glamor: Remove shader-based trapezoid implementation. Fixes Bug 76213.

I can't find any performance benefit to using the GL path and the code
renders this trapezoid incorrectly:

  		                 top: FIXED   29.50
		              bottom: FIXED   30.00
		            left top: POINT    0.00,   29.50
		         left bottom: POINT    0.00,   30.50
		           right top: POINT -127.50,   29.50
		        right bottom: POINT   52.50,   30.00

This should render a solid line from 0,30 to 52,30 but draws nothing.

The code also uses an area computation for trapezoid coverage which
does not conform to the Render specification which requires a specific
point sampling technique.

Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>

glamor/glamor.c

@@ -515,9 +515,6 @@ glamor_init(ScreenPtr screen, unsigned int flags)
 
     glamor_init_vbo(screen);
     glamor_init_pixmap_fbo(screen);
-#ifdef GLAMOR_TRAPEZOID_SHADER
-    glamor_init_trapezoid_shader(screen);
-#endif
     glamor_init_finish_access_shaders(screen);
 #ifdef GLAMOR_GRADIENT_SHADER
     glamor_init_gradient_shader(screen);
@@ -546,9 +543,6 @@ glamor_release_screen_priv(ScreenPtr screen)
 #endif
     glamor_fini_vbo(screen);
     glamor_fini_pixmap_fbo(screen);
-#ifdef GLAMOR_TRAPEZOID_SHADER
-    glamor_fini_trapezoid_shader(screen);
-#endif
     glamor_fini_finish_access_shaders(screen);
 #ifdef GLAMOR_GRADIENT_SHADER
     glamor_fini_gradient_shader(screen);

glamor/glamor_priv.h

@@ -306,9 +306,6 @@ typedef struct glamor_screen_private {
     int linear_max_nstops;
     int radial_max_nstops;
 
-    /* glamor trapezoid shader. */
-    GLint trapezoid_prog;
-
     PixmapPtr *back_pixmap;
     int screen_fbo;
     struct glamor_saved_procs saved_procs;
@@ -745,8 +742,6 @@ void glamor_composite_glyph_rects(CARD8 op,
 void glamor_composite_rects(CARD8 op,
                             PicturePtr pDst,
                             xRenderColor *color, int nRect, xRectangle *rects);
-void glamor_init_trapezoid_shader(ScreenPtr screen);
-void glamor_fini_trapezoid_shader(ScreenPtr screen);
 PicturePtr glamor_convert_gradient_picture(ScreenPtr screen,
                                            PicturePtr source,
                                            int x_source,
@@ -1089,7 +1084,6 @@ void glamor_xv_render(glamor_port_private *port_priv);
 
 #define GLAMOR_PIXMAP_DYNAMIC_UPLOAD
 #define GLAMOR_GRADIENT_SHADER
-#define GLAMOR_TRAPEZOID_SHADER
 #define GLAMOR_TEXTURED_LARGE_PIXMAP 1
 #define WALKAROUND_LARGE_TEXTURE_MAP
 #if 0