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, 36 insertions, 4 deletions

diff --git a/console.h b/console.h
index 6b72fa5e5a..93e3109d72 100644
--- a/console.h
+++ b/console.h
@@ -113,11 +113,18 @@ struct DisplayChangeListener {
     struct DisplayChangeListener *next;
 };
 
+struct DisplayAllocator {
+    DisplaySurface* (*create_displaysurface)(int width, int height);
+    DisplaySurface* (*resize_displaysurface)(DisplaySurface *surface, int width, int height);
+    void (*free_displaysurface)(DisplaySurface *surface);
+};
+
 struct DisplayState {
     struct DisplaySurface *surface;
     void *opaque;
     struct QEMUTimer *gui_timer;
 
+    struct DisplayAllocator* allocator;
     struct DisplayChangeListener* listeners;
 
     void (*mouse_set)(int x, int y, int on);
@@ -129,15 +136,40 @@ struct DisplayState {
 
 void register_displaystate(DisplayState *ds);
 DisplayState *get_displaystate(void);
-DisplaySurface* qemu_create_displaysurface(int width, int height, int bpp, int linesize);
-DisplaySurface* qemu_resize_displaysurface(DisplaySurface *surface,
-                                           int width, int height, int bpp, int linesize);
 DisplaySurface* qemu_create_displaysurface_from(int width, int height, int bpp,
                                                 int linesize, uint8_t *data);
-void qemu_free_displaysurface(DisplaySurface *surface);
 PixelFormat qemu_different_endianness_pixelformat(int bpp);
 PixelFormat qemu_default_pixelformat(int bpp);
 
+extern struct DisplayAllocator default_allocator;
+DisplayAllocator *register_displayallocator(DisplayState *ds, DisplayAllocator *da);
+DisplaySurface* defaultallocator_create_displaysurface(int width, int height);
+DisplaySurface* defaultallocator_resize_displaysurface(DisplaySurface *surface, int width, int height);
+void defaultallocator_free_displaysurface(DisplaySurface *surface);
+
+static inline DisplaySurface* qemu_create_displaysurface(DisplayState *ds, int width, int height)
+{
+    return ds->allocator->create_displaysurface(width, height);    
+}
+
+static inline DisplaySurface* qemu_resize_displaysurface(DisplayState *ds, int width, int height)
+{
+    return ds->allocator->resize_displaysurface(ds->surface, width, height);
+}
+
+static inline void qemu_free_displaysurface(DisplayState *ds)
+{
+    ds->allocator->free_displaysurface(ds->surface);
+}
+
+static inline int is_surface_bgr(DisplaySurface *surface)
+{
+    if (surface->pf.bits_per_pixel == 32 && surface->pf.rshift == 0)
+        return 1;
+    else
+        return 0;
+}
+
 static inline int is_buffer_shared(DisplaySurface *surface)
 {
     return (!(surface->flags & QEMU_ALLOCATED_FLAG));