Adds Style Preprocessor Plugin Capability

bazel/core.bzl

@@ -4,6 +4,7 @@ MLN_LAYER_PLUGIN_HEADERS = [
     "src/mbgl/plugin/plugin_layer_impl.hpp",
     "src/mbgl/plugin/plugin_layer_render.hpp",
     "src/mbgl/plugin/plugin_layer_properties.hpp",
+    "src/mbgl/plugin/plugin_style_filter.hpp",
 ]
 
 MLN_LAYER_PLUGIN_SOURCE = [
@@ -12,6 +13,7 @@ MLN_LAYER_PLUGIN_SOURCE = [
     "src/mbgl/plugin/plugin_layer_impl.cpp",
     "src/mbgl/plugin/plugin_layer_render.cpp",
     "src/mbgl/plugin/plugin_layer_properties.cpp",
+    "src/mbgl/plugin/plugin_style_filter.cpp",
 ]
 
 MLN_PUBLIC_GENERATED_STYLE_HEADERS = [

include/mbgl/style/style.hpp

@@ -20,6 +20,7 @@ namespace style {
 class Light;
 class Source;
 class Layer;
+class PluginStyleFilter;
 
 class Style {
 public:
@@ -71,6 +72,9 @@ class Style {
     void addLayer(std::unique_ptr<Layer>, const std::optional<std::string>& beforeLayerID = std::nullopt);
     std::unique_ptr<Layer> removeLayer(const std::string& layerID);
 
+    // Add style parsing filter
+    void addStyleFilter(std::shared_ptr<mbgl::style::PluginStyleFilter>);
+
     // Private implementation
     class Impl;
     const std::unique_ptr<Impl> impl;

platform/BUILD.bazel

@@ -271,6 +271,8 @@ objc_library(
         "//platform/darwin:app/CustomStyleLayerExample.m",
         "//platform/darwin:app/PluginLayerExample.h",
         "//platform/darwin:app/PluginLayerExample.mm",
+        "//platform/darwin:app/StyleFilterExample.h",
+        "//platform/darwin:app/StyleFilterExample.mm",
         "//platform/darwin:app/PluginLayerExampleMetalRendering.h",
         "//platform/darwin:app/PluginLayerExampleMetalRendering.mm",
         "//platform/ios:ios_app_srcs",

platform/darwin/BUILD.bazel

@@ -308,6 +308,8 @@ exports_files(
         "app/PluginLayerTestStyle.json",
         "app/PluginLayerExample.h",
         "app/PluginLayerExample.mm",
+        "app/StyleFilterExample.h",
+        "app/StyleFilterExample.mm",
         "app/PluginLayerExampleMetalRendering.h",
         "app/PluginLayerExampleMetalRendering.mm",
         "test/amsterdam.geojson",

platform/darwin/app/StyleFilterExample.h

@@ -0,0 +1,16 @@
+//
+//  StyleFilterExample.h
+//  MapLibre
+//
+//  Created by Malcolm Toon on 7/25/25.
+//
+
+#import "MLNStyleFilter.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface StyleFilterExample : MLNStyleFilter
+
+@end
+
+NS_ASSUME_NONNULL_END

platform/darwin/app/StyleFilterExample.mm

@@ -0,0 +1,60 @@
+#import "StyleFilterExample.h"
+
+@implementation StyleFilterExample
+
+// This will filter the data passed in
+-(NSData *)filterData:(NSData *)data {
+    // Don't call super
+
+    // This example will remove any layer that has "metal-rendering-layer" in the id
+
+    // Parse the JSON: Make the containers mutable
+    NSError *error = nil;
+    NSMutableDictionary *styleDictionary = [NSJSONSerialization JSONObjectWithData:data
+                                                                          options:NSJSONReadingMutableContainers
+                                                                            error:&error];
+
+    NSData *tempResult = data;
+    if (styleDictionary) {
+
+        // Get the layer array
+        NSMutableArray *layerArray = [styleDictionary objectForKey:@"layers"];
+
+        // Create an array to hold which objects to remove since we can't remove them in the loop
+        NSMutableArray *removedLayers = [NSMutableArray array];
+
+        // Loop the layers and look for any layers that have the search string in them
+        for (NSMutableDictionary *layer in layerArray) {
+            NSString *layerID = [layer objectForKey:@"id"];
+
+            // If we find the layers we're looking for, add them to the list of layers to remove
+            if ([layerID containsString:@"metal-rendering-layer"]) {
+                [removedLayers addObject:layer];
+            }
+        }
+
+        // Go through and remove any layers that were found
+        for (NSMutableDictionary *l in removedLayers) {
+            [layerArray removeObject:l];
+        }
+
+        // Re-create the JSON, this time the layers we filtered out won't be there
+        NSData *filteredStyleJSON = [NSJSONSerialization dataWithJSONObject:styleDictionary
+                                                                    options:0
+                                                                      error:&error];
+
+        // If the JSON write is successful, then set the output to the new json style
+        if (filteredStyleJSON) {
+            tempResult = filteredStyleJSON;
+        }
+
+    }
+
+    // Return the data
+    return tempResult;
+
+}
+
+
+
+@end

platform/darwin/bazel/files.bzl

@@ -109,7 +109,8 @@ MLN_DARWIN_OBJC_HEADERS = [
     "src/NSValue+MLNAdditions.h",
     "src/MLNPluginLayer.h",
     "src/MLNPluginStyleLayer.h",
-    "src/MLNNetworkResponse.h",
+    "src/MLNStyleFilter.h",
+    "src/MLNStyleFilter_Private.h",
 ]
 
 MLN_DARWIN_OBJCPP_HEADERS = [
@@ -226,6 +227,7 @@ MLN_DARWIN_PUBLIC_OBJCPP_SOURCE = [
     "src/MLNPluginLayer.mm",
     "src/MLNPluginStyleLayer.mm",
     "src/MLNNetworkResponse.mm",
+    "src/MLNStyleFilter.mm",
 ]
 MLN_DARWIN_PUBLIC_OBJCPP_CUSTOM_DRAWABLE_SOURCE = [
     "src/MLNCustomDrawableStyleLayer_Private.h",

platform/darwin/src/MLNStyleFilter.h

@@ -0,0 +1,12 @@
+#import <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface MLNStyleFilter : NSObject
+
+// This will filter the data passed in
+-(NSData *)filterData:(NSData *)data;
+
+@end
+
+NS_ASSUME_NONNULL_END

platform/darwin/src/MLNStyleFilter.mm

@@ -0,0 +1,23 @@
+#import "MLNStyleFilter.h"
+#include <mbgl/plugin/plugin_style_filter.hpp>
+
+@interface MLNStyleFilter () {
+    std::shared_ptr<mbgl::style::PluginStyleFilter> _coreFilter;
+}
+
+@end
+
+@implementation MLNStyleFilter
+
+-(NSData *)filterData:(NSData *)data {
+    // Base class does nothing but return the same data passed in
+    return data;
+}
+
+// Private
+-(void)setFilter:(std::shared_ptr<mbgl::style::PluginStyleFilter>)filter {
+    _coreFilter = filter;
+}
+
+
+@end

platform/darwin/src/MLNStyleFilter_Private.h

@@ -0,0 +1,14 @@
+
+#ifndef MLNStyleFilter_Private_h
+#define MLNStyleFilter_Private_h
+
+#import "MLNStyleFilter.h"
+#include <mbgl/plugin/plugin_style_filter.hpp>
+
+@interface MLNStyleFilter(Private)
+
+-(void)setFilter:(std::shared_ptr<mbgl::style::PluginStyleFilter>)filter;
+
+@end
+
+#endif /* MLNStyleFilter_Private_h */

platform/ios/app/MBXViewController.mm

@@ -27,6 +27,7 @@
 #import "PluginLayerExample.h"
 #import "PluginLayerExampleMetalRendering.h"
 #import "MLNPluginStyleLayer.h"
+#import "StyleFilterExample.h"
 
 static const CLLocationCoordinate2D WorldTourDestinations[] = {
     { .latitude = 38.8999418, .longitude = -77.033996 },
@@ -281,6 +282,7 @@ -(void)addPluginLayers {
 
     [self.mapView addPluginLayerType:[PluginLayerExample class]];
     [self.mapView addPluginLayerType:[PluginLayerExampleMetalRendering class]];
+    [self.mapView addStyleFilter:[[StyleFilterExample alloc] init]];
 
 }
 

platform/ios/src/MLNMapView.h

@@ -20,6 +20,7 @@ NS_ASSUME_NONNULL_BEGIN
 @class MLNScaleBar;
 @class MLNShape;
 @class MLNPluginLayer;
+@class MLNStyleFilter;
 
 @protocol MLNMapViewDelegate;
 @protocol MLNAnnotation;
@@ -2322,6 +2323,11 @@ of north, the map will automatically snap to exact north.
  */
 - (void)addPluginLayerType:(Class)pluginLayerClass;
 
+/**
+ Adds a style filter to the map view
+ */
+-(void)addStyleFilter:(MLNStyleFilter *)styleFilter;
+
 @end
 
 NS_ASSUME_NONNULL_END

platform/ios/src/MLNMapView.mm

@@ -30,6 +30,7 @@
 #include <mbgl/plugin/plugin_layer_factory.hpp>
 #include <mbgl/plugin/plugin_layer.hpp>
 #include <mbgl/plugin/plugin_layer_impl.hpp>
+#include <mbgl/plugin/plugin_style_filter.hpp>
 #include <mbgl/renderer/paint_parameters.hpp>
 #include <mbgl/mtl/mtl_fwd.hpp>
 #include <mbgl/mtl/render_pass.hpp>
@@ -82,6 +83,8 @@
 #import "MLNPluginLayer.h"
 #import "MLNStyleLayerManager.h"
 #include "MLNPluginStyleLayer_Private.h"
+#include "MLNStyleFilter.h"
+#include "MLNStyleFilter_Private.h"
 
 #include <algorithm>
 #include <cstdlib>
@@ -452,6 +455,9 @@ @interface MLNMapView () <UIGestureRecognizerDelegate,
 // Plugin Layers
 @property NSMutableArray *pluginLayers;
 
+// Style Filters
+@property NSMutableArray *styleFilters;
+
 @end
 
 @implementation MLNMapView
@@ -7851,6 +7857,42 @@ -(void)addPluginLayerType:(Class)pluginLayerClass {
 
 }
 
+/**
+ Adds a style filter to the map view
+ */
+-(void)addStyleFilter:(MLNStyleFilter *)styleFilter {
+
+    if (!self.styleFilters) {
+        self.styleFilters = [NSMutableArray array];
+    }
+    [self.styleFilters addObject:styleFilter];
+
+    auto coreStyleFilter = std::make_shared<mbgl::style::PluginStyleFilter>();
+    coreStyleFilter->_filterStyleFunction = [styleFilter](const std::string &filterData) -> const std::string {
+
+
+        std::string tempResult;
+
+        @autoreleasepool {
+            NSData *sourceData = [NSData dataWithBytesNoCopy:(void *)filterData.data()
+                                                      length:filterData.size()
+                                                freeWhenDone:NO];
+            NSData *filteredData = [styleFilter filterData:sourceData];
+            tempResult = std::string((const char*)[filteredData bytes], [filteredData length]);
+
+        }
+        return tempResult;
+
+    };
+
+    // Set the ivar
+    [styleFilter setFilter:coreStyleFilter];
+
+    _mbglMap->getStyle().addStyleFilter(coreStyleFilter);
+
+}
+
+
 - (NSArray<NSString*>*)getActionJournalLogFiles
 {
     const auto& actionJournal = _mbglMap->getActionJournal();

src/mbgl/plugin/plugin_style_filter.cpp

@@ -0,0 +1,14 @@
+#include <mbgl/plugin/plugin_style_filter.hpp>
+
+using namespace mbgl::style;
+
+// This method
+const std::string PluginStyleFilter::filterResponse(const std::string& res) {
+
+    if (_filterStyleFunction) {
+        auto tempResult = _filterStyleFunction(res);
+        return tempResult;
+    }
+    return res;
+
+}

src/mbgl/plugin/plugin_style_filter.hpp

@@ -0,0 +1,23 @@
+#pragma once
+
+#include <functional>
+
+
+namespace mbgl {
+
+namespace style {
+
+class PluginStyleFilter {
+public:
+
+    using OnFilterStyle = std::function<const std::string(const std::string&)>;
+
+    OnFilterStyle _filterStyleFunction;
+
+    // This method
+    const std::string filterResponse(const std::string&);
+};
+
+
+}
+}

src/mbgl/style/style.cpp

@@ -177,5 +177,13 @@ std::unique_ptr<Layer> Style::removeLayer(const std::string& id) {
     return impl->removeLayer(id);
 }
 
+// Add style parsing filter
+void Style::addStyleFilter(std::shared_ptr<mbgl::style::PluginStyleFilter> filter) {
+    impl->mutated = true;
+    return impl->addStyleFilter(filter);
+
+}
+
+
 } // namespace style
 } // namespace mbgl