lib/gamnit: intro the standalone triangle example for desktop only

[nit.git] / lib / gamnit / examples / triangle / src / standalone_triangle.nit

diff --git a/lib/gamnit/examples/triangle/src/standalone_triangle.nit b/lib/gamnit/examples/triangle/src/standalone_triangle.nit
new file mode 100644 (file)
index 0000000..04e14db
--- /dev/null
+++ b/lib/gamnit/examples/triangle/src/standalone_triangle.nit
@@ -0,0 +1,112 @@
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Example of using `GamnitDisplay` to setup a screen for custom calls to OpenGL ES 2.0
+#
+# This example does not support the lifecycle of mobile platforms, as such it only works on desktop computers.
+#
+# References:
+# * The book OpenGL ES 2.0 Programming Guide
+# * https://code.google.com/p/opengles-book-samples/source/browse/trunk/LinuxX11/Chapter_2/Hello_Triangle/Hello_Triangle.c
+module standalone_triangle
+
+import app
+import gamnit::display
+
+if "NIT_TESTING".environ == "true" then exit(0)
+
+# Setup gamnit
+var display = new GamnitDisplay
+display.setup
+
+var width = display.width
+var height = display.height
+print "Width: {width}"
+print "Height: {height}"
+
+# Custom calls to OpenGL ES 2.0
+assert_no_gl_error
+assert gl.shader_compiler else print "Cannot compile shaders"
+
+# GL program
+print gl.error.to_s
+var program = new GLProgram
+if not program.is_ok then
+       print "Program is not ok: {gl.error.to_s}\nLog:"
+       print program.info_log
+       abort
+end
+assert_no_gl_error
+
+# Vertex shader
+var vertex_shader = new GLVertexShader
+assert vertex_shader.is_ok else print "Vertex shader is not ok: {gl.error}"
+vertex_shader.source = """
+attribute vec4 vPosition;
+void main()
+{
+  gl_Position = vPosition;
+}
+"""@glsl_vertex_shader.to_cstring
+vertex_shader.compile
+assert vertex_shader.is_compiled else print "Vertex shader compilation failed with: {vertex_shader.info_log} {program.info_log}"
+assert_no_gl_error
+
+# Fragment shader
+var fragment_shader = new GLFragmentShader
+assert fragment_shader.is_ok else print "Fragment shader is not ok: {gl.error}"
+fragment_shader.source = """
+precision mediump float;
+void main()
+{
+       gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
+}
+"""@glsl_fragment_shader.to_cstring
+fragment_shader.compile
+assert fragment_shader.is_compiled else print "Fragment shader compilation failed with: {fragment_shader.info_log}"
+assert_no_gl_error
+
+# Attach to program
+program.attach_shader vertex_shader
+program.attach_shader fragment_shader
+program.bind_attrib_location(0, "vPosition")
+program.link
+assert program.is_linked else print "Linking failed: {program.info_log}"
+assert_no_gl_error
+
+# Draw!
+var vertices = [0.0, 0.5, 0.0, -0.5, -0.5, 0.0, 0.5, -0.5, 0.0]
+var vertex_array = new VertexArray(0, 3, vertices)
+vertex_array.attrib_pointer
+gl.clear_color(0.5, 0.0, 0.5, 1.0)
+for i in [0..1000[ do
+       printn "."
+       assert_no_gl_error
+       gl.viewport(0, 0, width, height)
+       gl.clear((new GLBuffer).color)
+       program.use
+       vertex_array.enable
+
+       glDrawArrays(new GLDrawMode.triangles, 0, 3)
+
+       display.flip
+end
+
+# Clean up
+program.delete
+vertex_shader.delete
+fragment_shader.delete
+
+# Close gamnit
+display.close