Rib: the thickness gets its handle, so the whole tool is draggable

Rib's depth already reused the Extrude arrow. Its thickness could not: the arrow
points along the plane normal, and thickness is an offset either side of the rib
line, IN the plane. Different direction, different handle.

Two square handles at mid ± perp·half, plus the slab's actual footprint drawn as
a thin closed rectangle — the footprint matters more than the dots, because what
a rib thickness means is how wide that slab lands on the body, and until now
there was no way to see it before committing.

A drag on either handle sets the FULL thickness, twice the perpendicular distance
from the line, because the slab is centred on the line and the handle sits at
half. Both handles behave identically for the same reason, so they share one
colour rather than pretending to be two different actions.

A zero-length line has no direction to grow a slab perpendicular to, so the
shared rib_frame() helper returns false and render and drag both draw nothing
rather than dividing by zero. Non-Line entities clear the gizmo instead of
guessing: the kernel is line-only and a gizmo that guesses would be lying about
what Confirm will build.

Unlike the helix callback this one goes through refresh_preview(), because Rib
builds a real solid ghost that has to rebuild. The helix has none and skips it
deliberately.

Both gizmos coexist and resolve the sketch and entity the same way, so the depth
arrow and the thickness handles can never disagree about which line they are on.

Reviewed and compiled (libslic3r_gui, RC=0); not exercised. snaporca-plew.

src/slic3r/GUI/DesignCanvas.cpp

@@ -861,6 +861,24 @@ void DesignCanvas::set_on_helix_changed(std::function<void(double, double, doubl
     m_sketch_tool.on_helix_changed = std::move(cb);
 }
 
+void DesignCanvas::set_rib_gizmo(const SketchPlane& plane, const Vec2d& p0, const Vec2d& p1,
+                                 double thickness)
+{
+    m_sketch_tool.set_rib_gizmo(plane, p0, p1, thickness);
+    request_repaint();
+}
+
+void DesignCanvas::clear_rib_gizmo()
+{
+    m_sketch_tool.clear_rib_gizmo();
+    request_repaint();
+}
+
+void DesignCanvas::set_on_rib_thickness_changed(std::function<void(double)> cb)
+{
+    m_sketch_tool.on_rib_thickness_changed = std::move(cb);
+}
+
 void DesignCanvas::set_base_pick(std::vector<SketchPlane> planes, std::vector<int> bases,
                                 std::vector<std::string> labels)
 {

src/slic3r/GUI/DesignCanvas.hpp

@@ -174,6 +174,9 @@ public:
                          double taper, bool left_handed);          // helix curve + 3 drag handles
     void clear_helix_gizmo();
     void set_on_helix_changed(std::function<void(double, double, double)> cb);
+    void set_rib_gizmo(const SketchPlane& plane, const Vec2d& p0, const Vec2d& p1, double thickness);  // rib slab footprint + 2 thickness handles
+    void clear_rib_gizmo();
+    void set_on_rib_thickness_changed(std::function<void(double)> cb);
     void set_base_pick(std::vector<SketchPlane> planes, std::vector<int> bases,
                        std::vector<std::string> labels = {});   // clickable labelled reference planes
     void clear_base_pick();

src/slic3r/GUI/DesignPanel.cpp

@@ -3544,6 +3544,12 @@ DesignPanel::DesignPanel(wxWindow* parent)
         m_viewport->request_repaint();
     });
 
+    // Rib thickness handle: writes the spin and re-feeds the ghost, same as the depth arrow.
+    m_viewport->set_on_rib_thickness_changed([this](double thickness) {
+        if (m_rib_thickness) m_rib_thickness->SetValue(thickness);
+        refresh_preview();   // Rib HAS a solid ghost, so the full preview path is correct here
+    });
+
     // Clicking a ghost base plane sets the base graphically (replaces the dropdown). A base pick
     // drops any offset-from-face choice so the picked base plane wins, then re-resolves the preview.
     m_viewport->set_on_datum_base_picked([this](int base) {
@@ -9122,6 +9128,25 @@ void DesignPanel::update_helix_gizmo()
                                 m_helix_left_handed && m_helix_left_handed->GetValue());
 }
 
+void DesignPanel::update_rib_gizmo()
+{
+    if (!m_viewport) return;
+    if (m_active != Tool::Rib) { m_viewport->clear_rib_gizmo(); return; }
+    // Same resolution the Tool::Rib branch of update_extrude_gizmo() uses — the depth arrow and
+    // this share one sketch and one entity, and must never disagree about which line that is.
+    const int ssel = m_rib_sketch ? m_rib_sketch->GetSelection() : wxNOT_FOUND;
+    const int ref  = (ssel != wxNOT_FOUND)
+                         ? int(reinterpret_cast<intptr_t>(m_rib_sketch->GetClientData(ssel))) : -1;
+    if (ref < 0 || ref >= int(m_doc.features.size())) { m_viewport->clear_rib_gizmo(); return; }
+    const CadFeature& sk = m_doc.features[ref];
+    const int ei = m_rib_entity ? m_rib_entity->GetValue() : 0;
+    if (ei < 0 || ei >= int(sk.entities.size())) { m_viewport->clear_rib_gizmo(); return; }
+    const SketchEntity& e = sk.entities[ei];
+    if (e.type != SketchEntity::Type::Line) { m_viewport->clear_rib_gizmo(); return; }   // rib is line-only
+    m_viewport->set_rib_gizmo(sk.plane, e.p0, e.p1,
+                              m_rib_thickness ? m_rib_thickness->GetValue() : 0.0);
+}
+
 // Onshape default planes: the XY/XZ/YZ reference planes are persistent, transparent, labelled, and
 // larger than the bed — shown as the FALLBACK when there is no object yet. When the Plane tool is
 // open they additionally surface existing datums so a base can be picked. Single authority for the
@@ -9297,6 +9322,8 @@ void DesignPanel::refresh_preview()
     update_datum_gizmo();
     // Helix curve + handles (self-gates: only while the Helix card is open).
     update_helix_gizmo();
+    // Rib slab footprint + thickness handles (self-gates: only while the Rib card is open).
+    update_rib_gizmo();
     update_operand_highlight();
 }
 

src/slic3r/GUI/DesignPanel.hpp

@@ -273,6 +273,7 @@ private:
     void       update_pattern_gizmo();    // linear spacing arrow / circular angle-arc (Pattern card)
     void       update_datum_gizmo();      // resize handles on the datum plane being created/edited (C3)
     void       update_helix_gizmo();      // live helix curve + radius/height/pitch handles (Helix card)
+    void       update_rib_gizmo();        // in-plane slab footprint + thickness handles (Rib card)
     void       refresh_datum_planes();    // push resolved datum frames + per-plane u/v extents to viewport
     void       refresh_mate_connectors(); // push connector frames so verse + polarity are visible
     void       update_reference_planes(); // persistent XY/XZ/YZ reference planes (fallback when no object)

src/slic3r/GUI/DesignSketchTool.cpp

@@ -3914,6 +3914,139 @@ void DesignSketchTool::drag_helix_handle(GLCanvas3D& canvas, const wxMouseEvent&
     if (on_helix_changed) on_helix_changed(m_hx_radius, m_hx_pitch, m_hx_height);
 }
 
+// ---- Rib thickness gizmo (in-plane slab footprint + 2 symmetric handles) -----------------
+void DesignSketchTool::set_rib_gizmo(const SketchPlane& plane, const Vec2d& p0, const Vec2d& p1,
+                                     double thickness)
+{
+    m_rb_active    = true;
+    m_rb_plane     = plane;
+    m_rb_p0        = p0;
+    m_rb_p1        = p1;
+    m_rb_thickness = thickness;
+}
+
+void DesignSketchTool::clear_rib_gizmo()
+{
+    m_rb_active = false;
+    m_rb_drag   = -1;
+}
+
+// Resolve the rib line's in-plane frame: unit direction d, perpendicular perp, midpoint, and
+// half-thickness. A degenerate line (zero length) has no direction to grow a slab perpendicular
+// to — return false so the caller draws nothing and never divides by zero.
+static bool rib_frame(const Vec2d& p0, const Vec2d& p1, double thickness,
+                      Vec2d& d, Vec2d& perp, Vec2d& mid, double& half)
+{
+    const Vec2d seg = p1 - p0;
+    const double len = seg.norm();
+    if (len < 1e-9) return false;
+    d    = seg / len;
+    perp = Vec2d(-d.y(), d.x());
+    mid  = 0.5 * (p0 + p1);
+    half = thickness * 0.5;
+    return true;
+}
+
+// Draw the rib slab's actual footprint (the rectangle p0±perp·half, p1±perp·half) as a thin
+// closed ribbon plus two square handles at mid ± perp·half. Both handles sit at half-thickness,
+// so a drag on either expresses the full thickness symmetrically.
+void DesignSketchTool::render_rib_gizmo()
+{
+    if (!m_rb_active) return;
+    Vec2d d, perp, mid; double half;
+    if (!rib_frame(m_rb_p0, m_rb_p1, m_rb_thickness, d, perp, mid, half)) return;
+    using EPT = GLModel::Geometry::EPrimitiveType;
+    using EVL = GLModel::Geometry::EVertexLayout;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const Vec3d right = cam.get_dir_right().normalized();
+    const Vec3d up    = cam.get_dir_up().normalized();
+    const Vec3d vd    = cam.get_dir_forward();
+    const double upp  = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double hs   = 6.0 * upp;                       // handle half-size (~6 px)
+    const double hw   = 1.5 * upp;                       // ribbon half-width
+
+    // Slab footprint outline (4 thin camera-facing ribbons).
+    const Vec3d c[4] = { m_rb_plane.to_world(m_rb_p0 + perp * half),
+                         m_rb_plane.to_world(m_rb_p1 + perp * half),
+                         m_rb_plane.to_world(m_rb_p1 - perp * half),
+                         m_rb_plane.to_world(m_rb_p0 - perp * half) };
+    GLModel::Geometry border; border.format = { EPT::Triangles, EVL::P3 };
+    unsigned int bb = 0;
+    for (int s = 0; s < 4; ++s) {
+        const Vec3d a = c[s], b = c[(s + 1) & 3];
+        Vec3d dir = b - a; if (dir.norm() < 1e-9) continue; dir.normalize();
+        Vec3d off = dir.cross(vd);
+        if (off.norm() < 1e-9) off = dir.cross(up);
+        if (off.norm() < 1e-9) continue;
+        off.normalize(); off *= hw;
+        border.add_vertex((Vec3f)(a + off).cast<float>()); border.add_vertex((Vec3f)(b + off).cast<float>());
+        border.add_vertex((Vec3f)(b - off).cast<float>()); border.add_vertex((Vec3f)(a - off).cast<float>());
+        border.add_triangle(bb, bb + 1, bb + 2); border.add_triangle(bb, bb + 2, bb + 3); bb += 4;
+    }
+
+    // Two handles: 0 = +perp side, 1 = -perp side (both at half-thickness).
+    const Vec3d hpts[2] = { m_rb_plane.to_world(mid + perp * half),
+                            m_rb_plane.to_world(mid - perp * half) };
+    const ColorRGBA hot(1.0f, 0.85f, 0.2f, 1.0f);
+
+    glsafe(::glDisable(GL_DEPTH_TEST));
+    if (bb > 0) {
+        GLModel m; m.init_from(std::move(border));
+        m.set_color(ColorRGBA(1.0f, 0.62f, 0.16f, 0.9f));   // CAD amber slab footprint
+        m.render();
+    }
+    for (int i = 0; i < 2; ++i) {
+        const Vec3d ctr = hpts[i];
+        const Vec3d q0 = ctr - right * hs - up * hs, q1 = ctr + right * hs - up * hs,
+                    q2 = ctr + right * hs + up * hs, q3 = ctr - right * hs + up * hs;
+        GLModel::Geometry sq; sq.format = { EPT::Triangles, EVL::P3 };
+        sq.add_vertex((Vec3f)q0.cast<float>()); sq.add_vertex((Vec3f)q1.cast<float>());
+        sq.add_vertex((Vec3f)q2.cast<float>()); sq.add_vertex((Vec3f)q3.cast<float>());
+        sq.add_triangle(0, 1, 2); sq.add_triangle(0, 2, 3);
+        GLModel m; m.init_from(std::move(sq));
+        m.set_color(m_rb_drag == i ? hot : ColorRGBA(0.30f, 0.80f, 0.34f, 1.0f));   // green
+        m.render();
+    }
+}
+
+bool DesignSketchTool::hit_test_rib_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int& which) const
+{
+    if (!m_rb_active) return false;
+    Vec2d d, perp, mid; double half;
+    if (!rib_frame(m_rb_p0, m_rb_p1, m_rb_thickness, d, perp, mid, half)) return false;
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double tol = 9.0 / std::max(cam.get_zoom(), 1e-6);   // ~9 px in world units
+    const Vec3d hpts[2] = { m_rb_plane.to_world(mid + perp * half),
+                            m_rb_plane.to_world(mid - perp * half) };
+    double best = tol; which = -1;
+    for (int i = 0; i < 2; ++i) {
+        const Vec3d w  = hpts[i] - ro;
+        const double t = w.dot(rd) / std::max(rd.dot(rd), 1e-12);
+        const double dd = (w - rd * t).norm();
+        if (dd < best) { best = dd; which = i; }
+    }
+    return which >= 0;
+}
+
+// Drag a handle: project the cursor ray onto the rib plane (the same call the helix radius drag
+// uses), take the perpendicular distance from the rib LINE to that point, and set the thickness
+// to twice that distance — the slab is centred on the line and the handle sits at half-thickness.
+void DesignSketchTool::drag_rib_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int which)
+{
+    (void)which;   // both handles behave identically: a drag on either sets the full thickness
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    Vec2d d, perp, mid; double half;
+    if (!rib_frame(m_rb_p0, m_rb_p1, m_rb_thickness, d, perp, mid, half)) return;
+    const Vec2d lp = m_rb_plane.project(ro, rd);
+    const Vec2d w  = lp - m_rb_p0;
+    const double dist = std::abs(w.x() * d.y() - w.y() * d.x());   // |cross(w, d)| = perp distance
+    m_rb_thickness = std::max(0.01, 2.0 * dist);                   // ×2: centred slab, handle at half
+    if (on_rib_thickness_changed) on_rib_thickness_changed(m_rb_thickness);
+}
+
 // ---- Reference/base planes (Onshape-style default planes) -----------------------------
 void DesignSketchTool::set_base_pick(std::vector<SketchPlane> planes, std::vector<int> bases,
                                      std::vector<std::string> labels)
@@ -7336,6 +7469,7 @@ void DesignSketchTool::render(GLCanvas3D& canvas)
         if (m_dbp_active) render_base_pick();
         if (m_dz_active) render_datum_gizmo();
         if (m_hx_active) render_helix_gizmo();
+        if (m_rb_active) render_rib_gizmo();
         if (m_ex_active) render_extrude_gizmo();
         if (m_mv_active) render_move_gizmo();
         if (m_fl_active) render_fillet_gizmo();
@@ -8158,6 +8292,21 @@ bool DesignSketchTool::on_mouse_impl(wxMouseEvent& evt, GLCanvas3D& canvas)
                 }
             }
         }
+        // Rib thickness gizmo: two in-plane handles on the slab footprint, while the Rib card is open.
+        if (m_rb_active) {
+            if (m_rb_drag >= 0 && evt.Dragging() && evt.LeftIsDown()) {
+                drag_rib_handle(canvas, evt, m_rb_drag);
+                return true;
+            }
+            if (evt.LeftUp() && m_rb_drag >= 0) { m_rb_drag = -1; return true; }
+            if (evt.LeftDown()) {
+                int which = -1;
+                if (hit_test_rib_handle(canvas, evt, which)) {
+                    m_rb_drag = which;
+                    return true;
+                }
+            }
+        }
         // Datum base picker: HOVER highlight only here. The CLICK is handled at the very end of the
         // selection fall-through (below), so picking existing geometry (committed sketch loops,
         // solid faces/edges) always wins over a base-plane click — the planes never block selection.

src/slic3r/GUI/DesignSketchTool.hpp

@@ -119,7 +119,7 @@ public:
                                       || m_show_planes || m_show_axes
                                       || m_ex_active || m_mv_active || m_fl_active
                                       || m_hl_active || m_th_active || m_sh_active
-                                      || m_dr_active || m_ct_active || m_dz_active || m_dbp_active || m_hx_active; }
+                                      || m_dr_active || m_ct_active || m_dz_active || m_dbp_active || m_hx_active || m_rb_active; }
 
     // View helpers: the 3 world origin planes (XY/XZ/YZ) and the world axis triad, each
     // shown/hidden by a toggle (keys P / A). Off by default so the idle scene stays clean.
@@ -214,6 +214,15 @@ public:
     void clear_helix_gizmo();
     std::function<void(double radius, double pitch, double height)> on_helix_changed;
 
+    // Visual Rib thickness gizmo. The rib is a thin slab grown either side of an open sketch
+    // line, so its thickness is an IN-PLANE offset perpendicular to that line — the depth arrow
+    // (which points along the plane normal) cannot express it. Two handles, one per side,
+    // dragged symmetrically: the slab is centred on the line, so a drag on either side sets the
+    // full thickness rather than one half.
+    void set_rib_gizmo(const SketchPlane& plane, const Vec2d& p0, const Vec2d& p1, double thickness);
+    void clear_rib_gizmo();
+    std::function<void(double thickness)> on_rib_thickness_changed;
+
     // Graphical base/origin pick: while the Plane card is open, the candidate base planes
     // (XY/XZ/YZ origin planes + existing datums) draw as translucent clickable ghosts. A click
     // on one fires on_datum_base_picked(base) with that plane's base index (0/1/2 or 3+N).
@@ -1039,6 +1048,19 @@ private:
     void  render_helix_gizmo();
     bool  hit_test_helix_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int& which) const;
     void  drag_helix_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int which);
+    // Rib thickness gizmo state (plane-anchored slab footprint + 2 drag handles). Fed by the
+    // panel while the Rib card is open (sketch tool NOT active); the tool draws the rib's
+    // footprint outline and a handle on each side of the line at half-thickness. Dragging either
+    // handle sets the full thickness (the slab is centred on the line).
+    bool        m_rb_active{false};
+    SketchPlane m_rb_plane;
+    Vec2d       m_rb_p0{Vec2d::Zero()};      // rib line endpoints, in plane coords
+    Vec2d       m_rb_p1{Vec2d::Zero()};
+    double      m_rb_thickness{2.0};
+    int         m_rb_drag{-1};               // 0 = +perp handle, 1 = -perp handle, -1 none
+    void  render_rib_gizmo();
+    bool  hit_test_rib_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int& which) const;
+    void  drag_rib_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int which);
     // Datum base picker (translucent clickable origin/datum planes)
     bool        m_dbp_active{false};
     std::vector<SketchPlane>  m_dbp_planes;