[PATCH xserver 2/4] glamor: fix no-reflect case for gradients

[Jeff Smith]

When compositing a no-reflect gradient, 'before' the gradient is empty,
but 'after' the gradient is padded with the final color.  Both sides are
supposed to be empty.

This is fixed by moving the virtual stops to match the first and last
client-supplied stops for no-reflect gradients, then causing everything
'before' the initial virtual stop and 'after' the final virtual stop to
emit rgba(0,0,0,0).  This does not impact gradients using the other
reflect modes.

Signed-off-by: Jeff Smith <whydoubt at gmail.com>
---
 glamor/glamor_gradient.c | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/glamor/glamor_gradient.c b/glamor/glamor_gradient.c
index d492f6951..bb024ae4c 100644
--- a/glamor/glamor_gradient.c
+++ b/glamor/glamor_gradient.c
@@ -55,10 +55,15 @@ _glamor_create_getcolor_fs_source(ScreenPtr screen, int stops_count,
 	    "    float new_alpha; \n"\
 	    "    vec4 gradient_color;\n"\
 	    "    float percentage; \n"\
-	    "    for(i = 0; i < n_stop - 1; i++) {\n"\
+	    "    \n"\
+	    "    if(stop_len < stops[0])\n"\
+	    "        return vec4(0.0, 0.0, 0.0, 0.0); \n"\
+	    "    for(i = 1; i < n_stop; i++) {\n"\
 	    "        if(stop_len < stops[i])\n"\
 	    "            break; \n"\
 	    "    }\n"\
+	    "    if(i == n_stop)\n"\
+	    "        return vec4(0.0, 0.0, 0.0, 0.0); \n"\
 	    "    \n"\
 	    "    if(stops[i] - stops[i-1] > 2.0)\n"\
 	    "        percentage = 0.0;\n" /*For comply with pixman, walker->stepper overflow.*/\
@@ -108,10 +113,10 @@ _glamor_create_getcolor_fs_source(ScreenPtr screen, int stops_count,
         "    float percentage; \n"
         "    \n"
         "    if((stop_len < stop0) && (n_stop >= 1)) {\n"
-        "        stop_color_before = stop_color0;\n"
-        "        stop_color_after = stop_color0;\n"
-        "        stop_after = stop0;\n"
-        "        stop_before = stop0;\n"
+        "        stop_color_before = vec4(0.0, 0.0, 0.0, 0.0);\n"
+        "        stop_color_after = vec4(0.0, 0.0, 0.0, 0.0);\n"
+        "        stop_after = 0.0;\n"
+        "        stop_before = 0.0;\n"
         "    } else if((stop_len < stop1) && (n_stop >= 2)) {\n"
         "        stop_color_before = stop_color0;\n"
         "        stop_color_after = stop_color1;\n"
@@ -148,10 +153,10 @@ _glamor_create_getcolor_fs_source(ScreenPtr screen, int stops_count,
         "        stop_after = stop7;\n"
         "        stop_before = stop6;\n"
         "    } else {\n"
-        "        stop_color_before = stop_color7;\n"
-        "        stop_color_after = stop_color7;\n"
-        "        stop_after = stop7;\n"
-        "        stop_before = stop7;\n"
+        "        stop_color_before = vec4(0.0, 0.0, 0.0, 0.0);\n"
+        "        stop_color_after = vec4(0.0, 0.0, 0.0, 0.0);\n"
+        "        stop_after = 0.0;\n"
+        "        stop_before = 0.0;\n"
         "    }\n"
         "    if(stop_after - stop_before > 2.0)\n"
         "        percentage = 0.0;\n" //For comply with pixman, walker->stepper overflow.
@@ -756,13 +761,13 @@ _glamor_gradient_set_stops(PicturePtr src_picture, PictGradient *pgradient,
         stop_colors[1] = 0.0;   //G
         stop_colors[2] = 0.0;   //B
         stop_colors[3] = 0.0;   //Alpha
-        n_stops[0] = -(float) INT_MAX;  //should be small enough.
+        n_stops[0] = n_stops[1];
 
         stop_colors[0 + (count - 1) * 4] = 0.0; //R
         stop_colors[1 + (count - 1) * 4] = 0.0; //G
         stop_colors[2 + (count - 1) * 4] = 0.0; //B
         stop_colors[3 + (count - 1) * 4] = 0.0; //Alpha
-        n_stops[count - 1] = (float) INT_MAX;   //should be large enough.
+        n_stops[count - 1] = n_stops[count - 2];
         break;
     case PIXMAN_REPEAT_NORMAL:
         REPEAT_FILL_STOPS(0, count - 2);
-- 
2.14.3