clients/simple-vulkan: New Vulkan client example

Example to serve as a reference of a basic Wayland client using
Vulkan, contained in a single source file and with a minimal set
of dependencies.
Features incremental present (similar to swap_buffers_with_damage
from EGL) which is not commonly used by other Vulkan demos and is
useful to test the compositor.
Based on weston-simple-egl.

Signed-off-by: Erico Nunes <nunes.erico@gmail.com>

clients/meson.build

@@ -172,6 +172,47 @@ simple_clients = [
 	},
 ]
 
+if dep_vulkan.found() and prog_glslang.found()
+	srcs_simple_vulkan_shaders = [
+		'simple_vulkan_vertex_shader.vert',
+		'simple_vulkan_fragment_shader.frag',
+	]
+
+	simple_vulkan_shaders = []
+	foreach s : srcs_simple_vulkan_shaders
+		simple_vulkan_shaders += custom_target(s + '.spv.h',
+			command: [ prog_glslang, '@INPUT@', '--quiet', '--variable-name', '@BASENAME@', '-V', '-x', '-o', '@OUTPUT@' ],
+			input: s,
+			output: '@BASENAME@.spv.h',
+		)
+	endforeach
+
+	simple_clients += {
+		'name': 'vulkan',
+		'sources': [
+			'simple-vulkan.c',
+			simple_vulkan_shaders,
+			fractional_scale_v1_client_protocol_h,
+			fractional_scale_v1_protocol_c,
+			tearing_control_v1_client_protocol_h,
+			tearing_control_v1_protocol_c,
+			viewporter_client_protocol_h,
+			viewporter_protocol_c,
+			xdg_shell_client_protocol_h,
+			xdg_shell_protocol_c,
+		],
+		'dep_objs': [
+			dep_vulkan,
+			dep_libm,
+			dep_libshared,
+			dep_matrix_c,
+			dep_wayland_client,
+		],
+		'deps': [ 'vulkan', 'wayland-cursor' ],
+		'options': [ 'renderer-gl' ]
+	}
+endif
+
 foreach t : simple_clients
 	if simple_build_all or simple_clients_enabled.contains(t.get('name'))
 		t_name = 'weston-simple-' + t.get('name')

clients/simple_vulkan_fragment_shader.frag

@@ -0,0 +1,9 @@
+#version 450 core
+
+layout(location = 0) in vec4 vVaryingColor;
+layout(location = 0) out vec4 f_color;
+
+void main()
+{
+	f_color = vVaryingColor;
+}

clients/simple_vulkan_vertex_shader.vert

@@ -0,0 +1,16 @@
+#version 450 core
+
+layout(std140, set = 0, binding = 0) uniform block {
+	uniform mat4 rotation;
+};
+
+layout(location = 0) in vec4 in_position;
+layout(location = 1) in vec4 in_color;
+
+layout(location = 0) out vec4 vVaryingColor;
+
+void main()
+{
+	gl_Position = rotation * in_position;
+	vVaryingColor = vec4(in_color.rgba);
+}