Add GL_ANGLE_pack_reverse_row_order. Performs vertical flip in readPixels and

may write direct to client ptr.

Bug=none
Test= Tested in a modified version of Chromium using canvas2D.
Review URL: http://codereview.appspot.com/5373104

git-svn-id: https://angleproject.googlecode.com/svn/trunk@889 736b8ea6-26fd-11df-bfd4-992fa37f6226

1 files changed, 164 insertions, 0 deletions

diff --git a/extensions/ANGLE_pack_reverse_row_order.txt b/extensions/ANGLE_pack_reverse_row_order.txt
new file mode 100644
index 00000000..cd9062ed
--- /dev/null
+++ b/extensions/ANGLE_pack_reverse_row_order.txt
@@ -0,0 +1,164 @@
+                                             
+Name
+
+    ANGLE_pack_reverse_row_order
+
+Name Strings
+
+    GL_ANGLE_pack_reverse_row_order
+
+Contact
+
+    Daniel Koch, TransGaming (daniel 'at' transgaming.com)
+
+Contributors
+
+    Brian Salomon
+    Daniel Koch
+
+Status
+
+    XXX - Not complete yet!!!
+
+Version
+
+    Last Modified Date: November 22, 2011
+    Author Revision: 1
+
+Number
+
+    XXX not yet
+
+Dependencies
+
+    OpenGL 1.5 or OpenGL ES 1.0 are required.
+
+    Some of the functionality of this extension is not supported
+    when implemented against OpenGL ES.
+
+    EXT_texture_rg interacts with this extension.
+
+    The extension is written against the OpenGL 3.2 Specification
+    (Core Profile).
+
+Overview
+
+    This extension introduces a mechanism to allow reversing the order
+    in which image rows are written into a pack destination. This
+    effectively allows an application to flip the results of a ReadPixels
+    in the y direction operation without having to render upside down.
+
+    The coordinate system of OpenGL is vertically reversed in comparison to a
+    number of other graphics systems such as native windowing APIs. Applications
+    that perform ReadPixels may have to either render to an intermediate color
+    buffer before calling ReadPixels or perform a flip in software after
+    ReadPixels. In some systems the GL can perform the row reversal during
+    ReadPixels without incurring additional cost.
+
+IP Status
+
+    No known IP claims.
+
+Issues
+
+
+New Procedures and Functions
+
+    None
+
+New Types
+
+    None
+
+New Tokens
+
+    Accepted by the <pname> parameter of PixelStore{if}, GetIntegerv(),
+    GetBooleanv(), and GetFloatv():
+
+        PACK_REVERSE_ROW_ORDER_ANGLE    0x93A4
+
+Additions to Chapter 3 of the OpenGL 3.2 Specification (Rasterization)
+
+    In Section 4.3.1 (Reading Pixels) add a row to table 4.7:
+
+        +------------------------------+---------+---------------+-------------+
+        | Parameter Name               | Type    | Initial Value | Valid Range |
+        +------------------------------+---------+---------------+-------------+
+        | PACK_REVERSE_ROW_ORDER_ANGLE | boolean | FALSE         | TRUE/FALSE  |
+        +------------------------------+---------+---------------+-------------+
+
+    In Section 4.3.1 (Reading Pixels) modify the second paragraph of subsection 
+    "Placement in Pixel Pack Buffer or Client Memory" to read:
+
+        When PACK_REVERSE_ROW_ORDER_ANGLE is FALSE groups of elements are placed
+        in memory just as they are taken from memory when transferring pixel
+        rectangles to the GL. That is, the ith group of the jth row
+        (corresponding to the ith pixel in the jth row) is placed in memory just
+        where the ith group of the jth row would be taken from when transferring
+        pixels. See Unpacking under section 3.7.2. The only difference is that
+        the storage mode parameters whose names begin with PACK_ are used
+        instead of those whose names begin with UNPACK_. If the format is RED,
+        GREEN, BLUE, or ALPHA, only the corresponding single element is written.
+        Likewise if the format is RG, RGB, or BGR, only the corresponding two or
+        three elements are written. Otherwise all the elements of each group are
+        written. When PACK_REVERSE_ROW_ORDER_ANGLE is TRUE the order of the rows
+        of elements is reversed before the data is packed. That is, the element
+        corresponding to pixel (x, y + height - 1) becomes the first element
+        packed, followed by (x + 1, y + height - 1), etc. Otherwise, pixel data
+        is packed in the same manner as when PACK_REVERSE_ROW_ORDER_ANGLE is
+        FALSE.
+
+    In Section 6.1.4 add the following sentence to the fifth paragraph
+    (beginning with "For three-dimensional and two-dimensional array
+    textures..."):
+        When PACK_REVERSE_ROW_ORDER_ANGLE is TRUE the order of rows within
+        each image are reversed without reordering the images themselves.
+
+Dependencies on OpenGL ES
+
+    If implemented for OpenGL ES, this extension behaves as specified, except:
+
+    -Delete all references to formats RED, GREEN, BLUE, RG, and BGR.
+
+    -The language about image order in Section 6.1.4 does not apply as OpenGL ES
+     does not have GetTexImage.
+
+Dependencies on EXT_texture_rg
+
+    If EXT_texture_rg is present reinsert language about formats RED and RG
+    into the OpenGL ES 2.0 specification.
+
+Errors
+
+    None
+
+New State
+                                                           Initial
+    Get Value                       Type  Get Command      Value    Description                    Sec.
+    ---------                       ----  -----------      -------  -----------                    ----
+    PACK_REVERSE_ROW_ORDER_ANGLE    B     GetIntegerv      FALSE    Pixel pack row order reversal  4.3.1
+
+New Implementation Dependent State
+
+    None
+
+Sample Code
+
+    /* Allocate space to hold the pixel data */
+    const GLvoid* pixels = malloc(width * height * 4);
+
+    /* Bind the framebuffer object to be read */
+    glBindFramebuffer(READ_FRAMEBUFFER, framebuffer);
+
+    /* Enable row order reversal */
+    glPixelStore(PACK_REVERSE_ROW_ORDER_ANGLE, TRUE);
+
+    /* The pixel data stored in pixels will be in top-down order, ready for
+     * use with a windowing system API that expects this order.
+     */
+    glReadPixels(x, y, width, height, RGBA, UNSIGNED_BYTE, pixels);
+
+Revision History
+
+    Revision 1, 2011/11/22 (Brian Salomon)
+      - First version