Bug 1560820 - Remove `sGfxLogLevel`. r=nical

`sGfxLogLevel` is a global variable whose value mirrors the value of the
"gfx.logging.level" pref in the prefs table, and is kept up to date by a
prefs callback.

But "gfx.logging.level" is a static pref that already has a mirror variable,
accessible via `StaticPrefs::gfx_logging_level()`.

So we can use the latter and remove the former, and this patch does that. The
patch also removes a sentence in a comment that refers to special treatment of
LOG_DEBUG and LOG_DEBUG_PRLOG, because that sentence appears to be referring to
something (another comment?) that is no longer present.

Differential Revision: https://phabricator.services.mozilla.com/D35625

--HG--
extra : moz-landing-system : lando

gfx/2d/Factory.cpp

@@ -190,10 +190,6 @@ void mozilla_UnlockFTLibrary(FT_Library aFTLibrary) {
 namespace mozilla {
 namespace gfx {
 
-// In Gecko, this value is managed by gfx.logging.level and gets updated when
-// the pref change.
-Atomic<int32_t> LoggingPrefs::sGfxLogLevel(LOG_DEFAULT);
-
 #ifdef MOZ_ENABLE_FREETYPE
 FT_Library Factory::mFTLibrary = nullptr;
 StaticMutex Factory::mFTLock;
@@ -219,18 +215,9 @@ DrawEventRecorder* Factory::mRecorder;
 
 mozilla::gfx::Config* Factory::sConfig = nullptr;
 
-static void PrefChanged(const char* aPref, void*) {
-  mozilla::gfx::LoggingPrefs::sGfxLogLevel =
-      Preferences::GetInt(StaticPrefs::GetPrefName_gfx_logging_level(),
-                          StaticPrefs::GetPrefDefault_gfx_logging_level());
-}
-
 void Factory::Init(const Config& aConfig) {
   MOZ_ASSERT(!sConfig);
   sConfig = new Config(aConfig);
-  Preferences::RegisterCallback(
-      PrefChanged,
-      nsDependentCString(StaticPrefs::GetPrefName_gfx_logging_level()));
 }
 
 void Factory::ShutDown() {

gfx/2d/Logging.h

@@ -22,6 +22,7 @@
 #endif
 #include "2D.h"
 #include "mozilla/Atomics.h"
+#include "mozilla/StaticPrefs.h"
 #include "Point.h"
 #include "BaseRect.h"
 #include "Matrix.h"
@@ -52,16 +53,6 @@ inline mozilla::LogLevel PRLogLevelForLevel(int aLevel) {
 }
 #endif
 
-class LoggingPrefs {
- public:
-  // Used to choose the level of logging we get.  The higher the number,
-  // the more logging we get.  Value of zero will give you no logging,
-  // 1 just errors, 2 adds warnings and 3 or 4 add debug logging.
-  // In addition to setting the value to 4, you will need to set the
-  // environment variable MOZ_LOG to gfx:4. See mozilla/Logging.h for details.
-  static Atomic<int32_t> sGfxLogLevel;
-};
-
 /// Graphics logging is available in both debug and release builds and is
 /// controlled with a gfx.logging.level preference. If not set, the default
 /// for the preference is 5 in the debug builds, 1 in the release builds.
@@ -146,7 +137,7 @@ struct BasicLogger {
   // OutputMessage below.  If making any changes here, also make it
   // in the appropriate places in that method.
   static bool ShouldOutputMessage(int aLevel) {
-    if (LoggingPrefs::sGfxLogLevel >= aLevel) {
+    if (StaticPrefs::gfx_logging_level() >= aLevel) {
 #if defined(MOZ_WIDGET_ANDROID)
       return true;
 #else
@@ -155,7 +146,7 @@ struct BasicLogger {
         return true;
       } else
 #  endif
-          if ((LoggingPrefs::sGfxLogLevel >= LOG_DEBUG_PRLOG) ||
+          if ((StaticPrefs::gfx_logging_level() >= LOG_DEBUG_PRLOG) ||
               (aLevel < LOG_DEBUG)) {
         return true;
       }
@@ -172,13 +163,12 @@ struct BasicLogger {
     // This behavior (the higher the preference, the more we log)
     // is consistent with what prlog does in general.  Note that if prlog
     // is in the build, but disabled, we will printf if the preferences
-    // requires us to log something (see sGfxLogLevel for the special
-    // treatment of LOG_DEBUG and LOG_DEBUG_PRLOG)
+    // requires us to log something.
     //
     // If making any logic changes to this method, you should probably
     // make the corresponding change in the ShouldOutputMessage method
     // above.
-    if (LoggingPrefs::sGfxLogLevel >= aLevel) {
+    if (StaticPrefs::gfx_logging_level() >= aLevel) {
 #if defined(MOZ_WIDGET_ANDROID)
       printf_stderr("%s%s", aString.c_str(), aNoNewline ? "" : "\n");
 #else
@@ -188,7 +178,7 @@ struct BasicLogger {
                 ("%s%s", aString.c_str(), aNoNewline ? "" : "\n"));
       } else
 #  endif
-          if ((LoggingPrefs::sGfxLogLevel >= LOG_DEBUG_PRLOG) ||
+          if ((StaticPrefs::gfx_logging_level() >= LOG_DEBUG_PRLOG) ||
               (aLevel < LOG_DEBUG)) {
         printf("%s%s", aString.c_str(), aNoNewline ? "" : "\n");
       }

modules/libpref/StaticPrefs.h

@@ -9,7 +9,6 @@
 #ifndef mozilla_StaticPrefs_h
 #define mozilla_StaticPrefs_h
 
-#include "gfxPlatform.h"
 #include "mozilla/Assertions.h"
 #include "mozilla/Atomics.h"
 #include "mozilla/TypeTraits.h"

modules/libpref/init/StaticPrefList.yaml

@@ -2658,7 +2658,13 @@
   value: 23456
   mirror: always
 
-# Note that        "gfx.logging.level" is defined in Logging.h.
+# The level of logging:
+# - 0: no logging;
+# - 1: adds errors;
+# - 2: adds warnings;
+# - 3 or 4: adds debug logging.
+# If you set the value to 4, you will also need to set the environment
+# variable MOZ_LOG to gfx:4. See mozilla/Logging.h for details.
 - name: gfx.logging.level
   type: RelaxedAtomicInt32
   value: mozilla::gfx::LOG_DEFAULT