From 7852ba061c7bbfba6431335305e18b772f3ebd94 Mon Sep 17 00:00:00 2001
From: Lukas Matena <lukasmatena@seznam.cz>
Date: Fri, 27 Aug 2021 12:10:25 +0200
Subject: [PATCH] Slightly reworded the 'Empty layers detected' warning, it
 mentions the layers between which the problem occurs, not just the upper one
 (which may be unclear).

---
 src/libslic3r/GCode.cpp | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index 254f1d4fd..85e6f810b 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -13,6 +13,7 @@
 #include "ClipperUtils.hpp"
 #include "libslic3r.h"
 #include "LocalesUtils.hpp"
+#include "libslic3r/format.hpp"
 
 #include <algorithm>
 #include <cstdlib>
@@ -512,7 +513,8 @@ std::vector<GCode::LayerToPrint> GCode::collect_layers_to_print(const PrintObjec
         bool has_extrusions = (layer_to_print.object_layer && layer_to_print.object_layer->has_extrusions())
             || (layer_to_print.support_layer && layer_to_print.support_layer->has_extrusions());
 
-        // Check that there are extrusions on the very first layer.
+        // Check that there are extrusions on the very first layer. The case with empty
+        // first layer may result in skirt/brim in the air and maybe other issues.
         if (layers_to_print.size() == 1u) {
             if (!has_extrusions)
                 throw Slic3r::SlicingError(_(L("There is an object with no extrusions in the first layer.")) + "\n" +
@@ -534,11 +536,12 @@ std::vector<GCode::LayerToPrint> GCode::collect_layers_to_print(const PrintObjec
 
             if (has_extrusions && layer_to_print.print_z() > maximal_print_z + 2. * EPSILON) {
                 const_cast<Print*>(object.print())->active_step_add_warning(PrintStateBase::WarningLevel::CRITICAL,
-                    _(L("Empty layers detected. Make sure the object is printable.")) + "\n" +
-                    _(L("Object name")) + ": " + object.model_object()->name + "\n" + _(L("Print z")) + ": " +
-                    std::to_string(layers_to_print.back().print_z()) + "\n\n" + _(L("This is "
-                        "usually caused by negligibly small extrusions or by a faulty model. Try to repair "
-                        "the model or change its orientation on the bed.")));
+                    Slic3r::format(_(L("Empty layer detected between heights %1% and %2%. Make sure the object is printable.")),
+                                   (last_extrusion_layer ? last_extrusion_layer->print_z() : 0.),
+                                   layers_to_print.back().print_z())
+                    + "\n" + Slic3r::format(_(L("Object name: %1%")), object.model_object()->name) + "\n\n"
+                    + _(L("This is usually caused by negligibly small extrusions or by a faulty model. "
+                          "Try to repair the model or change its orientation on the bed.")));
             }
 
             // Remember last layer with extrusions.