reuse agg stroker for simple and dashed lines

This cuts down on the number of memory allocations happening, by
avoiding the creation and destruction of agg strokers for each
feature.

mapagg.cpp

@@ -130,7 +130,23 @@ class AGG2Renderer
     m_renderer_primitives(m_renderer_base),
     m_rasterizer_primitives(m_renderer_primitives)
 #endif
-  {}
+  {
+    stroke = NULL;
+    dash = NULL;
+    stroke_dash = NULL;
+  }
+
+  ~AGG2Renderer() {
+    if(stroke) {
+      delete stroke;
+    }
+    if(dash) {
+      delete dash;
+    }
+    if(stroke_dash) {
+      delete stroke_dash;
+    }
+  }
 
   band_type* buffer;
   rendering_buffer m_rendering_buffer;
@@ -148,6 +164,9 @@ class AGG2Renderer
   mapserver::scanline_u8 sl_line; /*unpacked scanlines, works faster if the area is roughly
     equal to the perimeter, in number of pixels*/
   bool use_alpha;
+  mapserver::conv_stroke<line_adaptor> *stroke;
+  mapserver::conv_dash<line_adaptor> *dash;
+  mapserver::conv_stroke<mapserver::conv_dash<line_adaptor> > *stroke_dash;
 };
 
 #define AGG_RENDERER(image) ((AGG2Renderer*) (image)->img.plugin)
@@ -220,22 +239,36 @@ int agg2RenderLine(imageObj *img, shapeObj *p, strokeStyleObj *style)
   r->m_renderer_scanline.color(aggColor(style->color));
 
   if (style->patternlength <= 0) {
-    mapserver::conv_stroke<line_adaptor> stroke(lines);
-    stroke.width(style->width);
+    if(!r->stroke) {
+      r->stroke = new mapserver::conv_stroke<line_adaptor>(lines);
+    } else {
+      r->stroke->attach(lines);
+    }
+    r->stroke->width(style->width);
     if(style->width>1) {
-      applyCJC(stroke, style->linecap, style->linejoin);
+      applyCJC(*r->stroke, style->linecap, style->linejoin);
     } else {
-      stroke.inner_join(mapserver::inner_bevel);
-      stroke.line_join(mapserver::bevel_join);
+      r->stroke->inner_join(mapserver::inner_bevel);
+      r->stroke->line_join(mapserver::bevel_join);
     }
-    r->m_rasterizer_aa.add_path(stroke);
+    r->m_rasterizer_aa.add_path(*r->stroke);
   } else {
-    mapserver::conv_dash<line_adaptor> dash(lines);
-    mapserver::conv_stroke<mapserver::conv_dash<line_adaptor> > stroke_dash(dash);
+    if(!r->dash) {
+      r->dash = new mapserver::conv_dash<line_adaptor>(lines);
+    } else {
+      r->dash->remove_all_dashes();
+      r->dash->dash_start(0.0);
+      r->dash->attach(lines);
+    }
+    if(!r->stroke_dash) {
+      r->stroke_dash = new mapserver::conv_stroke<mapserver::conv_dash<line_adaptor> > (*r->dash);
+    } else {
+      r->stroke_dash->attach(*r->dash);
+    }
     int patt_length = 0;
     for (int i = 0; i < style->patternlength; i += 2) {
       if (i < style->patternlength - 1) {
-        dash.add_dash(MS_MAX(1,MS_NINT(style->pattern[i])),
+        r->dash->add_dash(MS_MAX(1,MS_NINT(style->pattern[i])),
                       MS_MAX(1,MS_NINT(style->pattern[i + 1])));
         if(style->patternoffset) {
           patt_length += MS_MAX(1,MS_NINT(style->pattern[i])) +
@@ -244,16 +277,16 @@ int agg2RenderLine(imageObj *img, shapeObj *p, strokeStyleObj *style)
       }
     }
     if(style->patternoffset > 0) {
-      dash.dash_start(patt_length - style->patternoffset);
+      r->dash->dash_start(patt_length - style->patternoffset);
     }
-    stroke_dash.width(style->width);
+    r->stroke_dash->width(style->width);
     if(style->width>1) {
-      applyCJC(stroke_dash, style->linecap, style->linejoin);
+      applyCJC(*r->stroke_dash, style->linecap, style->linejoin);
     } else {
-      stroke_dash.inner_join(mapserver::inner_bevel);
-      stroke_dash.line_join(mapserver::bevel_join);
+      r->stroke_dash->inner_join(mapserver::inner_bevel);
+      r->stroke_dash->line_join(mapserver::bevel_join);
     }
-    r->m_rasterizer_aa.add_path(stroke_dash);
+    r->m_rasterizer_aa.add_path(*r->stroke_dash);
   }
   mapserver::render_scanlines(r->m_rasterizer_aa, r->sl_line, r->m_renderer_scanline);
   return MS_SUCCESS;