Merge remote-tracking branch 'origin/5.12' into 5.13

Conflicts:
	src/gui/painting/qdrawhelper.cpp
	src/gui/painting/qdrawhelper_p.h
	src/gui/painting/qdrawhelper_sse2.cpp
	src/gui/painting/qdrawhelper_x86_p.h

Change-Id: I83256bb38ab3a705776e353bc0629315b6c59a0f

4 files changed, 38 insertions, 17 deletions

diff --git a/src/corelib/tools/qstring.cpp b/src/corelib/tools/qstring.cpp
index b3ea553b51..b25685923c 100644
--- a/src/corelib/tools/qstring.cpp
+++ b/src/corelib/tools/qstring.cpp
@@ -1199,10 +1199,10 @@ static int qt_compare_strings(QLatin1String lhs, QStringView rhs, Qt::CaseSensit
 
 static int qt_compare_strings(QLatin1String lhs, QLatin1String rhs, Qt::CaseSensitivity cs) Q_DECL_NOTHROW
 {
-    if (cs == Qt::CaseInsensitive)
-        return qstrnicmp(lhs.data(), lhs.size(), rhs.data(), rhs.size());
     if (lhs.isEmpty())
         return lencmp(0, rhs.size());
+    if (cs == Qt::CaseInsensitive)
+        return qstrnicmp(lhs.data(), lhs.size(), rhs.data(), rhs.size());
     const auto l = std::min(lhs.size(), rhs.size());
     int r = qstrncmp(lhs.data(), rhs.data(), l);
     return r ? r : lencmp(lhs.size(), rhs.size());
diff --git a/src/gui/painting/qbackingstore.cpp b/src/gui/painting/qbackingstore.cpp
index 3240b83451..b0393aff95 100644
--- a/src/gui/painting/qbackingstore.cpp
+++ b/src/gui/painting/qbackingstore.cpp
@@ -95,6 +95,11 @@ public:
 QBackingStore::QBackingStore(QWindow *window)
     : d_ptr(new QBackingStorePrivate(window))
 {
+    if (window->handle()) {
+        // Create platform backingstore up front if we have a platform window,
+        // otherwise delay the creation until absolutely necessary.
+        handle();
+    }
 }
 
 /*!
diff --git a/src/plugins/platforms/cocoa/qcocoabackingstore.mm b/src/plugins/platforms/cocoa/qcocoabackingstore.mm
index 5c36ce00f7..5550f0586b 100644
--- a/src/plugins/platforms/cocoa/qcocoabackingstore.mm
+++ b/src/plugins/platforms/cocoa/qcocoabackingstore.mm
@@ -75,6 +75,37 @@ QCFType<CGColorSpaceRef> QCocoaBackingStore::colorSpace() const
 QNSWindowBackingStore::QNSWindowBackingStore(QWindow *window)
     : QCocoaBackingStore(window)
 {
+    // Choose an appropriate window depth based on the requested surface format.
+    // On deep color displays the default bit depth is 16-bit, so unless we need
+    // that level of precision we opt out of it (and the expensive RGB32 -> RGB64
+    // conversions that come with it if our backingstore depth does not match).
+
+    NSWindow *nsWindow = static_cast<QCocoaWindow *>(window->handle())->view().window;
+    auto colorSpaceName = NSColorSpaceFromDepth(nsWindow.depthLimit);
+
+    static const int kDefaultBitDepth = 8;
+    auto surfaceFormat = window->requestedFormat();
+    auto bitsPerSample = qMax(kDefaultBitDepth, qMax(surfaceFormat.redBufferSize(),
+        qMax(surfaceFormat.greenBufferSize(), surfaceFormat.blueBufferSize())));
+
+    // NSBestDepth does not seem to guarantee a window depth deep enough for the
+    // given bits per sample, even if documented as such. For example, requesting
+    // 10 bits per sample will not give us a 16-bit format, even if that's what's
+    // available. Work around this by manually bumping the bit depth.
+    bitsPerSample = !(bitsPerSample & (bitsPerSample - 1))
+        ? bitsPerSample : qNextPowerOfTwo(bitsPerSample);
+
+    auto bestDepth = NSBestDepth(colorSpaceName, bitsPerSample, 0, NO, nullptr);
+
+    // Disable dynamic depth limit, otherwise our depth limit will be overwritten
+    // by AppKit if the window moves to a screen with a different depth. We call
+    // this before setting the depth limit, as the call will reset the depth to 0.
+    [nsWindow setDynamicDepthLimit:NO];
+
+    qCDebug(lcQpaBackingStore) << "Using" << NSBitsPerSampleFromDepth(bestDepth)
+        << "bit window depth for" << nsWindow;
+
+    nsWindow.depthLimit = bestDepth;
 }
 
 QNSWindowBackingStore::~QNSWindowBackingStore()
diff --git a/src/plugins/platforms/cocoa/qcocoawindow.mm b/src/plugins/platforms/cocoa/qcocoawindow.mm
index bda8183167..db4bc12210 100644
--- a/src/plugins/platforms/cocoa/qcocoawindow.mm
+++ b/src/plugins/platforms/cocoa/qcocoawindow.mm
@@ -1660,21 +1660,6 @@ QCocoaNSWindow *QCocoaWindow::createNSWindow(bool shouldBePanel)
 
     applyContentBorderThickness(nsWindow);
 
-    // Prevent CoreGraphics RGB32 -> RGB64 backing store conversions on deep color
-    // displays by forcing 8-bit components, unless a deep color format has been
-    // requested. This conversion uses significant CPU time.
-    QSurface::SurfaceType surfaceType = QPlatformWindow::window()->surfaceType();
-    bool usesCoreGraphics = surfaceType == QSurface::RasterSurface || surfaceType == QSurface::RasterGLSurface;
-    QSurfaceFormat surfaceFormat = QPlatformWindow::window()->format();
-    bool usesDeepColor = surfaceFormat.redBufferSize() > 8 ||
-                         surfaceFormat.greenBufferSize() > 8 ||
-                         surfaceFormat.blueBufferSize() > 8;
-    bool usesLayer = view().layer;
-    if (usesCoreGraphics && !usesDeepColor && !usesLayer) {
-        [nsWindow setDynamicDepthLimit:NO];
-        [nsWindow setDepthLimit:NSWindowDepthTwentyfourBitRGB];
-    }
-
     if (format().colorSpace() == QSurfaceFormat::sRGBColorSpace)
         nsWindow.colorSpace = NSColorSpace.sRGBColorSpace;