ofGetCurrentMatrix(OF_MATRIX_PROJECTION) returns wrong matrix when camera is enclosed in FBO

Without fbo:

#include "ofMain.h"

class ofApp : public ofBaseApp
{
  public:
    void setup();
    void draw();

    ofCamera cam;
};

int main()
{
  ofGLFWWindowSettings settings;

  auto window = ofCreateWindow(settings);
  auto app = make_shared<ofApp>();
  ofRunApp(window, app);

  return ofRunMainLoop();
}

void ofApp::setup()
{
}

void ofApp::draw()
{
  cam.begin();
    cout << ofGetCurrentMatrix(OF_MATRIX_PROJECTION) << endl << endl;
  cam.end();
}

With fbo:

#include "ofMain.h"

class ofApp : public ofBaseApp
{
  public:
    void setup();
    void draw();

    ofFbo fbo;
    ofCamera cam;
};

int main()
{
  ofGLFWWindowSettings settings;

  auto window = ofCreateWindow(settings);
  auto app = make_shared<ofApp>();
  ofRunApp(window, app);

  return ofRunMainLoop();
}

void ofApp::setup()
{
  fbo.allocate(ofGetWidth(), ofGetHeight());
}

void ofApp::draw()
{
  fbo.begin();
    cam.begin();
      cout << ofGetCurrentMatrix(OF_MATRIX_PROJECTION) << endl << endl;
    cam.end();
  fbo.end();
  fbo.draw(0,0);
}

Projection matrix without fbo (correct):

 1.29904,        0,        0,        0
       0,  1.73205,        0,        0
       0,        0,   -1.002,       -1
       0,        0, -13.3155,        0

Projection matrix with fbo (wrong):

 1.29904,       -0,        0,        0
       0, -1.73205,        0,        0
       0,        0,   -1.002,       -1
       0,        0, -13.3155,        0

Projection matrix with fbo taken both from cam and ofGetCurrentMatrix(OF_MATRIX_PROJECTION), side by side:

void ofApp::draw()
{
  fbo.begin();
    cam.begin();

      cout << "Matrix from cam: " << endl
           << cam.getProjectionMatrix() << endl;

      cout << "Matrix from ofGetCurrentMatrix: " << endl
           << ofGetCurrentMatrix(OF_MATRIX_PROJECTION) << endl << endl;

    cam.end();
  fbo.end();
  fbo.draw(0,0);
}

Should be the same, but they're not:

Matrix from cam: 
 1.29904,        0,        0,        0
       0,  1.73205,        0,        0
       0,        0,   -1.002,       -1
       0,        0, -13.3155,        0
Matrix from ofGetCurrentMatrix: 
 1.29904,       -0,        0,        0
       0, -1.73205,        0,        0
       0,        0,   -1.002,       -1
       0,        0, -13.3155,        0

Currently addons which rely on ofGetCurrentMatrix(OF_MATRIX_PROJECTION) command are all broken because it returns incorrect matrix if one wants record an FBO. For workaround you can pass camera directly as a parameter to custom draw() function.

Compiled against latest commit.

Start by reproducing the provided comparison using ofFbo, ofCamera, ofGetCurrentMatrix(OF_MATRIX_PROJECTION), and cam.getProjectionMatrix(). Trace how the current projection matrix is handled while an FBO and camera are active. Done means both APIs return the same projection matrix in the FBO case without changing the no-FBO result.