last step in fixing the g-code stuff up

src/libslic3r/GCode/GCodeProcessor.cpp

@@ -2530,6 +2530,7 @@ void GCodeProcessorResult::reset() {
     long_retraction_when_cut = false;
     timelapse_warning_code = 0;
     printable_height = 0.0f;
+    machine_frame_transform_active = false;
     settings_ids.reset();
     filaments_count = 0;
     backtrace_enabled = false;
@@ -3061,6 +3062,7 @@ void GCodeProcessor::apply_config(const PrintConfig& config)
     // multi-extruder validator can undo it and compare against build-volume
     // bounds rather than machine-frame positions.
     m_machine_frame_transform.init_from_config(config);
+    m_result.machine_frame_transform_active = m_machine_frame_transform.is_active();
 
     auto filament_maps = config.option<ConfigOptionInts>("filament_map");
     if (filament_maps != nullptr) {

src/libslic3r/GCode/GCodeProcessor.hpp

@@ -285,6 +285,11 @@ class Print;
         // as gcode_Z + this offset, so the designed-view back-transform must subtract it
         // to recover the model's belt coordinate.
         float belt_z_origin{ 0.f };
+        // Belt printer: post-gcode shear/scale/post_remap is configured and
+        // non-identity.  When set, the layer Z values in `moves` are in the
+        // machine frame and should not be compared against `printable_height`
+        // (which lives in the build-volume frame).
+        bool machine_frame_transform_active{ false };
         RemapAxis preslice_remap_x{ RemapAxis::PosX };
         RemapAxis preslice_remap_y{ RemapAxis::PosY };
         RemapAxis preslice_remap_z{ RemapAxis::PosZ };
@@ -377,6 +382,7 @@ class Print;
             initial_layer_time = other.initial_layer_time;
             belt_tilt_angle = other.belt_tilt_angle;
             belt_z_origin = other.belt_z_origin;
+            machine_frame_transform_active = other.machine_frame_transform_active;
             preslice_remap_x = other.preslice_remap_x;
             preslice_remap_y = other.preslice_remap_y;
             preslice_remap_z = other.preslice_remap_z;

src/libslic3r/Print.cpp

@@ -14,6 +14,7 @@
 #include "GCode.hpp"
 #include "BeltGCode.hpp"
 #include "BeltTransform.hpp"
+#include "GCode/MachineFrameTransform.hpp"
 #include "GCode/WipeTower.hpp"
 #include "GCode/WipeTower2.hpp"
 #include "Utils.hpp"
@@ -1436,9 +1437,17 @@ StringObjectException Print::validate(std::vector<StringObjectException> *warnin
     // is not comparable to printable_height (which is gantry clearance in the
     // build-volume frame).  Compare against the model's pre-shear Z instead,
     // mirroring the bbox computed in PrintObject::update_slicing_parameters.
+    // When the post-gcode MachineFrameTransform is active the printer's
+    // physical Z mapping is non-trivial — skip the check entirely.
     const bool belt_printer = this->config().belt_printer.value;
+    bool skip_max_height_check = false;
+    if (belt_printer) {
+        MachineFrameTransform machine_frame;
+        machine_frame.init_from_config(this->config());
+        skip_max_height_check = machine_frame.is_active();
+    }
     const double shrinkage_compensation_z = this->shrinkage_compensation().z();
-    for (size_t print_object_idx = 0; print_object_idx < m_objects.size(); ++ print_object_idx) {
+    for (size_t print_object_idx = 0; !skip_max_height_check && print_object_idx < m_objects.size(); ++ print_object_idx) {
         const PrintObject &print_object = *m_objects[print_object_idx];
 
         double effective_max_z       = 0;

src/slic3r/GUI/GCodeViewer.cpp

@@ -1521,6 +1521,7 @@ void GCodeViewer::load_as_gcode(const GCodeProcessorResult& gcode_result, const
         m_custom_gcode_per_print_z = gcode_result.custom_gcode_per_print_z;
 
     m_max_print_height = gcode_result.printable_height;
+    m_machine_frame_transform_active = gcode_result.machine_frame_transform_active;
     m_z_offset = gcode_result.z_offset;
 
 
@@ -1736,6 +1737,7 @@ void GCodeViewer::reset()
     m_paths_bounding_box = BoundingBoxf3();
     m_max_bounding_box = BoundingBoxf3();
     m_max_print_height = 0.0f;
+    m_machine_frame_transform_active = false;
     m_z_offset = 0.0f;
     m_extruders_count = 0;
     m_filament_diameters = std::vector<float>();

src/slic3r/GUI/GCodeViewer.hpp

@@ -203,6 +203,7 @@ private:
     //BBS: add shell bounding box
     BoundingBoxf3 m_shell_bounding_box;
     float m_max_print_height{ 0.0f };
+    bool  m_machine_frame_transform_active{ false };
     float m_z_offset{ 0.0f };
 
     ConfigOptionMode m_user_mode;
@@ -289,6 +290,7 @@ public:
     std::vector<int> get_plater_extruder();
 
     const float                get_max_print_height() const { return m_max_print_height; }
+    bool                       is_machine_frame_transform_active() const { return m_machine_frame_transform_active; }
     const BoundingBoxf3& get_paths_bounding_box() const { return m_paths_bounding_box; }
     const BoundingBoxf3& get_max_bounding_box() const { return m_max_bounding_box; }
     const BoundingBoxf3& get_shell_bounding_box() const { return m_shell_bounding_box; }

src/slic3r/GUI/GLCanvas3D.cpp

@@ -10315,7 +10315,11 @@ void GLCanvas3D::_set_warning_notification_if_needed(EWarning warning)
             if (current_printer_technology() != ptSLA) {
                 unsigned int max_z_layer = m_gcode_viewer.get_layers_z_range().back();
                 if (warning == EWarning::ToolHeightOutside) // check if max z_layer height exceed max print height
-                    show = m_gcode_viewer.has_data() && (m_gcode_viewer.get_layers_zs()[max_z_layer] - m_gcode_viewer.get_max_print_height() >= 1e-6);
+                    // Belt printer with active post-gcode machine-frame transform: layer Z values
+                    // live in the machine frame, not the build-volume frame, so the comparison
+                    // against printable_height is meaningless.  Suppress the warning entirely.
+                    show = m_gcode_viewer.has_data() && !m_gcode_viewer.is_machine_frame_transform_active()
+                        && (m_gcode_viewer.get_layers_zs()[max_z_layer] - m_gcode_viewer.get_max_print_height() >= 1e-6);
                 else if (warning == EWarning::ToolpathOutside) { // check if max x,y coords exceed bed area
                     show = m_gcode_viewer.has_data() && !m_gcode_viewer.is_contained_in_bed() &&
                            (m_gcode_viewer.get_max_print_height() -m_gcode_viewer.get_layers_zs()[max_z_layer] >= 1e-6);