Implement EXT_blend_minmax.
BUG=angle:555
Change-Id: I1ae6a9783e718d16ee08bda5463f11cd52ad0967
Reviewed-on: https://chromium-review.googlesource.com/186123
Tested-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
diff --git a/extensions/EXT_blend_minmax.txt b/extensions/EXT_blend_minmax.txt
new file mode 100644
index 0000000..522ac20
--- /dev/null
+++ b/extensions/EXT_blend_minmax.txt
@@ -0,0 +1,164 @@
+Name
+
+ EXT_blend_minmax
+
+Name Strings
+
+ GL_EXT_blend_minmax
+
+Version
+
+ Last Modified Date: September 17, 2009
+ Version: 1.5
+
+Number
+
+ OpenGL Extension #37
+ OpenGL ES Extension #65
+
+Dependencies
+
+ There is an interaction with OpenGL ES.
+
+Overview
+
+ Blending capability is extended by respecifying the entire blend
+ equation. While this document defines only two new equations, the
+ BlendEquationEXT procedure that it defines will be used by subsequent
+ extensions to define additional blending equations.
+
+ The two new equations defined by this extension produce the minimum
+ (or maximum) color components of the source and destination colors.
+ Taking the maximum is useful for applications such as maximum projection
+ in medical imaging.
+
+Issues
+
+ * I've prefixed the ADD token with FUNC, to indicate that the blend
+ equation includes the parameters specified by BlendFunc. (The min
+ and max equations don't.) Is this necessary? Is it too ugly?
+ Is there a better way to accomplish the same thing?
+
+New Procedures and Functions
+
+ void BlendEquationEXT(enum mode);
+
+New Tokens
+
+ Accepted by the <mode> parameter of BlendEquationEXT:
+
+ FUNC_ADD_EXT 0x8006
+ MIN_EXT 0x8007
+ MAX_EXT 0x8008
+
+ Accepted by the <pname> parameter of GetBooleanv, GetIntegerv,
+ GetFloatv, and GetDoublev:
+
+ BLEND_EQUATION_EXT 0x8009
+
+Additions to Chapter 2 of the GL Specification (OpenGL Operation)
+
+ None
+
+Additions to Chapter 3 of the GL Specification (Rasterization)
+
+ None
+
+Additions to Chapter 4 of the GL Specification (Per-Fragment Operations
+and the Framebuffer)
+
+ The GL Specification defines a single blending equation. This
+ extension introduces a blend equation mode that is specified by calling
+ BlendEquationEXT with one of three enumerated values. The default
+ value FUNC_ADD_EXT specifies that the blending equation defined in
+ the GL Specification be used. This equation is
+
+ C' = (Cs * S) + (Cd * D)
+
+ / 1.0 C' > 1.0
+ C = (
+ \ C' C' <= 1.0
+
+ where Cs and Cd are the source and destination colors, and S and D are
+ as specified by BlendFunc.
+
+ If BlendEquationEXT is called with <mode> set to MIN_EXT, the
+ blending equation becomes
+
+ C = min (Cs, Cd)
+
+ Finally, if BlendEquationEXT is called with <mode> set to MAX_EXT, the
+ blending equation becomes
+
+ C = max (Cs, Cd)
+
+ In all cases the blending equation is evaluated separately for each
+ color component.
+
+Additions to Chapter 5 of the GL Specification (Special Functions)
+
+ None
+
+Additions to Chapter 6 of the GL Specification (State and State Requests)
+
+ None
+
+Additions to the GLX Specification
+
+ None
+
+GLX Protocol
+
+ A new GL rendering command is added. The following command is sent to the
+ server as part of a glXRender request:
+
+ BlendEquationEXT
+ 2 8 rendering command length
+ 2 4097 rendering command opcode
+ 4 ENUM mode
+
+Dependencies on OpenGL ES
+
+ If the GL is OpenGL ES, only the new MIN_EXT and MAX_EXT blend equations
+ are introduced by this extension. BlendEquationOES, FUNC_ADD_OES, and
+ BLEND_EQUATION_OES are introduced by the OES_blend_subtract extension,
+ which is required for this extension to operate. Alternatively,
+ OpenGL ES 2.0 is required, which introduces BlendEquation, FUNC_ADD, and
+ BLEND_EQUATION without the suffixes.
+
+ MIN_EXT and MAX_EXT should be added to Table 4.blendeq described in the
+ OES_blend_subtract extension specification, and Table 4.1 of the OpenGL
+ ES 2.0 specification.
+
+ Mentions of GetDoublev, Begin/End, and GLX in this extension specification
+ can be ignored for OpenGL ES. Also, BlendEquationEXT and FUNC_ADD_EXT
+ instead have the OES suffix courtesy of OES_blend_subtract, or no suffix
+ courtesy of core OpenGL ES 2.0.
+
+Errors
+
+ INVALID_ENUM is generated by BlendEquationEXT if its single parameter
+ is not FUNC_ADD_EXT, MIN_EXT, or MAX_EXT.
+
+ INVALID_OPERATION is generated if BlendEquationEXT is executed between
+ the execution of Begin and the corresponding execution to End.
+
+New State
+
+ Get Value Get Command Type Initial Value Attribute
+ --------- ----------- ---- ------------- ---------
+ BLEND_EQUATION_EXT GetIntegerv Z3 FUNC_ADD_EXT color-buffer
+
+New Implementation Dependent State
+
+ None
+
+Revision History
+
+ Version 1.5, September 17, 2009 (Jon Leech) -
+ Merge into OpenGL Registry version of the extension and assign
+ OpenGL ES extension number.
+ Version 1.4, May 19, 2009 (Benj Lipchak) -
+ Adapted for OpenGL ES.
+ Version 1.3, May 31, 1995 -
+ Last SGI revision.