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gui-wl: Correct the previous cursor fix

The Plan 9 cursor bitmap is transformed into an ARGB8888 surface to be displayed by the
Wayland compositor. However, the mask used to decide the pixel colour was incorrect.

When j = 0 the mask is 1<<16 which is not valid.
When j = 15 the mask is 1<<1 which is not the final pixel.
This results in the cursor image being shifted 1px right, off the edge of the surface.
The correct mask is (1<<15) >> j;

Thanks moody for cleaning up the patch.

--- a/gui-wl/wl-util.c

+++ b/gui-wl/wl-util.c

@@ -54,7 +54,7 @@

 	depth = 4;

 	screensize = wl->monx * wl->mony * depth;

-	cursorsize = 32 * 32 * depth;

+	cursorsize = 16 * 16 * depth;

 	fd = wlcreateshm(screensize+cursorsize);

 	if(fd < 0)

@@ -90,7 +90,7 @@

 		wl_buffer_destroy(wl->cursorbuffer);

 	wl->screenbuffer = wl_shm_pool_create_buffer(wl->pool, 0, wl->dx, wl->dy, wl->dx*4, WL_SHM_FORMAT_XRGB8888);

-	wl->cursorbuffer = wl_shm_pool_create_buffer(wl->pool, size, 32, 32, 32*4, WL_SHM_FORMAT_ARGB8888);

+	wl->cursorbuffer = wl_shm_pool_create_buffer(wl->pool, size, 16, 16, 16*4, WL_SHM_FORMAT_ARGB8888);

 }

 enum {

@@ -109,26 +109,27 @@

 	uint16_t clr[16], set[16];

 	buf = wl->shm_data+(wl->dx*wl->dy*4);

-	for(i=0,j=0; i < 16; i++,j+=2){

+	for(i = 0, j = 0; i < 16; i++, j += 2){

 		clr[i] = c->clr[j]<<8 | c->clr[j+1];

 		set[i] = c->set[j]<<8 | c->set[j+1];

 	}

-	for(i=0; i < 32; i++){

-		for(j = 0; j < 32; j++){

-			pos = i*32 + j;

-			mask = (1<<16) >> j;

+	for(i = 0, pos = 0; i < 16; i++){

+		for(j = 0; j < 16; j++, pos++){

+			mask = (1<<15) >> j;

 			buf[pos] = Transparent;

-			if(i < 16 && clr[i] & mask)

+			if(clr[i] & mask)

 				buf[pos] = White;

-			if(i < 16 && set[i] & mask)

+			if(set[i] & mask)

 				buf[pos] = Black;

 		}

 	}

+

 	if(wl->cursorsurface == nil)

 		wl->cursorsurface = wl_compositor_create_surface(wl->compositor);

+

 	wl_surface_attach(wl->cursorsurface, wl->cursorbuffer, 0, 0);

-	wl_surface_damage(wl->cursorsurface, 0, 0, 32, 32);

+	wl_surface_damage(wl->cursorsurface, 0, 0, 16, 16);

 	wl_surface_commit(wl->cursorsurface);

 	wl_pointer_set_cursor(wl->pointer, wl->pointerserial, wl->cursorsurface, -c->offset.x, -c->offset.y);

 }