activate grid button and widget size

src/Vtk/uLibVtkViewer.cpp

@@ -38,6 +38,13 @@
 #include <vtkObjectFactory.h>
 #include <vtkTextProperty.h>
 #include <vtkRenderWindow.h>
+#include <vtkButtonWidget.h>
+#include <vtkTexturedButtonRepresentation2D.h>
+#include <vtkImageData.h>
+#include <vtkImageCanvasSource2D.h>
+#include <vtkCallbackCommand.h>
+#include <vtkCoordinate.h>
+#include <vtkRenderer.h>
 
 #include "uLibVtkViewer.h"
 
@@ -82,6 +89,9 @@ void Viewer::InstallPipe() {
 
   // Common setup
   Viewport::SetupPipeline(renderWindowInteractor);
+  
+  // Setup native grid button
+  SetupGridButton();
 
   // BUT we want to override the style with our custom NoSpin version
   vtkSmartPointer<vtkInteractorStyleNoSpin> style =
@@ -114,6 +124,89 @@ Viewer::MakeCameraOrientationWidget(vtkRenderWindowInteractor *interactor,
   return widget;
 }
 
+void Viewer::SetupGridButton() {
+  if (!m_RenderWindow || !m_RenderWindow->GetInteractor()) return;
+
+  // Create procedural textures for the button using canvas
+  vtkNew<vtkImageCanvasSource2D> canvas;
+  canvas->SetScalarTypeToUnsignedChar();
+  canvas->SetNumberOfScalarComponents(4);
+  canvas->SetExtent(0, 63, 0, 63, 0, 0);
+
+  // State 0: OFF (Gray circle, transparent background)
+  canvas->SetDrawColor(0, 0, 0, 0);
+  canvas->FillBox(0, 63, 0, 63);
+  canvas->SetDrawColor(120, 120, 120, 255);
+  canvas->DrawCircle(32, 32, 25);
+  canvas->Update();
+
+  vtkNew<vtkImageData> imgOff;
+  imgOff->DeepCopy(canvas->GetOutput());
+
+  // State 1: ON (White circle, transparent background)
+  canvas->SetDrawColor(0, 0, 0, 0);
+  canvas->FillBox(0, 63, 0, 63);
+  canvas->SetDrawColor(255, 255, 255, 255);
+  canvas->DrawCircle(32, 32, 25);
+  canvas->Update();
+
+  vtkNew<vtkImageData> imgOn;
+  imgOn->DeepCopy(canvas->GetOutput());
+
+  vtkNew<vtkTexturedButtonRepresentation2D> rep;
+  rep->SetNumberOfStates(2);
+  rep->SetButtonTexture(0, imgOff);
+  rep->SetButtonTexture(1, imgOn);
+
+  m_GridButton = vtkSmartPointer<vtkButtonWidget>::New();
+  m_GridButton->SetInteractor(m_RenderWindow->GetInteractor());
+  m_GridButton->SetRepresentation(rep);
+
+  // Position it initially
+  UpdateGridButtonPosition();
+
+  // Callback for resize (ModifiedEvent on RenderWindow)
+  vtkNew<vtkCallbackCommand> resizeCallback;
+  resizeCallback->SetClientData(this);
+  resizeCallback->SetCallback([](vtkObject*, unsigned long, void* clientdata, void*){
+      auto* v = static_cast<Viewer*>(clientdata);
+      v->UpdateGridButtonPosition();
+  });
+  m_RenderWindow->AddObserver(vtkCommand::ModifiedEvent, resizeCallback);
+
+  // Callback for state change
+  vtkNew<vtkCallbackCommand> stateCallback;
+  stateCallback->SetClientData(this);
+  stateCallback->SetCallback([](vtkObject* caller, unsigned long, void* clientdata, void*){
+      auto* btn = vtkButtonWidget::SafeDownCast(caller);
+      auto* v = static_cast<Viewer*>(clientdata);
+      auto* r = vtkTexturedButtonRepresentation2D::SafeDownCast(btn->GetRepresentation());
+      v->SetGridVisible(r->GetState() == 1);
+  });
+  
+  m_GridButton->AddObserver(vtkCommand::StateChangedEvent, stateCallback);
+  m_GridButton->On();
+  
+  // Set initial state
+  rep->SetState(GetGridVisible() ? 1 : 0);
+}
+
+void Viewer::UpdateGridButtonPosition() {
+  if (!m_GridButton || !m_RenderWindow) return;
+  auto* rep = vtkTexturedButtonRepresentation2D::SafeDownCast(m_GridButton->GetRepresentation());
+  if (!rep) return;
+
+  int *sz = m_RenderWindow->GetSize();
+  if (sz[0] == 0 || sz[1] == 0) return; // Window not yet sized or hidden
+
+  int margin_rigth = 23;
+  int margin_top = 170;
+  int btnSz = 100; // Button size in display coordinates
+  double bds[6] = { (double)sz[0] - btnSz - margin_rigth, (double)sz[0] - margin_rigth,
+                    (double)sz[1] - margin_top  - btnSz/2.0, (double)sz[1] - margin_top + btnSz/2.0, 0, 0 };
+  rep->PlaceWidget(bds);
+}
+
 void Viewer::Start() { m_RenderWindow->GetInteractor()->Start(); }
 
 vtkRenderWindow *Viewer::GetRenderWindow() { return m_RenderWindow; }