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region-utils: Add API to scale an integer region with a double

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The added API lets the caller decide whether to shrink or grow the
rectangles if there are rounding issues.

Related: https://gitlab.gnome.org/GNOME/mutter/issues/300
This commit is contained in:
Jonas Ådahl 2018-09-14 18:51:10 +02:00
parent 0ae7ef4bc4
commit 9c77e52ad3
2 changed files with 55 additions and 0 deletions
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45
src/compositor/region-utils.c
View File

@ -172,6 +172,51 @@ meta_region_iterator_next (MetaRegionIterator *iter)
}
}
cairo_region_t *
meta_region_scale_double (cairo_region_t *region,
double scale,
MetaRoundingStrategy rounding_strategy)
{
int n_rects, i;
cairo_rectangle_int_t *rects;
cairo_region_t *scaled_region;
g_return_val_if_fail (scale > 0.0, NULL);
if (scale == 1.0)
return cairo_region_copy (region);
n_rects = cairo_region_num_rectangles (region);
rects = g_malloc (sizeof(cairo_rectangle_int_t) * n_rects);
for (i = 0; i < n_rects; i++)
{
cairo_region_get_rectangle (region, i, &rects[i]);
switch (rounding_strategy)
{
case META_ROUNDING_STRATEGY_SHRINK:
rects[i].x = (int) ceil (rects[i].x * scale);
rects[i].y = (int) ceil (rects[i].y * scale);
rects[i].width = (int) floor (rects[i].width * scale);
rects[i].height = (int) floor (rects[i].height * scale);
break;
case META_ROUNDING_STRATEGY_GROW:
rects[i].x = (int) floor (rects[i].x * scale);
rects[i].y = (int) floor (rects[i].y * scale);
rects[i].width = (int) ceil (rects[i].width * scale);
rects[i].height = (int) ceil (rects[i].height * scale);
break;
}
}
scaled_region = cairo_region_create_rectangles (rects, n_rects);
g_free (rects);
return scaled_region;
}
cairo_region_t *
meta_region_scale (cairo_region_t *region, int scale)
{

10
src/compositor/region-utils.h
View File

@ -26,6 +26,12 @@
#include <cairo.h>
#include <glib.h>
typedef enum _MetaRoundingStrategy
{
META_ROUNDING_STRATEGY_SHRINK,
META_ROUNDING_STRATEGY_GROW,
} MetaRoundingStrategy;
/**
* MetaRegionIterator:
* @region: region being iterated
@ -95,6 +101,10 @@ void meta_region_iterator_next (MetaRegionIterator *iter);
cairo_region_t * meta_region_scale (cairo_region_t *region,
int scale);
cairo_region_t * meta_region_scale_double (cairo_region_t *region,
double scale,
MetaRoundingStrategy rounding_strategy);
cairo_region_t * meta_make_border_region (cairo_region_t *region,
int x_amount,
int y_amount,