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// Copyright 2019 Google LLC.
// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
// This is an example of a minimal iOS application that uses Skia to draw to
// a Metal drawable.
// Much of this code is copied from the default application created by XCode.
#include "tools/skottie_ios_app/SkMetalViewBridge.h"
#include "include/core/SkCanvas.h"
#include "include/core/SkPaint.h"
#include "include/core/SkSurface.h"
#include "include/core/SkTime.h"
#include "include/effects/SkGradientShader.h"
#include "include/gpu/GrBackendSurface.h"
#include "include/gpu/GrDirectContext.h"
#include "include/gpu/mtl/GrMtlTypes.h"
#import <Metal/Metal.h>
#import <MetalKit/MetalKit.h>
#import <UIKit/UIKit.h>
static void config_paint(SkPaint* paint) {
if (!paint->getShader()) {
const SkColor4f colors[2] = {SkColors::kBlack, SkColors::kWhite};
const SkPoint points[2] = {{0, -1024}, {0, 1024}};
paint->setShader(SkGradientShader::MakeLinear(points, colors, nullptr, nullptr, 2,
SkTileMode::kClamp, 0, nullptr));
static void draw_example(SkSurface* surface, const SkPaint& paint, double rotation) {
SkCanvas* canvas = surface->getCanvas();
canvas->translate(surface->width() * 0.5f, surface->height() * 0.5f);
@interface AppViewDelegate : NSObject <MTKViewDelegate>
@property (assign, nonatomic) GrDirectContext* grContext; // non-owning pointer.
@property (assign, nonatomic) id<MTLCommandQueue> metalQueue;
@implementation AppViewDelegate {
SkPaint fPaint;
- (void)drawInMTKView:(nonnull MTKView *)view {
if (![self grContext] || !view) {
// Do as much as possible before creating surface.
float rotation = (float)(180 * 1e-9 * SkTime::GetNSecs());
// Create surface:
sk_sp<SkSurface> surface = SkMtkViewToSurface(view, [self grContext]);
if (!surface) {
NSLog(@"error: no sksurface");
draw_example(surface.get(), fPaint, rotation);
// Must flush *and* present for this to work!
surface = nullptr;
id<MTLCommandBuffer> commandBuffer = [[self metalQueue] commandBuffer];
[commandBuffer presentDrawable:[view currentDrawable]];
[commandBuffer commit];
- (void)mtkView:(nonnull MTKView *)view drawableSizeWillChange:(CGSize)size {
// change anything on size change?
@interface AppViewController : UIViewController
@property (strong, nonatomic) id<MTLDevice> metalDevice;
@property (strong, nonatomic) id<MTLCommandQueue> metalQueue;
@implementation AppViewController {
GrContextHolder fGrContext;
- (void)loadView {
[self setView:[[MTKView alloc] initWithFrame:[[UIScreen mainScreen] bounds] device:nil]];
- (void)viewDidLoad {
[super viewDidLoad];
if (!fGrContext) {
[self setMetalDevice:MTLCreateSystemDefaultDevice()];
[self setMetalQueue:[[self metalDevice] newCommandQueue]];
fGrContext = SkMetalDeviceToGrContext([self metalDevice], [self metalQueue]);
if (![self view] || ![self metalDevice]) {
NSLog(@"Metal is not supported on this device");
self.view = [[UIView alloc] initWithFrame:self.view.frame];
MTKView* mtkView = (MTKView*)[self view];
[mtkView setDevice:[self metalDevice]];
[mtkView setBackgroundColor:[UIColor blackColor]];
AppViewDelegate* viewDelegate = [[AppViewDelegate alloc] init];
[viewDelegate setGrContext:fGrContext.get()];
[viewDelegate setMetalQueue:[self metalQueue]];
[viewDelegate mtkView:mtkView drawableSizeWillChange:[mtkView bounds].size];
[mtkView setDelegate:viewDelegate];
@interface AppDelegate : UIResponder <UIApplicationDelegate>
@property (strong, nonatomic) UIWindow *window;
@implementation AppDelegate
- (BOOL)application:(UIApplication *)app didFinishLaunchingWithOptions:(NSDictionary*)opts {
// Override point for customization after application launch.
[self setWindow:[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]]];
[[self window] setFrame:[[UIScreen mainScreen] bounds]];
[[self window] setRootViewController:[[AppViewController alloc] init]];
[[self window] makeKeyAndVisible];
return YES;
int main(int argc, char* argv[]) {
@autoreleasepool {
return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));