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/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at */
#include "GLContextProvider.h"
#include "GLContextCGL.h"
#include "GLLibraryLoader.h"
#include "nsDebug.h"
#include "nsIWidget.h"
#include <OpenGL/gl.h>
#include "gfxFailure.h"
#include "mozilla/IntegerRange.h"
#include "mozilla/StaticPrefs_gfx.h"
#include "mozilla/StaticPrefs_gl.h"
#include "mozilla/StaticPrefs_layout.h"
#include "prenv.h"
#include "prlink.h"
#include "mozilla/ProfilerLabels.h"
#include "MozFramebuffer.h"
#include "mozilla/layers/CompositorOptions.h"
#include "mozilla/widget/CompositorWidget.h"
#include "ScopedGLHelpers.h"
#include <OpenGL/OpenGL.h>
namespace mozilla {
namespace gl {
using namespace mozilla::gfx;
using namespace mozilla::widget;
class CGLLibrary {
bool EnsureInitialized() {
if (mInitialized) {
return true;
if (!mOGLLibrary) {
mOGLLibrary = PR_LoadLibrary("/System/Library/Frameworks/OpenGL.framework/OpenGL");
if (!mOGLLibrary) {
NS_WARNING("Couldn't load OpenGL Framework.");
return false;
mInitialized = true;
return true;
const auto& Library() const { return mOGLLibrary; }
bool mInitialized = false;
PRLibrary* mOGLLibrary = nullptr;
CGLLibrary sCGLLibrary;
GLContextCGL::GLContextCGL(const GLContextDesc& desc, NSOpenGLContext* context)
: GLContext(desc), mContext(context) {
CGDisplayRegisterReconfigurationCallback(DisplayReconfigurationCallback, this);
GLContextCGL::~GLContextCGL() {
CGDisplayRemoveReconfigurationCallback(DisplayReconfigurationCallback, this);
if (mContext) {
if ([NSOpenGLContext currentContext] == mContext) {
// Clear the current context before releasing. If we don't do
// this, the next time we call [NSOpenGLContext currentContext],
// "invalid context" will be printed to the console.
[NSOpenGLContext clearCurrentContext];
[mContext release];
CGLContextObj GLContextCGL::GetCGLContext() const {
return static_cast<CGLContextObj>([mContext CGLContextObj]);
bool GLContextCGL::MakeCurrentImpl() const {
if (mContext) {
[mContext makeCurrentContext];
// Use non-blocking swap in "ASAP mode".
// ASAP mode means that rendering is iterated as fast as possible.
// ASAP mode is entered when layout.frame_rate=0 (requires restart).
// If swapInt is 1, then glSwapBuffers will block and wait for a vblank signal.
// When we're iterating as fast as possible, however, we want a non-blocking
// glSwapBuffers, which will happen when swapInt==0.
GLint swapInt = StaticPrefs::layout_frame_rate() == 0 ? 0 : 1;
[mContext setValues:&swapInt forParameter:NSOpenGLCPSwapInterval];
return true;
bool GLContextCGL::IsCurrentImpl() const { return [NSOpenGLContext currentContext] == mContext; }
/* static */ void GLContextCGL::DisplayReconfigurationCallback(CGDirectDisplayID aDisplay,
CGDisplayChangeSummaryFlags aFlags,
void* aUserInfo) {
if (aFlags & kCGDisplaySetModeFlag) {
static_cast<GLContextCGL*>(aUserInfo)->mActiveGPUSwitchMayHaveOccurred = true;
static NSOpenGLContext* CreateWithFormat(const NSOpenGLPixelFormatAttribute* attribs) {
NSOpenGLPixelFormat* format = [[NSOpenGLPixelFormat alloc] initWithAttributes:attribs];
if (!format) {
NS_WARNING("Failed to create NSOpenGLPixelFormat.");
return nullptr;
NSOpenGLContext* context = [[NSOpenGLContext alloc] initWithFormat:format shareContext:nullptr];
[format release];
return context;
// Get the "OpenGL display mask" for a fresh context. The return value of this
// function depends on the time at which this function is called.
// In practice, on a Macbook Pro with an integrated and a discrete GPU, this function returns the
// display mask for the GPU that currently drives the internal display.
// Quick reference of the concepts involved in the code below:
// GPU switch: On Mac devices with an integrated and a discrete GPU, a GPU switch changes which
// GPU drives the internal display. Both GPUs are still usable at all times. (When the
// integrated GPU is driving the internal display, using the discrete GPU can incur a longer
// warm-up cost.)
// Virtual screen: A CGL concept. A "virtual screen" corresponds to a GL renderer. There's one
// for the integrated GPU, one for each discrete GPU, and one for the Apple software renderer.
// The list of virtual screens is per-NSOpenGLPixelFormat; it is filtered down to only the
// renderers that support the requirements from the pixel format attributes. Indexes into this
// list (such as currentVirtualScreen) cannot be used interchangably across different
// NSOpenGLPixelFormat instances.
// Display mask: A bitset per GL renderer. Different renderers have disjoint display masks. The
// Apple software renderer has all bits zeroed. For each CGDirectDisplayID,
// CGDisplayIDToOpenGLDisplayMask(displayID) returns a single bit in the display mask.
// CGDirectDisplayID: An ID for each (physical screen, GPU which can drive this screen) pair. The
// current CGDirectDisplayID for an NSScreen object can be obtained using [[[screen
// deviceDescription] objectForKey:@"NSScreenNumber"] unsignedIntValue]; it changes depending on
// which GPU is currently driving the screen.
static CGOpenGLDisplayMask GetFreshContextDisplayMask() {
NSOpenGLPixelFormatAttribute attribs[] = {NSOpenGLPFAAllowOfflineRenderers, 0};
NSOpenGLPixelFormat* pixelFormat = [[NSOpenGLPixelFormat alloc] initWithAttributes:attribs];
NSOpenGLContext* context = [[NSOpenGLContext alloc] initWithFormat:pixelFormat
GLint displayMask = 0;
[pixelFormat getValues:&displayMask
forVirtualScreen:[context currentVirtualScreen]];
[pixelFormat release];
[context release];
return static_cast<CGOpenGLDisplayMask>(displayMask);
static bool IsSameGPU(CGOpenGLDisplayMask mask1, CGOpenGLDisplayMask mask2) {
if ((mask1 & mask2) != 0) {
return true;
// Both masks can be zero, when using the Apple software renderer.
return !mask1 && !mask2;
void GLContextCGL::MigrateToActiveGPU() {
if (!mActiveGPUSwitchMayHaveOccurred.compareExchange(true, false)) {
CGOpenGLDisplayMask newPreferredDisplayMask = GetFreshContextDisplayMask();
NSOpenGLPixelFormat* pixelFormat = [mContext pixelFormat];
GLint currentVirtualScreen = [mContext currentVirtualScreen];
GLint currentDisplayMask = 0;
[pixelFormat getValues:&currentDisplayMask
if (IsSameGPU(currentDisplayMask, newPreferredDisplayMask)) {
// No "virtual screen" change needed.
// Find the "virtual screen" with a display mask that matches newPreferredDisplayMask, if
// available, and switch the context over to it.
// This code was inspired by equivalent functionality in -[NSOpenGLContext update] which only
// kicks in for contexts that present via a CAOpenGLLayer.
for (const auto i : IntegerRange([pixelFormat numberOfVirtualScreens])) {
GLint displayMask = 0;
[pixelFormat getValues:&displayMask forAttribute:NSOpenGLPFAScreenMask forVirtualScreen:i];
if (IsSameGPU(displayMask, newPreferredDisplayMask)) {
CGLSetVirtualScreen([mContext CGLContextObj], i);
GLenum GLContextCGL::GetPreferredARGB32Format() const { return LOCAL_GL_BGRA; }
bool GLContextCGL::SwapBuffers() {
// We do not have a default framebuffer. Just do a flush.
// Flushing is necessary if we want our IOSurfaces to have the correct
// content once they're picked up by the WindowServer from our CALayers.
return true;
void GLContextCGL::GetWSIInfo(nsCString* const out) const { out->AppendLiteral("CGL"); }
Maybe<SymbolLoader> GLContextCGL::GetSymbolLoader() const {
const auto& lib = sCGLLibrary.Library();
return Some(SymbolLoader(*lib));
already_AddRefed<GLContext> GLContextProviderCGL::CreateForCompositorWidget(
CompositorWidget* aCompositorWidget, bool aHardwareWebRender, bool aForceAccelerated) {
CreateContextFlags flags = CreateContextFlags::ALLOW_OFFLINE_RENDERER;
if (aForceAccelerated) {
flags |= CreateContextFlags::FORCE_ENABLE_HARDWARE;
if (!aHardwareWebRender) {
flags |= CreateContextFlags::REQUIRE_COMPAT_PROFILE;
nsCString failureUnused;
return CreateHeadless({flags}, &failureUnused);
static RefPtr<GLContextCGL> CreateOffscreenFBOContext(GLContextCreateDesc desc) {
if (!sCGLLibrary.EnsureInitialized()) {
return nullptr;
NSOpenGLContext* context = nullptr;
std::vector<NSOpenGLPixelFormatAttribute> attribs;
auto& flags = desc.flags;
if (!StaticPrefs::gl_allow_high_power()) {
flags &= ~CreateContextFlags::HIGH_POWER;
if (flags & CreateContextFlags::ALLOW_OFFLINE_RENDERER ||
!(flags & CreateContextFlags::HIGH_POWER)) {
// This is really poorly named on Apple's part, but "AllowOfflineRenderers" means
// that we want to allow running on the iGPU instead of requiring the dGPU.
if (flags & CreateContextFlags::FORCE_ENABLE_HARDWARE) {
if (!(flags & CreateContextFlags::REQUIRE_COMPAT_PROFILE)) {
auto coreAttribs = attribs;
context = CreateWithFormat(;
if (!context) {
context = CreateWithFormat(;
if (!context) {
NS_WARNING("Failed to create NSOpenGLContext.");
return nullptr;
RefPtr<GLContextCGL> glContext = new GLContextCGL({desc, true}, context);
if (flags & CreateContextFlags::PREFER_MULTITHREADED) {
CGLEnable(glContext->GetCGLContext(), kCGLCEMPEngine);
return glContext;
already_AddRefed<GLContext> GLContextProviderCGL::CreateHeadless(const GLContextCreateDesc& desc,
nsACString* const out_failureId) {
auto gl = CreateOffscreenFBOContext(desc);
if (!gl) {
*out_failureId = "FEATURE_FAILURE_CGL_FBO"_ns;
return nullptr;
if (!gl->Init()) {
*out_failureId = "FEATURE_FAILURE_CGL_INIT"_ns;
NS_WARNING("Failed during Init.");
return nullptr;
return gl.forget();
static RefPtr<GLContext> gGlobalContext;
GLContext* GLContextProviderCGL::GetGlobalContext() {
static bool triedToCreateContext = false;
if (!triedToCreateContext) {
triedToCreateContext = true;
nsCString discardFailureId;
RefPtr<GLContext> temp = CreateHeadless({}, &discardFailureId);
gGlobalContext = temp;
if (!gGlobalContext) {
NS_WARNING("Couldn't init gGlobalContext.");
return gGlobalContext;
void GLContextProviderCGL::Shutdown() { gGlobalContext = nullptr; }
} /* namespace gl */
} /* namespace mozilla */