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>

sdl_zoom_template.h

@@ -0,0 +1,225 @@
+/*
+ * SDL_zoom_template - 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.
+ *
+ */
+
+#if BPP == 16
+#define SDL_TYPE Uint16
+#elif BPP == 32
+#define SDL_TYPE Uint32
+#else
+#error unsupport depth
+#endif
+
+/*  
+ *  Simple helper functions to make the code looks nicer
+ *
+ *  Assume spf = source SDL_PixelFormat
+ *         dpf = dest SDL_PixelFormat
+ *
+ */
+#define getRed(color)   (((color) & spf->Rmask) >> spf->Rshift)
+#define getGreen(color) (((color) & spf->Gmask) >> spf->Gshift)
+#define getBlue(color)  (((color) & spf->Bmask) >> spf->Bshift)
+#define getAlpha(color) (((color) & spf->Amask) >> spf->Ashift)
+
+#define setRed(r, pcolor) do { \
+    *pcolor = ((*pcolor) & (~(dpf->Rmask))) + \
+              (((r) & (dpf->Rmask >> dpf->Rshift)) << dpf->Rshift); \
+} while (0);
+
+#define setGreen(g, pcolor) do { \
+    *pcolor = ((*pcolor) & (~(dpf->Gmask))) + \
+              (((g) & (dpf->Gmask >> dpf->Gshift)) << dpf->Gshift); \
+} while (0);
+
+#define setBlue(b, pcolor) do { \
+    *pcolor = ((*pcolor) & (~(dpf->Bmask))) + \
+              (((b) & (dpf->Bmask >> dpf->Bshift)) << dpf->Bshift); \
+} while (0);
+
+#define setAlpha(a, pcolor) do { \
+    *pcolor = ((*pcolor) & (~(dpf->Amask))) + \
+              (((a) & (dpf->Amask >> dpf->Ashift)) << dpf->Ashift); \
+} while (0);
+
+static int glue(sdl_zoom_rgb, BPP)(SDL_Surface *src, SDL_Surface *dst, int smooth,
+                                   SDL_Rect *dst_rect)
+{
+    int x, y, sx, sy, *sax, *say, *csax, *csay, csx, csy, ex, ey, t1, t2, sstep, sstep_jump;
+    SDL_TYPE *c00, *c01, *c10, *c11, *sp, *csp, *dp;
+    int d_gap;
+    SDL_PixelFormat *spf = src->format;
+    SDL_PixelFormat *dpf = dst->format;
+
+    if (smooth) { 
+        /* For interpolation: assume source dimension is one pixel.
+         * Smaller here to avoid overflow on right and bottom edge.
+         */
+        sx = (int) (65536.0 * (float) (src->w - 1) / (float) dst->w);
+        sy = (int) (65536.0 * (float) (src->h - 1) / (float) dst->h);
+    } else {
+        sx = (int) (65536.0 * (float) src->w / (float) dst->w);
+        sy = (int) (65536.0 * (float) src->h / (float) dst->h);
+    }
+
+    if ((sax = (int *) malloc((dst->w + 1) * sizeof(Uint32))) == NULL) {
+        return (-1);
+    }
+    if ((say = (int *) malloc((dst->h + 1) * sizeof(Uint32))) == NULL) {
+        free(sax);
+        return (-1);
+    }
+
+    sp = csp = (SDL_TYPE *) src->pixels;
+    dp = (SDL_TYPE *) (dst->pixels + dst_rect->y * dst->pitch +
+                       dst_rect->x * dst->format->BytesPerPixel);
+
+    csx = 0;
+    csax = sax;
+    for (x = 0; x <= dst->w; x++) {
+        *csax = csx;
+        csax++;
+        csx &= 0xffff;
+        csx += sx;
+    }
+    csy = 0;
+    csay = say;
+    for (y = 0; y <= dst->h; y++) {
+        *csay = csy;
+        csay++;
+        csy &= 0xffff;
+        csy += sy;
+    }
+
+    d_gap = dst->pitch - dst_rect->w * dst->format->BytesPerPixel;
+
+    if (smooth) {
+        csay = say;
+        for (y = 0; y < dst_rect->y; y++) {
+            csay++;
+            sstep = (*csay >> 16) * src->pitch;
+            csp = (SDL_TYPE *) ((Uint8 *) csp + sstep);
+        }
+
+        /* Calculate sstep_jump */
+        csax = sax; 
+        sstep_jump = 0;
+        for (x = 0; x < dst_rect->x; x++) {
+            csax++; 
+            sstep = (*csax >> 16);
+            sstep_jump += sstep;
+        }
+
+        for (y = 0; y < dst_rect->h ; y++) {
+            /* Setup colour source pointers */
+            c00 = csp + sstep_jump;
+            c01 = c00 + 1;
+            c10 = (SDL_TYPE *) ((Uint8 *) csp + src->pitch) + sstep_jump;
+            c11 = c10 + 1;
+            csax = sax + dst_rect->x; 
+
+            for (x = 0; x < dst_rect->w; x++) {
+
+                /* Interpolate colours */
+                ex = (*csax & 0xffff);
+                ey = (*csay & 0xffff);
+                t1 = ((((getRed(*c01) - getRed(*c00)) * ex) >> 16) +
+                     getRed(*c00)) & (dpf->Rmask >> dpf->Rshift);
+                t2 = ((((getRed(*c11) - getRed(*c10)) * ex) >> 16) +
+                     getRed(*c10)) & (dpf->Rmask >> dpf->Rshift);
+                setRed((((t2 - t1) * ey) >> 16) + t1, dp);
+                t1 = ((((getGreen(*c01) - getGreen(*c00)) * ex) >> 16) +
+                     getGreen(*c00)) & (dpf->Gmask >> dpf->Gshift);
+                t2 = ((((getGreen(*c11) - getGreen(*c10)) * ex) >> 16) +
+                     getGreen(*c10)) & (dpf->Gmask >> dpf->Gshift);
+                setGreen((((t2 - t1) * ey) >> 16) + t1, dp);
+                t1 = ((((getBlue(*c01) - getBlue(*c00)) * ex) >> 16) +
+                     getBlue(*c00)) & (dpf->Bmask >> dpf->Bshift);
+                t2 = ((((getBlue(*c11) - getBlue(*c10)) * ex) >> 16) +
+                     getBlue(*c10)) & (dpf->Bmask >> dpf->Bshift);
+                setBlue((((t2 - t1) * ey) >> 16) + t1, dp);
+                t1 = ((((getAlpha(*c01) - getAlpha(*c00)) * ex) >> 16) +
+                     getAlpha(*c00)) & (dpf->Amask >> dpf->Ashift);
+                t2 = ((((getAlpha(*c11) - getAlpha(*c10)) * ex) >> 16) +
+                     getAlpha(*c10)) & (dpf->Amask >> dpf->Ashift);
+                setAlpha((((t2 - t1) * ey) >> 16) + t1, dp); 
+
+                /* Advance source pointers */
+                csax++; 
+                sstep = (*csax >> 16);
+                c00 += sstep;
+                c01 += sstep;
+                c10 += sstep;
+                c11 += sstep;
+                /* Advance destination pointer */
+                dp++;
+            }
+            /* Advance source pointer */
+            csay++;
+            csp = (SDL_TYPE *) ((Uint8 *) csp + (*csay >> 16) * src->pitch);
+            /* Advance destination pointers */
+            dp = (SDL_TYPE *) ((Uint8 *) dp + d_gap);
+        }
+
+
+    } else {
+        csay = say;
+
+        for (y = 0; y < dst_rect->y; y++) {
+            csay++;
+            sstep = (*csay >> 16) * src->pitch;
+            csp = (SDL_TYPE *) ((Uint8 *) csp + sstep);
+        }
+
+        /* Calculate sstep_jump */
+        csax = sax; 
+        sstep_jump = 0;
+        for (x = 0; x < dst_rect->x; x++) {
+            csax++; 
+            sstep = (*csax >> 16);
+            sstep_jump += sstep;
+        }
+
+        for (y = 0 ; y < dst_rect->h ; y++) {
+            sp = csp + sstep_jump;
+            csax = sax + dst_rect->x;
+
+            for (x = 0; x < dst_rect->w; x++) {
+
+                /* Draw */
+                *dp = *sp;
+
+                /* Advance source pointers */
+                csax++;
+                sstep = (*csax >> 16);
+                sp += sstep;
+
+                /* Advance destination pointer */
+                dp++;
+            }
+            /* Advance source pointers */
+            csay++;
+            sstep = (*csay >> 16) * src->pitch;
+            csp = (SDL_TYPE *) ((Uint8 *) csp + sstep);
+
+            /* Advance destination pointer */
+            dp = (SDL_TYPE *) ((Uint8 *) dp + d_gap);
+        }
+    }
+
+    free(sax);
+    free(say);
+    return (0);
+}
+
+#undef SDL_TYPE
+