[scintilla:bugs] #2488 SCI_SETSELECTIONNSTART and END set anchor and caret instead

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Tom Mewett

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Sep 27, 2025, 12:07:06 PMSep 27
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[bugs:#2488] SCI_SETSELECTIONNSTART and END set anchor and caret instead

Status: open
Group: Bug
Labels: scintilla
Created: Sat Sep 27, 2025 04:06 PM UTC by Tom Mewett
Last Updated: Sat Sep 27, 2025 04:06 PM UTC
Owner: nobody

SCI_SETSELECTIONNSTART sets the selection anchor, instead of the selection start. Similarly, SCI_SETSELECTIONNEND sets the selection caret, instead of the selection end.

This can be seen in Editor.cxx:

    case Message::SetSelectionNStart:
        sel.Range(wParam).anchor.SetPosition(lParam);
        break;

    case Message::SetSelectionNEnd:
        sel.Range(wParam).caret.SetPosition(lParam);
        break;

Contrast this with SCI_GETSELECTIONNSTART and END, which correctly get the start and end:

    case Message::GetSelectionNStart:
        return sel.Range(wParam).Start().Position();

// ...

    case Message::GetSelectionNEnd:
        return sel.Range(wParam).End().Position();

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Neil Hodgson

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Sep 27, 2025, 6:31:10 PMSep 27
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This issue does not describe the desired solution.

Please specify the behaviour you want completely.

The main justification for these calls is symmetry - there are GetSelectionNStart and GetSelectionNEnd calls so adding the 'set' calls makes it simpler for applications to treat them as properties.

Tom Mewett

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Sep 28, 2025, 7:30:11 AMSep 28
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Hi Neil

The desired solution is that SCI_SETSELECTIONNSTART sets the selection start point, as the function name implies. Same for SCI_SETSELECTIONNEND. Currently they set the anchor and caret respectively, which is a problem as the anchor isn't always at the start and the caret isn't always at the end.

The main justification for these calls is symmetry

Exactly - the issue is that they currently aren't symmetric. In other words, the Set call does not modify the property that the Get call retrieves.

[bugs:#2488] SCI_SETSELECTIONNSTART and END set anchor and caret instead

Status: open
Group: Bug
Labels: scintilla
Created: Sat Sep 27, 2025 04:06 PM UTC by Tom Mewett

Last Updated: Sat Sep 27, 2025 10:31 PM UTC
Owner: nobody

Neil Hodgson

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Sep 28, 2025, 6:24:22 PMSep 28
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The desired solution is that SCI_SETSELECTIONNSTART sets the selection start point

When I said "specify ... completely" I meant "completely", not just restating the title.

Specify the algorithm you want. In detail.

[bugs:#2488] SCI_SETSELECTIONNSTART and END set anchor and caret instead

Status: open
Group: Bug
Labels: scintilla
Created: Sat Sep 27, 2025 04:06 PM UTC by Tom Mewett

Last Updated: Sun Sep 28, 2025 11:30 AM UTC
Owner: nobody

Neil Hodgson

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Oct 11, 2025, 4:36:58 PM (3 days ago) Oct 11
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If you don't know how to write out an algorithm, examine each possible situation and say what the result should be.

For example, if caretN=1,anchorN=2 what should be the resulting caret and anchor after SCI_SETSELECTIONNSTART(N,3)? If both caret and anchor are 2, what should the results of SCI_SETSELECTIONNSTART(N,3) be? Work through all the possible configurations and see if it produces a coherent design.

[bugs:#2488] SCI_SETSELECTIONNSTART and END set anchor and caret instead

Status: open
Group: Bug
Labels: scintilla
Created: Sat Sep 27, 2025 04:06 PM UTC by Tom Mewett

Last Updated: Sun Sep 28, 2025 10:24 PM UTC
Owner: nobody

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