3 files changed, 326 insertions, 103 deletions

diff --git a/twin/compton-tde/common.h b/twin/compton-tde/common.h
index 759e64698..9ff5a2148 100644
--- a/twin/compton-tde/common.h
+++ b/twin/compton-tde/common.h
@@ -490,6 +490,21 @@ typedef struct {
 } glx_blur_cache_t;
 
 typedef struct {
+  /// Fragment shader for greyscale.
+  GLuint frag_shader;
+  /// GLSL program for greyscale.
+  GLuint prog;
+  /// Location of uniform "greyscale_weights" in greyscale GLSL program.
+  GLint unifm_greyscale_weights;
+  /// Location of uniform "enable_blend" in greyscale GLSL program.
+  GLint unifm_enable_blend;
+  /// Location of uniform "tex_scr" in greyscale GLSL program.
+  GLint unifm_tex_scr;
+  /// Location of uniform "alpha_scr" in greyscale GLSL program.
+  GLint unifm_alpha_scr;
+} glx_greyscale_t;
+
+typedef struct {
   /// Framebuffer used for greyscale conversion.
   GLuint fbo;
   /// Textures used for greyscale conversion.
@@ -817,6 +832,9 @@ typedef struct {
 #ifdef CONFIG_VSYNC_OPENGL_GLSL
   glx_blur_pass_t blur_passes[MAX_BLUR_PASS];
 #endif
+#ifdef CONFIG_VSYNC_OPENGL_GLSL
+  glx_greyscale_t greyscale_glsl;
+#endif
 } glx_session_t;
 
 #define CGLX_SESSION_INIT { .context = NULL }
@@ -1068,6 +1086,8 @@ typedef struct _session_t {
   Atom atom_win_type_tde_transparent_to_desktop;
   /// Atom of property <code>_TDE_TRANSPARENCY_FILTER_GREYSCALE</code>.
   Atom atom_win_type_tde_transparency_filter_greyscale;
+  /// Atom of property <code>_TDE_TRANSPARENCY_FILTER_GREYSCALE_BLEND</code>.
+  Atom atom_win_type_tde_transparency_filter_greyscale_blend;
   /// Array of atoms of all possible window types.
   Atom atoms_wintypes[NUM_WINTYPES];
   /// Linked list of additional atoms to track.
@@ -1263,6 +1283,11 @@ typedef struct _win {
   /// Background state on last paint.
   bool greyscale_background_last;
 
+  /// Whether to set window background to blended greyscale.
+  bool greyscale_blended_background;
+  /// Blended greyscale alpha divisor.
+  int greyscale_blended_background_alpha_divisor;
+
   /// Whether to show black background
   bool show_black_background;
 
@@ -2202,6 +2227,9 @@ glx_on_root_change(session_t *ps);
 bool
 glx_init_blur(session_t *ps);
 
+bool
+glx_init_greyscale(session_t *ps);
+
 #ifdef CONFIG_VSYNC_OPENGL_GLSL
 bool
 glx_load_prog_main(session_t *ps,
@@ -2245,7 +2273,7 @@ glx_dim_dst(session_t *ps, int dx, int dy, int width, int height, float z,
 
 bool
 glx_greyscale_dst(session_t *ps, int dx, int dy, int width, int height, float z,
-    XserverRegion reg_tgt, const reg_data_t *pcache_reg, glx_greyscale_cache_t *pbc);
+    glx_texture_t *ptex, XserverRegion reg_tgt, const reg_data_t *pcache_reg, glx_greyscale_cache_t *pbc);
 
 bool
 glx_render_(session_t *ps, const glx_texture_t *ptex,
@@ -2342,7 +2370,6 @@ free_glx_bc(session_t *ps, glx_blur_cache_t *pbc) {
 static inline void
 free_glx_gc_resize(session_t *ps, glx_greyscale_cache_t *pbc) {
   free_texture_r(ps, &pbc->textures[0]);
-  free_texture_r(ps, &pbc->textures[1]);
   pbc->width = 0;
   pbc->height = 0;
 }
diff --git a/twin/compton-tde/compton.c b/twin/compton-tde/compton.c
index dea363f60..d2095123f 100644
--- a/twin/compton-tde/compton.c
+++ b/twin/compton-tde/compton.c
@@ -944,6 +944,9 @@ static Bool
 determine_window_transparency_filter_greyscale(const session_t *ps, Window w);
 
 static Bool
+determine_window_transparency_filter_greyscale_blended(const session_t *ps, Window w);
+
+static Bool
 determine_window_transparent_to_black(const session_t *ps, Window w);
 
 static Bool
@@ -1590,6 +1593,7 @@ xr_greyscale_dst(session_t *ps, Picture tgt_buffer,
 
   XRenderComposite(ps->dpy, PictOpSrc, ps->black_picture, None,
       tmp_picture, 0, 0, 0, 0, 0, 0, wid, hei);
+
   XRenderComposite(ps->dpy, PictOpHSLLuminosity, tgt_buffer, None,
       tmp_picture, x, y, 0, 0, 0, 0, wid, hei);
 
@@ -1723,7 +1727,7 @@ win_greyscale_background(session_t *ps, win *w, Picture tgt_buffer,
 #ifdef CONFIG_VSYNC_OPENGL_GLSL
     case BKEND_GLX:
       glx_greyscale_dst(ps, x, y, wid, hei, ps->psglx->z - 0.5,
-          reg_paint, pcache_reg, &w->glx_greyscale_cache);
+          NULL, reg_paint, pcache_reg, &w->glx_greyscale_cache);
       break;
 #endif
     default:
@@ -1821,6 +1825,71 @@ win_paint_win(session_t *ps, win *w, XserverRegion reg_paint,
 
   Picture pict = w->paint.pict;
 
+  if (w->greyscale_blended_background) {
+    // Set window background to greyscale
+    switch (ps->o.backend) {
+      case BKEND_XRENDER:
+      case BKEND_XR_GLX_HYBRID:
+        {
+          // Blend here such that 0 window alpha is fully colored and 100 window alpha is fully greyscale
+          // PictOpInReverse is used to copy alpha from the source to the destination while preserving destination color
+          // provided that the source has alpha set to 1 (equivalent of CAIRO_OPERATOR_DEST_IN)
+          const int x = w->a.x;
+          const int y = w->a.y;
+          const int wid = w->widthb;
+          const int hei = w->heightb;
+          XserverRegion reg_clip = reg_paint;
+          Picture tgt_buffer = ps->tgt_buffer.pict;
+
+          // Apply clipping region to save some CPU
+          if (reg_paint) {
+            XserverRegion reg = copy_region(ps, reg_paint);
+            XFixesTranslateRegion(ps->dpy, reg, -x, -y);
+            XFixesSetPictureClipRegion(ps->dpy, pict, 0, 0, reg);
+            free_region(ps, &reg);
+          }
+
+          // Create greyscale version of background
+          Picture greyscale_picture = xr_build_picture(ps, wid, hei, w->pictfmt);
+          XRenderComposite(ps->dpy, PictOpSrc, tgt_buffer, None,
+              greyscale_picture, x, y, 0, 0, 0, 0, wid, hei);
+          win_greyscale_background(ps, w, greyscale_picture, reg_paint, pcache_reg);
+
+          Picture tmp_picture = xr_build_picture(ps, wid, hei, w->pictfmt);
+
+          if (!tmp_picture) {
+            printf_errf("(): Failed to build intermediate Picture.");
+          }
+          else {
+            if (reg_clip && tmp_picture)
+              XFixesSetPictureClipRegion(ps->dpy, tmp_picture, reg_clip, 0, 0);
+
+            // Transfer greyscale picture to temporary picture
+            XRenderComposite(ps->dpy, PictOpSrc, greyscale_picture, None,
+              tmp_picture, 0, 0, 0, 0, 0, 0, wid, hei);
+
+            // Transfer alpha of window to temporary picture
+            XRenderComposite(ps->dpy, PictOpInReverse, pict, None,
+                tmp_picture, 0, 0, 0, 0, 0, 0, wid, hei);
+
+            // Blend greyscale picture over main color buffer
+            XRenderComposite(ps->dpy, PictOpOver, tmp_picture, None, tgt_buffer,
+                0, 0, 0, 0, x, y, wid, hei);
+
+            free_picture(ps, &tmp_picture);
+            free_picture(ps, &greyscale_picture);
+          }
+        }
+        break;
+#ifdef CONFIG_VSYNC_OPENGL
+      case BKEND_GLX:
+        glx_greyscale_dst(ps, x, y, wid, hei, ps->psglx->z - 0.5,
+            w->paint.ptex, reg_paint, pcache_reg, &w->glx_greyscale_cache);
+        break;
+#endif
+    }
+  }
+
   // Invert window color, if required
   if (bkend_use_xrender(ps) && w->invert_color) {
     Picture newpict = xr_build_picture(ps, wid, hei, w->pictfmt);
@@ -1846,7 +1915,12 @@ win_paint_win(session_t *ps, win *w, XserverRegion reg_paint,
     }
   }
 
-  const double dopacity = get_opacity_percent(w);
+  double dopacity = get_opacity_percent(w);
+
+  if (w->greyscale_blended_background) {
+    double scaling_factor = (1.0 / w->greyscale_blended_background_alpha_divisor);
+    dopacity = dopacity * scaling_factor;
+  }
 
   if (!w->frame_opacity) {
     win_render(ps, w, 0, 0, wid, hei, dopacity, reg_paint, pcache_reg, pict);
@@ -2439,6 +2513,7 @@ map_win(session_t *ps, Window id) {
   /* This needs to be here since we don't get PropertyNotify when unmapped */
   w->opacity = wid_get_opacity_prop(ps, w->id, OPAQUE);
   w->greyscale_background = determine_window_transparency_filter_greyscale(ps, id);
+  w->greyscale_blended_background = determine_window_transparency_filter_greyscale_blended(ps, id);
   w->show_root_tile = determine_window_transparent_to_desktop(ps, id);
   w->show_black_background = determine_window_transparent_to_black(ps, id);
 
@@ -2632,6 +2707,28 @@ get_window_transparency_filter_greyscale(const session_t *ps, Window w)
 }
 
 static Bool
+get_window_transparency_filter_greyscale_blended(const session_t *ps, Window w)
+{
+	Atom actual;
+	int format;
+	unsigned long n, left;
+
+	unsigned char *data;
+	int result = XGetWindowProperty (ps->dpy, w, ps->atom_win_type_tde_transparency_filter_greyscale_blend, 0L, 1L, False,
+			XA_ATOM, &actual, &format,
+			&n, &left, &data);
+
+	if (result == Success && data != None && format == 32 )
+	{
+		Atom a;
+		a = *(long*)data;
+		XFree ( (void *) data);
+		return True;
+	}
+	return False;
+}
+
+static Bool
 get_window_transparent_to_desktop(const session_t *ps, Window w)
 {
 	Atom actual;
@@ -2711,6 +2808,41 @@ determine_window_transparency_filter_greyscale (const session_t *ps, Window w)
 }
 
 static Bool
+determine_window_transparency_filter_greyscale_blended (const session_t *ps, Window w)
+{
+	Window       root_return, parent_return;
+	Window      *children = NULL;
+	unsigned int nchildren, i;
+	Bool         type;
+
+	type = get_window_transparency_filter_greyscale_blended (ps, w);
+	if (type == True) {
+		return True;
+	}
+
+	if (!XQueryTree (ps->dpy, w, &root_return, &parent_return, &children,
+				&nchildren))
+	{
+		/* XQueryTree failed. */
+		if (children)
+			XFree ((void *)children);
+		return False;
+	}
+
+	for (i = 0;i < nchildren;i++)
+	{
+		type = determine_window_transparency_filter_greyscale_blended (ps, children[i]);
+		if (type == True)
+			return True;
+	}
+
+	if (children)
+		XFree ((void *)children);
+
+	return False;
+}
+
+static Bool
 determine_window_transparent_to_desktop (const session_t *ps, Window w)
 {
 	Window       root_return, parent_return;
@@ -3449,6 +3581,8 @@ add_win(session_t *ps, Window id, Window prev) {
 
     .blur_background = false,
     .greyscale_background = false,
+    .greyscale_blended_background = false,
+    .greyscale_blended_background_alpha_divisor = 2,
 
     .show_black_background = false,
     .show_root_tile = false,
@@ -6696,6 +6830,7 @@ init_atoms(session_t *ps) {
   ps->atom_win_type_tde_transparent_to_black = get_atom(ps, "_TDE_TRANSPARENT_TO_BLACK");
   ps->atom_win_type_tde_transparent_to_desktop = get_atom(ps, "_TDE_TRANSPARENT_TO_DESKTOP");
   ps->atom_win_type_tde_transparency_filter_greyscale = get_atom(ps, "_TDE_TRANSPARENCY_FILTER_GREYSCALE");
+  ps->atom_win_type_tde_transparency_filter_greyscale_blend = get_atom(ps, "_TDE_TRANSPARENCY_FILTER_GREYSCALE_BLEND");
 }
 
 #ifdef CONFIG_XRANDR
@@ -7136,6 +7271,22 @@ init_filters(session_t *ps) {
     }
   }
 
+  // Greyscale filter
+  switch (ps->o.backend) {
+    case BKEND_XRENDER:
+    case BKEND_XR_GLX_HYBRID:
+      {
+        break;
+      }
+#ifdef CONFIG_VSYNC_OPENGL
+    case BKEND_GLX:
+      {
+        if (!glx_init_greyscale(ps))
+          return false;
+      }
+#endif
+  }
+
   return true;
 }
 
@@ -7666,6 +7817,7 @@ session_init(session_t *ps_old, int argc, char **argv) {
     .atom_win_type_tde_transparent_to_black = None,
     .atom_win_type_tde_transparent_to_desktop = None,
     .atom_win_type_tde_transparency_filter_greyscale = None,
+    .atom_win_type_tde_transparency_filter_greyscale_blend = None,
     .atoms_wintypes = { 0 },
     .track_atom_lst = NULL,
 
diff --git a/twin/compton-tde/opengl.c b/twin/compton-tde/opengl.c
index de485de74..4cbfeb455 100644
--- a/twin/compton-tde/opengl.c
+++ b/twin/compton-tde/opengl.c
@@ -531,6 +531,106 @@ glx_init_blur(session_t *ps) {
 #endif
 }
 
+// RAJJA FIXME
+/**
+ * Initialize GLX greyscale filter.
+ */
+bool
+glx_init_greyscale(session_t *ps) {
+#ifdef CONFIG_VSYNC_OPENGL_GLSL
+  {
+    char *lc_numeric_old = mstrcpy(setlocale(LC_NUMERIC, NULL));
+    // Enforce LC_NUMERIC locale "C" here to make sure decimal point is sane
+    setlocale(LC_NUMERIC, "C");
+
+    // Adapted from http://trac.openscenegraph.org/projects/osg//wiki/Support/Tutorials/ShadersSampleGrayingOut
+    static const char *FRAG_SHADER_GREYSCALE =
+      "#version 110\n"
+      "uniform sampler2D tex_scr;\n"
+      "uniform sampler2D alpha_scr;\n"
+      "uniform int enable_blend;\n"
+      "uniform vec4 greyscale_weights; // [0.3, 0.59, 0.11, 1.0]\n"
+      "\n"
+      "void main( void )\n"
+      "{\n"
+      "    // Fetch the regular RGB texel color from the source texture\n"
+      "    vec4 texel_color = texture2D( tex_scr, gl_TexCoord[0].xy );\n"
+      "\n"
+      "    //\n"
+      "    // Converting to grayscale:\n"
+      "    //\n"
+      "    // Converting an image to grayscale is done by taking a weighted average of\n"
+      "    // the red, green and blue color components. The standard weights for this\n" 
+      "    // type of conversion are (0.30, 0.59, 0.11). Therefore, the gray component\n" 
+      "    // or luminance that we need to compute can be defined as a luminance\n" 
+      "    // filter like so:\n"
+      "    //\n"
+      "    // luminance = 0.30*R + 0.59*G + 0.11*B\n"
+      "    //\n"
+      "    // If we think of our RGB colors as vectors, we can see that this \n"
+      "    // calculation is actually just a dot product.\n"
+      "    //\n"
+      "\n"
+      "    vec4 scaledColor = texel_color * greyscale_weights;\n"
+      "    float luminance = scaledColor.r + scaledColor.g + scaledColor.b;\n"
+      "\n"
+      "    if (enable_blend == 1) {\n"
+      "       // Fetch the regular RGB texel color from the blend texture\n"
+      "       vec4 blend_texel = texture2D( alpha_scr, vec2(gl_TexCoord[0].x, 1.0 - gl_TexCoord[0].y) );\n"
+      "       vec4 grey_pixel = vec4(luminance,luminance,luminance,1);\n"
+      "       gl_FragColor = mix(texel_color, grey_pixel, blend_texel.a);\n"
+      "    }\n"
+      "    else {\n"
+      "       gl_FragColor = vec4(luminance,luminance,luminance,1);\n"
+      "    }\n"
+      "\n"
+      "}";
+
+      glx_greyscale_t *greyscale_glsl = &ps->psglx->greyscale_glsl;
+      greyscale_glsl->frag_shader = glx_create_shader(GL_FRAGMENT_SHADER, FRAG_SHADER_GREYSCALE);
+
+      if (!greyscale_glsl->frag_shader) {
+        printf_errf("(): Failed to create fragment shader.");
+        return false;
+      }
+
+      // Build program
+      greyscale_glsl->prog = glx_create_program(&greyscale_glsl->frag_shader, 1);
+      if (!greyscale_glsl->prog) {
+        printf_errf("(): Failed to create GLSL program.");
+        return false;
+      }
+
+      // Get uniform addresses
+#define P_GET_UNIFM_LOC(name, target) { \
+      greyscale_glsl->target = glGetUniformLocation(greyscale_glsl->prog, name); \
+      if (greyscale_glsl->target < 0) { \
+        printf_errf("(): Failed to get location of uniform '" name "'. Might be troublesome."); \
+      } \
+    }
+
+      P_GET_UNIFM_LOC("greyscale_weights", unifm_greyscale_weights);
+      P_GET_UNIFM_LOC("enable_blend", unifm_enable_blend);
+      P_GET_UNIFM_LOC("tex_scr", unifm_tex_scr);
+      P_GET_UNIFM_LOC("alpha_scr", unifm_alpha_scr);
+
+#undef P_GET_UNIFM_LOC
+
+    // Restore LC_NUMERIC
+    setlocale(LC_NUMERIC, lc_numeric_old);
+    free(lc_numeric_old);
+  }
+
+
+  glx_check_err(ps);
+
+  return true;
+#else
+  printf_errf("(): GLSL support not compiled in. Cannot do greyscale with GLX backend.");
+  return false;
+#endif
+}
+
 #ifdef CONFIG_VSYNC_OPENGL_GLSL
 
 /**
@@ -1387,113 +1487,62 @@ glx_blur_dst_end:
 
 bool
 glx_greyscale_dst(session_t *ps, int dx, int dy, int width, int height, float z,
-    XserverRegion reg_tgt, const reg_data_t *pcache_reg, glx_greyscale_cache_t *pbc) {
+    glx_texture_t *ptex, XserverRegion reg_tgt, const reg_data_t *pcache_reg, glx_greyscale_cache_t *gsc) {
+
+  glx_greyscale_t *greyscale_glsl = &ps->psglx->greyscale_glsl;
+  assert(greyscale_glsl->prog);
+
   bool ret = false;
 
   // Calculate copy region size
   glx_greyscale_cache_t ibc = { .width = 0, .height = 0 };
-  if (!pbc)
-    pbc = &ibc;
+  if (!gsc)
+    gsc = &ibc;
 
 #ifdef DEBUG_GLX
   printf_dbgf("(): %d, %d, %d, %d\n", dx, dy, width, height);
 #endif
 
   // Free textures if size inconsistency discovered
-  if (width != pbc->width || height != pbc->height)
-    free_glx_gc_resize(ps, pbc);
+  if (width != gsc->width || height != gsc->height)
+    free_glx_gc_resize(ps, gsc);
 
-  // Generate FBO and textures if needed
-  if (!pbc->textures[0])
-    pbc->textures[0] = glx_gen_texture(ps, GL_TEXTURE_2D, width, height);
-  GLuint tex_scr1 = pbc->textures[0];
-  pbc->width = width;
-  pbc->height = height;
+  // Generate textures
+  if (!gsc->textures[0])
+    gsc->textures[0] = glx_gen_texture(ps, GL_TEXTURE_2D, width, height);
+  GLuint tex_scr1 = gsc->textures[0];
+  gsc->width = width;
+  gsc->height = height;
 
   if (!tex_scr1) {
     printf_errf("(): Failed to allocate texture.");
     goto glx_greyscale_dst_end;
   }
 
-  // Texture scaling factor
-  GLfloat texfac_x = 1.0f, texfac_y = 1.0f;
-  texfac_x /= width;
-  texfac_y /= height;
-
-  // Greyscale conversion in OpenGL ES taken nearly verbatim from this answer on Stack Overflow: http://stackoverflow.com/a/9690145
-
-  // Enable texture unit 0 to divide RGB values in our texture by 2
-  glActiveTexture(GL_TEXTURE0);
   glEnable(GL_TEXTURE_2D);
+  glActiveTexture(GL_TEXTURE0);
   glBindTexture(GL_TEXTURE_2D, tex_scr1);
+  if (ptex) {
+    glActiveTexture(GL_TEXTURE1);
+    glBindTexture(GL_TEXTURE_2D, ptex->texture);
+  }
+  glActiveTexture(GL_TEXTURE0);
 
   // Read destination pixels into the GL texture
   glx_copy_region_to_tex(ps, GL_TEXTURE_2D, dx, dy, dx, dy, width, height);
 
-  // Finish setting up texture
-  glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE);
-  glClientActiveTexture(GL_TEXTURE0);
-
-  // GL_MODULATE is Arg0 * Arg1    
-  glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_RGB, GL_MODULATE);
-
-  // Configure Arg0
-  glTexEnvi(GL_TEXTURE_ENV, GL_SRC0_RGB, GL_TEXTURE);
-  glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND0_RGB, GL_SRC_COLOR);
-
-  // Configure Arg1
-  float multipliers[4] = {.5, .5, .5, 0.0};
-  glTexEnvi(GL_TEXTURE_ENV, GL_SRC1_RGB, GL_CONSTANT);
-  glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND1_RGB, GL_SRC_COLOR);
-  glTexEnvfv(GL_TEXTURE_ENV, GL_TEXTURE_ENV_COLOR, (GLfloat*)&multipliers);
-
-  // Enable texture unit 1 to increase RGB values by .5
-  glActiveTexture(GL_TEXTURE1);
-  glEnable(GL_TEXTURE_2D);
-  glBindTexture(GL_TEXTURE_2D, tex_scr1);
-  glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE);
-  glClientActiveTexture(GL_TEXTURE1);
-
-  // GL_ADD is Arg0 + Arg1
-  glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_RGB, GL_ADD);
-
-  // Configure Arg0
-  glTexEnvi(GL_TEXTURE_ENV, GL_SRC0_RGB, GL_PREVIOUS);
-  glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND0_RGB, GL_SRC_COLOR);
-
-  // Configure Arg1
-  GLfloat additions[4] = {.5, .5, .5, 0.0};
-  glTexEnvi(GL_TEXTURE_ENV, GL_SRC1_RGB, GL_CONSTANT);
-  glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND1_RGB, GL_SRC_COLOR);
-  glTexEnvfv(GL_TEXTURE_ENV, GL_TEXTURE_ENV_COLOR, (GLfloat*)&additions);
+  // Texture scaling factor
+  GLfloat texfac_x = 1.0f, texfac_y = 1.0f;
+  texfac_x /= width;
+  texfac_y /= height;
 
-  // Enable texture combiner 2 to get a DOT3_RGB product of your RGB values
-  glActiveTexture(GL_TEXTURE2);
-  glEnable(GL_TEXTURE_2D);
-  glBindTexture(GL_TEXTURE_2D, tex_scr1);
-  glClientActiveTexture(GL_TEXTURE2);
-  glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE);
-
-  // GL_DOT3_RGB is 4*((Arg0r - 0.5) * (Arg1r - 0.5) + (Arg0g - 0.5) * (Arg1g - 0.5) + (Arg0b - 0.5) * (Arg1b - 0.5))
-  glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_RGB, GL_DOT3_RGB);   
-
-  // Configure Arg0
-  glTexEnvi(GL_TEXTURE_ENV, GL_SRC0_RGB, GL_PREVIOUS);
-  glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND0_RGB, GL_SRC_COLOR);
-
-  // Configure Arg1
-  // We want this to adjust our DOT3 by R*0.3 + G*0.59 + B*0.11
-  // So, our actual adjustment will need to take into consideration
-  // the fact that OpenGL will subtract .5 from our Arg1
-  // and we need to also take into consideration that we have divided 
-  // our RGB values by 2 and we are multiplying the entire
-  // DOT3 product by 4
-  // So, for Red adjustment you will get :
-  //    .65 = (4*(0.3))/2 + 0.5  = (0.3/2) + 0.5
-  GLfloat weights[4] = {.65, .795, .555, 1.};
-  glTexEnvi(GL_TEXTURE_ENV, GL_SRC1_RGB, GL_CONSTANT);
-  glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND1_RGB, GL_SRC_COLOR);
-  glTexEnvfv(GL_TEXTURE_ENV, GL_TEXTURE_ENV_COLOR, (GLfloat*)&weights);
+//   glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
+  glUseProgram(greyscale_glsl->prog);
+  // These coefficients exactly match the non-GL greyscale conversion which uses the XRender PictOpHSLLuminosity operation
+  glUniform4f(greyscale_glsl->unifm_greyscale_weights, 0.3, 0.59, 0.11, 1.0);
+  glUniform1i(greyscale_glsl->unifm_enable_blend, ((ptex)?1:0));
+  glUniform1i(greyscale_glsl->unifm_tex_scr, 0);
+  glUniform1i(greyscale_glsl->unifm_alpha_scr, 1);
 
   // Render!
   {
@@ -1527,26 +1576,21 @@ glx_greyscale_dst(session_t *ps, int dx, int dy, int width, int height, float z,
     P_PAINTREG_END();
   }
 
-  glEnd();
-
-  // Clean up by disabling your texture combiners or texture units.
-  glActiveTexture(GL_TEXTURE2);
-  glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
-  glDisable(GL_TEXTURE_2D);
-
-  glActiveTexture(GL_TEXTURE1);
-  glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
-  glDisable(GL_TEXTURE_2D);
-
-  glActiveTexture(GL_TEXTURE0);
-  glClientActiveTexture(GL_TEXTURE0);
-  glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
+  glUseProgram(0);
 
   ret = true;
 
 glx_greyscale_dst_end:
-  if (&ibc == pbc) {
-    free_glx_gc(ps, pbc);
+  if (ptex) {
+    glActiveTexture(GL_TEXTURE1);
+    glBindTexture(GL_TEXTURE_2D, 0);
+  }
+  glActiveTexture(GL_TEXTURE0);
+  glBindTexture(GL_TEXTURE_2D, 0);
+  glDisable(GL_TEXTURE_2D);
+
+  if (&ibc == gsc) {
+    free_glx_gc(ps, gsc);
   }
 
   glx_check_err(ps);