[Spice-devel] [PATCH v2 spice-gtk] Adjust to window scaling

[Frediano Ziglio]

> 
> When GDK_SCALE is != 1 and egl is used, the image presented does not
> fit to the window (scale of 2 is often used with hidpi monitors).
> Usually this is not a problem since all components are adjusted by
> gdk/gtk but with egl, pixel-based data is not being scaled. In this
> case window's scale value can be used in order to determine whether
> to use a pixel resource with higher resolution data.
> 
> In order to reproduce the problem set spice with virgl/Intel-vGPU
> and run spice-gtk with GDK_SCALE=2

I still didn't try. So from what I understand the sizes and coordinated
from GTK when GDK_SCALE == 2 (for instance) are half of the pixel sizes,
right? So for instance width == 1024 means 2048 pixels.

> ---
> Changes from v1:
> -commit msg
> -replace var naming (ws with win_scale)
> 
> 
> This patch is kind of RFC, it fixes the issue, but it's a bit hacky
> and specific. I didn't come across other scale issues but it is likely
> that more of these exist and better and generic fix is needed.
> 
> ---
>  src/spice-widget-egl.c  | 15 +++++++++++++--
>  src/spice-widget-priv.h |  1 +
>  2 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/src/spice-widget-egl.c b/src/spice-widget-egl.c
> index 43fccd7..600c87a 100644
> --- a/src/spice-widget-egl.c
> +++ b/src/spice-widget-egl.c
> @@ -326,6 +326,8 @@ static gboolean spice_widget_init_egl_win(SpiceDisplay
> *display, GdkWindow *win,
>      if (d->egl.surface)
>          return TRUE;
>  
> +    d->egl.scale = gdk_window_get_scale_factor(win);
> +
>  #ifdef GDK_WINDOWING_X11
>      if (GDK_IS_X11_WINDOW(win)) {
>          native = (EGLNativeWindowType)GDK_WINDOW_XID(win);

This factor is only read on initialization, what would happen changing
resolution while the client is open or attaching a new HiDPI monitor?

Can't we keep the "win" and avoid caching it? It should not take long
to read the factor.

> @@ -431,15 +433,17 @@ void spice_egl_resize_display(SpiceDisplay *display,
> int w, int h)
>  {
>      SpiceDisplayPrivate *d = display->priv;
>      int prog;
> +    gint win_scale;
>  
>      if (!gl_make_current(display, NULL))
>          return;
>  
> +    win_scale = d->egl.scale;
>      glGetIntegerv(GL_CURRENT_PROGRAM, &prog);
>  
>      glUseProgram(d->egl.prog);
> -    apply_ortho(d->egl.mproj, 0, w, 0, h, -1, 1);
> -    glViewport(0, 0, w, h);
> +    apply_ortho(d->egl.mproj, 0, w * win_scale , 0, h * win_scale, -1, 1);
> +    glViewport(0, 0, w * win_scale, h * win_scale);
>  

Why not multiplying w and h by d->egl.scale like in other function?

>      if (d->ready)
>          spice_egl_update_display(display);
> @@ -559,6 +563,13 @@ void spice_egl_update_display(SpiceDisplay *display)
>  
>      spice_display_get_scaling(display, &s, &x, &y, &w, &h);
>  
> +    // Adjust to gdk scale
> +    s *= d->egl.scale;
> +    x *= d->egl.scale;
> +    y *= d->egl.scale;
> +    w *= d->egl.scale;
> +    h *= d->egl.scale;
> +
>      glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
>      glClear(GL_COLOR_BUFFER_BIT);
>  
> diff --git a/src/spice-widget-priv.h b/src/spice-widget-priv.h
> index 65eb404..8f110ac 100644
> --- a/src/spice-widget-priv.h
> +++ b/src/spice-widget-priv.h
> @@ -149,6 +149,7 @@ struct _SpiceDisplayPrivate {
>          EGLImageKHR         image;
>          gboolean            call_draw_done;
>          SpiceGlScanout      scanout;
> +        gint                scale;

Why in egl? It's not a property related to egl.

>      } egl;
>  #endif // HAVE_EGL
>      double scroll_delta_y;

Frediano