kaizen/examples/example_apple_metal/main.mm

// Dear ImGui: standalone example application for OSX + Metal.

// Learn about Dear ImGui:
// - FAQ                  https://dearimgui.com/faq
// - Getting Started      https://dearimgui.com/getting-started
// - Documentation        https://dearimgui.com/docs (same as your local docs/ folder).
// - Introduction, links and more at the top of imgui.cpp

#import <Foundation/Foundation.h>

#if TARGET_OS_OSX
#import <Cocoa/Cocoa.h>
#else
#import <UIKit/UIKit.h>
#endif

#import <Metal/Metal.h>
#import <MetalKit/MetalKit.h>

#include "imgui.h"
#include "imgui_impl_metal.h"
#if TARGET_OS_OSX
#include "imgui_impl_osx.h"
@interface AppViewController : NSViewController<NSWindowDelegate>
@end
#else
@interface AppViewController : UIViewController
@end
#endif

@interface AppViewController () <MTKViewDelegate>
@property (nonatomic, readonly) MTKView *mtkView;
@property (nonatomic, strong) id <MTLDevice> device;
@property (nonatomic, strong) id <MTLCommandQueue> commandQueue;
@end

//-----------------------------------------------------------------------------------
// AppViewController
//-----------------------------------------------------------------------------------

@implementation AppViewController

-(instancetype)initWithNibName:(nullable NSString *)nibNameOrNil bundle:(nullable NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];

    _device = MTLCreateSystemDefaultDevice();
    _commandQueue = [_device newCommandQueue];

    if (!self.device)
    {
        NSLog(@"Metal is not supported");
        abort();
    }

    // Setup Dear ImGui context
    // FIXME: This example doesn't have proper cleanup...
    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    ImGuiIO& io = ImGui::GetIO(); (void)io;
    io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
    io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows

    // Setup Dear ImGui style
    ImGui::StyleColorsDark();
    //ImGui::StyleColorsLight();

    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
    ImGuiStyle& style = ImGui::GetStyle();
    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
    {
        style.WindowRounding = 0.0f;
        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
    }

    // Setup Renderer backend
    ImGui_ImplMetal_Init(_device);

    // Load Fonts
    // - If no fonts are loaded, dear imgui will use the default font. You can also load multiple fonts and use ImGui::PushFont()/PopFont() to select them.
    // - AddFontFromFileTTF() will return the ImFont* so you can store it if you need to select the font among multiple.
    // - If the file cannot be loaded, the function will return a nullptr. Please handle those errors in your application (e.g. use an assertion, or display an error and quit).
    // - Use '#define IMGUI_ENABLE_FREETYPE' in your imconfig file to use Freetype for higher quality font rendering.
    // - Read 'docs/FONTS.md' for more instructions and details.
    // - Remember that in C/C++ if you want to include a backslash \ in a string literal you need to write a double backslash \\ !
    //style.FontSizeBase = 20.0f;
    //io.Fonts->AddFontDefault();
    //io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\segoeui.ttf");
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/DroidSans.ttf");
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Roboto-Medium.ttf");
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Cousine-Regular.ttf");
    //ImFont* font = io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\ArialUni.ttf");
    //IM_ASSERT(font != nullptr);

    return self;
}

-(MTKView *)mtkView
{
    return (MTKView *)self.view;
}

-(void)loadView
{
    self.view = [[MTKView alloc] initWithFrame:CGRectMake(0, 0, 1200, 720)];
}

-(void)viewDidLoad
{
    [super viewDidLoad];

    self.mtkView.device = self.device;
    self.mtkView.delegate = self;

#if TARGET_OS_OSX
    ImGui_ImplOSX_Init(self.view);
    [NSApp activateIgnoringOtherApps:YES];
#endif
}

-(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);

    id<MTLCommandBuffer> commandBuffer = [self.commandQueue commandBuffer];

    MTLRenderPassDescriptor* renderPassDescriptor = view.currentRenderPassDescriptor;
    if (renderPassDescriptor == nil)
    {
        [commandBuffer commit];
        return;
    }

    // Start the Dear ImGui frame
    ImGui_ImplMetal_NewFrame(renderPassDescriptor);
#if TARGET_OS_OSX
    ImGui_ImplOSX_NewFrame(view);
#endif
    ImGui::NewFrame();

    // Our state (make them static = more or less global) as a convenience to keep the example terse.
    static bool show_demo_window = true;
    static bool show_another_window = false;
    static ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);

    // 1. Show the big demo window (Most of the sample code is in ImGui::ShowDemoWindow()! You can browse its code to learn more about Dear ImGui!).
    if (show_demo_window)
        ImGui::ShowDemoWindow(&show_demo_window);

    // 2. Show a simple window that we create ourselves. We use a Begin/End pair to create a named window.
    {
        static float f = 0.0f;
        static int counter = 0;

        ImGui::Begin("Hello, world!");                          // Create a window called "Hello, world!" and append into it.

        ImGui::Text("This is some useful text.");               // Display some text (you can use a format strings too)
        ImGui::Checkbox("Demo Window", &show_demo_window);      // Edit bools storing our window open/close state
        ImGui::Checkbox("Another Window", &show_another_window);

        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

        if (ImGui::Button("Button"))                            // Buttons return true when clicked (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 / io.Framerate, io.Framerate);
        ImGui::End();
    }

    // 3. Show another simple window.
    if (show_another_window)
    {
        ImGui::Begin("Another Window", &show_another_window);   // Pass a pointer to our bool variable (the window will have a closing button that will clear the bool when clicked)
        ImGui::Text("Hello from another window!");
        if (ImGui::Button("Close Me"))
            show_another_window = false;
        ImGui::End();
    }

    // Rendering
    ImGui::Render();
    ImDrawData* draw_data = ImGui::GetDrawData();

    renderPassDescriptor.colorAttachments[0].clearColor = MTLClearColorMake(clear_color.x * clear_color.w, clear_color.y * clear_color.w, clear_color.z * clear_color.w, clear_color.w);
    id <MTLRenderCommandEncoder> renderEncoder = [commandBuffer renderCommandEncoderWithDescriptor:renderPassDescriptor];
    [renderEncoder pushDebugGroup:@"Dear ImGui rendering"];
    ImGui_ImplMetal_RenderDrawData(draw_data, commandBuffer, renderEncoder);
    [renderEncoder popDebugGroup];
    [renderEncoder endEncoding];

    // Present
    [commandBuffer presentDrawable:view.currentDrawable];
    [commandBuffer commit];

    // Update and Render additional Platform Windows
    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
    {
        ImGui::UpdatePlatformWindows();
        ImGui::RenderPlatformWindowsDefault();
    }
}

-(void)mtkView:(MTKView*)view drawableSizeWillChange:(CGSize)size
{
}

//-----------------------------------------------------------------------------------
// Input processing
//-----------------------------------------------------------------------------------

#if TARGET_OS_OSX

- (void)viewWillAppear
{
    [super viewWillAppear];
    self.view.window.delegate = self;
}

- (void)windowWillClose:(NSNotification *)notification
{
    ImGui_ImplMetal_Shutdown();
    ImGui_ImplOSX_Shutdown();
    ImGui::DestroyContext();
}

#else

// 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.AddMouseSourceEvent(ImGuiMouseSource_TouchScreen);
    io.AddMousePosEvent(touchLocation.x, touchLocation.y);

    BOOL hasActiveTouch = NO;
    for (UITouch *touch in event.allTouches)
    {
        if (touch.phase != UITouchPhaseEnded && touch.phase != UITouchPhaseCancelled)
        {
            hasActiveTouch = YES;
            break;
        }
    }
    io.AddMouseButtonEvent(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

//-----------------------------------------------------------------------------------
// AppDelegate
//-----------------------------------------------------------------------------------

#if TARGET_OS_OSX

@interface AppDelegate : NSObject <NSApplicationDelegate>
@property (nonatomic, strong) NSWindow *window;
@end

@implementation AppDelegate

-(BOOL)applicationShouldTerminateAfterLastWindowClosed:(NSApplication *)sender
{
    return YES;
}

-(instancetype)init
{
    if (self = [super init])
    {
        NSViewController *rootViewController = [[AppViewController alloc] initWithNibName:nil bundle:nil];
        self.window = [[NSWindow alloc] initWithContentRect:NSZeroRect
                                                  styleMask:NSWindowStyleMaskTitled | NSWindowStyleMaskClosable | NSWindowStyleMaskResizable | NSWindowStyleMaskMiniaturizable
                                                    backing:NSBackingStoreBuffered
                                                      defer:NO];
        self.window.contentViewController = rootViewController;
        [self.window center];
        [self.window makeKeyAndOrderFront:self];
    }
    return self;
}

@end

#else

@interface AppDelegate : UIResponder <UIApplicationDelegate>
@property (strong, nonatomic) UIWindow *window;
@end

@implementation AppDelegate

-(BOOL)application:(UIApplication *)application
    didFinishLaunchingWithOptions:(NSDictionary<UIApplicationLaunchOptionsKey,id> *)launchOptions
{
    UIViewController *rootViewController = [[AppViewController alloc] init];
    self.window = [[UIWindow alloc] initWithFrame:UIScreen.mainScreen.bounds];
    self.window.rootViewController = rootViewController;
    [self.window makeKeyAndVisible];
    return YES;
}

@end

#endif

//-----------------------------------------------------------------------------------
// Application main() function
//-----------------------------------------------------------------------------------

#if TARGET_OS_OSX

int main(int, const char**)
{
    @autoreleasepool
    {
        [NSApplication sharedApplication];
        [NSApp setActivationPolicy:NSApplicationActivationPolicyRegular];

        AppDelegate *appDelegate = [[AppDelegate alloc] init];   // creates window
        [NSApp setDelegate:appDelegate];

        [NSApp activateIgnoringOtherApps:YES];
        [NSApp run];
    }
    return 0;
}

#else

int main(int argc, char * argv[])
{
    @autoreleasepool
    {
        return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
    }
}

#endif