Fix hang and wrong check states in data grid column selection on macOS - #2559
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ansgarbecker merged 1 commit intoJul 23, 2026
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Fixes the reported hang (issue 2554): closing the column selection popup with OK could run FormClose twice on macOS, freeing FCheckedColumns two times. The resulting access violation raised the crash dialog inside a paint cycle, freezing the application. FCheckedColumns is now freed in FormDestroy, which runs exactly once. While verifying that fix, a second bug in the same popup showed up: checked columns were not applied correctly to the grid. The click handler used ItemIndex to detect the toggled item, but on Cocoa the check event fires before the list selection is updated, so the wrong item was added or removed. The handler now syncs the check states of all displayed items instead.
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Fixes #2554
Debugged with lldb on an M-series Mac. There were two separate bugs in the column selection popup, both fixed here:
1. The reported hang (double-free of FCheckedColumns)
Clicking OK closes the popup, which frees
FCheckedColumnsinFormClose. But the form itself is only released deferred (caFree), and the grid reload triggered by OK makes the main window key again while the popup object still exists. The LCL then sendsCM_DEACTIVATEto the popup →FormDeactivate→btnCancelClick→Closeruns a second time →FCheckedColumns.Freeon the already freed list. The resulting access violation raises the crash dialog withShowModalinside the data grid's paint cycle, where nothing can be drawn anymore - the app freezes with an invisible modal dialog.Backtrace of the crash (captured with lldb, trimmed):
frame #1: SYSTEM$$TOBJECT$$$FREE
frame #2: TFRMCOLUMNSELECTION$$$FORMCLOSE ← 2nd time
frame #5: TFRMCOLUMNSELECTION$$$BTNCANCELCLICK
frame #6: TFRMCOLUMNSELECTION$$$FORMDEACTIVATE
frame #14: TSCREEN$$$SETFOCUSEDFORM
frame #23: -[TCocoaWindow windowDidBecomeKey:]
frame #31: -[NSWindow makeKeyWindow]
frame #38: APPHELPERS$$$TRYSETFOCUS
frame #39: TMAINFORM$__$$_DATAGRIDBEFOREPAINT ← grid reload after OK
Fix: free
FCheckedColumnsinFormDestroy, which runs exactly once.TApplication.ReleaseComponentalready tolerates the duplicateRelease, so the second close pass is harmless otherwise.2. Checked columns were applied wrongly (stale ItemIndex)
After fixing the hang, selecting e.g. 3 columns still showed only 1 in the grid.
chklistColumnsClickCheckusedchklistColumns.ItemIndexto detect the toggled item. On Cocoa the checkbox is anNSButtoninside the table row, and its action fires before the table selection is updated - soItemIndexstill points at the previously clicked row, or is -1. Verified with lldb: clicking checkboxes of rows 0, 2, 1 deliveredLM_CHANGEDfor rows 0, 2, 1 whileselectedRowwas -1, 0, 4 at those moments - the internal list diverged from the visible check marks on every click.Fix: sync the check states of all currently displayed items into
FCheckedColumnsinstead of guessing viaItemIndex. Items hidden by the filter box are not touched, so filtering still works, and behavior on Windows is unchanged (no ifdefs).Tested on macOS 15 (Apple Silicon): the reported hang scenario, multiple checkbox clicks without/with row selection changes in between, select/deselect all, sorting and filtering.