compositor: use floats in computing bounding box

In surface_compute_bbox(), call surface_to_global_float() instead of
weston_surface_to_global(). This avoids the recursion:

weston_surface_update_transform()
  weston_surface_update_transform_enable()
    surface_compute_bbox()
       weston_surface_to_global()
         weston_surface_update_transform()

which might be non-obvious when reading the code.

Computing the min and max coordinates in floats, we can have a tight
rounding margin by using floor() and ceil().

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>

diff --git a/src/compositor.c b/src/compositor.c
index f631e23..0c62fb0 100644 (file)
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -277,18 +277,20 @@ surface_compute_bbox(struct weston_surface *surface, int32_t sx, int32_t sy,
                     int32_t width, int32_t height,
                     pixman_region32_t *bbox)
 {
-       int min_x = INT_MAX, min_y = INT_MAX, max_x = INT_MIN, max_y = INT_MIN;
+       GLfloat min_x = HUGE_VALF,  min_y = HUGE_VALF;
+       GLfloat max_x = -HUGE_VALF, max_y = -HUGE_VALF;
        int32_t s[4][2] = {
                { sx,         sy },
                { sx,         sy + height },
                { sx + width, sy },
                { sx + width, sy + height }
        };
+       GLfloat int_x, int_y;
        int i;
 
        for (i = 0; i < 4; ++i) {
-               int32_t x, y;
-               weston_surface_to_global(surface, s[i][0], s[i][1], &x, &y);
+               GLfloat x, y;
+               surface_to_global_float(surface, s[i][0], s[i][1], &x, &y);
                if (x < min_x)
                        min_x = x;
                if (x > max_x)
@@ -299,11 +301,10 @@ surface_compute_bbox(struct weston_surface *surface, int32_t sx, int32_t sy,
                        max_y = y;
        }
 
-       /* weston_surface_to_global rounds with floor(), add the
-        * minimum required safety margin.
-        */
-       pixman_region32_init_rect(bbox, min_x, min_y,
-                                 max_x - min_x + 1, max_y - min_y + 1);
+       int_x = floorf(min_x);
+       int_y = floorf(min_y);
+       pixman_region32_init_rect(bbox, int_x, int_y,
+                                 ceilf(max_x) - int_x, ceilf(max_y) - int_y);
 }
 
 static void