[sailfishos][gecko] Add support for prefers-color-scheme. JB#58394

Adds support to qt/nsLookAndFeel for the prefers-color-scheme media tag.
The renderer already supports it by setting the ui.systemUsesDarkTheme
preference to 0 or 1.

This patch allows, in addition, for the colour scheme to be controlled
by sending an "ambience-theme-changed" notification with a data payload
of either "light" or "dark". If the ui.systemUsesDarkTheme preference is
unset or set to something other than 0 or 1, the notification value will
be used to control the theme instead.

This functionality is used to update the colour scheme based on the
ambience of the device.

rpm/0093-sailfishos-gecko-Add-support-for-prefers-color-schem.patch

@@ -0,0 +1,154 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: David Llewellyn-Jones <david.llewellyn-jones@jolla.com>
+Date: Wed, 23 Nov 2022 09:08:22 +0200
+Subject: [PATCH] [sailfishos][gecko] Add support for prefers-color-scheme.
+ JB#58394
+
+Adds support to qt/nsLookAndFeel for the prefers-color-scheme media tag.
+The renderer already supports it by setting the ui.systemUsesDarkTheme
+preference to 0 or 1.
+
+This patch allows, in addition, for the colour scheme to be controlled
+by sending a "ambience-theme-changed" notification with a data payload
+of either "light" or "dark". If the ui.systemUsesDarkTheme preference is
+unset or set to something other than 0 or 1, the notification value will
+be used to control the theme instead.
+
+This functionality is used to update the colour scheme based on the
+ambience of the device.
+---
+ widget/qt/nsLookAndFeel.cpp | 71 ++++++++++++++++++++++++++++++++++++-
+ widget/qt/nsLookAndFeel.h   |  4 +++
+ 2 files changed, 74 insertions(+), 1 deletion(-)
+
+diff --git a/widget/qt/nsLookAndFeel.cpp b/widget/qt/nsLookAndFeel.cpp
+index 6a0f91d1cd87..495b25e057ec 100644
+--- a/widget/qt/nsLookAndFeel.cpp
++++ b/widget/qt/nsLookAndFeel.cpp
+@@ -26,6 +26,33 @@
+ #include "mozilla/gfx/2D.h"
+ #include "mozilla/FontPropertyTypes.h"
+ #include "mozilla/StaticPrefs_widget.h"
++#include "mozilla/Services.h"
++#include "mozilla/Logging.h"
++#include "nsIObserver.h"
++
++using namespace mozilla;
++
++LazyLogModule sLookAndFeel("LookAndFeel");
++
++class nsLookAndFeel::Observer final : public nsIObserver
++{
++public:
++    NS_DECL_ISUPPORTS
++
++    explicit Observer() : mDarkAmbience(false) {}
++
++    NS_IMETHOD Observe(nsISupports*, const char* aTopic,
++                       const char16_t* aData) override;
++
++    bool GetDarkAmbience();
++private:
++    virtual ~Observer() = default;
++
++public:
++    bool mDarkAmbience;
++};
++
++NS_IMPL_ISUPPORTS(nsLookAndFeel::Observer, nsIObserver)
+
+ static const char16_t UNICODE_BULLET = 0x2022;
+
+@@ -35,12 +62,48 @@ static const char16_t UNICODE_BULLET = 0x2022;
+ nsLookAndFeel::nsLookAndFeel()
+     : nsXPLookAndFeel()
+ {
++    mObserver = new nsLookAndFeel::Observer();
++    nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
++    if (os) {
++        os->AddObserver(mObserver, "ambience-theme-changed", false);
++    }
+ }
+
+ nsLookAndFeel::~nsLookAndFeel()
+ {
++    nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
++    if (os) {
++        os->RemoveObserver(mObserver, "ambience-theme-changed");
++    }
++    mObserver = nullptr;
++}
++
++NS_IMETHODIMP nsLookAndFeel::Observer::Observe(nsISupports*, const char* aTopic, const char16_t* aData) {
++    MOZ_ASSERT(!strcmp(aTopic, "ambience-theme-changed"));
++
++    bool darkAmbience = false;
++    nsDependentString data(aData);
++    if (data.EqualsLiteral("dark")) {
++        darkAmbience = true;
++    }
++
++    if (mDarkAmbience != darkAmbience) {
++        mDarkAmbience = darkAmbience;
++        MOZ_LOG(sLookAndFeel, LogLevel::Info, ("Ambience set to %s", mDarkAmbience ? "dark" : "light"));
++        if (nsCOMPtr<nsIObserverService> obs = services::GetObserverService()) {
++            obs->NotifyObservers(nullptr, "look-and-feel-changed", nullptr);
++        }
++    }
++
++    return NS_OK;
++}
++
++bool nsLookAndFeel::Observer::GetDarkAmbience()
++{
++    return mDarkAmbience;
+ }
+
++
+ void nsLookAndFeel::NativeInit() { }
+
+ nsresult
+@@ -304,7 +367,8 @@ nsresult
+ nsLookAndFeel::GetIntImpl(IntID aID, int32_t &aResult)
+ {
+     nsresult rv = nsXPLookAndFeel::GetIntImpl(aID, aResult);
+-    if (NS_SUCCEEDED(rv))
++    // Make an exception for eIntID_SystemUsesDarkTheme as this is handled below
++    if (NS_SUCCEEDED(rv) && ((aID != eIntID_SystemUsesDarkTheme) || (aResult != 2)))
+         return rv;
+
+     rv = NS_OK;
+@@ -383,6 +447,11 @@ nsLookAndFeel::GetIntImpl(IntID aID, int32_t &aResult)
+             aResult = 2;
+             break;
+
++        case eIntID_SystemUsesDarkTheme:
++            // Choose theme based on ambience
++            aResult = mObserver->GetDarkAmbience() ? 1 : 0;
++            break;
++
+         default:
+             aResult = 0;
+             rv = NS_ERROR_FAILURE;
+diff --git a/widget/qt/nsLookAndFeel.h b/widget/qt/nsLookAndFeel.h
+index e8a134b93f3f..c9982e45c7ab 100644
+--- a/widget/qt/nsLookAndFeel.h
++++ b/widget/qt/nsLookAndFeel.h
+@@ -21,6 +21,7 @@
+
+ class nsLookAndFeel : public nsXPLookAndFeel
+ {
++    class Observer;
+ public:
+     nsLookAndFeel();
+     virtual ~nsLookAndFeel();
+@@ -36,6 +37,9 @@ public:
+
+ protected:
+     virtual nsresult NativeGetColor(ColorID aID, nscolor &aColor) override;
++
++private:
++    RefPtr<Observer> mObserver;
+ };
+
+ #endif

rpm/xulrunner-qt5.spec

@@ -147,6 +147,7 @@ Patch89:    0089-sailfishos-gecko-Add-a-video-decoder-based-on-gecko-.patch
 Patch90:    0090-sailfishos-gecko-Disable-debug-info-for-rust.patch
 Patch91:    0091-sailfishos-gecko-Initialise-SVGGeometryProperty-Reso.patch
 Patch92:    0092-sailfishos-build-Add-support-for-aarch64-to-elfhack..patch
+Patch93:    0093-sailfishos-gecko-Add-support-for-prefers-color-schem.patch
 
 #Patch20:    0020-sailfishos-loginmanager-Adapt-LoginManager-to-EmbedL.patch
 #Patch51:    0051-sailfishos-gecko-Remove-android-define-from-logging.patch