/*************************************************************************/
/*  context_gl_osx.mm                                                    */
/*************************************************************************/
/*                       This file is part of:                           */
/*                           GODOT ENGINE                                */
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/* Copyright (c) 2007-2019 Juan Linietsky, Ariel Manzur.                 */
/* Copyright (c) 2014-2019 Godot Engine contributors (cf. AUTHORS.md)    */
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#include "context_gl_osx.h"

#if defined(OPENGL_ENABLED) || defined(GLES_ENABLED)

// DisplayLinkCallback is called from our DisplayLink OS thread informing us right before
// a screen update is required. We can use it to work around the broken vsync.
static CVReturn DisplayLinkCallback(CVDisplayLinkRef displayLink, const CVTimeStamp *now, const CVTimeStamp *outputTime, CVOptionFlags flagsIn, CVOptionFlags *flagsOut, void *displayLinkContext) {
	ContextGL_OSX *gl_ctx = (ContextGL_OSX *)displayLinkContext;

	// Set flag so we know we can output our next frame and signal our conditional lock
	// if we're not doing vsync this will be ignored
	[gl_ctx->vsync_condition lock];
	gl_ctx->waiting_for_vsync = false;
	[gl_ctx->vsync_condition signal];
	[gl_ctx->vsync_condition unlock];

	return kCVReturnSuccess;
}

void ContextGL_OSX::release_current() {

	[NSOpenGLContext clearCurrentContext];
}

void ContextGL_OSX::make_current() {

	[context makeCurrentContext];
}

void ContextGL_OSX::update() {

	[context update];
}

void ContextGL_OSX::set_opacity(GLint p_opacity) {

	[context setValues:&p_opacity forParameter:NSOpenGLCPSurfaceOpacity];
}

int ContextGL_OSX::get_window_width() {

	return OS::get_singleton()->get_video_mode().width;
}

int ContextGL_OSX::get_window_height() {

	return OS::get_singleton()->get_video_mode().height;
}

void ContextGL_OSX::swap_buffers() {

	if (use_vsync) {
		// Wait until our DisplayLink callback unsets our flag...
		[vsync_condition lock];
		while (waiting_for_vsync)
			[vsync_condition wait];

		// Make sure we wait again next frame around
		waiting_for_vsync = true;

		[vsync_condition unlock];
	}

	[context flushBuffer];
}

void ContextGL_OSX::set_use_vsync(bool p_use) {
	// CGLCPSwapInterval broke in OSX 10.14 and it seems Apple is not interested in fixing
	// it as OpenGL is now deprecated and Metal solves this differently.
	// Following SDLs example we're working around this using DisplayLink
	// When vsync is enabled we set a flag "waiting_for_vsync" to true.
	// This flag is set to false when DisplayLink informs us our display is about to refresh.

	///TODO Maybe pause/unpause display link?
	use_vsync = p_use;
	waiting_for_vsync = p_use;
}

bool ContextGL_OSX::is_using_vsync() const {

	return use_vsync;
}

Error ContextGL_OSX::initialize() {

	framework = CFBundleGetBundleWithIdentifier(CFSTR("com.apple.opengl"));
	ERR_FAIL_COND_V(!framework, ERR_CANT_CREATE);

	unsigned int attributeCount = 0;

	// OS X needs non-zero color size, so set reasonable values
	int colorBits = 32;

	// Fail if a robustness strategy was requested

#define ADD_ATTR(x) \
	{ attributes[attributeCount++] = x; }
#define ADD_ATTR2(x, y) \
	{                   \
		ADD_ATTR(x);    \
		ADD_ATTR(y);    \
	}

	// Arbitrary array size here
	NSOpenGLPixelFormatAttribute attributes[40];

	ADD_ATTR(NSOpenGLPFADoubleBuffer);
	ADD_ATTR(NSOpenGLPFAClosestPolicy);

	if (!opengl_3_context) {
		ADD_ATTR2(NSOpenGLPFAOpenGLProfile, NSOpenGLProfileVersionLegacy);
	} else {
		//we now need OpenGL 3 or better, maybe even change this to 3_3Core ?
		ADD_ATTR2(NSOpenGLPFAOpenGLProfile, NSOpenGLProfileVersion3_2Core);
	}

	ADD_ATTR2(NSOpenGLPFAColorSize, colorBits);

	/*
	if (fbconfig->alphaBits > 0)
		ADD_ATTR2(NSOpenGLPFAAlphaSize, fbconfig->alphaBits);
*/

	ADD_ATTR2(NSOpenGLPFADepthSize, 24);

	ADD_ATTR2(NSOpenGLPFAStencilSize, 8);

	/*
	if (fbconfig->stereo)
		ADD_ATTR(NSOpenGLPFAStereo);
*/

	/*
	if (fbconfig->samples > 0) {
		ADD_ATTR2(NSOpenGLPFASampleBuffers, 1);
		ADD_ATTR2(NSOpenGLPFASamples, fbconfig->samples);
	}
*/

	// NOTE: All NSOpenGLPixelFormats on the relevant cards support sRGB
	//       framebuffer, so there's no need (and no way) to request it

	ADD_ATTR(0);

#undef ADD_ATTR
#undef ADD_ATTR2

	pixelFormat = [[NSOpenGLPixelFormat alloc] initWithAttributes:attributes];
	ERR_FAIL_COND_V(pixelFormat == nil, ERR_CANT_CREATE);

	context = [[NSOpenGLContext alloc] initWithFormat:pixelFormat shareContext:nil];

	ERR_FAIL_COND_V(context == nil, ERR_CANT_CREATE);

	[context setView:window_view];

	[context makeCurrentContext];

	// setup our display link, this will inform us when a refresh is needed
	CVDisplayLinkCreateWithActiveCGDisplays(&displayLink);
	CVDisplayLinkSetOutputCallback(displayLink, &DisplayLinkCallback, this);
	CVDisplayLinkSetCurrentCGDisplayFromOpenGLContext(displayLink, context.CGLContextObj, pixelFormat.CGLPixelFormatObj);
	CVDisplayLinkStart(displayLink);

	// initialise a conditional lock object
	vsync_condition = [[NSCondition alloc] init];

	return OK;
}

ContextGL_OSX::ContextGL_OSX(id p_view, bool p_opengl_3_context) {

	opengl_3_context = p_opengl_3_context;
	window_view = p_view;
	use_vsync = false;
}

ContextGL_OSX::~ContextGL_OSX() {

	if (displayLink) {
		CVDisplayLinkRelease(displayLink);
	}
	[vsync_condition release];
}

#endif