MapLibreParticleLab/platform/darwin/app/PluginLayerExampleMetalRendering.mm

/*
 PluginLayerExampleMetalRendering

 This is a port lf the CustomStyleLayerExample into the plug-in architecture.   It assumes
 that the rendering is being done in metal since it's added to the core via a darwin method

 */

#import "PluginLayerExampleMetalRendering.h"
#import <MetalKit/MetalKit.h>
#import "Mapbox.h"

typedef struct {
  vector_float2 position;
  vector_float4 color;
} Vertex;

@interface PluginLayerExampleMetalRendering () {
  // The render pipeline state
  id<MTLRenderPipelineState> _pipelineState;
  id<MTLDepthStencilState> _depthStencilStateWithoutStencil;

  // Properties
  float _offsetX;
  float _offsetY;
  float _scale;
  float _r, _g, _b, _a;
}

@end

@implementation PluginLayerExampleMetalRendering

// This is a static class method that is used by the MLNMapView to create the
// required marshalling classes to interface with the MapLibre core.
+ (MLNPluginLayerCapabilities *)layerCapabilities {
  MLNPluginLayerCapabilities *tempResult = [[MLNPluginLayerCapabilities alloc] init];
  tempResult.layerID = @"plugin-layer-metal-rendering";
  tempResult.requiresPass3D = YES;

  // Define the paint properties that this layer implements and
  // what types they are
  tempResult.layerProperties = @[
    // The scale property
    [MLNPluginLayerProperty propertyWithName:@"scale"
                                propertyType:MLNPluginLayerPropertyTypeSingleFloat
                                defaultValue:@(1.0)],

    // The fill color property
    [MLNPluginLayerProperty propertyWithName:@"fill-color"
                                propertyType:MLNPluginLayerPropertyTypeColor
                                defaultValue:[UIColor blueColor]]

  ];

  return tempResult;
}

- (void)createShaders:(MLNMapView *)mapView {
  MLNBackendResource *resource = [mapView backendResource];

  NSString *shaderSource =
      @
"    #include <metal_stdlib>\n"
       "    using namespace metal;\n"
       "    typedef struct\n"
       "    {\n"
       "        vector_float2 position;\n"
       "        vector_float4 color;\n"
       "    } Vertex;\n"
       "    struct RasterizerData\n"
       "    {\n"
       "        float4 position [[position]];\n"
       "        float4 color;\n"
       "    };\n"
       "    vertex RasterizerData\n"
       "    vertexShader(uint vertexID [[vertex_id]],\n"
       "                 constant Vertex *vertices [[buffer(0)]],\n"
       "                 constant vector_uint2 *viewportSizePointer [[buffer(1)]])\n"
       "    {\n"
       "        RasterizerData out;\n"
       "        float2 pixelSpacePosition = vertices[vertexID].position.xy;\n"
       "        vector_float2 viewportSize = vector_float2(*viewportSizePointer);\n"
       "        out.position = vector_float4(0.0, 0.0, 0.0, 1.0);\n"
       "        out.position.xy = pixelSpacePosition / (viewportSize / 2.0);\n"
       "        out.color = vertices[vertexID].color;\n"
       "        return out;\n"
       "    }\n"
       "    fragment float4 fragmentShader(RasterizerData in [[stage_in]])\n"
       "    {\n"
       "        return in.color;\n"
       "    }\n";

  NSError *error = nil;
  id<MTLDevice> _device = resource.device;
  id<MTLLibrary> library = [_device newLibraryWithSource:shaderSource options:nil error:&error];
  NSAssert(library, @"Error compiling shaders: %@", error);
  id<MTLFunction> vertexFunction = [library newFunctionWithName:@"vertexShader"];
  id<MTLFunction> fragmentFunction = [library newFunctionWithName:@"fragmentShader"];

  // Configure a pipeline descriptor that is used to create a pipeline state.
  MTLRenderPipelineDescriptor *pipelineStateDescriptor = [[MTLRenderPipelineDescriptor alloc] init];
  pipelineStateDescriptor.label = @"Simple Pipeline";
  pipelineStateDescriptor.vertexFunction = vertexFunction;
  pipelineStateDescriptor.fragmentFunction = fragmentFunction;
  pipelineStateDescriptor.colorAttachments[0].pixelFormat = resource.mtkView.colorPixelFormat;
  pipelineStateDescriptor.depthAttachmentPixelFormat = MTLPixelFormatDepth32Float_Stencil8;
  pipelineStateDescriptor.stencilAttachmentPixelFormat = MTLPixelFormatDepth32Float_Stencil8;

  _pipelineState = [_device newRenderPipelineStateWithDescriptor:pipelineStateDescriptor
                                                           error:&error];
  NSAssert(_pipelineState, @"Failed to create pipeline state: %@", error);

  // Notice that we don't configure the stencilTest property, leaving stencil testing disabled
  MTLDepthStencilDescriptor *depthStencilDescriptor = [[MTLDepthStencilDescriptor alloc] init];
  depthStencilDescriptor.depthCompareFunction =
      MTLCompareFunctionAlways;  // Or another value as needed
  depthStencilDescriptor.depthWriteEnabled = NO;

  _depthStencilStateWithoutStencil =
      [_device newDepthStencilStateWithDescriptor:depthStencilDescriptor];
}

// Setup the rendering environment
- (void)setupRendering:(MLNMapView *)mapView {
  [self createShaders:mapView];
  if (_scale == 0) {
    _scale = 1;
  }
  // Set the initial
  _a = 1;
}

// The overrides
- (void)onRenderLayer:(MLNMapView *)mapView
        renderEncoder:(id<MTLRenderCommandEncoder>)renderEncoder {
  MLNBackendResource *resource = [mapView backendResource];

  if (_pipelineState == nil) {
    [self setupRendering:mapView];
  }

  if (renderEncoder == nil) {
    return;
  }

  vector_uint2 _viewportSize;
  _viewportSize.x = resource.mtkView.drawableSize.width;
  _viewportSize.y = resource.mtkView.drawableSize.height;

  Vertex triangleVerticesWithColor[] = {
      // 2D positions,    RGBA colors
      {{(250 + _offsetX) * _scale, (-250 + _offsetY) * _scale}, {1, 1, 1, _a}},
      {{(-250 + _offsetX) * _scale, (-250 + _offsetY) * _scale}, {1, 1, 1, _a}},
      {{(0 + _offsetX) * _scale, (250 + _offsetY) * _scale}, {_r, _g, _b, _a}},
  };

  [renderEncoder setRenderPipelineState:_pipelineState];
  [renderEncoder setDepthStencilState:_depthStencilStateWithoutStencil];

  // Pass in the parameter data.
  [renderEncoder setVertexBytes:triangleVerticesWithColor
                         length:sizeof(triangleVerticesWithColor)
                        atIndex:0];

  [renderEncoder setVertexBytes:&_viewportSize length:sizeof(_viewportSize) atIndex:1];

  // Draw the triangle.
  [renderEncoder drawPrimitives:MTLPrimitiveTypeTriangle vertexStart:0 vertexCount:3];
}

- (void)onUpdateLayer:(MLNPluginLayerDrawingContext)drawingContext {
  // This is called before the render call and is a place where
  // any animations/etc can be updated
}

- (void)onUpdateLayerProperties:(NSDictionary *)layerProperties {
  // NSLog(@"Metal Layer Rendering Properties: %@", layerProperties);

  // These two properties are in the "properties" section of the style sheet and
  // are passed in at layer creation.  These are not expression based properties
  NSNumber *offsetX = [layerProperties objectForKey:@"offset-x"];
  if (offsetX) {
    _offsetX = [[layerProperties objectForKey:@"offset-x"] floatValue];
  }

  NSNumber *offsetY = [layerProperties objectForKey:@"offset-y"];
  if (offsetY) {
    _offsetY = [[layerProperties objectForKey:@"offset-y"] floatValue];
  }

  // These are the paint properties and can be updated each frame or zoom level
  // change/etc depending on if they are static or expression based/etc.
  NSNumber *scale = [layerProperties objectForKey:@"scale"];
  if (scale) {
    if ([scale isKindOfClass:[NSNumber class]]) {
      _scale = [scale floatValue];
    }
  }

  NSString *fillColor = [layerProperties objectForKey:@"fill-color"];
  if (fillColor) {
    // NSLog(@"Fill Color: %@", fillColor);
    fillColor = [fillColor stringByReplacingOccurrencesOfString:@"rgba(" withString:@""];
    fillColor = [fillColor stringByReplacingOccurrencesOfString:@")" withString:@""];
    NSArray *components = [fillColor componentsSeparatedByString:@","];
    if ([components count] == 4) {
      // Convert to float since they come in as 0..255
      _r = [[components objectAtIndex:0] floatValue] / 255.0;
      _g = [[components objectAtIndex:1] floatValue] / 255.0;
      _b = [[components objectAtIndex:2] floatValue] / 255.0;
      _a = [[components objectAtIndex:3] floatValue];
    }
  }
}

@end