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monitor-transform: Fix transform() and drop relative_transform()

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The following implicit definition for `transform()` did not
correctly apply:
```
a * b = c
c * invert(b) = a
```

Crucially the following did not apply for `FLIPPED-90`
and `FLIPPED-270`:
```
a * invert(a) = identity
```

Fix this by applying the operations, first the flip, then the
rotation, in this order and add tests to ensure correct results
for the requirement above.

Also drop `relative_transform()` as it only had a single user and
can be replaced by `transform()`:
```
invert(a) * b = c
a * c = b
```

As this is not very intuitive, ensure in tests as well.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2459>
This commit is contained in:
Robert Mader 2022-07-01 16:03:20 +02:00 committed by Marge Bot
parent c6cf4bd9c3
commit 29cafe6f6c
4 changed files with 71 additions and 35 deletions
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69
src/backends/meta-monitor-transform.c
View file

@ -58,47 +58,56 @@ meta_monitor_transform_invert (MetaMonitorTransform transform)
return 0;
}
static MetaMonitorTransform
meta_monitor_transform_flip (MetaMonitorTransform transform)
{
switch (transform)
{
case META_MONITOR_TRANSFORM_NORMAL:
return META_MONITOR_TRANSFORM_FLIPPED;
case META_MONITOR_TRANSFORM_90:
return META_MONITOR_TRANSFORM_FLIPPED_270;
case META_MONITOR_TRANSFORM_180:
return META_MONITOR_TRANSFORM_FLIPPED_180;
case META_MONITOR_TRANSFORM_270:
return META_MONITOR_TRANSFORM_FLIPPED_90;
case META_MONITOR_TRANSFORM_FLIPPED:
return META_MONITOR_TRANSFORM_NORMAL;
case META_MONITOR_TRANSFORM_FLIPPED_90:
return META_MONITOR_TRANSFORM_270;
case META_MONITOR_TRANSFORM_FLIPPED_180:
return META_MONITOR_TRANSFORM_180;
case META_MONITOR_TRANSFORM_FLIPPED_270:
return META_MONITOR_TRANSFORM_90;
}
g_assert_not_reached ();
return 0;
}
MetaMonitorTransform
meta_monitor_transform_transform (MetaMonitorTransform transform,
MetaMonitorTransform other)
{
MetaMonitorTransform new_transform;
gboolean needs_flip = FALSE;
new_transform = (transform + other) % META_MONITOR_TRANSFORM_FLIPPED;
if (meta_monitor_transform_is_flipped (transform) !=
meta_monitor_transform_is_flipped (other))
if (meta_monitor_transform_is_flipped (other))
new_transform = meta_monitor_transform_flip (transform);
else
new_transform = transform;
if (meta_monitor_transform_is_flipped (new_transform))
needs_flip = TRUE;
new_transform += other;
new_transform %= META_MONITOR_TRANSFORM_FLIPPED;
if (needs_flip)
new_transform += META_MONITOR_TRANSFORM_FLIPPED;
return new_transform;
}
/**
* meta_monitor_transform_relative_transform:
* @transform: The transform to start from
* @other: The transform to go to
*
* Return value: a transform to get from @transform to @other
*/
MetaMonitorTransform
meta_monitor_transform_relative_transform (MetaMonitorTransform transform,
MetaMonitorTransform other)
{
MetaMonitorTransform relative_transform;
relative_transform = ((other % META_MONITOR_TRANSFORM_FLIPPED -
transform % META_MONITOR_TRANSFORM_FLIPPED) %
META_MONITOR_TRANSFORM_FLIPPED);
if (meta_monitor_transform_is_flipped (transform) !=
meta_monitor_transform_is_flipped (other))
{
relative_transform = (meta_monitor_transform_invert (relative_transform) +
META_MONITOR_TRANSFORM_FLIPPED);
}
return relative_transform;
}
void
meta_monitor_transform_transform_point (MetaMonitorTransform transform,
int area_width,

3
src/backends/meta-monitor-transform.h
View file

@ -64,9 +64,6 @@ META_EXPORT_TEST
MetaMonitorTransform meta_monitor_transform_transform (MetaMonitorTransform transform,
MetaMonitorTransform other);
MetaMonitorTransform meta_monitor_transform_relative_transform (MetaMonitorTransform transform,
MetaMonitorTransform other);
void meta_monitor_transform_transform_point (MetaMonitorTransform transform,
int area_width,
int area_height,

5
src/backends/native/meta-cursor-renderer-native.c
View file

@ -816,8 +816,9 @@ get_common_crtc_sprite_transform_for_logical_monitors (MetaCursorRenderer *ren
{
MetaMonitor *monitor = l_mon->data;
tmp_transform = meta_monitor_transform_relative_transform (
meta_cursor_sprite_get_texture_transform (cursor_sprite),
tmp_transform = meta_monitor_transform_transform (
meta_monitor_transform_invert (
meta_cursor_sprite_get_texture_transform (cursor_sprite)),
meta_monitor_logical_to_crtc_transform (monitor, logical_transform));
if (has_visible_crtc_sprite && transform != tmp_transform)

29
src/tests/monitor-transform-tests.c
View file

@ -83,6 +83,7 @@ test_transform (void)
},
};
int i;
MetaMonitorTransform transform;
for (i = 0; i < G_N_ELEMENTS (tests); i++)
{
@ -92,6 +93,34 @@ test_transform (void)
tests[i].other);
g_assert_cmpint (result, ==, tests[i].expect);
}
for (transform = 0; transform <= META_MONITOR_TRANSFORM_FLIPPED_270; transform++)
{
MetaMonitorTransform other;
MetaMonitorTransform result1;
result1 =
meta_monitor_transform_transform (transform,
meta_monitor_transform_invert (transform));
g_assert_cmpint (result1, ==, META_MONITOR_TRANSFORM_NORMAL);
for (other = 0; other <= META_MONITOR_TRANSFORM_FLIPPED_270; other++)
{
MetaMonitorTransform result2;
result1 = meta_monitor_transform_transform (transform, other);
result2 =
meta_monitor_transform_transform (result1,
meta_monitor_transform_invert (other));
g_assert_cmpint (result2, ==, transform);
result1 =
meta_monitor_transform_transform (meta_monitor_transform_invert (transform),
other);
result2 = meta_monitor_transform_transform (transform, result1);
g_assert_cmpint (result2, ==, other);
}
}
}
void