Tab icon glitch when pasting

[alankilborn]

Description of the Issue

When experimenting with Notepad++ 8.6's new multi-select feature, in certain circumstances when pasting, I noticed a visual glitch of the tab's icon. Looking closer it briefly changes to a "lock" icon before quickly changing back to a "pencil" icon.

Steps to Reproduce the Issue

1. Checkmark Alternate icons in the Editing preferences.
2. Create some text in a new tab:

bbbbbbbbbb
bbbbbbbbbb
bbbbbbbbbb
bbbbbbbbbb
bbbbbbbbbb
bbbbbbbbbb
ccccccccc
ddddddddd
eeeeeeeee

3. Make a column block selection:
   
4. Press Ctrl+c to copy that selection.
5. Create some "multi-carets":
   
6. Press Ctrl+v to paste, while (IMPORTANT!) watching the file tab icon closely.

Expected Behavior

No visual glitch of tab icon at paste.

Actual Behavior

Visual glitch of tab icon at paste.
I see the "lock" briefly before it switches back to the "pencil".

Debug Information

Notepad++ v8.6 (64-bit)
Build time : Nov 23 2023 - 16:58:44
Path : C:\NotepadPlusPlus\Misc_NoBackup\Releases\npp.8.6\npp.8.6.portable.x64\notepad++.exe
Command Line : -multiInst
Admin mode : OFF
Local Conf mode : ON
Cloud Config : OFF
OS Name : Windows 11 Pro (64-bit)
OS Version : 22H2
OS Build : 22621.2428
Current ANSI codepage : 1252
Plugins :
mimeTools (2.9)
NppConverter (4.5)
NppExport (0.4)

[alankilborn]

I think I tracked the glitch to this line in the code:

// Hack for preventing the char "SYN" (0x16) from being adding into edit zone 
buf->setUserReadOnly(true);

https://github.com/notepad-plus-plus/notepad-plus-plus/blob/2768cf5422e6a443e7ed043ddd21a961e5c9859d/PowerEditor/src/ScintillaComponent/ScintillaEditView.cpp#L687C8-L687C8

If I comment-out this line and run, then do the STR (Steps To Reproduce) above, I don't see the glitching I described.

And...I don't see a "SYN" character added into the edit zone; using this setup:

[alankilborn]

@donho Are you sure you were getting a "SYN" character put into the edit zone, before adding the hack? If you remove the hack, can you give some STR (steps to reproduce) so that I could see it as well?

[pryrt]

I forgot step1, but I was able to replicate with my screen-capture software running. The read-only mode lasts about 130ms.

[donho]

@alankilborn @pryrt
This is intentional hack, due to between Ctrl-V keyDown & keyUp there is SYN char added.
The solution (hack) is make document read-only to prevent SYN from being added, then while keyUp, remove read-only from document.

I have no better solution so far. Please create a PR if you've got one.

If you remove the hack, can you give some STR (steps to reproduce) so that I could see it as well?

Just turn on "Show All Characters".

[alankilborn]

Just turn on "Show All Characters".

But...from my screenshot earlier I have Show Control Characters... on already, and SYN is a control character. I wonder why I do not see it?

[donho]

@alankilborn
If you comment set read-only as following:

// Hack for preventing the char "SYN" (0x16) from being adding into edit zone 
//buf->setUserReadOnly(true);

Then do as following: #14338 (comment)

What do you see?

[alankilborn]

What do you see?

After the paste, I see the following (incorrect) result, but no SYN character:

---

To show that I have visible control characters turned on, I move to lower in the file and type some Ctrl+e (an unmapped shortcut) characters:

[donho]

@alankilborn

Now you modify the code to the following:

if (pasteToMultiSelection())
{
	// Hack for preventing the char "SYN" (0x16) from being adding into edit zone 
	//buf->setUserReadOnly(true);

	//_isMultiPasteActive = true; // It will be set false with WM_KEYUP message
	return TRUE;
}

and do the same manipulation, you will see SYN char appear.

[alankilborn]

Ok, got it, thank you:

I'll see if I have some ideas about it...