QMacStyle: Fix appearance of selected inactive tab bar button

Because we use toggle NSButton for selected tabs, the inactive
appearance doesn't follow what NSSegmentedControl would have
shown. Therefore, we fall back to our good old habits, i.e.,
render on a pixmap and do some pixel transformations.

Change-Id: I838a2f23abee5846219ba67328c79fa8cc359a9b
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

1 files changed, 50 insertions, 9 deletions

diff --git a/src/plugins/styles/mac/qmacstyle_mac.mm b/src/plugins/styles/mac/qmacstyle_mac.mm
index 81abbc6caf..4dc3cfd634 100644
--- a/src/plugins/styles/mac/qmacstyle_mac.mm
+++ b/src/plugins/styles/mac/qmacstyle_mac.mm
@@ -3602,6 +3602,7 @@ void QMacStyle::drawControl(ControlElement ce, const QStyleOption *opt, QPainter
                 return;
             }
 
+            const bool isActive = tabOpt->state & State_Active;
             const bool isEnabled = tabOpt->state & State_Enabled;
             const bool isPressed = tabOpt->state & State_Sunken;
             const bool isSelected = tabOpt->state & State_Selected;
@@ -3630,17 +3631,20 @@ void QMacStyle::drawControl(ControlElement ce, const QStyleOption *opt, QPainter
             // a push NSButton instead and clip the CGContext.
 
             const auto cs = d->effectiveAquaSizeConstrain(opt, w);
-            // Extra hack to get the proper pressed appreance when not selected
-            const auto ct = isSelected || tp == QStyleOptionTab::OnlyOneTab ?
+            // Extra hacks to get the proper pressed appreance when not selected or selected and inactive
+            const bool needsInactiveHack = (!isActive && isSelected);
+            const auto ct = !needsInactiveHack && (isSelected || tp == QStyleOptionTab::OnlyOneTab) ?
                     QMacStylePrivate::Button_PushButton :
                     QMacStylePrivate::Button_PopupButton;
+            const bool isPopupButton = ct == QMacStylePrivate::Button_PopupButton;
             const auto cw = QMacStylePrivate::CocoaControl(ct, cs);
             auto *pb = static_cast<NSButton *>(d->cocoaControl(cw));
-            auto vOffset = isSelected ? 2 : 1;
+
+            auto vOffset = isPopupButton ? 1 : 2;
             if (tabDirection == QMacStylePrivate::East)
                 vOffset -= 1;
-            const auto outerAdjust = isSelected ? 4 : 1;
-            const auto innerAdjust = isSelected ? 10 : 20;
+            const auto outerAdjust = isPopupButton ? 1 : 4;
+            const auto innerAdjust = isPopupButton ? 20 : 10;
             QRectF frameRect = tabOpt->rect;
             if (verticalTabs)
                 frameRect = QRectF(frameRect.y(), frameRect.x(), frameRect.height(), frameRect.width());
@@ -3672,10 +3676,12 @@ void QMacStyle::drawControl(ControlElement ce, const QStyleOption *opt, QPainter
 
             pb.enabled = isEnabled;
             [pb highlight:isPressed];
-            pb.state = isSelected && !isPressed ? NSOnState : NSOffState;
-            d->drawNSViewInRect(pb, frameRect, p, ^(CGContextRef ctx, const CGRect &r) {
+            // Set off state when inactive. See needsInactiveHack for when it's selected
+            pb.state = (isActive && isSelected && !isPressed) ? NSOnState : NSOffState;
+
+            const auto drawBezelBlock = ^(CGContextRef ctx, const CGRect &r) {
                 CGContextClipToRect(ctx, opt->rect.toCGRect());
-                if (!isSelected) {
+                if (!isSelected || needsInactiveHack) {
                     // Final stage of the pressed state hack: flip NSPopupButton rendering
                     if (!verticalTabs && tp == QStyleOptionTab::End) {
                         CGContextTranslateCTM(ctx, opt->rect.right(), 0);
@@ -3703,7 +3709,42 @@ void QMacStyle::drawControl(ControlElement ce, const QStyleOption *opt, QPainter
                 }
 
                 [pb.cell drawBezelWithFrame:r inView:pb.superview];
-            });
+            };
+
+            if (needsInactiveHack) {
+                // First, render tab as non-selected tab on a pixamp
+                const qreal pixelRatio = p->device()->devicePixelRatioF();
+                QImage tabPixmap(opt->rect.size() * pixelRatio, QImage::Format_ARGB32_Premultiplied);
+                tabPixmap.setDevicePixelRatio(pixelRatio);
+                tabPixmap.fill(Qt::transparent);
+                QPainter tabPainter(&tabPixmap);
+                d->drawNSViewInRect(pb, frameRect, &tabPainter, ^(CGContextRef ctx, const CGRect &r) {
+                    CGContextTranslateCTM(ctx, -opt->rect.left(), -opt->rect.top());
+                    drawBezelBlock(ctx, r);
+                });
+                tabPainter.end();
+
+                // Then, darken it with the proper shade of gray
+                const qreal inactiveGray = 0.898; // As measured
+                const int inactiveGray8 = qRound(inactiveGray * 255.0);
+                const QRgb inactiveGrayRGB = qRgb(inactiveGray8, inactiveGray8, inactiveGray8);
+                for (int l = 0; l < tabPixmap.height(); ++l) {
+                    auto *line = reinterpret_cast<QRgb*>(tabPixmap.scanLine(l));
+                    for (int i = 0; i < tabPixmap.width(); ++i) {
+                        if (qAlpha(line[i]) == 255) {
+                            line[i] = inactiveGrayRGB;
+                        } else if (qAlpha(line[i]) > 128) {
+                            const int g = qRound(inactiveGray * qRed(line[i]));
+                            line[i] = qRgba(g, g, g, qAlpha(line[i]));
+                        }
+                    }
+                }
+
+                // Finally, draw the tab pixmap on the current painter
+                p->drawImage(opt->rect, tabPixmap);
+            } else {
+                d->drawNSViewInRect(pb, frameRect, p, drawBezelBlock);
+            }
 
             if (!isSelected && sp != QStyleOptionTab::NextIsSelected
                     && tp != QStyleOptionTab::End