feat: Add X, Y, Z labels to ViewCube axes

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

src/ViewCube.cpp

@@ -7,6 +7,7 @@
 #include <QScreen>
 #include <QSvgRenderer>
 #include <QVector>
+#include <QVector3D>
 
 namespace
 {
@@ -74,6 +75,35 @@ void ViewCube::paintGL(QOpenGLShaderProgram* simpleShader, int simpleShaderColor
     drawViewCube(viewCubeProjection, viewMatrix, opacity);
     drawAxes(simpleShader, simpleShaderColorLoc, viewCubeProjection, viewMatrix);
 
+    QMatrix4x4 mvp = viewCubeProjection * viewMatrix;
+    const float axisLen = 1.7f;
+
+    QVector3D xAxisEnd(axisLen, 0.0f, 0.0f);
+    QVector3D yAxisEnd(0.0f, 0.0f, axisLen);
+    QVector3D zAxisEnd(0.0f, axisLen, 0.0f);
+
+    QVector3D xAxisNdc = mvp.map(xAxisEnd);
+    QVector3D yAxisNdc = mvp.map(yAxisEnd);
+    QVector3D zAxisNdc = mvp.map(zAxisEnd);
+
+    const int vpX = width - viewCubeSize;
+    const int vpY = height - viewCubeSize;
+    const int vpW = viewCubeSize;
+    const int vpH = viewCubeSize;
+    const float dpr = QGuiApplication::primaryScreen()->devicePixelRatio();
+
+    m_xAxisLabelPos.setX( (xAxisNdc.x() + 1.0f) * vpW / 2.0f + vpX );
+    m_xAxisLabelPos.setY( (1.0f - xAxisNdc.y()) * vpH / 2.0f + vpY );
+    m_xAxisLabelPos /= dpr;
+
+    m_yAxisLabelPos.setX( (yAxisNdc.x() + 1.0f) * vpW / 2.0f + vpX );
+    m_yAxisLabelPos.setY( (1.0f - yAxisNdc.y()) * vpH / 2.0f + vpY );
+    m_yAxisLabelPos /= dpr;
+
+    m_zAxisLabelPos.setX( (zAxisNdc.x() + 1.0f) * vpW / 2.0f + vpX );
+    m_zAxisLabelPos.setY( (1.0f - zAxisNdc.y()) * vpH / 2.0f + vpY );
+    m_zAxisLabelPos /= dpr;
+
     glDisable(GL_BLEND);
 }
 
@@ -229,6 +259,23 @@ void ViewCube::drawAxes(QOpenGLShaderProgram* simpleShader, int colorLoc, const
 
 void ViewCube::paint2D(QPainter& painter, int widgetWidth, int widgetHeight)
 {
+    QFont font("Arial", 10, QFont::Bold);
+    painter.setFont(font);
+    painter.setPen(Qt::black);
+    QFontMetrics fm(font);
+
+    QRect xRect = fm.boundingRect("X");
+    xRect.moveCenter(m_xAxisLabelPos);
+    painter.drawText(xRect, Qt::AlignCenter, "X");
+
+    QRect yRect = fm.boundingRect("Y");
+    yRect.moveCenter(m_yAxisLabelPos);
+    painter.drawText(yRect, Qt::AlignCenter, "Y");
+
+    QRect zRect = fm.boundingRect("Z");
+    zRect.moveCenter(m_zAxisLabelPos);
+    painter.drawText(zRect, Qt::AlignCenter, "Z");
+
     if (!m_isHovered) {
         return;
     }

src/ViewCube.h

@@ -34,6 +34,10 @@ private:
     QRect m_homeButtonRect;
     QSvgRenderer* m_homeButtonRenderer = nullptr;
 
+    QPoint m_xAxisLabelPos;
+    QPoint m_yAxisLabelPos;
+    QPoint m_zAxisLabelPos;
+
     QOpenGLTexture* m_faceTextures[6];
 
     QOpenGLShaderProgram* m_textureShaderProgram = nullptr;