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material: Don't prune ancestry if it owns some layers

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Each time a material property changes we look to see if any of its
ancestry has become redundant and if so we prune that redundant
ancestry.

There was a problem with the logic that handles this though because we
weren't considering that a material which is a layer state authority may
still defer to ancestors to define the state of individual layers.

For example a material that derives from a parent with 5 layers can
become a STATE_LAYERS authority by simply changing it's ->n_layers count
to 4 and in that case it can still defer to its ancestors to define the
state of those 4 layers.

This patch checks first if a material is a layer state authority and if
so only tries to prune its ancestry if it also *owns* all the individual
layers it depends on. (I.e. if g_list_length
(material->layer_differences) != material->n_layers then it's not safe
to try pruning its ancestry!)

http://bugzilla-attachments.gnome.org/attachment.cgi?id=170907
This commit is contained in:
Robert Bragg 2010-09-23 22:18:42 +01:00
parent 256f83973c
commit 14dbe81deb
1 changed files with 21 additions and 0 deletions
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21
cogl/cogl-material.c
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@ -3537,6 +3537,27 @@ _cogl_material_prune_redundant_ancestry (CoglMaterial *material)
{
CoglMaterial *new_parent = _cogl_material_get_parent (material);
/* Before considering pruning redundant ancestry we check if this
* material is an authority for layer state and if so only consider
* reparenting if it *owns* all the layers it depends on. NB: A
* material can be be a STATE_LAYERS authority but it may still
* defer to its ancestors to define the state for some of its
* layers.
*
* For example a material that derives from a parent with 5 layers
* can become a STATE_LAYERS authority by simply changing it's
* ->n_layers count to 4 and in that case it can still defer to its
* ancestors to define the state of those 4 layers.
*
* If a material depends on any ancestors for layer state then we
* immediatly bail out.
*/
if (material->differences & COGL_MATERIAL_STATE_LAYERS)
{
if (material->n_layers != g_list_length (material->layer_differences))
return;
}
/* walk up past ancestors that are now redundant and potentially
* reparent the material. */
while (_cogl_material_get_parent (new_parent) &&