Add support for framebuffer blit extension

Resolving of blit function and method in GLRenderTarget to blit
from the framebuffer to the RenderTarget.

REVIEW: 102354

libkwineffects/kwinglutils.cpp

@@ -869,14 +869,17 @@ void ShaderManager::resetShader(ShaderType type)
 
 /***  GLRenderTarget  ***/
 bool GLRenderTarget::sSupported = false;
+bool GLRenderTarget::s_blitSupported = false;
 QStack<GLRenderTarget*> GLRenderTarget::s_renderTargets = QStack<GLRenderTarget*>();
 
 void GLRenderTarget::initStatic()
 {
 #ifdef KWIN_HAVE_OPENGLES
     sSupported = true;
+    s_blitSupported = false;
 #else
     sSupported = hasGLExtension("GL_EXT_framebuffer_object") && glFramebufferTexture2D;
+    s_blitSupported = hasGLExtension("GL_EXT_framebuffer_blit");
 #endif
 }
 
@@ -885,6 +888,11 @@ bool GLRenderTarget::isRenderTargetBound()
     return !s_renderTargets.isEmpty();
 }
 
+bool GLRenderTarget::blitSupported()
+{
+    return s_blitSupported;
+}
+
 void GLRenderTarget::pushRenderTarget(GLRenderTarget* target)
 {
     target->enable();
@@ -1037,6 +1045,25 @@ void GLRenderTarget::initFBO()
     mValid = true;
 }
 
+void GLRenderTarget::blitFromFramebuffer(const QRect &source, const QRect &destination, GLenum filter)
+{
+    if (!GLRenderTarget::blitSupported()) {
+        return;
+    }
+#ifndef KWIN_HAVE_OPENGLES
+    GLRenderTarget::pushRenderTarget(this);
+    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, mFramebuffer);
+    glBindFramebuffer(GL_READ_FRAMEBUFFER, 0);
+    const QRect s = source.isNull() ? QRect(0, 0, displayWidth(), displayHeight()) : source;
+    const QRect d = destination.isNull() ? QRect(0, 0, mTexture->width(), mTexture->height()) : destination;
+
+    glBlitFramebuffer(s.x(), displayHeight() - s.y() - s.height(), s.x() + s.width(), displayHeight() - s.y(),
+                      d.x(), mTexture->height() - d.y() - d.height(), d.x() + d.width(), mTexture->height() - d.y(),
+                      GL_COLOR_BUFFER_BIT, filter);
+    GLRenderTarget::popRenderTarget();
+#endif
+}
+
 
 //*********************************
 // GLVertexBufferPrivate

libkwineffects/kwinglutils.h

@@ -412,6 +412,27 @@ public:
     static void pushRenderTarget(GLRenderTarget *target);
     static GLRenderTarget *popRenderTarget();
     static bool isRenderTargetBound();
+    /**
+     * Whether the GL_EXT_framebuffer_blit extension is supported.
+     * This functionality is not available in OpenGL ES 2.0.
+     *
+     * @returns whether framebuffer blitting is supported.
+     * @since 4.8
+     **/
+    static bool blitSupported();
+
+    /**
+     * Blits the content of the current draw framebuffer into the texture attached to this FBO.
+     *
+     * Be aware that framebuffer blitting may not be supported on all hardware. Use @link blitSupported to check whether
+     * it is supported.
+     * @param source Geometry in screen coordinates which should be blitted, if not specified complete framebuffer is used
+     * @param destination Geometry in attached texture, if not specified complete texture is used as destination
+     * @param filter The filter to use if blitted content needs to be scaled.
+     * @see blitSupported
+     * @since 4.8
+     **/
+    void blitFromFramebuffer(const QRect &source = QRect(), const QRect &destination = QRect(), GLenum filter = GL_LINEAR);
 
 
 protected:
@@ -420,6 +441,7 @@ protected:
 
 private:
     static bool sSupported;
+    static bool s_blitSupported;
     static QStack<GLRenderTarget*> s_renderTargets;
 
     GLTexture* mTexture;

libkwineffects/kwinglutils_funcs.cpp

@@ -79,6 +79,7 @@ glFramebufferTexture3D_func glFramebufferTexture3D;
 glFramebufferRenderbuffer_func glFramebufferRenderbuffer;
 glGetFramebufferAttachmentParameteriv_func glGetFramebufferAttachmentParameteriv;
 glGenerateMipmap_func glGenerateMipmap;
+glBlitFramebuffer_func glBlitFramebuffer;
 // Shader functions
 glCreateShader_func glCreateShader;
 glShaderSource_func glShaderSource;
@@ -225,6 +226,11 @@ void glResolveFunctions()
         glGetFramebufferAttachmentParameteriv = NULL;
         glGenerateMipmap = NULL;
     }
+    if (hasGLExtension("GL_EXT_framebuffer_blit")) {
+        glBlitFramebuffer = (glBlitFramebuffer_func) getProcAddress("glBlitFramebufferEXT");
+    } else {
+        glBlitFramebuffer = NULL;
+    }
     if (hasGLExtension("GL_ARB_shading_language_100") && hasGLExtension("GL_ARB_fragment_shader")) {
         GL_RESOLVE_WITH_EXT(glCreateShader, glCreateShaderObjectARB);
         GL_RESOLVE_WITH_EXT(glShaderSource, glShaderSourceARB);

libkwineffects/kwinglutils_funcs.h

@@ -232,6 +232,7 @@ typedef void (*glFramebufferTexture3D_func)(GLenum target, GLenum attachment, GL
 typedef void (*glFramebufferRenderbuffer_func)(GLenum target, GLenum attachment, GLenum renderbuffertarget, GLuint renderbuffer);
 typedef void (*glGetFramebufferAttachmentParameteriv_func)(GLenum target, GLenum attachment, GLenum pname, GLint *params);
 typedef void (*glGenerateMipmap_func)(GLenum target);
+typedef void (*glBlitFramebuffer_func)(GLint srcX0, GLint srcY0, GLint srcX1, GLint srcY1, GLint dstX0, GLint dstY0, GLint dstX1, GLint dstY1, GLbitfield mask, GLenum filter);
 extern KWIN_EXPORT glIsRenderbuffer_func glIsRenderbuffer;
 extern KWIN_EXPORT glBindRenderbuffer_func glBindRenderbuffer;
 extern KWIN_EXPORT glDeleteRenderbuffers_func glDeleteRenderbuffers;
@@ -249,6 +250,7 @@ extern KWIN_EXPORT glFramebufferTexture3D_func glFramebufferTexture3D;
 extern KWIN_EXPORT glFramebufferRenderbuffer_func glFramebufferRenderbuffer;
 extern KWIN_EXPORT glGetFramebufferAttachmentParameteriv_func glGetFramebufferAttachmentParameteriv;
 extern KWIN_EXPORT glGenerateMipmap_func glGenerateMipmap;
+extern KWIN_EXPORT glBlitFramebuffer_func glBlitFramebuffer;
 // Shader stuff
 typedef GLuint(*glCreateShader_func)(GLenum);
 typedef GLvoid(*glShaderSource_func)(GLuint, GLsizei, const GLchar**, const GLint*);