sdl zooming

Hi all,
this patch implements zooming capabilities for the sdl interface.
A new sdl_zoom_blit function is added that is able to scale and blit a
portion of a surface into another.
This way we can enable SDL_RESIZABLE and have a real_screen surface with
a different size than the guest surface and let sdl_zoom_blit take care
of the problem.

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

1 files changed, 94 insertions, 0 deletions

diff --git a/sdl_zoom.c b/sdl_zoom.c
new file mode 100644
index 0000000000..56d3604fc3
--- /dev/null
+++ b/sdl_zoom.c
@@ -0,0 +1,94 @@
+/*
+ * SDL_zoom - surface scaling
+ * 
+ * Copyright (c) 2009 Citrix Systems, Inc.
+ *
+ * Derived from: SDL_rotozoom,  LGPL (c) A. Schiffler from the SDL_gfx library.
+ * Modifications by Stefano Stabellini.
+ *
+ * This work is licensed under the terms of the GNU GPL version 2.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "sdl_zoom.h"
+#include "osdep.h"
+#include <stdint.h>
+
+static int sdl_zoom_rgb16(SDL_Surface *src, SDL_Surface *dst, int smooth,
+                          SDL_Rect *dst_rect);
+static int sdl_zoom_rgb32(SDL_Surface *src, SDL_Surface *dst, int smooth,
+                          SDL_Rect *dst_rect);
+
+#define BPP 32
+#include  "sdl_zoom_template.h"
+#undef BPP
+#define BPP 16
+#include  "sdl_zoom_template.h"
+#undef BPP
+
+int sdl_zoom_blit(SDL_Surface *src_sfc, SDL_Surface *dst_sfc, int smooth,
+                  SDL_Rect *in_rect)
+{
+    SDL_Rect zoom, src_rect;
+    int extra;
+
+    /* Grow the size of the modified rectangle to avoid edge artefacts */
+    src_rect.x = (in_rect->x > 0) ? (in_rect->x - 1) : 0;
+    src_rect.y = (in_rect->y > 0) ? (in_rect->y - 1) : 0;
+
+    src_rect.w = in_rect->w + 1;
+    if (src_rect.x + src_rect.w > src_sfc->w)
+        src_rect.w = src_sfc->w - src_rect.x;
+
+    src_rect.h = in_rect->h + 1;
+    if (src_rect.y + src_rect.h > src_sfc->h)
+        src_rect.h = src_sfc->h - src_rect.y;
+
+    /* (x,y) : round down */
+    zoom.x = (int)(((float)(src_rect.x * dst_sfc->w)) / (float)(src_sfc->w));
+    zoom.y = (int)(((float)(src_rect.y * dst_sfc->h)) / (float)(src_sfc->h));
+
+    /* (w,h) : round up */
+    zoom.w = (int)( ((double)((src_rect.w * dst_sfc->w) + (src_sfc->w - 1))) /
+                     (double)(src_sfc->w));
+
+    zoom.h = (int)( ((double)((src_rect.h * dst_sfc->h) + (src_sfc->h - 1))) /
+                     (double)(src_sfc->h));
+
+    /* Account for any (x,y) rounding by adding one-source-pixel's worth
+     * of destination pixels and then edge checking.
+     */
+
+    extra = ((dst_sfc->w-1) / src_sfc->w) + 1;
+
+    if ((zoom.x + zoom.w) < (dst_sfc->w - extra))
+        zoom.w += extra;
+    else
+        zoom.w = dst_sfc->w - zoom.x;
+
+    extra = ((dst_sfc->h-1) / src_sfc->h) + 1;
+
+    if ((zoom.y + zoom.h) < (dst_sfc->h - extra))
+        zoom.h += extra;
+    else
+        zoom.h = dst_sfc->h - zoom.y;
+
+    /* The rectangle (zoom.x, zoom.y, zoom.w, zoom.h) is the area on the
+     * destination surface that needs to be updated.
+     */
+    if (src_sfc->format->BitsPerPixel == 32)
+        sdl_zoom_rgb32(src_sfc, dst_sfc, smooth, &zoom);
+    else if (src_sfc->format->BitsPerPixel == 16)
+        sdl_zoom_rgb16(src_sfc, dst_sfc, smooth, &zoom);
+    else {
+        fprintf(stderr, "pixel format not supported\n");
+        return -1;
+    }
+
+    /* Return the rectangle of the update to the caller */
+    *in_rect = zoom;
+
+    return 0;
+}
+