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We have found several times now when writing code using Cogl that it would really help if Cogl's matrix stack api was public as a utility api. In Rig for example we want to avoid redundant arithmetic when deriving the matrices of entities used to render and we aren't able to simply use the framebuffer's matrix stack to achieve this. Also when implementing cairo-cogl we found that it would be really useful if we could have a matrix stack utility api. (cherry picked from commit d17a01fd935d88fab96fe6cc0b906c84026c0067)
620 lines
22 KiB
C
620 lines
22 KiB
C
/*
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* Cogl
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*
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* An object oriented GL/GLES Abstraction/Utility Layer
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*
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* Copyright (C) 2009,2010,2012 Intel Corporation.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but 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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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library. If not, see
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* <http://www.gnu.org/licenses/>.
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*
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*
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*
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* Authors:
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* Havoc Pennington <hp@pobox.com> for litl
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* Robert Bragg <robert@linux.intel.com>
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*/
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#ifndef _COGL_MATRIX_STACK_H_
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#define _COGL_MATRIX_STACK_H_
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#if !defined(__COGL_H_INSIDE__) && !defined(COGL_COMPILATION)
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#error "Only <cogl/cogl.h> can be included directly."
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#endif
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#include "cogl-matrix.h"
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#include "cogl-context.h"
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/**
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* SECTION:cogl-matrix-stack
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* @short_description: Functions for efficiently tracking many
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* related transformations
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*
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* Matrices can be used (for example) to describe the model-view
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* transforms of objects, texture transforms, and projective
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* transforms.
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*
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* The #CoglMatrix api provides a good way to manipulate individual
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* matrices representing a single transformation but if you need to
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* track many-many such transformations for many objects that are
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* organized in a scenegraph for example then using a separate
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* #CoglMatrix for each object may not be the most efficient way.
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*
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* A #CoglMatrixStack enables applications to track lots of
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* transformations that are related to each other in some kind of
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* hierarchy. In a scenegraph for example if you want to know how to
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* transform a particular node then you usually have to walk up
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* through the ancestors and accumulate their transforms before
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* finally applying the transform of the node itself. In this model
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* things are grouped together spatially according to their ancestry
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* and all siblings with the same parent share the same initial
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* transformation. The #CoglMatrixStack API is suited to tracking lots
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* of transformations that fit this kind of model.
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*
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* Compared to using the #CoglMatrix api directly to track many
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* related transforms, these can be some advantages to using a
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* #CoglMatrixStack:
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* <ul>
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* <li>Faster equality comparisons of transformations</li>
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* <li>Efficient comparisons of the differences between arbitrary
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* transformations</li>
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* <li>Avoid redundant arithmetic related to common transforms</li>
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* <li>Can be more space efficient (not always though)</li>
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* </ul>
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*
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* For reference (to give an idea of when a #CoglMatrixStack can
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* provide a space saving) a #CoglMatrix can be expected to take 72
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* bytes whereas a single #CoglMatrixEntry in a #CoglMatrixStack is
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* currently around 32 bytes on a 32bit CPU or 36 bytes on a 64bit
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* CPU. An entry is needed for each individual operation applied to
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* the stack (such as rotate, scale, translate) so if most of your
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* leaf node transformations only need one or two simple operations
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* relative to their parent then a matrix stack will likely take less
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* space than having a #CoglMatrix for each node.
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*
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* Even without any space saving though the ability to perform fast
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* comparisons and avoid redundant arithmetic (especially sine and
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* cosine calculations for rotations) can make using a matrix stack
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* worthwhile.
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*/
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/**
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* CoglMatrixStack:
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*
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* Tracks your current position within a hierarchy and lets you build
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* up a graph of transformations as you traverse through a hierarchy
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* such as a scenegraph.
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*
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* A #CoglMatrixStack always maintains a reference to a single
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* transformation at any point in time, representing the
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* transformation at the current position in the hierarchy. You can
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* get a reference to the current transformation by calling
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* cogl_matrix_stack_get_entry().
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*
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* When a #CoglMatrixStack is first created with
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* cogl_matrix_stack_new() then it is conceptually positioned at the
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* root of your hierarchy and the current transformation simply
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* represents an identity transformation.
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*
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* As you traverse your object hierarchy (your scenegraph) then you
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* should call cogl_matrix_stack_push() whenever you move down one
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* level and call cogl_matrix_stack_pop() whenever you move back up
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* one level towards the root.
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*
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* At any time you can apply a set of operations, such as "rotate",
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* "scale", "translate" on top of the current transformation of a
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* #CoglMatrixStack using functions such as
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* cogl_matrix_stack_rotate(), cogl_matrix_stack_scale() and
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* cogl_matrix_stack_translate(). These operations will derive a new
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* current transformation and will never affect a transformation
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* that you have referenced using cogl_matrix_stack_get_entry().
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*
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* Internally applying operations to a #CoglMatrixStack builds up a
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* graph of #CoglMatrixEntry structures which each represent a single
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* immutable transform.
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*/
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typedef struct _CoglMatrixStack CoglMatrixStack;
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/**
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* CoglMatrixEntry:
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*
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* Represents a single immutable transformation that was retrieved
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* from a #CoglMatrixStack using cogl_matrix_stack_get_entry().
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*
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* Internally a #CoglMatrixEntry represents a single matrix
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* operation (such as "rotate", "scale", "translate") which is applied
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* to the transform of a single parent entry.
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*
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* Using the #CoglMatrixStack api effectively builds up a graph of
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* these immutable #CoglMatrixEntry structures whereby operations
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* that can be shared between multiple transformations will result
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* in shared #CoglMatrixEntry nodes in the graph.
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*
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* When a #CoglMatrixStack is first created it references one
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* #CoglMatrixEntry that represents a single "load identity"
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* operation. This serves as the root entry and all operations
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* that are then applied to the stack will extend the graph
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* starting from this root "load identity" entry.
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*
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* Given the typical usage model for a #CoglMatrixStack and the way
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* the entries are built up while traversing a scenegraph then in most
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* cases where an application is interested in comparing two
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* transformations for equality then it is enough to simply compare
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* two #CoglMatrixEntry pointers directly. Technically this can lead
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* to false negatives that could be identified with a deeper
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* comparison but often these false negatives are unlikely and
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* don't matter anyway so this enables extremely cheap comparisons.
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*
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* <note>#CoglMatrixEntry<!-- -->s are reference counted using
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* cogl_matrix_entry_ref() and cogl_matrix_entry_unref() not with
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* cogl_object_ref() and cogl_object_unref().</note>
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*/
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typedef struct _CoglMatrixEntry CoglMatrixEntry;
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/**
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* cogl_matrix_stack_new:
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* @context: A #CoglContext
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*
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* Allocates a new #CoglMatrixStack that can be used to build up
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* transformations relating to objects in a scenegraph like hierarchy.
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* (See the description of #CoglMatrixStack and #CoglMatrixEntry for
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* more details of what a matrix stack is best suited for)
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*
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* When a #CoglMatrixStack is first allocated it is conceptually
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* positioned at the root of your scenegraph hierarchy. As you
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* traverse your scenegraph then you should call
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* cogl_matrix_stack_push() whenever you move down a level and
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* cogl_matrix_stack_pop() whenever you move back up a level towards
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* the root.
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*
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* Once you have allocated a #CoglMatrixStack you can get a reference
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* to the current transformation for the current position in the
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* hierarchy by calling cogl_matrix_stack_get_entry().
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*
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* Once you have allocated a #CoglMatrixStack you can apply operations
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* such as rotate, scale and translate to modify the current transform
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* for the current position in the hierarchy by calling
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* cogl_matrix_stack_rotate(), cogl_matrix_stack_scale() and
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* cogl_matrix_stack_translate().
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*
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* Return value: A newly allocated #CoglMatrixStack
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*/
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CoglMatrixStack *
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cogl_matrix_stack_new (CoglContext *ctx);
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/**
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* cogl_matrix_stack_push:
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* @stack: A #CoglMatrixStack
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*
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* Saves the current transform and starts a new transform that derives
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* from the current transform.
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*
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* This is usually called while traversing a scenegraph whenever you
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* traverse one level deeper. cogl_matrix_stack_pop() can then be
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* called when going back up one layer to restore the previous
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* transform of an ancestor.
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*/
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void
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cogl_matrix_stack_push (CoglMatrixStack *stack);
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/**
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* cogl_matrix_stack_pop:
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* @stack: A #CoglMatrixStack
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*
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* Restores the previous transform that was last saved by calling
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* cogl_matrix_stack_push().
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*
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* This is usually called while traversing a scenegraph whenever you
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* return up one level in the graph towards the root node.
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*/
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void
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cogl_matrix_stack_pop (CoglMatrixStack *stack);
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/**
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* cogl_matrix_stack_load_identity:
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* @stack: A #CoglMatrixStack
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*
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* Resets the current matrix to the identity matrix.
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*/
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void
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cogl_matrix_stack_load_identity (CoglMatrixStack *stack);
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/**
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* cogl_matrix_stack_scale:
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* @stack: A #CoglMatrixStack
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* @x: Amount to scale along the x-axis
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* @y: Amount to scale along the y-axis
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* @z: Amount to scale along the z-axis
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*
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* Multiplies the current matrix by one that scales the x, y and z
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* axes by the given values.
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*/
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void
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cogl_matrix_stack_scale (CoglMatrixStack *stack,
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float x,
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float y,
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float z);
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/**
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* cogl_matrix_stack_translate:
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* @stack: A #CoglMatrixStack
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* @x: Distance to translate along the x-axis
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* @y: Distance to translate along the y-axis
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* @z: Distance to translate along the z-axis
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*
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* Multiplies the current matrix by one that translates along all
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* three axes according to the given values.
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*/
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void
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cogl_matrix_stack_translate (CoglMatrixStack *stack,
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float x,
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float y,
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float z);
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/**
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* cogl_matrix_stack_rotate:
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* @stack: A #CoglMatrixStack
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* @angle: Angle in degrees to rotate.
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* @x: X-component of vertex to rotate around.
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* @y: Y-component of vertex to rotate around.
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* @z: Z-component of vertex to rotate around.
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*
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* Multiplies the current matrix by one that rotates the around the
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* axis-vector specified by @x, @y and @z. The rotation follows the
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* right-hand thumb rule so for example rotating by 10 degrees about
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* the axis-vector (0, 0, 1) causes a small counter-clockwise
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* rotation.
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*/
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void
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cogl_matrix_stack_rotate (CoglMatrixStack *stack,
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float angle,
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float x,
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float y,
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float z);
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/**
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* cogl_matrix_stack_rotate_quaternion:
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* @stack: A #CoglMatrixStack
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* @quaternion: A #CoglQuaternion
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*
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* Multiplies the current matrix by one that rotates according to the
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* rotation described by @quaternion.
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*/
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void
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cogl_matrix_stack_rotate_quaternion (CoglMatrixStack *stack,
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const CoglQuaternion *quaternion);
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/**
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* cogl_matrix_stack_rotate_euler:
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* @stack: A #CoglMatrixStack
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* @euler: A #CoglEuler
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*
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* Multiplies the current matrix by one that rotates according to the
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* rotation described by @euler.
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*/
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void
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cogl_matrix_stack_rotate_euler (CoglMatrixStack *stack,
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const CoglEuler *euler);
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/**
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* cogl_matrix_stack_multiply:
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* @stack: A #CoglMatrixStack
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* @matrix: the matrix to multiply with the current model-view
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*
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* Multiplies the current matrix by the given matrix.
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*/
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void
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cogl_matrix_stack_multiply (CoglMatrixStack *stack,
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const CoglMatrix *matrix);
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/**
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* cogl_matrix_stack_frustum:
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* @stack: A #CoglMatrixStack
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* @left: X position of the left clipping plane where it
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* intersects the near clipping plane
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* @right: X position of the right clipping plane where it
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* intersects the near clipping plane
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* @bottom: Y position of the bottom clipping plane where it
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* intersects the near clipping plane
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* @top: Y position of the top clipping plane where it intersects
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* the near clipping plane
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* @z_near: The distance to the near clipping plane (Must be positive)
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* @z_far: The distance to the far clipping plane (Must be positive)
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*
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* Replaces the current matrix with a perspective matrix for a given
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* viewing frustum defined by 4 side clip planes that all cross
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* through the origin and 2 near and far clip planes.
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*/
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void
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cogl_matrix_stack_frustum (CoglMatrixStack *stack,
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float left,
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float right,
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float bottom,
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float top,
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float z_near,
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float z_far);
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/**
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* cogl_matrix_stack_perspective:
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* @stack: A #CoglMatrixStack
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* @fov_y: Vertical field of view angle in degrees.
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* @aspect: The (width over height) aspect ratio for display
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* @z_near: The distance to the near clipping plane (Must be positive,
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* and must not be 0)
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* @z_far: The distance to the far clipping plane (Must be positive)
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*
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* Replaces the current matrix with a perspective matrix based on the
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* provided values.
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*
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* <note>You should be careful not to have too great a @z_far / @z_near
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* ratio since that will reduce the effectiveness of depth testing
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* since there wont be enough precision to identify the depth of
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* objects near to each other.</note>
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*/
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void
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cogl_matrix_stack_perspective (CoglMatrixStack *stack,
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float fov_y,
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float aspect,
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float z_near,
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float z_far);
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/**
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* cogl_matrix_stack_orthographic:
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* @stack: A #CoglMatrixStack
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* @x_1: The x coordinate for the first vertical clipping plane
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* @y_1: The y coordinate for the first horizontal clipping plane
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* @x_2: The x coordinate for the second vertical clipping plane
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* @y_2: The y coordinate for the second horizontal clipping plane
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* @near: The <emphasis>distance</emphasis> to the near clipping
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* plane (will be <emphasis>negative</emphasis> if the plane is
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* behind the viewer)
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* @far: The <emphasis>distance</emphasis> to the far clipping
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* plane (will be <emphasis>negative</emphasis> if the plane is
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* behind the viewer)
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*
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* Replaces the current matrix with an orthographic projection matrix.
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*/
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void
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cogl_matrix_stack_orthographic (CoglMatrixStack *stack,
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float x_1,
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float y_1,
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float x_2,
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float y_2,
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float near,
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float far);
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/**
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* cogl_matrix_stack_get_inverse:
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* @stack: A #CoglMatrixStack
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* @inverse: (out): The destination for a 4x4 inverse transformation matrix
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*
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* Gets the inverse transform of the current matrix and uses it to
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* initialize a new #CoglMatrix.
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*
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* Return value: %TRUE if the inverse was successfully calculated or %FALSE
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* for degenerate transformations that can't be inverted (in this case the
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* @inverse matrix will simply be initialized with the identity matrix)
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*/
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CoglBool
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cogl_matrix_stack_get_inverse (CoglMatrixStack *stack,
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CoglMatrix *inverse);
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/**
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* cogl_matrix_stack_get_entry:
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* @stack: A #CoglMatrixStack
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*
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* Gets a reference to the current transform represented by a
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* #CoglMatrixEntry pointer.
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*
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* <note>The transform represented by a #CoglMatrixEntry is
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* immutable.</note>
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*
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* <note>#CoglMatrixEntry<!-- -->s are reference counted using
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* cogl_matrix_entry_ref() and cogl_matrix_entry_unref() and you
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* should call cogl_matrix_entry_unref() when you are finished with
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* and entry you get via cogl_matrix_stack_get_entry().</note>
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*
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* Return value: (transfer none): A pointer to the #CoglMatrixEntry
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* representing the current matrix stack transform.
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*/
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CoglMatrixEntry *
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cogl_matrix_stack_get_entry (CoglMatrixStack *stack);
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/**
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* cogl_matrix_stack_get:
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* @stack: A #CoglMatrixStack
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* @matrix: (out): The potential destination for the current matrix
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*
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* Resolves the current @stack transform into a #CoglMatrix by
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* combining the operations that have been applied to build up the
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* current transform.
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*
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* There are two possible ways that this function may return its
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* result depending on whether the stack is able to directly point
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* to an internal #CoglMatrix or whether the result needs to be
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* composed of multiple operations.
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*
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* If an internal matrix contains the required result then this
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* function will directly return a pointer to that matrix, otherwise
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* if the function returns %NULL then @matrix will be initialized
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* to match the current transform of @stack.
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*
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* <note>@matrix will be left untouched if a direct pointer is
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* returned.</note>
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*
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* Return value: A direct pointer to the current transform or %NULL
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* and in that case @matrix will be initialized with
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* the value of the current transform.
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*/
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CoglMatrix *
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cogl_matrix_stack_get (CoglMatrixStack *stack,
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CoglMatrix *matrix);
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/**
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* cogl_matrix_entry_get:
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* @entry: A #CoglMatrixEntry
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* @matrix: (out): The potential destination for the transform as
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* a matrix
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*
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* Resolves the current @entry transform into a #CoglMatrix by
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* combining the sequence of operations that have been applied to
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* build up the current transform.
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*
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* There are two possible ways that this function may return its
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* result depending on whether it's possible to directly point
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* to an internal #CoglMatrix or whether the result needs to be
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* composed of multiple operations.
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*
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* If an internal matrix contains the required result then this
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* function will directly return a pointer to that matrix, otherwise
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* if the function returns %NULL then @matrix will be initialized
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* to match the transform of @entry.
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*
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* <note>@matrix will be left untouched if a direct pointer is
|
|
* returned.</note>
|
|
*
|
|
* Return value: A direct pointer to a #CoglMatrix transform or %NULL
|
|
* and in that case @matrix will be initialized with
|
|
* the effective transform represented by @entry.
|
|
*/
|
|
CoglMatrix *
|
|
cogl_matrix_entry_get (CoglMatrixEntry *entry,
|
|
CoglMatrix *matrix);
|
|
|
|
/**
|
|
* cogl_matrix_stack_set:
|
|
* @stack: A #CoglMatrixStack
|
|
* @matrix: A #CoglMatrix replace the current matrix value with
|
|
*
|
|
* Replaces the current @stack matrix value with the value of @matrix.
|
|
* This effectively discards any other operations that were applied
|
|
* since the last time cogl_matrix_stack_push() was called or since
|
|
* the stack was initialized.
|
|
*/
|
|
void
|
|
cogl_matrix_stack_set (CoglMatrixStack *stack,
|
|
const CoglMatrix *matrix);
|
|
|
|
/**
|
|
* cogl_is_matrix_stack:
|
|
* @object: a #CoglObject
|
|
*
|
|
* Determines if the given #CoglObject refers to a #CoglMatrixStack.
|
|
*
|
|
* Return value: %TRUE if @object is a #CoglMatrixStack, otherwise
|
|
* %FALSE.
|
|
*/
|
|
CoglBool
|
|
cogl_is_matrix_stack (void *object);
|
|
|
|
/**
|
|
* cogl_matrix_entry_calculate_translation:
|
|
* @entry0: The first reference transform
|
|
* @entry1: A second reference transform
|
|
* @x: (out): The destination for the x-component of the translation
|
|
* @y: (out): The destination for the y-component of the translation
|
|
* @z: (out): The destination for the z-component of the translation
|
|
*
|
|
* Determines if the only difference between two transforms is a
|
|
* translation and if so returns what the @x, @y, and @z components of
|
|
* the translation are.
|
|
*
|
|
* If the difference between the two translations involves anything
|
|
* other than a translation then the function returns %FALSE.
|
|
*
|
|
* Return value: %TRUE if the only difference between the transform of
|
|
* @entry0 and the transform of @entry1 is a translation,
|
|
* otherwise %FALSE.
|
|
*/
|
|
CoglBool
|
|
cogl_matrix_entry_calculate_translation (CoglMatrixEntry *entry0,
|
|
CoglMatrixEntry *entry1,
|
|
float *x,
|
|
float *y,
|
|
float *z);
|
|
|
|
/**
|
|
* cogl_matrix_entry_is_identity:
|
|
* @entry: A #CoglMatrixEntry
|
|
*
|
|
* Determines whether @entry is known to represent an identity
|
|
* transform.
|
|
*
|
|
* If this returns %TRUE then the entry is definitely the identity
|
|
* matrix. If it returns %FALSE it may or may not be the identity
|
|
* matrix but no expensive comparison is performed to verify it.
|
|
*
|
|
* Return value: %TRUE if @entry is definitely an identity transform,
|
|
* otherwise %FALSE.
|
|
*/
|
|
CoglBool
|
|
cogl_matrix_entry_is_identity (CoglMatrixEntry *entry);
|
|
|
|
/**
|
|
* cogl_matrix_entry_equal:
|
|
* @entry0: The first #CoglMatrixEntry to compare
|
|
* @entry1: A second #CoglMatrixEntry to compare
|
|
*
|
|
* Compares two arbitrary #CoglMatrixEntry transforms for equality
|
|
* returning %TRUE if they are equal or %FALSE otherwise.
|
|
*
|
|
* <note>In many cases it is unnecessary to use this api and instead
|
|
* direct pointer comparisons of entries are good enough and much
|
|
* cheaper too.</note>
|
|
*
|
|
* Return value: %TRUE if @entry0 represents the same transform as
|
|
* @entry1, otherwise %FALSE.
|
|
*/
|
|
CoglBool
|
|
cogl_matrix_entry_equal (CoglMatrixEntry *entry0,
|
|
CoglMatrixEntry *entry1);
|
|
|
|
/**
|
|
* cogl_debug_matrix_entry_print:
|
|
* @entry: A #CoglMatrixEntry
|
|
*
|
|
* Allows visualizing the operations that build up the given @entry
|
|
* for debugging purposes by printing to stdout.
|
|
*/
|
|
void
|
|
cogl_debug_matrix_entry_print (CoglMatrixEntry *entry);
|
|
|
|
/**
|
|
* cogl_matrix_entry_ref:
|
|
* @entry: A #CoglMatrixEntry
|
|
*
|
|
* Takes a reference on the given @entry to ensure the @entry stays
|
|
* alive and remains valid. When you are finished with the @entry then
|
|
* you should call cogl_matrix_entry_unref().
|
|
*
|
|
* It is an error to pass an @entry pointer to cogl_object_ref() and
|
|
* cogl_object_unref()
|
|
*/
|
|
CoglMatrixEntry *
|
|
cogl_matrix_entry_ref (CoglMatrixEntry *entry);
|
|
|
|
/**
|
|
* cogl_matrix_entry_unref:
|
|
* @entry: A #CoglMatrixEntry
|
|
*
|
|
* Releases a reference on @entry either taken by calling
|
|
* cogl_matrix_entry_unref() or to release the reference given when
|
|
* calling cogl_matrix_stack_get_entry().
|
|
*/
|
|
void
|
|
cogl_matrix_entry_unref (CoglMatrixEntry *entry);
|
|
|
|
#endif /* _COGL_MATRIX_STACK_H_ */
|