Mostly complete from the Python original

src/canvas.cpp

@@ -0,0 +1,129 @@
+#include <QMouseEvent>
+#include <QDebug>
+
+#include "canvas.h"
+#include "glmesh.h"
+#include "mesh.h"
+
+Canvas::Canvas(const QGLFormat& format, QWidget *parent)
+    : QGLWidget(format, parent), mesh(NULL),
+      scale(1), tilt(90), yaw(0)
+{
+    // Nothing to do here
+}
+
+Canvas::~Canvas()
+{
+    delete mesh;
+}
+
+void Canvas::load_mesh(Mesh* m)
+{
+    mesh = new GLMesh(m);
+    center = QVector3D(m->xmin() + m->xmax(),
+                       m->ymin() + m->ymax(),
+                       m->zmin() + m->zmax()) / 2;
+    scale = 2 / sqrt(
+                pow(m->xmax() - m->xmin(), 2) +
+                pow(m->ymax() - m->ymin(), 2) +
+                pow(m->zmax() - m->zmin(), 2));
+
+    update();
+
+    delete m;
+}
+
+void Canvas::initializeGL()
+{
+    mesh_shader.addShaderFromSourceFile(QGLShader::Vertex, ":/gl/mesh.vert");
+    mesh_shader.addShaderFromSourceFile(QGLShader::Fragment, ":/gl/mesh.frag");
+    mesh_shader.link();
+
+    glClearColor(0.0, 0.0, 0.0, 0.0);
+    glEnable(GL_DEPTH_TEST);
+}
+
+void Canvas::paintGL()
+{
+    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+    if (mesh)  draw_mesh();
+}
+
+void Canvas::draw_mesh()
+{
+    mesh_shader.bind();
+
+    // Load the transform and view matrices into the shader
+    glUniformMatrix4fv(
+                mesh_shader.uniformLocation("transform_matrix"),
+                1, GL_FALSE, transform_matrix().data());
+    glUniformMatrix4fv(
+                mesh_shader.uniformLocation("view_matrix"),
+                1, GL_FALSE, view_matrix().data());
+
+    // Find and enable the attribute location for vertex position
+    const GLuint vp = mesh_shader.attributeLocation("vertex_position");
+    glEnableVertexAttribArray(vp);
+
+    // Then draw the mesh with that vertex position
+    mesh->draw(vp);
+
+    // Clean up state machine
+    glDisableVertexAttribArray(vp);
+    mesh_shader.release();
+}
+
+QMatrix4x4 Canvas::transform_matrix() const
+{
+    QMatrix4x4 m;
+    m.rotate(tilt, QVector3D(1, 0, 0));
+    m.rotate(yaw,  QVector3D(0, 0, 1));
+    m.scale(scale);
+    m.translate(-center);
+    return m;
+}
+
+QMatrix4x4 Canvas::view_matrix() const
+{
+    QMatrix4x4 m;
+    if (width() > height())
+    {
+        m.scale(height() / float(width()), 1, 0.5);
+    }
+    else
+    {
+        m.scale(1, width() / float(height()), 0.5);
+    }
+    return m;
+}
+
+void Canvas::mousePressEvent(QMouseEvent* event)
+{
+    if (event->button() == Qt::LeftButton)
+    {
+        mouse_pos = event->pos();
+        setCursor(Qt::ClosedHandCursor);
+    }
+}
+
+void Canvas::mouseReleaseEvent(QMouseEvent* event)
+{
+    if (event->button() == Qt::LeftButton)
+    {
+        unsetCursor();
+    }
+}
+
+void Canvas::mouseMoveEvent(QMouseEvent* event)
+{
+    if (event->buttons() & Qt::LeftButton)
+    {
+        auto p = event->pos();
+        auto d = p - mouse_pos;
+        yaw = fmod(yaw + d.x(), 360);
+        tilt = fmax(0, fmin(180, tilt - d.y()));
+        mouse_pos = p;
+        update();
+    }
+}