DisplayAllocator interface (Stefano Stabellini)

Hi all,
this patch adds a DisplayAllocator interface that allows display
frontends (sdl in particular) to provide a preallocated display buffer
for the graphical backend to use.

Whenever a graphical backend cannot use
qemu_create_displaysurface_from because its own internal pixel format
cannot be exported directly (text mode or graphical mode with color
depth 8 or 24), it creates another display buffer in memory using
qemu_create_displaysurface and does the conversion.
This new buffer needs to be blitted into the sdl surface buffer every time
we need to update portions of the screen.
We can avoid this using the DisplayAllocator interace: sdl provides its
own implementation of qemu_create_displaysurface, giving back the sdl
surface buffer directly (as we used to do before the DisplayState
changes).
Since the buffer returned by sdl could be in bgr format we need to put
back in the handlers of that case.

This approach is good if the two following conditions are true:

1) the sdl surface is a software surface that resides in main memory;

2) the host display color depth is either 16 or 32 bpp.

If first condition is false we can have bad performances using sdl
and vnc together.
If the second condition is false performances are certainly not going to
improve but they shouldn't get worse either.

The first condition is always true, at least on linux/X11 systems; but I
believe is true also on other platforms.
The second condition is true in the vast majority of the cases.

This patch should also have the good side effect of solving the sdl
2D slowness malc was reporting on MacOS, because SDL_BlitSurface is not
going to be called anymore when the guest is in text mode or 24bpp.
However the root problem is still present so I suspect we may
still see some slowness on MacOS when the guest is in 32 or 16 bpp.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6839 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 118 insertions, 13 deletions

diff --git a/sdl.c b/sdl.c
index a748426abc..843a6fc89a 100644
--- a/sdl.c
+++ b/sdl.c
@@ -53,17 +53,20 @@ static int absolute_enabled = 0;
 static int guest_cursor = 0;
 static int guest_x, guest_y;
 static SDL_Cursor *guest_sprite = 0;
+static uint8_t allocator;
+static uint8_t hostbpp;
 
 static void sdl_update(DisplayState *ds, int x, int y, int w, int h)
 {
-    SDL_Rect rec;
-    rec.x = x;
-    rec.y = y;
-    rec.w = w;
-    rec.h = h;
     //    printf("updating x=%d y=%d w=%d h=%d\n", x, y, w, h);
-
-    SDL_BlitSurface(guest_screen, &rec, real_screen, &rec);
+    if (guest_screen) {
+        SDL_Rect rec;
+        rec.x = x;
+        rec.y = y;
+        rec.w = w;
+        rec.h = h;
+        SDL_BlitSurface(guest_screen, &rec, real_screen, &rec);
+    }
     SDL_UpdateRect(real_screen, x, y, w, h);
 }
 
@@ -83,7 +86,7 @@ static void sdl_setdata(DisplayState *ds)
                                             ds->surface->pf.bmask, ds->surface->pf.amask);
 }
 
-static void sdl_resize(DisplayState *ds)
+static void do_sdl_resize(int width, int height, int bpp)
 {
     int flags;
 
@@ -95,15 +98,101 @@ static void sdl_resize(DisplayState *ds)
     if (gui_noframe)
         flags |= SDL_NOFRAME;
 
-    width = ds_get_width(ds);
-    height = ds_get_height(ds);
-    real_screen = SDL_SetVideoMode(width, height, 0, flags);
+    real_screen = SDL_SetVideoMode(width, height, bpp, flags);
     if (!real_screen) {
         fprintf(stderr, "Could not open SDL display\n");
         exit(1);
     }
+}
+
+static void sdl_resize(DisplayState *ds)
+{
+    if  (!allocator) {
+        do_sdl_resize(ds_get_width(ds), ds_get_height(ds), 0);
+        sdl_setdata(ds);
+    } else {
+        if (guest_screen != NULL) {
+            SDL_FreeSurface(guest_screen);
+            guest_screen = NULL;
+        }
+    }
+}
+
+static PixelFormat sdl_to_qemu_pixelformat(SDL_PixelFormat *sdl_pf)
+{
+    PixelFormat qemu_pf;
+
+    memset(&qemu_pf, 0x00, sizeof(PixelFormat));
+
+    qemu_pf.bits_per_pixel = sdl_pf->BitsPerPixel;
+    qemu_pf.bytes_per_pixel = sdl_pf->BytesPerPixel;
+    qemu_pf.depth = (qemu_pf.bits_per_pixel) == 32 ? 24 : (qemu_pf.bits_per_pixel);
+
+    qemu_pf.rmask = sdl_pf->Rmask;
+    qemu_pf.gmask = sdl_pf->Gmask;
+    qemu_pf.bmask = sdl_pf->Bmask;
+    qemu_pf.amask = sdl_pf->Amask;
+
+    qemu_pf.rshift = sdl_pf->Rshift;
+    qemu_pf.gshift = sdl_pf->Gshift;
+    qemu_pf.bshift = sdl_pf->Bshift;
+    qemu_pf.ashift = sdl_pf->Ashift;
+
+    qemu_pf.rbits = 8 - sdl_pf->Rloss;
+    qemu_pf.gbits = 8 - sdl_pf->Gloss;
+    qemu_pf.bbits = 8 - sdl_pf->Bloss;
+    qemu_pf.abits = 8 - sdl_pf->Aloss;
+
+    qemu_pf.rmax = ((1 << qemu_pf.rbits) - 1);
+    qemu_pf.gmax = ((1 << qemu_pf.gbits) - 1);
+    qemu_pf.bmax = ((1 << qemu_pf.bbits) - 1);
+    qemu_pf.amax = ((1 << qemu_pf.abits) - 1);
+
+    return qemu_pf;
+}
+
+static DisplaySurface* sdl_create_displaysurface(int width, int height)
+{
+    DisplaySurface *surface = (DisplaySurface*) qemu_mallocz(sizeof(DisplaySurface));
+    if (surface == NULL) {
+        fprintf(stderr, "sdl_create_displaysurface: malloc failed\n");
+        exit(1);
+    }
+
+    surface->width = width;
+    surface->height = height;
 
-    sdl_setdata(ds);
+    if (hostbpp == 16)
+        do_sdl_resize(width, height, 16);
+    else
+        do_sdl_resize(width, height, 32);
+
+    surface->pf = sdl_to_qemu_pixelformat(real_screen->format);
+    surface->linesize = real_screen->pitch;
+    surface->data = real_screen->pixels;
+
+#ifdef WORDS_BIGENDIAN
+    surface->flags = QEMU_ALLOCATED_FLAG | QEMU_BIG_ENDIAN_FLAG;
+#else
+    surface->flags = QEMU_ALLOCATED_FLAG;
+#endif
+    allocator = 1;
+
+    return surface;
+}
+
+static void sdl_free_displaysurface(DisplaySurface *surface)
+{
+    allocator = 0;
+    if (surface == NULL)
+        return;
+    qemu_free(surface);
+}
+
+static DisplaySurface* sdl_resize_displaysurface(DisplaySurface *surface, int width, int height)
+{
+    sdl_free_displaysurface(surface);
+    return sdl_create_displaysurface(width, height);
 }
 
 /* generic keyboard conversion */
@@ -391,7 +480,7 @@ static void sdl_send_mouse_event(int dx, int dy, int dz, int x, int y, int state
 static void toggle_full_screen(DisplayState *ds)
 {
     gui_fullscreen = !gui_fullscreen;
-    sdl_resize(ds);
+    do_sdl_resize(real_screen->w, real_screen->h, real_screen->format->BitsPerPixel);
     if (gui_fullscreen) {
         gui_saved_grab = gui_grab;
         sdl_grab_start();
@@ -669,6 +758,8 @@ void sdl_display_init(DisplayState *ds, int full_screen, int no_frame)
 {
     int flags;
     uint8_t data = 0;
+    DisplayAllocator *da;
+    const SDL_VideoInfo *vi;
 
 #if defined(__APPLE__)
     /* always use generic keymaps */
@@ -689,6 +780,8 @@ void sdl_display_init(DisplayState *ds, int full_screen, int no_frame)
         fprintf(stderr, "Could not initialize SDL - exiting\n");
         exit(1);
     }
+    vi = SDL_GetVideoInfo();
+    hostbpp = vi->vfmt->BitsPerPixel;
 
     dcl = qemu_mallocz(sizeof(DisplayChangeListener));
     dcl->dpy_update = sdl_update;
@@ -700,6 +793,18 @@ void sdl_display_init(DisplayState *ds, int full_screen, int no_frame)
     ds->cursor_define = sdl_mouse_define;
     register_displaychangelistener(ds, dcl);
 
+    da = qemu_mallocz(sizeof(DisplayAllocator));
+    da->create_displaysurface = sdl_create_displaysurface;
+    da->resize_displaysurface = sdl_resize_displaysurface;
+    da->free_displaysurface = sdl_free_displaysurface;
+    if (register_displayallocator(ds, da) == da) {
+        DisplaySurface *surf;
+        surf = sdl_create_displaysurface(ds_get_width(ds), ds_get_height(ds));
+        defaultallocator_free_displaysurface(ds->surface);
+        ds->surface = surf;
+        dpy_resize(ds);
+    }
+
     sdl_update_caption();
     SDL_EnableKeyRepeat(250, 50);
     gui_grab = 0;