It is possible for an application to bind more than one
attribute name to the same location. This is referred to as
aliasing. It is allowed in: OpenGL 2.0 (and above) and
OpenGL ES 2.0. This test varifies that aliasing can be used
successfully in a vertex shader.

Signed-off-by: Anuj Phogat <[email protected]>
---
 tests/spec/CMakeLists.txt                          |   1 +
 .../arb_explicit_attrib_location/CMakeLists.gl.txt |  13 ++
 .../arb_explicit_attrib_location/CMakeLists.txt    |   1 +
 .../overlapping-locations-input-attribs.c          | 215 +++++++++++++++++++++
 4 files changed, 230 insertions(+)
 create mode 100644 tests/spec/arb_explicit_attrib_location/CMakeLists.gl.txt
 create mode 100644 tests/spec/arb_explicit_attrib_location/CMakeLists.txt
 create mode 100644 
tests/spec/arb_explicit_attrib_location/overlapping-locations-input-attribs.c

diff --git a/tests/spec/CMakeLists.txt b/tests/spec/CMakeLists.txt
index 0a513c1..840ac9a 100644
--- a/tests/spec/CMakeLists.txt
+++ b/tests/spec/CMakeLists.txt
@@ -9,6 +9,7 @@ add_subdirectory (khr_debug)
 add_subdirectory (arb_depth_clamp)
 add_subdirectory (arb_draw_instanced)
 add_subdirectory (arb_es2_compatibility)
+add_subdirectory (arb_explicit_attrib_location)
 add_subdirectory (arb_framebuffer_object)
 add_subdirectory (arb_framebuffer_srgb)
 add_subdirectory (arb_geometry_shader4)
diff --git a/tests/spec/arb_explicit_attrib_location/CMakeLists.gl.txt 
b/tests/spec/arb_explicit_attrib_location/CMakeLists.gl.txt
new file mode 100644
index 0000000..4926401
--- /dev/null
+++ b/tests/spec/arb_explicit_attrib_location/CMakeLists.gl.txt
@@ -0,0 +1,13 @@
+include_directories(
+       ${GLEXT_INCLUDE_DIR}
+       ${OPENGL_INCLUDE_PATH}
+       ${piglit_SOURCE_DIR}/tests/mesa/util
+)
+
+link_libraries (
+       piglitutil_${piglit_target_api}
+       ${OPENGL_gl_LIBRARY}
+       ${OPENGL_glu_LIBRARY}
+)
+
+piglit_add_executable 
(arb_explicit_attrib_location-overlapping-locations-input-attribs 
overlapping-locations-input-attribs.c)
diff --git a/tests/spec/arb_explicit_attrib_location/CMakeLists.txt 
b/tests/spec/arb_explicit_attrib_location/CMakeLists.txt
new file mode 100644
index 0000000..4a012b9
--- /dev/null
+++ b/tests/spec/arb_explicit_attrib_location/CMakeLists.txt
@@ -0,0 +1 @@
+piglit_include_target_api()
\ No newline at end of file
diff --git 
a/tests/spec/arb_explicit_attrib_location/overlapping-locations-input-attribs.c 
b/tests/spec/arb_explicit_attrib_location/overlapping-locations-input-attribs.c
new file mode 100644
index 0000000..5fd1296
--- /dev/null
+++ 
b/tests/spec/arb_explicit_attrib_location/overlapping-locations-input-attribs.c
@@ -0,0 +1,215 @@
+/*
+ * Copyright © 2014 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.
+ */
+
+/** \file overlapping-locations-input-attribs.c
+ * From OpenGL 4.0 spec, page 61:
+ *
+ *     "It is possible for an application to bind more than one
+ *     attribute name to the same location. This is referred to as
+ *     aliasing. This will only work if only one of the aliased
+ *     attributes is active in the executable program, or if no
+ *     path through the shader consumes more than one attribute of
+ *     a set of attributes aliased to the same location. A link
+ *     error can occur if the linker determines that every path
+ *     through the shader consumes multiple aliased attributes,
+ *     but implementations are not required to generate an error
+ *     in this case."
+ *
+ *     Aliasing of vertex input variables is allowed in: OpenGL
+ *     2.0 (and above) and OpenGL ES 2.0. This test varifies
+ *     that aliasing can be used successfully in a vertex shader
+ *     under the constraints defined in OpenGL spec.
+ */
+
+#include "piglit-util-gl-common.h"
+
+PIGLIT_GL_TEST_CONFIG_BEGIN
+
+       config.supports_gl_compat_version = 21;
+       config.supports_gl_core_version = 31;
+
+       config.window_width = 128;
+       config.window_height = 128;
+       config.window_visual = PIGLIT_GL_VISUAL_DOUBLE | PIGLIT_GL_VISUAL_RGBA;
+
+PIGLIT_GL_TEST_CONFIG_END
+
+static bool locations_in_shader;
+static unsigned prog, vao, vertex_buf;
+
+void
+compile_shader(void)
+{
+       GLuint element_buf;
+       unsigned int indices[6] = { 0, 1, 2, 0, 2, 3 };
+       float vertex_data[4][11] = {
+               /* vertex     color0:green    color1:blue     color2:yellow */
+               {-1.0, -1.0,  0.0, 1.0, 0.0,  0.0, 0.0, 1.0,  1.0, 1.0, 0.0},
+               {-1.0,  1.0,  0.0, 1.0, 0.0,  0.0, 0.0, 1.0,  1.0, 1.0, 0.0},
+               { 1.0,  1.0,  0.0, 1.0, 0.0,  0.0, 0.0, 1.0,  1.0, 1.0, 0.0},
+               { 1.0, -1.0,  0.0, 1.0, 0.0,  0.0, 0.0, 1.0,  1.0, 1.0, 0.0}};
+
+       static const char *vert_template =
+               "#version 130\n"
+               "%s\n"
+               "out vec4 color;\n"
+               "uniform int x;\n"
+               "void main()\n"
+               "{\n"
+               "  gl_Position =vec4(vertex, 0, 1);\n"
+               "  switch(x) {\n"
+               "  case 0:\n"
+               "    color =vec4(color0, 1.0);\n"
+               "    break;\n"
+               "  case 1:\n"
+               "    color = vec4(color1, 1.0);\n"
+               "    break;\n"
+               "  case 2:\n"
+               "    color = vec4(color2, 1.0);\n"
+               "    break;\n"
+               "  default:\n"
+               "    color = vec4(1.0);;\n"
+               "  }\n"
+               "}\n";
+
+       static const char *frag =
+               "#version 130\n"
+               "in vec4 color;\n"
+               "out vec4 out_color;\n"
+               "void main()\n"
+               "{\n"
+               "    out_color = color;\n"
+               "}\n";
+
+       char *vert;
+       asprintf(&vert, vert_template, locations_in_shader ?
+                "#extension GL_ARB_explicit_attrib_location : require\n"
+                "layout (location = 0) in vec2 vertex;\n"
+                "layout (location = 1) in vec3 color0;\n"
+                "layout (location = 1) in vec3 color1;\n"
+                "layout (location = 1) in vec3 color2;\n" :
+                "in vec2 vertex;\n"
+                "in vec3 color0;\n"
+                "in vec3 color1;\n"
+                "in vec3 color2;\n");
+
+       prog = piglit_build_simple_program_unlinked(vert, frag);
+       if (!locations_in_shader) {
+               glBindAttribLocation(prog, 0, "vertex");
+               glBindAttribLocation(prog, 1, "color0");
+               glBindAttribLocation(prog, 1, "color1");
+               glBindAttribLocation(prog, 1, "color2");
+       }
+       glLinkProgram(prog);
+
+       if (!piglit_link_check_status(prog))
+               piglit_report_result(PIGLIT_FAIL);
+
+       /* Set up vertex array object */
+       glGenVertexArrays(1, &vao);
+       glBindVertexArray(vao);
+
+       /* Set up vertex input buffer */
+       glGenBuffers(1, &vertex_buf);
+       glBindBuffer(GL_ARRAY_BUFFER, vertex_buf);
+       glBufferData(GL_ARRAY_BUFFER, sizeof(vertex_data), vertex_data,
+                    GL_STREAM_DRAW);
+
+       glEnableVertexAttribArray(0);
+       glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 11*sizeof(float),
+                             (void *) 0);
+       glEnableVertexAttribArray(1);
+
+       /* Set up element input buffer to tesselate a quad into
+        * triangles
+        */
+       glGenBuffers(1, &element_buf);
+       glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, element_buf);
+       glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices,
+                    GL_STATIC_DRAW);
+}
+
+static void
+print_usage_and_exit(char *prog_name)
+{
+       printf("Usage: %s <set_location>\n"
+              "  where <set_location> is one of:\n"
+              "    shader: set locations of input variables in shader 
program\n"
+              "    api: set locations of input variables using api\n",
+              prog_name);
+
+       piglit_report_result(PIGLIT_FAIL);
+}
+
+void
+piglit_init(int argc, char **argv)
+{
+       if (argc != 2)
+               print_usage_and_exit(argv[0]);
+
+       /* 1st arg: location */
+       if(strcmp(argv[1], "shader") != 0 &&
+          strcmp(argv[1], "api") != 0)
+               print_usage_and_exit(argv[0]);
+
+       locations_in_shader = strcmp(argv[1], "shader") == 0;
+
+       if (locations_in_shader)
+               piglit_require_extension("GL_ARB_explicit_attrib_location");
+
+       piglit_require_extension("GL_ARB_vertex_array_object");
+       piglit_require_GLSL_version(130);
+       compile_shader();
+       if (!piglit_check_gl_error(GL_NO_ERROR))
+               piglit_report_result(PIGLIT_FAIL);
+}
+
+enum piglit_result
+piglit_display()
+{
+       int i;
+       bool pass = true;
+       float expected[3][4] = {
+               {0.0, 1.0, 0.0, 1.0}, /* green */
+               {0.0, 0.0, 1.0, 1.0}, /* blue */
+               {1.0, 1.0, 0.0, 1.0}}; /* yellow */
+
+       glUseProgram(prog);
+
+       for(i = 0; i < 3; i++) {
+               glUniform1i(glGetUniformLocation(prog, "x"), i);
+
+               /* Setup VertexAttribPointer for location=1. There should be
+                * only one active attribute pointer set to the shared location
+                * '1' at a time.
+                */
+               glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 
11*sizeof(float),
+                                     (void *) ((2 + 3*i) * sizeof(float)));
+
+               glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, (void *) 0);
+               pass = piglit_probe_rect_rgba(0, 0, piglit_width, piglit_height,
+                                             expected[i]) && pass;
+               piglit_present_results();
+       }
+       return pass ? PIGLIT_PASS : PIGLIT_FAIL;
+}
-- 
1.8.3.1

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