From 7fd4cf02272673956adfdba3e1e4d3402c635f0d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fredrik=20H=C3=B6glund?= <fredrik@kde.org>
Date: Sat, 13 Dec 2014 14:30:59 +0100
Subject: [PATCH] Add GLTexture::setSwizzle()

This method allows the caller to specify which component of a texel
is placed in each respective component of the vector returned to the
shader.
---
 libkwineffects/kwingltexture.cpp | 23 +++++++++++++++++++++++
 libkwineffects/kwingltexture.h   | 20 ++++++++++++++++++++
 libkwineffects/kwingltexture_p.h |  1 +
 3 files changed, 44 insertions(+)

diff --git a/libkwineffects/kwingltexture.cpp b/libkwineffects/kwingltexture.cpp
index 78e21382fd..a84fddcef6 100644
--- a/libkwineffects/kwingltexture.cpp
+++ b/libkwineffects/kwingltexture.cpp
@@ -46,6 +46,7 @@ bool GLTexturePrivate::s_supportsFramebufferObjects = false;
 bool GLTexturePrivate::s_supportsARGB32 = false;
 bool GLTexturePrivate::s_supportsUnpack = false;
 bool GLTexturePrivate::s_supportsTextureStorage = false;
+bool GLTexturePrivate::s_supportsTextureSwizzle = false;
 uint GLTexturePrivate::s_textureObjectCounter = 0;
 uint GLTexturePrivate::s_fbo = 0;
 
@@ -234,11 +235,13 @@ void GLTexturePrivate::initStatic()
         s_supportsFramebufferObjects = hasGLVersion(3, 0) ||
             hasGLExtension("GL_ARB_framebuffer_object") || hasGLExtension(QByteArrayLiteral("GL_EXT_framebuffer_object"));
         s_supportsTextureStorage = hasGLVersion(4, 2) || hasGLExtension(QByteArrayLiteral("GL_ARB_texture_storage"));
+        s_supportsTextureSwizzle = hasGLVersion(3, 3) || hasGLExtension(QByteArrayLiteral("GL_ARB_texture_swizzle"));
         s_supportsARGB32 = true;
         s_supportsUnpack = true;
     } else {
         s_supportsFramebufferObjects = true;
         s_supportsTextureStorage = hasGLVersion(3, 0) || hasGLExtension(QByteArrayLiteral("GL_EXT_texture_storage"));
+        s_supportsTextureSwizzle = hasGLVersion(3, 0);
 
         // QImage::Format_ARGB32_Premultiplied is a packed-pixel format, so it's only
         // equivalent to GL_BGRA/GL_UNSIGNED_BYTE on little-endian systems.
@@ -551,6 +554,21 @@ void GLTexture::setYInverted(bool inverted)
     d->updateMatrix();
 }
 
+void GLTexture::setSwizzle(GLenum red, GLenum green, GLenum blue, GLenum alpha)
+{
+    Q_D(GLTexture);
+
+    if (!GLPlatform::instance()->isGLES()) {
+        const GLuint swizzle[] = { red, green, blue, alpha };
+        glTexParameteriv(d->m_target, GL_TEXTURE_SWIZZLE_RGBA, (const GLint *) swizzle);
+    } else {
+        glTexParameteri(d->m_target, GL_TEXTURE_SWIZZLE_R, red);
+        glTexParameteri(d->m_target, GL_TEXTURE_SWIZZLE_G, green);
+        glTexParameteri(d->m_target, GL_TEXTURE_SWIZZLE_B, blue);
+        glTexParameteri(d->m_target, GL_TEXTURE_SWIZZLE_A, alpha);
+    }
+}
+
 int GLTexture::width() const
 {
     Q_D(const GLTexture);
@@ -574,4 +592,9 @@ bool GLTexture::framebufferObjectSupported()
     return GLTexturePrivate::s_supportsFramebufferObjects;
 }
 
+bool GLTexture::supportsSwizzle()
+{
+    return GLTexturePrivate::s_supportsTextureSwizzle;
+}
+
 } // namespace KWin
diff --git a/libkwineffects/kwingltexture.h b/libkwineffects/kwingltexture.h
index 5d2e9e65be..250a273f71 100644
--- a/libkwineffects/kwingltexture.h
+++ b/libkwineffects/kwingltexture.h
@@ -74,6 +74,17 @@ public:
      **/
     void setYInverted(bool inverted);
 
+    /**
+     * Specifies which component of a texel is placed in each respective
+     * component of the vector returned to the shader.
+     *
+     * Valid values are GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_ONE and GL_ZERO.
+     *
+     * @see swizzleSupported()
+     * @since 5.2
+     */
+    void setSwizzle(GLenum red, GLenum green, GLenum blue, GLenum alpha);
+
     /**
      * Returns a matrix that transforms texture coordinates of the given type,
      * taking the texture target and the y-inversion flag into account.
@@ -107,6 +118,15 @@ public:
 
     static bool framebufferObjectSupported();
 
+    /**
+     * Returns true if texture swizzle is supported, and false otherwise
+     *
+     * Texture swizzle requires OpenGL 3.3, GL_ARB_texture_swizzle, or OpenGL ES 3.0.
+     *
+     * @since 5.2
+     */
+    static bool supportsSwizzle();
+
 protected:
     QExplicitlySharedDataPointer<GLTexturePrivate> d_ptr;
     GLTexture(GLTexturePrivate& dd);
diff --git a/libkwineffects/kwingltexture_p.h b/libkwineffects/kwingltexture_p.h
index 94189268f8..656f2944fa 100644
--- a/libkwineffects/kwingltexture_p.h
+++ b/libkwineffects/kwingltexture_p.h
@@ -73,6 +73,7 @@ public:
     static bool s_supportsARGB32;
     static bool s_supportsUnpack;
     static bool s_supportsTextureStorage;
+    static bool s_supportsTextureSwizzle;
     static GLuint s_fbo;
     static uint s_textureObjectCounter;
 private: