[igt-dev] [PATCH i-g-t] tests/kms_plane_alpha_blend: Paint FBs with cairo source operator

[Nicholas Kazlauskas]

Cairo defaults to using a blended fill, so when IGT tries to paint on
top of a framebuffer in these tests with an alpha less than 1.0 the
previous framebuffer contents will still be present underneath.

On amdgpu this is an issue because the framebuffer is created in
an unitialized state and can have contents from previous tests
still within memory.

This patch explicitly sets the cairo filling operator to SOURCE to
overwrite the contents when performing fills with alpha < 1.0 in
this test.

It also fixes the creation of the transparent FB. My guess as for why
this test previously passed on i915 is because the primary FB was
also black, so the CRC would match even if the black overlay plane
was partially transparent.

Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
---
 tests/kms_plane_alpha_blend.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tests/kms_plane_alpha_blend.c b/tests/kms_plane_alpha_blend.c
index 1d9d8933..d7dc44ab 100644
--- a/tests/kms_plane_alpha_blend.c
+++ b/tests/kms_plane_alpha_blend.c
@@ -83,6 +83,7 @@ static void draw_squares(struct igt_fb *fb, int w, int h, double a)
 {
 	cairo_t *cr = igt_get_cairo_ctx(fb->fd, fb);
 
+	cairo_set_operator(cr, CAIRO_OPERATOR_SOURCE);
 	igt_paint_color_alpha(cr, 0, 0,         w / 2, h / 2, 1., 0., 0., a);
 	igt_paint_color_alpha(cr, w / 2, 0,     w / 2, h / 2, 0., 1., 0., a);
 	igt_paint_color_alpha(cr, 0, h / 2,     w / 2, h / 2, 0., 0., 1., a);
@@ -197,7 +198,8 @@ static void prepare_crtc(data_t *data, igt_output_t *output, enum pipe pipe)
 			      &data->argb_fb_0);
 
 		cr = igt_get_cairo_ctx(data->gfx_fd, &data->argb_fb_0);
-		igt_paint_color_alpha(cr, 0, 0, w, h, 0., 0., 0., 1.0);
+		cairo_set_operator(cr, CAIRO_OPERATOR_SOURCE);
+		igt_paint_color_alpha(cr, 0, 0, w, h, 0., 0., 0., 0.0);
 		igt_put_cairo_ctx(data->gfx_fd, &data->argb_fb_0, cr);
 
 		igt_create_fb(data->gfx_fd, w, h,
-- 
2.17.1