fragment-center: New test for where the implementation samples fragments.

All drivers I've seen implement the fragment location this way (pixel
center), but I'm having a hard time locating exact specification
claiming this for polygons even though a lot of text suggests this.

3 files changed, 101 insertions, 0 deletions

diff --git a/tests/all.tests b/tests/all.tests
index edcd32ea6..77e402464 100644
--- a/tests/all.tests
+++ b/tests/all.tests
@@ -181,6 +181,7 @@ add_plain_test(general, 'draw-instanced-divisor')
 add_plain_test(general, 'draw-vertices')
 add_plain_test(general, 'draw-vertices-half-float')
 add_plain_test(general, 'fog-modes')
+add_plain_test(general, 'fragment-center')
 add_plain_test(general, 'framebuffer-srgb')
 add_plain_test(general, 'geterror-invalid-enum')
 add_plain_test(general, 'geterror-inside-begin')
diff --git a/tests/general/CMakeLists.gl.txt b/tests/general/CMakeLists.gl.txt
index 63b00e131..be8097af9 100644
--- a/tests/general/CMakeLists.gl.txt
+++ b/tests/general/CMakeLists.gl.txt
@@ -42,6 +42,7 @@ add_executable (fog-modes fog-modes.c)
 IF (UNIX)
 	target_link_libraries (fog-modes m)
 ENDIF (UNIX)
+add_executable (fragment-center fragment-center.c)
 add_executable (framebuffer-srgb framebuffer-srgb.c)
 IF (UNIX)
 	target_link_libraries (framebuffer-srgb m)
diff --git a/tests/general/fragment-center.c b/tests/general/fragment-center.c
new file mode 100644
index 000000000..631668d0a
--- /dev/null
+++ b/tests/general/fragment-center.c
@@ -0,0 +1,99 @@
+/*
+ * Copyright © 2011 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "piglit-util.h"
+
+int piglit_width = 96, piglit_height = 96;
+int piglit_window_mode = GLUT_RGB | GLUT_ALPHA | GLUT_DOUBLE;
+
+enum piglit_result
+piglit_display(void)
+{
+	bool pass = true;
+	int x, y;
+	float gray[4] = {0.5, 0.5, 0.5, 0.5};
+	float green[4] = {0.0, 1.0, 0.0, 0.0};
+
+	glClearColor(0.5, 0.5, 0.5, 0.5);
+	glClear(GL_COLOR_BUFFER_BIT);
+
+	glLoadIdentity();
+	piglit_ortho_projection(piglit_width, piglit_height, false);
+
+	glColor4f(0.0, 1.0, 0.0, 0.0);
+	for (x = 0; x <= 5; x++) {
+		for (y = 0; y <= 5; y++) {
+			float x1 = 5 + (10 + 5) * x + y * 0.2;
+			float y1 = 5 + (10 + 5) * y + x * 0.2;
+
+			piglit_draw_rect(x1, y1, 10, 10);
+		}
+	}
+
+	for (x = 0; x <= 5; x++) {
+		for (y = 0; y <= 5; y++) {
+			int x1 = 5 + (10 + 5) * x;
+			int y1 = 5 + (10 + 5) * y;
+			bool p = true;
+
+			if (x >= 3)
+				y1++;
+			if (y >= 3)
+				x1++;
+
+			p = p && piglit_probe_rect_rgba(x1, y1, 10, 10, green);
+
+			p = p && piglit_probe_rect_rgba(x1 - 1, y1,
+							1, 10, gray);
+			p = p && piglit_probe_rect_rgba(x1 + 10, y1,
+							1, 10, gray);
+			p = p && piglit_probe_rect_rgba(x1, y1 - 1,
+							10, 1, gray);
+			p = p && piglit_probe_rect_rgba(x1, y1 + 10,
+							10, 1, gray);
+
+			if (!p) {
+				printf("Failure on rectangle (%d, %d): "
+				       "offset (%f, %f)\n",
+				       x, y, y * 0.2, x * 0.2);
+				pass = false;
+			}
+		}
+	}
+
+	glutSwapBuffers();
+
+	return pass ? PIGLIT_PASS : PIGLIT_FAIL;
+}
+
+void
+piglit_init(int argc, char **argv)
+{
+
+	printf("The test's expectation is that the implementation samples\n"
+	       "at pixel centers to produce fragments, so the fourth\n"
+	       "(subpixel offset = 0.6) rectangle in each axis will\n"
+	       "be offset compared to the previous.\n\n");
+
+	piglit_ortho_projection(piglit_width, piglit_height, GL_FALSE);
+}