From fd961048eaec51363db9984f59eb494e6ce7962c Mon Sep 17 00:00:00 2001
From: Raul Marin <git@rmr.ninja>
Date: Fri, 25 May 2018 17:12:05 +0200
Subject: [PATCH 1/2] Improve padding calculation

---
 include/mapnik/offset_converter.hpp           |  4 +++-
 src/agg/process_line_pattern_symbolizer.cpp   | 11 +++++-----
 src/agg/process_line_symbolizer.cpp           | 20 ++++---------------
 src/cairo/process_line_pattern_symbolizer.cpp | 12 +++++------
 src/cairo/process_line_symbolizer.cpp         | 12 +++++------
 src/grid/process_line_pattern_symbolizer.cpp  | 12 +++++------
 src/grid/process_line_symbolizer.cpp          | 12 +++++------
 7 files changed, 32 insertions(+), 51 deletions(-)

diff --git a/include/mapnik/offset_converter.hpp b/include/mapnik/offset_converter.hpp
index 8bbb9aa50..1ebf92b3c 100644
--- a/include/mapnik/offset_converter.hpp
+++ b/include/mapnik/offset_converter.hpp
@@ -40,6 +40,8 @@
 namespace mapnik
 {
 
+static constexpr double offset_converter_default_threshold = 5.0;
+
 template <typename Geometry>
 struct offset_converter
 {
@@ -48,7 +50,7 @@ struct offset_converter
     offset_converter(Geometry & geom)
         : geom_(geom)
         , offset_(0.0)
-        , threshold_(5.0)
+        , threshold_(offset_converter_default_threshold)
         , half_turn_segments_(16)
         , status_(initial)
         , pre_first_(vertex2d::no_init)
diff --git a/src/agg/process_line_pattern_symbolizer.cpp b/src/agg/process_line_pattern_symbolizer.cpp
index e8770e2cd..2033f1bf0 100644
--- a/src/agg/process_line_pattern_symbolizer.cpp
+++ b/src/agg/process_line_pattern_symbolizer.cpp
@@ -134,12 +134,11 @@ private:
         box2d<double> clip_box = clipping_extent(common_);
         if (clip)
         {
-            double padding = (double)(common_.query_extent_.width()/pixmap_.width());
-            if (half_stroke > 1)
-                padding *= half_stroke;
-            if (std::fabs(offset) > 0)
-                padding *= std::fabs(offset) * 1.2;
-            padding *= common_.scale_factor_;
+            double pad_per_pixel = static_cast<double>(common_.query_extent_.width()/common_.width_);
+            double pixels = std::ceil(std::max(width / 2.0 + std::fabs(offset),
+                                              (std::fabs(offset) * offset_converter_default_threshold)));
+            double padding = pad_per_pixel * pixels * common_.scale_factor_;
+
             clip_box.pad(padding);
         }
         using vertex_converter_type = vertex_converter<clip_line_tag, transform_tag,
diff --git a/src/agg/process_line_symbolizer.cpp b/src/agg/process_line_symbolizer.cpp
index 9bace2539..f0e259ca4 100644
--- a/src/agg/process_line_symbolizer.cpp
+++ b/src/agg/process_line_symbolizer.cpp
@@ -139,23 +139,11 @@ void agg_renderer<T0,T1>::process(line_symbolizer const& sym,
     line_rasterizer_enum rasterizer_e = get<line_rasterizer_enum, keys::line_rasterizer>(sym, feature, common_.vars_);
     if (clip)
     {
-        double padding = static_cast<double>(common_.query_extent_.width()/pixmap_.width());
-        double half_stroke = 0.5 * width;
-        if (half_stroke > 1)
-        {
-            padding *= half_stroke;
-        }
-        if (std::fabs(offset) > 0)
-        {
-            padding *= std::fabs(offset) * 1.2;
-        }
-
-        padding *= common_.scale_factor_;
+        double pad_per_pixel = static_cast<double>(common_.query_extent_.width()/common_.width_);
+        double pixels = std::ceil(std::max(width / 2.0 + std::fabs(offset),
+                                          (std::fabs(offset) * offset_converter_default_threshold)));
+        double padding = pad_per_pixel * pixels * common_.scale_factor_;
         clip_box.pad(padding);
-        // debugging
-        //box2d<double> inverse = query_extent_;
-        //inverse.pad(-padding);
-        //draw_geo_extent(inverse,mapnik::color("red"));
     }
 
     if (rasterizer_e == RASTERIZER_FAST)
diff --git a/src/cairo/process_line_pattern_symbolizer.cpp b/src/cairo/process_line_pattern_symbolizer.cpp
index f53d850a6..1f457b845 100644
--- a/src/cairo/process_line_pattern_symbolizer.cpp
+++ b/src/cairo/process_line_pattern_symbolizer.cpp
@@ -131,13 +131,11 @@ void cairo_renderer<T>::process(line_pattern_symbolizer const& sym,
     box2d<double> clipping_extent = common_.query_extent_;
     if (clip)
     {
-        double padding = (double)(common_.query_extent_.width()/common_.width_);
-        double half_stroke = width/2.0;
-        if (half_stroke > 1)
-            padding *= half_stroke;
-        if (std::fabs(offset) > 0)
-            padding *= std::fabs(offset) * 1.2;
-        padding *= common_.scale_factor_;
+        double pad_per_pixel = static_cast<double>(common_.query_extent_.width()/common_.width_);
+        double pixels = std::ceil(std::max(width / 2.0 + std::fabs(offset),
+                                          (std::fabs(offset) * offset_converter_default_threshold)));
+        double padding = pad_per_pixel * pixels * common_.scale_factor_;
+
         clipping_extent.pad(padding);
     }
 
diff --git a/src/cairo/process_line_symbolizer.cpp b/src/cairo/process_line_symbolizer.cpp
index ed64d5c01..0e4bb3f49 100644
--- a/src/cairo/process_line_symbolizer.cpp
+++ b/src/cairo/process_line_symbolizer.cpp
@@ -73,13 +73,11 @@ void cairo_renderer<T>::process(line_symbolizer const& sym,
     box2d<double> clipping_extent = common_.query_extent_;
     if (clip)
     {
-        double padding = (double)(common_.query_extent_.width()/common_.width_);
-        double half_stroke = width/2.0;
-        if (half_stroke > 1)
-            padding *= half_stroke;
-        if (std::fabs(offset) > 0)
-            padding *= std::fabs(offset) * 1.2;
-        padding *= common_.scale_factor_;
+        double pad_per_pixel = static_cast<double>(common_.query_extent_.width()/common_.width_);
+        double pixels = std::ceil(std::max(width / 2.0 + std::fabs(offset),
+                                          (std::fabs(offset) * offset_converter_default_threshold)));
+        double padding = pad_per_pixel * pixels * common_.scale_factor_;
+
         clipping_extent.pad(padding);
     }
     using vertex_converter_type =  vertex_converter<clip_line_tag,
diff --git a/src/grid/process_line_pattern_symbolizer.cpp b/src/grid/process_line_pattern_symbolizer.cpp
index af54ac5b6..91b1f2a6b 100644
--- a/src/grid/process_line_pattern_symbolizer.cpp
+++ b/src/grid/process_line_pattern_symbolizer.cpp
@@ -97,13 +97,11 @@ void grid_renderer<T>::process(line_pattern_symbolizer const& sym,
     box2d<double> clipping_extent = common_.query_extent_;
     if (clip)
     {
-        double padding = (double)(common_.query_extent_.width()/pixmap_.width());
-        double half_stroke = stroke_width/2.0;
-        if (half_stroke > 1)
-            padding *= half_stroke;
-        if (std::fabs(offset) > 0)
-            padding *= std::fabs(offset) * 1.2;
-        padding *= common_.scale_factor_;
+        double pad_per_pixel = static_cast<double>(common_.query_extent_.width()/common_.width_);
+        double pixels = std::ceil(std::max(stroke_width / 2.0 + std::fabs(offset),
+                                          (std::fabs(offset) * offset_converter_default_threshold)));
+        double padding = pad_per_pixel * pixels * common_.scale_factor_;
+
         clipping_extent.pad(padding);
     }
 
diff --git a/src/grid/process_line_symbolizer.cpp b/src/grid/process_line_symbolizer.cpp
index b65dd8502..ca8cfb0ed 100644
--- a/src/grid/process_line_symbolizer.cpp
+++ b/src/grid/process_line_symbolizer.cpp
@@ -84,13 +84,11 @@ void grid_renderer<T>::process(line_symbolizer const& sym,
 
     if (clip)
     {
-        double padding = (double)(common_.query_extent_.width()/pixmap_.width());
-        double half_stroke = width/2.0;
-        if (half_stroke > 1)
-            padding *= half_stroke;
-        if (std::fabs(offset) > 0)
-            padding *= std::fabs(offset) * 1.2;
-        padding *= common_.scale_factor_;
+        double pad_per_pixel = static_cast<double>(common_.query_extent_.width()/common_.width_);
+        double pixels = std::ceil(std::max(width / 2.0 + std::fabs(offset),
+                                          (std::fabs(offset) * offset_converter_default_threshold)));
+        double padding = pad_per_pixel * pixels * common_.scale_factor_;
+
         clipping_extent.pad(padding);
     }
     using vertex_converter_type = vertex_converter<clip_line_tag, clip_poly_tag, transform_tag,

From 3f9970075d03cd19173edf80fb97758c1ad73082 Mon Sep 17 00:00:00 2001
From: Jiri Drbalek <jiri.drbalek@firma.seznam.cz>
Date: Sun, 21 Oct 2018 19:54:36 +0000
Subject: [PATCH 2/2] Update visual tests

---
 test/data-visual | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/data-visual b/test/data-visual
index 13163a419..0a804e64b 160000
--- a/test/data-visual
+++ b/test/data-visual
@@ -1 +1 @@
-Subproject commit 13163a419eec939d189a371427022402b98bb08a
+Subproject commit 0a804e64beee9af6b1388f45d89554fddbba89c5