Merge branch 'port-c'

# Conflicts:
#	AGENTS.md

tests/MaskAloneTests.cpp

@@ -18,6 +18,8 @@ private slots:
     void aPlacedOrDisabledMaskShowsAlone();
     void theBadgeNamesTheMaskAndTakesItsOwnClicks();
     void altClickOnTheThumbnailTogglesItAndOutlinesItWhite();
+    void theViewOutlastsUndoRedoAndTargetingTheMaskAgain();
+    void aPendingGradientElsewhereStaysOutOfTheView();
 };
 
 namespace {
@@ -294,5 +296,55 @@ void MaskAloneTests::altClickOnTheThumbnailTogglesItAndOutlinesItWhite()
     QCOMPARE(accent, thumbnail->palette().color(QPalette::Highlight));
 }
 
+void MaskAloneTests::theViewOutlastsUndoRedoAndTargetingTheMaskAgain()
+{
+    QUuid id;
+    const auto session = maskedSession(id);
+    session->toggleMaskAlone(id);
+    // A plain click on the shown mask targets it again.
+    session->selectLayerTarget(id, true);
+    QCOMPARE(session->maskAloneLayer().value().id, id);
+    // A stroke on it, undone and redone, keeps the view.
+    session->selectTool(NavigationTool::brush);
+    session->setBrushSettings(brush(20, 1, 0, 0, 0));
+    session->beginBrush(QPointF(50, 50));
+    QVERIFY(session->finishBrushImmediately());
+    QCOMPARE(session->history.undoName(), QString("Paint Mask"));
+    session->undo();
+    QCOMPARE(session->maskAloneLayer().value().id, id);
+    session->redo();
+    QCOMPARE(session->maskAloneLayer().value().id, id);
+}
+
+void MaskAloneTests::aPendingGradientElsewhereStaysOutOfTheView()
+{
+    Canvas shown;
+    EditorSession &session = shown.session;
+    session.setForegroundColor(PaletteColor{0, 0, 1});
+    session.selectTool(NavigationTool::gradient);
+    // The layer's own pixels take a blue gradient, still pending.
+    session.selectLayerTarget(shown.id, false);
+    session.beginGradient(QPointF(0, 80));
+    session.moveGradient(std::nullopt, QPointF(200, 80));
+    QVERIFY(session.gradientEdit().has_value() && !session.gradientEdit()->raster->isMask);
+    session.toggleMaskAlone(shown.id);
+    // The commit is posted: the pixels' raster lingers, unshown.
+    QVERIFY(session.maskAloneLayer().has_value() && session.gradientEdit().has_value());
+    QVERIFY(gray(shown.at(QPointF(50, 50)), 255) && gray(shown.at(QPointF(150, 50)), 0));
+    QTRY_VERIFY(!session.gradientEdit().has_value());
+    // Another layer's mask gradient stays out of this view.
+    session.addBlankLayer();
+    const QUuid other = session.activeLayerID().value();
+    session.addLayerMask();
+    session.beginGradient(QPointF(0, 80));
+    session.moveGradient(std::nullopt, QPointF(200, 80));
+    QVERIFY(session.gradientEdit().has_value() && session.gradientEdit()->raster->isMask && session.gradientEdit()->raster->layer.id == other);
+    session.toggleMaskAlone(shown.id);
+    QCOMPARE(session.maskAloneLayer().value().id, shown.id);
+    QVERIFY(session.gradientEdit().has_value());
+    QVERIFY(gray(shown.at(QPointF(50, 50)), 255) && gray(shown.at(QPointF(150, 50)), 0));
+    QTRY_VERIFY(!session.gradientEdit().has_value());
+}
+
 QTEST_MAIN(MaskAloneTests)
 #include "MaskAloneTests.moc"

tests/PaintRefusalTests.cpp

@@ -8,6 +8,7 @@ private slots:
     void eachRefusalSaysWhy();
     void theGradientAndTheSmearSayWhyToo();
     void aBusyEditorOrAnotherToolSaysNothing();
+    void theEarlierReasonWinsAtEverySeam();
 };
 
 namespace {
@@ -144,5 +145,32 @@ void PaintRefusalTests::aBusyEditorOrAnotherToolSaysNothing()
     QCOMPARE(session->brushError(), std::optional<QString>("Earlier"));
 }
 
+void PaintRefusalTests::theEarlierReasonWinsAtEverySeam()
+{
+    const auto session = makeSession();
+    const QUuid layer = session->activeLayerID().value();
+    // A hidden folder's pixels: the folder, not the hiding.
+    session->addGroup();
+    const QUuid folder = session->activeLayerID().value();
+    session->toggleLayerVisibility(folder);
+    QCOMPARE(pressed(*session), std::optional<QString>("“Folder 1” is a folder, which has no pixels of its own. Paint on a layer inside it, or on the "
+                                                       "folder’s mask."));
+    session->toggleLayerVisibility(folder);
+    // A hidden layer's mask turned off: the hiding.
+    session->selectLayer(layer);
+    session->addLayerMask();
+    session->toggleLayerMask();
+    session->toggleLayerVisibility(layer);
+    QCOMPARE(pressed(*session), std::optional<QString>("“Layer 1” is hidden, or inside a hidden folder. Show it to paint on it."));
+    session->toggleLayerVisibility(layer);
+    session->toggleLayerMask();
+    // An adjustment's pixels in an empty selection: the adjustment.
+    session->addAdjustment(AdjustmentKind::levels);
+    session->setAdjustmentEditingID(std::nullopt);
+    session->selectLayerTarget(session->activeLayerID().value(), false);
+    emptySelection(*session);
+    QCOMPARE(pressed(*session), std::optional<QString>("“Levels” is an adjustment layer, with no pixels to paint. Paint on its mask instead."));
+}
+
 QTEST_GUILESS_MAIN(PaintRefusalTests)
 #include "PaintRefusalTests.moc"

tests/SelectionCanvasTests.cpp

@@ -346,6 +346,9 @@ void SelectionCanvasTests::shiftKeepsMovedPixelsOnALine()
     // Lengths, not signs: left beats a shorter down.
     shown.move(QPointF(0, 50), Qt::ControlModifier | Qt::ShiftModifier);
     QCOMPARE(box(), QRectF(-20, 20, 40, 40));
+    // And up beats a shorter right.
+    shown.move(QPointF(45, 0), Qt::ControlModifier | Qt::ShiftModifier);
+    QCOMPARE(box(), QRectF(20, -20, 40, 40));
     // Without Shift both ways.
     shown.move(QPointF(60, 55), Qt::ControlModifier);
     QCOMPARE(box(), QRectF(40, 35, 40, 40));