CODEWITHSUNDEEP
linuxopenglx11
Dean
Dean

Reputation: 6950

X11 window resizing stutters

I'm creating an openGL window in X11 and using glxswapbuffers for double buffering.

The problem is: rendering seems fine but I get openGL contents bouncing around and the window border stuttering when resizing.

I tried filtering the ConfigureNotify events, delaying them, setting vsync off with glXSwapInterval... nothing worked.

This is the code I'm using

void Window::redraw() { // Called by any control which needs redrawing
  XEvent event;
  memset(&event, 0, sizeof(event));
  event.type = Expose;
  event.xexpose.display = display;
  XSendEvent(display, window, False, ExposureMask, &event);
}

void Window::resize(int width, int height) {
  this->Width = width;
  this->Height = height;
}

bool Window::wndProc(XEvent *evt) {
  switch (evt->type) {

      case Expose: {

        if (evt->xexpose.count == 0) { // handle last one only

          while (XCheckTypedWindowEvent(display, window, Expose, evt));

            if (Width != oldWidth || Height != oldHeight)
              resizeViewportAndUpdateDimensions();

          Renderer.drawGLStuff();

          this->redraw();
        }

        return true;

      } break;

      case ConfigureNotify: {
        this->resize(evt->xconfigure.width, evt->xconfigure.height);

        this->redraw();
        return true;
      } break;
  }
}

Notice that this is a different issue (strictly linked to resizing) than this previous post which I solved via XCheckTypedWindowEvent.

Upvotes: 4

Views: 3317

Answers (1)

Andreas
Andreas

Reputation: 5301

https://tronche.com/gui/x/xlib/events/window-state-change/configure.html

https://tronche.com/gui/x/xlib/events/structure-control/resize.html

From what I can read from those two links ConfigureNotify happens when a change has completed. ResizeRequest happens when a resize is attempted. Specifically:

The X server can report ResizeRequest events to clients wanting information about another client's attempts to change the size of a window.

I don´t like the sound of "CAN report", but I suppose you should give it a shot. Don´t forget to set proper event bit as instructed in the link. As for what you should do when capturing event I´m not too sure... I would clear the front buffer and await resize to complete.

Upvotes: 2

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