Reset state of shared NSTableHeaderCell before drawing in wxRendererMac (PR #26910)
Daniel Kulp
DrawMacHeaderCell() draws every header cell with a single cached NSTableHeaderCell (see GetTableHeaderCell()), but unlike DrawMacCell() it never sets the cell's state before drawing. Whatever state a previous draw left behind (e.g. from drawing the sort indicator or a pressed column) therefore leaks into subsequent draws, and header cells can end up rendered with the highlighted/selected appearance — visible as wxListCtrl headers drawing highlighted on recent macOS versions.
Explicitly set a neutral state before drawing so all header cells get the standard header background.
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You can view, comment on, or merge this pull request online at:
https://github.com/wxWidgets/wxWidgets/pull/26910
Commit Summary
- e264152 Reset state of shared NSTableHeaderCell before drawing in wxRendererMac
File Changes
(1 file)
Patch Links:
- https://github.com/wxWidgets/wxWidgets/pull/26910.patch
- https://github.com/wxWidgets/wxWidgets/pull/26910.diff
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Pull request overview
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Fixes macOS table header rendering by preventing NSTableHeaderCell state leakage across draws when using a cached header cell.
Changes:
- Removes a stray blank line in
CellDrawHelper(). - Explicitly sets a header cell state prior to drawing to avoid “stuck” highlighted/pressed appearance.
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> }
else
{
cell.title = @("");
cell.alignment = NSTextAlignmentLeft;
}
+ cell.state = NSControlStateValueMixed;
NSControlStateValueMixed is not a neutral/default state; it represents an indeterminate (“mixed”) control state and may itself affect drawing. If the goal is to reset to a standard, non-pressed/non-selected appearance, set the state to a neutral value such as NSControlStateValueOff (or the appropriate default state used elsewhere in this renderer, e.g. in DrawMacCell()). Consider also explicitly clearing any related highlight/pressed flags if those are used on this code path.
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VZ
@vadz commented on this pull request.
@csomor Maybe you know which value is better to use here?
I agree that we need to set the state explicitly, but I don't know to which one...
> }
else
{
cell.title = @("");
cell.alignment = NSTextAlignmentLeft;
}
+ cell.state = NSControlStateValueMixed;
Is this wrong? No idea which one of 2 LLMs is correct...
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Daniel Kulp
@dkulp pushed 1 commit.
- 6d5bdce Set explicit state on the NSTableHeaderCell used by wxRendererMac
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Daniel Kulp
@dkulp commented on this pull request.
> }
else
{
cell.title = @("");
cell.alignment = NSTextAlignmentLeft;
}
+ cell.state = NSControlStateValueMixed;
I measured this on macOS 26 rather than guessing, by rendering the cell through wx's drawing path (wxGCDC over a bitmap, real NSView passed to drawWithFrame:inView:) for every state, in both appearances, and comparing full-bitmap hashes, plus capturing a real wxListCtrl before/after (capture attached in the PR comment below):
- state unset (what master does today) and
NSControlStateValueOffrender identically: the cell paints an opaque plate behind the label — pure white in light mode, pure black in dark mode. That plate is the bug: it doesn't match the standard header background at all (glaring in dark mode). NSControlStateValueMixedandNSControlStateValueOnalso render identically to each other: the standard header background (242,242,242 light / 26,26,26 dark), matching what a native NSTableView header shows.
So "off" isn't a neutral value here — it's exactly the current broken rendering. Between mixed and on, which draw the same today, I kept mixed since "on" is the value AppKit associates with a selected/sorted column and could plausibly diverge again on a future macOS; mixed has also been shipping in xLights for a while.
I've updated the commit and PR description accordingly (the original "state leaks between draws" theory was wrong — the state never changes, the default is simply wrong for plain headers).
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Daniel Kulp
dkulp left a comment (wxWidgets/wxWidgets#26910)—
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Stefan Csomor
csomor left a comment (wxWidgets/wxWidgets#26910)@dkulp thanks for looking at this, i'm not sure yet if this is the best way: if you compare the table to a listview in finder, IMHO in light mode does look closer to the BEFORE than the AFTER state
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Daniel Kulp
dkulp left a comment (wxWidgets/wxWidgets#26910)—
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Stefan Csomor
csomor left a comment (wxWidgets/wxWidgets#26910)@dkulp yes, agreed for dark mode, I was just editing this, but for light mode I don't see a gray
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Daniel Kulp
dkulp left a comment (wxWidgets/wxWidgets#26910)On macOS 27, it's gray:
Image: Screenshot 2026-08-26 at 11 58 08 AM (view on web)—
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Stefan Csomor
csomor left a comment (wxWidgets/wxWidgets#26910)very strange, both macOS 26 and 27 on my machines show the headers in the finder list as #FFFFFF
Image: macOS26 (view on web)
Image: macOS27 (view on web)
Also when using a Swift UI Table the headers show up the same, are there some general preferences or side effects which might interfere with that ?
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Stefan Csomor
csomor left a comment (wxWidgets/wxWidgets#26910)—
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Daniel Kulp
@dkulp pushed 1 commit.
- 435e5e4 Only use the mixed header cell state in dark mode
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Daniel Kulp
dkulp left a comment (wxWidgets/wxWidgets#26910)Updated the PR to just set mixed for dark mode, off for light mode. Kind of strange, but visually it better matches the system.
Image: wxlistctrl-header-appearance-conditional (view on web)—
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VZ
vadz left a comment (wxWidgets/wxWidgets#26910)@csomor Please let me know if I should merge this or if you prefer to do it yourself.
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Stefan Csomor
csomor left a comment (wxWidgets/wxWidgets#26910)@csomor Please let me know if I should merge this or if you prefer to do it yourself.
please go ahead, @dkulp thanks a lot
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Stefan Csomor
csomor left a comment (wxWidgets/wxWidgets#26910)Updated the PR to just set mixed for dark mode, off for light mode. Kind of strange, but visually it better matches the system.
I have no idea. I've been debugging the native NSTable rendering in an Obj-C app and it never changes the state, but it renders differently. When I'm changing the cell's background color in wx, it is ignoring that completely, and I don't know why ...
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Stefan Csomor
csomor left a comment (wxWidgets/wxWidgets#26910)ok, found that reason at least, per default the drawsBackground on the cell is set to NO, that explains this part, but changing it to YES and setting the backgroundColor manually to "headerColor" still results in solid black ...
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VZ
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