Introduced a new Metal renderer implementation and a new example illustrating usage of Metal on macOS and iOS (partially addresses #1873)

examples/example_apple_metal/Shared/AppDelegate.h

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+
+#import <TargetConditionals.h>
+
+#if TARGET_OS_IPHONE
+
+#import <UIKit/UIKit.h>
+
+@interface AppDelegate : UIResponder <UIApplicationDelegate>
+@property (strong, nonatomic) UIWindow *window;
+@end
+
+#else
+
+#import <Cocoa/Cocoa.h>
+
+@interface AppDelegate : NSObject <NSApplicationDelegate>
+@end
+
+#endif

examples/example_apple_metal/Shared/AppDelegate.m

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+
+#import "AppDelegate.h"
+
+@implementation AppDelegate
+
+#if TARGET_OS_OSX
+- (BOOL)applicationShouldTerminateAfterLastWindowClosed:(NSApplication *)sender {
+    return YES;
+}
+#endif
+
+@end

examples/example_apple_metal/Shared/Renderer.h

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+
+#import <MetalKit/MetalKit.h>
+
+@interface Renderer : NSObject <MTKViewDelegate>
+
+-(nonnull instancetype)initWithView:(nonnull MTKView *)view;
+
+@end
+

examples/example_apple_metal/Shared/Renderer.mm

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+
+#import "Renderer.h"
+#import <Metal/Metal.h>
+
+#include "imgui.h"
+#include "imgui_impl_metal.h"
+
+#if TARGET_OS_OSX
+#include "imgui_impl_osx.h"
+#endif
+
+@interface Renderer ()
+@property (nonatomic, strong) id <MTLDevice> device;
+@property (nonatomic, strong) id <MTLCommandQueue> commandQueue;
+@end
+
+@implementation Renderer
+
+-(nonnull instancetype)initWithView:(nonnull MTKView *)view;
+{
+    self = [super init];
+    if(self)
+    {
+        _device = view.device;
+        _commandQueue = [_device newCommandQueue];
+
+        IMGUI_CHECKVERSION();
+        ImGui::CreateContext();
+        (void)ImGui::GetIO();
+        
+        ImGui_ImplMetal_Init(_device);
+
+        ImGui::StyleColorsDark();
+    }
+
+    return self;
+}
+
+- (void)drawInMTKView:(MTKView *)view
+{
+    ImGuiIO &io = ImGui::GetIO();
+    io.DisplaySize.x = view.bounds.size.width;
+    io.DisplaySize.y = view.bounds.size.height;
+
+#if TARGET_OS_OSX
+    CGFloat framebufferScale = view.window.screen.backingScaleFactor ?: NSScreen.mainScreen.backingScaleFactor;
+#else
+    CGFloat framebufferScale = view.window.screen.scale ?: UIScreen.mainScreen.scale;
+#endif
+    io.DisplayFramebufferScale = ImVec2(framebufferScale, framebufferScale);
+
+    io.DeltaTime = 1 / float(view.preferredFramesPerSecond ?: 60);
+
+    id<MTLCommandBuffer> commandBuffer = [self.commandQueue commandBuffer];
+    
+    static bool show_demo_window = true;
+    static bool show_another_window = false;
+    static float clear_color[4] = { 0.28f, 0.36f, 0.5f, 1.0f };
+
+    MTLRenderPassDescriptor *renderPassDescriptor = view.currentRenderPassDescriptor;
+    if(renderPassDescriptor != nil)
+    {
+        renderPassDescriptor.colorAttachments[0].clearColor = MTLClearColorMake(clear_color[0], clear_color[1], clear_color[2], clear_color[3]);
+
+        // Here, you could do additional rendering work, including other passes as necessary.
+
+        id <MTLRenderCommandEncoder> renderEncoder = [commandBuffer renderCommandEncoderWithDescriptor:renderPassDescriptor];
+
+        [renderEncoder pushDebugGroup:@"Draw ImGui"];
+
+        ImGui_ImplMetal_NewFrame(renderPassDescriptor);
+#if TARGET_OS_OSX
+        ImGui_ImplOSX_NewFrame(view);
+#endif
+        ImGui::NewFrame();
+
+        {
+            static float f = 0.0f;
+            static int counter = 0;
+            ImGui::Text("Hello, world!");                           // Display some text (you can use a format string too)
+            ImGui::SliderFloat("float", &f, 0.0f, 1.0f);            // Edit 1 float using a slider from 0.0f to 1.0f
+            ImGui::ColorEdit3("clear color", (float*)&clear_color); // Edit 3 floats representing a color
+
+            ImGui::Checkbox("Demo Window", &show_demo_window);      // Edit bools storing our windows open/close state
+            ImGui::Checkbox("Another Window", &show_another_window);
+
+            if (ImGui::Button("Button"))                            // Buttons return true when clicked (NB: most widgets return true when edited/activated)
+                counter++;
+            ImGui::SameLine();
+            ImGui::Text("counter = %d", counter);
+
+            ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / ImGui::GetIO().Framerate, ImGui::GetIO().Framerate);
+        }
+        
+        // 2. Show another simple window. In most cases you will use an explicit Begin/End pair to name your windows.
+        if (show_another_window)
+        {
+            ImGui::Begin("Another Window", &show_another_window);
+            ImGui::Text("Hello from another window!");
+            if (ImGui::Button("Close Me"))
+                show_another_window = false;
+            ImGui::End();
+        }
+        
+        // 3. Show the ImGui demo window. Most of the sample code is in ImGui::ShowDemoWindow(). Read its code to learn more about Dear ImGui!
+        if (show_demo_window)
+        {
+            // Normally user code doesn't need/want to call this because positions are saved in .ini file anyway.
+            // Here we just want to make the demo initial state a bit more friendly!
+            ImGui::SetNextWindowPos(ImVec2(650, 20), ImGuiCond_FirstUseEver);
+            ImGui::ShowDemoWindow(&show_demo_window);
+        }
+        
+        ImGui::Render();
+        ImDrawData *drawData = ImGui::GetDrawData();
+        ImGui_ImplMetal_RenderDrawData(drawData, commandBuffer, renderEncoder);
+        
+        [renderEncoder popDebugGroup];
+
+        [renderEncoder endEncoding];
+
+        [commandBuffer presentDrawable:view.currentDrawable];
+    }
+    
+    [commandBuffer commit];
+}
+
+- (void)mtkView:(MTKView *)view drawableSizeWillChange:(CGSize)size
+{
+}
+
+@end

examples/example_apple_metal/Shared/ViewController.h

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+
+#import <Metal/Metal.h>
+#import <MetalKit/MetalKit.h>
+#import "Renderer.h"
+
+#if TARGET_OS_IPHONE
+
+#import <UIKit/UIKit.h>
+
+@interface ViewController : UIViewController
+@end
+
+#else
+
+#import <Cocoa/Cocoa.h>
+
+@interface ViewController : NSViewController
+@end
+
+#endif

examples/example_apple_metal/Shared/ViewController.mm

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+
+#import "ViewController.h"
+#import "Renderer.h"
+#include "imgui.h"
+
+#if TARGET_OS_OSX
+#include "imgui_impl_osx.h"
+#endif
+
+@interface ViewController ()
+@property (nonatomic, readonly) MTKView *mtkView;
+@property (nonatomic, strong) Renderer *renderer;
+@end
+
+@implementation ViewController
+
+- (MTKView *)mtkView {
+    return (MTKView *)self.view;
+}
+
+- (void)viewDidLoad
+{
+    [super viewDidLoad];
+    
+    self.mtkView.device = MTLCreateSystemDefaultDevice();
+    
+    if (!self.mtkView.device) {
+        NSLog(@"Metal is not supported");
+        abort();
+    }
+
+    self.renderer = [[Renderer alloc] initWithView:self.mtkView];
+
+    [self.renderer mtkView:self.mtkView drawableSizeWillChange:self.mtkView.bounds.size];
+
+    self.mtkView.delegate = self.renderer;
+
+#if TARGET_OS_OSX
+    // Add a tracking area in order to receive mouse events whenever the mouse is within the bounds of our view
+    NSTrackingArea *trackingArea = [[NSTrackingArea alloc] initWithRect:NSZeroRect
+                                                                options:NSTrackingMouseMoved | NSTrackingInVisibleRect | NSTrackingActiveAlways
+                                                                  owner:self
+                                                               userInfo:nil];
+    [self.view addTrackingArea:trackingArea];
+    
+    // If we want to receive key events, we either need to be in the responder chain of the key view,
+    // or else we can install a local monitor. The consequence of this heavy-handed approach is that
+    // we receive events for all controls, not just ImGui widgets. If we had native controls in our
+    // window, we'd want to be much more careful than just ingesting the complete event stream, though
+    // we do make an effort to be good citizens by passing along events when ImGui doesn't want to capture.
+    NSEventMask eventMask = NSEventMaskKeyDown | NSEventMaskKeyUp | NSEventMaskFlagsChanged | NSEventTypeScrollWheel;
+    [NSEvent addLocalMonitorForEventsMatchingMask:eventMask handler:^NSEvent * _Nullable(NSEvent *event) {
+        BOOL wantsCapture = ImGui_ImplOSX_HandleEvent(event, self.view);
+        if (event.type == NSEventTypeKeyDown && wantsCapture) {
+            return nil;
+        } else {
+            return event;
+        }
+        
+    }];
+    
+    ImGui_ImplOSX_Init();
+#endif
+}
+
+#if TARGET_OS_OSX
+
+- (void)mouseMoved:(NSEvent *)event {
+    ImGui_ImplOSX_HandleEvent(event, self.view);
+}
+
+- (void)mouseDown:(NSEvent *)event {
+    ImGui_ImplOSX_HandleEvent(event, self.view);
+}
+
+- (void)mouseUp:(NSEvent *)event {
+    ImGui_ImplOSX_HandleEvent(event, self.view);
+}
+
+- (void)mouseDragged:(NSEvent *)event {
+    ImGui_ImplOSX_HandleEvent(event, self.view);
+}
+
+- (void)scrollWheel:(NSEvent *)event {
+    ImGui_ImplOSX_HandleEvent(event, self.view);
+}
+
+#elif TARGET_OS_IOS
+
+// This touch mapping is super cheesy/hacky. We treat any touch on the screen
+// as if it were a depressed left mouse button, and we don't bother handling
+// multitouch correctly at all. This causes the "cursor" to behave very erratically
+// when there are multiple active touches. But for demo purposes, single-touch
+// interaction actually works surprisingly well.
+- (void)updateIOWithTouchEvent:(UIEvent *)event {
+    UITouch *anyTouch = event.allTouches.anyObject;
+    CGPoint touchLocation = [anyTouch locationInView:self.view];
+    ImGuiIO &io = ImGui::GetIO();
+    io.MousePos = ImVec2(touchLocation.x, touchLocation.y);
+    
+    BOOL hasActiveTouch = NO;
+    for (UITouch *touch in event.allTouches) {
+        if (touch.phase != UITouchPhaseEnded && touch.phase != UITouchPhaseCancelled) {
+            hasActiveTouch = YES;
+            break;
+        }
+    }
+    io.MouseDown[0] = hasActiveTouch;
+}
+
+- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
+    [self updateIOWithTouchEvent:event];
+}
+
+- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
+    [self updateIOWithTouchEvent:event];
+}
+
+- (void)touchesCancelled:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
+    [self updateIOWithTouchEvent:event];
+}
+
+- (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
+    [self updateIOWithTouchEvent:event];
+}
+
+#endif
+
+@end
+

examples/example_apple_metal/Shared/main.m

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+
+#import <TargetConditionals.h>
+
+#if TARGET_OS_IPHONE
+
+#import <UIKit/UIKit.h>
+#import "AppDelegate.h"
+
+int main(int argc, char * argv[]) {
+    @autoreleasepool {
+        return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
+    }
+}
+
+#else
+
+#import <Cocoa/Cocoa.h>
+
+int main(int argc, const char * argv[]) {
+    return NSApplicationMain(argc, argv);
+}
+
+#endif