refactor: Move axis label drawing logic from ViewportWidget to SketchGrid

Co-authored-by: aider (gemini/gemini-2.5-pro) <aider@aider.chat>

src/SketchGrid.cpp

@@ -1,10 +1,12 @@
 #include "SketchGrid.h"
+#include "ViewportWidget.h"
 #include <QOpenGLContext>
 #include <QOpenGLExtraFunctions>
 #include <QOpenGLShaderProgram>
+#include <QPainter>
 #include <QVector>
 
-SketchGrid::SketchGrid()
+SketchGrid::SketchGrid(ViewportWidget* viewport) : m_viewport(viewport)
 {
 }
 
@@ -123,3 +125,36 @@ void SketchGrid::drawAxes(SketchPlane plane, QOpenGLShaderProgram* shaderProgram
     m_vbo.allocate(vertices.constData(), vertices.size() * sizeof(GLfloat));
     glDrawArrays(GL_POINTS, 0, 1);
 }
+
+void SketchGrid::paintAxisLabels(QPainter& painter, SketchGrid::SketchPlane plane, const QMatrix4x4& modelView, const QMatrix4x4& projection)
+{
+    painter.setPen(Qt::white);
+    painter.setFont(QFont("Arial", 10));
+
+    const int range = 50;
+    const int step = 5;
+
+    auto drawLabelsForAxis = [&](int axis_idx) {
+        for (int i = -range; i <= range; i += step) {
+            if (i == 0) continue;
+            QVector3D worldCoord;
+            worldCoord[axis_idx] = i;
+
+            QVector3D screenPos = m_viewport->project(worldCoord, modelView, projection, m_viewport->rect());
+            if (screenPos.z() < 1.0f) { // Not clipped
+                painter.drawText(screenPos.toPoint(), QString::number(i));
+            }
+        }
+    };
+
+    if (plane == SketchGrid::XY) {
+        drawLabelsForAxis(0); // X
+        drawLabelsForAxis(2); // Y
+    } else if (plane == SketchGrid::XZ) {
+        drawLabelsForAxis(0); // X
+        drawLabelsForAxis(1); // Z
+    } else if (plane == SketchGrid::YZ) {
+        drawLabelsForAxis(1); // Y
+        drawLabelsForAxis(2); // Z
+    }
+}