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/Renderer.mm

@@ -0,0 +1,132 @@
+
+#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