Add utility function piglit_draw_triangle

These utility functions to draw triangle would help in testing antialiasing
and depth related issues.

v2: Defined piglit_draw_triangle in terms of piglit_draw_triangle_z. Modified
    the comments
Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Brian Paul <brianp@vmware.com>

tests/util/piglit-util-gl.c

@@ -707,6 +707,46 @@ piglit_escape_exit_key(unsigned char key, int x, int y)
 	glutPostRedisplay();
 }
 
+/**
+ * Convenience function to draw a triangle.
+ */
+GLvoid
+piglit_draw_triangle(float x1, float y1, float x2, float y2,
+		     float x3, float y3)
+{
+	piglit_draw_triangle_z(0.0, x1, y1, x2, y2, x3, y3);
+}
+
+/**
+ * Convenience function to draw a triangle at a given depth.
+ */
+GLvoid
+piglit_draw_triangle_z(float z, float x1, float y1, float x2, float y2,
+		     float x3, float y3)
+{
+	float verts[3][4];
+
+	verts[0][0] = x1;
+	verts[0][1] = y1;
+	verts[0][2] = z;
+	verts[0][3] = 1.0;
+	verts[1][0] = x2;
+	verts[1][1] = y2;
+	verts[1][2] = z;
+	verts[1][3] = 1.0;
+	verts[2][0] = x3;
+	verts[2][1] = y3;
+	verts[2][2] = z;
+	verts[2][3] = 1.0;
+
+	glVertexPointer(4, GL_FLOAT, 0, verts);
+	glEnableClientState(GL_VERTEX_ARRAY);
+
+	glDrawArrays(GL_TRIANGLES, 0, 3);
+
+	glDisableClientState(GL_VERTEX_ARRAY);
+}
+
 /**
  * Convenience function to draw an axis-aligned rectangle.
  */

tests/util/piglit-util.h

@@ -232,6 +232,10 @@ int piglit_use_vertex_program(void);
 void piglit_require_fragment_program(void);
 void piglit_require_vertex_program(void);
 GLuint piglit_compile_program(GLenum target, const char* text);
+GLvoid piglit_draw_triangle(float x1, float y1, float x2, float y2,
+			    float x3, float y3);
+GLvoid piglit_draw_triangle_z(float z, float x1, float y1, float x2, float y2,
+			      float x3, float y3);
 GLvoid piglit_draw_rect(float x, float y, float w, float h);
 GLvoid piglit_draw_rect_z(float z, float x, float y, float w, float h);
 GLvoid piglit_draw_rect_tex(float x, float y, float w, float h,