Feature idea: show the macOS window-modified dot when a project has unsaved changes

[ispyisail]

Forum thread: https://qelectrotech.org/forum/viewtopic.php?pid=17934#p17934
Qt reference: https://doc.qt.io/qt-5/qwidget.html#windowModified-prop

Problem

On macOS there's no way to tell from the window chrome alone whether the active project has unsaved changes — the request specifically points at the small black dot Cocoa apps show inside the red traffic-light close button for a modified document. Qt exposes this natively via the windowModified property; QET doesn't set it anywhere today.

What exists today

• QETDiagramEditor : public QETMainWindow (qetdiagrameditor.h:52) is the actual top-level window. Its title is set once in the constructor to a static string and never updated afterward: setWindowTitle(tr("QElectroTech", "window title")); (qetdiagrameditor.cpp:112).
• Each open project gets its own ProjectView (a plain QWidget, projectview.h:79) added as a tab. ProjectView::updateWindowTitle() (projectview.cpp:967-979) sets windowTitle() from project->pathNameTitle() (qetproject.cpp:424) — used for the tab label, not the OS window title — and is already wired to fire on every modification: connect(m_project, &QETProject::projectModified, this, &ProjectView::updateWindowTitle); (projectview.cpp:84).
• QETProject already tracks a clean/dirty flag and emits it on change: QETProject::setModified(bool) (qetproject.cpp:1414-1420) flips m_modified and emits projectModified(QETProject*, bool), triggered whenever the undo stack leaves the clean state (undoStackChanged, qetproject.h:247) or on save.
• QETDiagramEditor::activateProject(ProjectView*) (qetdiagrameditor.cpp:2210-2213) is the single choke point already used whenever the visible/active project tab changes.
• Qt's windowModified property is built exactly for this case: once the top-level widget's windowTitle() contains a [*] placeholder, QWidget::setWindowModified(true) makes Qt draw the platform-native modified indicator — on macOS, the dot in the close button — with no custom painting needed.

Proposed scope

• Give QETDiagramEditor's window title a [*] placeholder, built from the active project's title the same way ProjectView::updateWindowTitle() already does for its tab label (e.g. "%1[*] - QElectroTech").
• Call setWindowModified(bool) on the main window whenever the active project's modified state changes, via two triggers:
  • QETProject::projectModified on whichever project is currently active — same pattern as the existing projectview.cpp:84 connection.
  • QETDiagramEditor::activateProject(ProjectView*), so switching tabs immediately reflects the newly active project's own state instead of carrying over the previous tab's.
• Purely additive and cosmetic: platforms without native windowModified rendering are unaffected — macOS is where this becomes visible, matching the request.

Related, not proposed here

The same forum post also asks why the toolbar save icon stays black instead of greying out after saving. Per scorpio810's reply in the thread, that's existing intentional behavior (kept since ~2010 to support saving a backup without altering "needs save" state) and is out of scope for this proposal.

Happy to build this if the scope above sounds right.

[ispyisail]

Opened a PR implementing the scope above: #624

[ispyisail]

Status: in progress — PR #624: #624