Fix wrong compute of width from external periemter spacing.

Also better rounding for scripted float.
#4082

src/libslic3r/Flow.cpp

@@ -287,6 +287,14 @@ Flow Flow::new_from_config(FlowRole role, const DynamicConfig& print_config, flo
     if (role == frExternalPerimeter) {
         config_width = print_config.opt<ConfigOptionFloatOrPercent>("external_perimeter_extrusion_width");
         config_spacing = print_config.opt<ConfigOptionFloatOrPercent>("external_perimeter_extrusion_spacing");
+        // external peri spacing is only half spacing -> transform it into a full spacing
+        if (!config_spacing.is_phony() && !config_spacing.value == 0) {
+            double raw_spacing = config_spacing.get_abs_value(nozzle_diameter);
+            config_spacing.percent = false;
+            config_spacing.value = rounded_rectangle_extrusion_spacing(
+                rounded_rectangle_extrusion_width_from_spacing(raw_spacing, layer_height, 0.5f),
+                layer_height, 1.f);
+        }
         overlap = (float)print_config.get_abs_value("external_perimeter_overlap", 1.0);
     } else if (role == frPerimeter) {
         config_width = print_config.opt<ConfigOptionFloatOrPercent>("perimeter_extrusion_width");

src/slic3r/GUI/ScriptExecutor.cpp

@@ -173,10 +173,20 @@ float as_get_float(std::string& key)
     }
 }
 
-double round(float f) {
+double round(float value) {
+    double intpart;
+    if (modf(value, &intpart) == 0.0) {
+        // shortcut for int
+        return value;
+    }
     std::stringstream ss;
+    //first, get the int part, to see how many digit it takes
+    int long10 = 0;
+    if (intpart > 9)
+        long10 = (int)std::floor(std::log10(std::abs(intpart)));
+        //set the usable precision: there is only ~7 decimal digit in a float (15-16 decimal digit in a double)
+        ss << std::fixed << std::setprecision(7 - long10) << value;
     double dbl_val;
-    ss << f;
     ss >> dbl_val;
     return dbl_val;
 }