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842bc4421c
actor_is_untransformed is a function meta-window-group uses to determine if an actor is relatively pixel aligned and not contorted. It then returns the coordinates of the actor. In a subsequent commit will need the function in a different file, so this commit separates it out. https://bugzilla.gnome.org/show_bug.cgi?id=682427
121 lines
4.1 KiB
C
121 lines
4.1 KiB
C
/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
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/*
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* Utilities for use with Cogl
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*
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* Copyright 2010 Red Hat, Inc.
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* Copyright 2010 Intel Corporation
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
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* 02111-1307, USA.
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*/
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#include "clutter-utils.h"
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#include <math.h>
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/* This file uses pixel-aligned region computation to determine what
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* can be clipped out. This only really works if everything is aligned
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* to the pixel grid - not scaled or rotated and at integer offsets.
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*
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* (This could be relaxed - if we turned off filtering for unscaled
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* windows then windows would be, by definition aligned to the pixel
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* grid. And for rectangular windows without a shape, the outline that
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* we draw for an unrotated window is always a rectangle because we
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* don't use antialasing for the window boundary - with or without
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* filtering, with or without a scale. But figuring out exactly
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* what pixels will be drawn by the graphics system in these cases
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* gets tricky, so we just go for the easiest part - no scale,
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* and at integer offsets.)
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*
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* The way we check for pixel-aligned is by looking at the
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* transformation into screen space of the allocation box of an actor
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* and and checking if the corners are "close enough" to integral
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* pixel values.
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*/
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/* The definition of "close enough" to integral pixel values is
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* equality when we convert to 24.8 fixed-point.
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*/
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static inline int
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round_to_fixed (float x)
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{
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return roundf (x * 256);
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}
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/* This helper function checks if (according to our fixed point precision)
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* the vertices @verts form a box of width @widthf and height @heightf
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* located at integral coordinates. These coordinates are returned
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* in @x_origin and @y_origin.
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*/
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gboolean
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meta_actor_vertices_are_untransformed (ClutterVertex *verts,
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float widthf,
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float heightf,
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int *x_origin,
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int *y_origin)
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{
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int width, height;
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int v0x, v0y, v1x, v1y, v2x, v2y, v3x, v3y;
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int x, y;
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width = round_to_fixed (widthf); height = round_to_fixed (heightf);
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v0x = round_to_fixed (verts[0].x); v0y = round_to_fixed (verts[0].y);
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v1x = round_to_fixed (verts[1].x); v1y = round_to_fixed (verts[1].y);
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v2x = round_to_fixed (verts[2].x); v2y = round_to_fixed (verts[2].y);
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v3x = round_to_fixed (verts[3].x); v3y = round_to_fixed (verts[3].y);
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/* Using shifting for converting fixed => int, gets things right for
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* negative values. / 256. wouldn't do the same
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*/
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x = v0x >> 8;
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y = v0y >> 8;
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/* At integral coordinates? */
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if (x * 256 != v0x || y * 256 != v0y)
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return FALSE;
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/* Not scaled? */
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if (v1x - v0x != width || v2y - v0y != height)
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return FALSE;
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/* Not rotated/skewed? */
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if (v0x != v2x || v0y != v1y ||
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v3x != v1x || v3y != v2y)
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return FALSE;
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*x_origin = x;
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*y_origin = y;
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return TRUE;
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}
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/* Check if an actor is "untransformed" - which actually means transformed by
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* at most a integer-translation. The integer translation, if any, is returned.
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*/
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gboolean
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meta_actor_is_untransformed (ClutterActor *actor,
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int *x_origin,
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int *y_origin)
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{
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gfloat widthf, heightf;
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ClutterVertex verts[4];
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clutter_actor_get_size (actor, &widthf, &heightf);
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clutter_actor_get_abs_allocation_vertices (actor, verts);
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return meta_actor_vertices_are_untransformed (verts, widthf, heightf, x_origin, y_origin);
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}
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