The misnamed "ANSI" code page (later known as "Windows code page", since they weren't defined by ANSI) defaults to CP1252 in the US... and one of the benefits of the Windows code pages is that they consistently use the control code region (0..31) as control codes, so that the 0-prefixed alt codes should consistently give the GS character, regardless of region or Windows settings.

(Also note that numlock can have an effect on whether the Alt-codes work as expected: for some codes, it means nothing happens; for others, it chooses a third character: for example, NumLockOff, Alt+227 gives me a small bulletpoint, NumLockOn Alt+227 gives me π and Alt+0227 gives me ã.)

And if you have the hex alt codes enabled, Alt++1D (yes, hold down the Alt, then type the numeric keypad +, numeric keypad 1, then the d character) will give you the U+001D character from unicode, which is the GS control character. (The hex code versions generally work for me whatever the state of NumLock, but I won't guarantee that.)

Final note is that in newer Notepad++, Settings > Preferences > Editing 2 > ☑ Prevent control character (C0 code) typing into document will prevent GS from being inserted by any of those alt codes.

[xomx]

Steps To Reproduce

Press and hold alt + 2 + 9 + to release alt = GS (control character).

• add also zero (hold Alt and type 0+2+9), Settings > Preferences > Editing 2 > Prevent control character... check box must be unchecked
• when the above checkbox is checked, you can still use the Edit > Characters Panel for entering the GS control char by doubleclicking exactly the GS symbol area in the Character-column of the 30th line in the "ASCII Codes Insertion Panel" (IMO it's a bug, it should not be possible to do that with that Preferences setting ON).

[alankilborn]

when the above checkbox is checked, you can still use the Edit > Characters Panel for entering the GS control char by doubleclicking exactly the GS symbol area in the Character-column of the 30th line in the "ASCII Codes Insertion Panel"

(IMO it's a bug, it should not be possible to do that with that Preferences setting ON).

IMO, the preference setting refers to typing. Double-clicking in the Character Panel is different; you're intentionally trying to insert from the panel into the document. Thus, IMO, no bug.

[xomx]

@alankilborn
Ok. Thinking about it more - it should be like that as there are also other ways that would be difficult to prevent (e.g. by pasting via Ctrl+V).

[layfolk233]

Thank you for your answers. At present, I wonder why I can't output the double arrow symbol of the other party no matter how I set it. I want him to output GS characters with white characters on black background through alt+2+9. Is there any way to do that?

[pryrt]

At present, I wonder why I can't output the double arrow symbol of the other party no matter how I set it.

Did you make sure that Settings > Preferences > Editing 2 > Prevent control character (C0 code) typing into document is NOT checkmarked? That makes it not work.

I want him to output GS characters with white characters on black background through alt+2+9. Is there any way to do that?

With Alt + 2 + 9? No. As I already said, that's OEM codepage dependent, and you aren't going to be able to control that for him (*). With Alt + 0 + 2 + 9 should always work. Or, as @xomx said, use the Character Panel to insert the character instead. So there are two alternatives. You will have to have him use one of those two.

(Footnote *: Theoretically, there's some setting buried deep in Windows that might be able to change what OEM codepage is selected... but good luck figuring that out, because most of your search results are going to be dealing with the "ANSI" [Windows] Code Page