GL windows in Fl_Tile

I am new to FLTK. I want to put several OpenGL windows in an Fl_Tile. I started with Erco's cheat at

http://seriss.com/people/erco/fltk/#GL4PortResizable

which worked OK. However, I want the FL_DOWN_BOX borders to be visible between the tiles. So I enclosed each Fl_Gl_Window in a larger Fl_Window and put these in the Fl_Tile.

My layout for testing is like this:
+----------+----------+
|       gltileb       |
+----------+----------+
| +------+ | +------+ |
| |\    /| | |\    /| |
| | \  / | | | \  / | |
| |  \/  | | |  \/  | |
| |  /\  | | |  /\  | |
| | /  \ | | | /  \ | |
| |/    \| | |/    \| |
| +------+ | +------+ |
+----------+----------+
| +------+ | +------+ |
| |\    /| | |\    /| |
| | \  / | | | \  / | |
| |  \/  | | |  \/  | |
| |  /\  | | |  /\  | |
| | /  \ | | | /  \ | |
| |/    \| | |/    \| |
| +------+ | +------+ |
+----------+----------+

I was hoping for Four Xs in four squares, each with a colored border inside a tile. The X and squares are drawn by GL with colored borders drawn by FLTK, surrounded by regular FL_DOWN_FRAMEs.

The problem is that only the left two of the four GL windows get drawn. This is with fltk1.3.0 tested under linux and Windows. What am I doing wrong? I am not really clear on how/when/if my FLGL::draw() gets called in this hierarchy.

Robert Strickland

Here is my test code:

/**
  Test by Robert Strickland to tile four OpenGL windows.
  Based on Erco's cheat:
  http://seriss.com/people/erco/fltk/#GL4PortResizable
  but without the code to do the proportional resizing
*/
#include <FL/Fl.H>
#include <FL/Fl_Double_Window.H>
#include <FL/Fl_Tile.H>
#include <FL/Fl_Gl_Window.H>
#include <FL/gl.h>

/**
  A Fl_Gl_Window that draws an X in a box
*/
class FLGL : public Fl_Gl_Window {
public:
  FLGL(int x, int y, int w, int h, const char* l=0) :
      Fl_Gl_Window(x, y, w, h, l) {
    end();
  }
protected:
  void draw() {
    if ( !valid() ) {
      // First time? init viewport, etc.
      valid(1);
      glLoadIdentity();
      glViewport(0, 0, w(), h());
      glOrtho(-w(), w(), -h(), h(), -1, 1);
    }
    // Clear screen
    glClear(GL_COLOR_BUFFER_BIT);
    // Draw white 'X'
    glColor3f(1.0, 1.0, 1.0);
    glBegin(GL_LINES);
    glVertex2f(w(),  h());
    glVertex2f(-w(), -h());
    glVertex2f(w(), -h());
    glVertex2f(-w(),  h());
    glEnd();
    // Draw yellow border last, around the outer edge
    glColor3f(1.0, 1.0, 0.0);
    glBegin(GL_LINE_LOOP);
    glVertex2f(-w()+1, -h());
    glVertex2f(w(), -h());
    glVertex2f(w(), h()-1);
    glVertex2f(-w()+1, h()-1);
    glEnd();
  }
};

/**
  A container for a FLGL window that leaves room for a border
*/
class Viewport : public Fl_Window {
protected:
  FLGL *gl;
public:
  Viewport(int x, int y, int w, int h, const char* l=0) :
        Fl_Window(x, y, w, h, l) {
    box(FL_DOWN_FRAME);
    gl = new FLGL( x+10, x+10, w-20, w-20 ); // wide border for testing
    resizable(gl);
    end();
  }
};

/**
  A 2x2 tile of OpenGL windows in Viewport containers with borders
*/
class Layout:public Fl_Tile {
private:
  Viewport *view[4];
public:
  Layout(int x, int y, int w, int h) : Fl_Tile(x, y, w, h) {
    box(FL_DOWN_BOX);
    color(FL_RED);          // (shouldn't be seen)
    // Create the 4 Viewports
    int k = 0;
    for (int j = 0; j < 2; j++) {
      for (int i = 0; i < 2; i++) {
        view[k] = new Viewport(i*200, j*200, 200, 200);
        view[k]->box(FL_DOWN_BOX);
        view[k]->color(9+k);
        view[k]->align(FL_ALIGN_CLIP);
        k++;
      }
    }
    end();
  }
};

int main() {
  Fl_Double_Window *win = new Fl_Double_Window(400, 400, "gltileb");
  Layout *layout = new Layout(0, 0, win->w(), win->h());
  win->resizable(layout);
  win->end();
  win->show();
  return(Fl::run());
}

// End of test code