render/gles2: move shaders to individual files

Instead of having a C file with strings for each shader, move each
shader into its own file. Use a small POSIX shell script to convert
the files into C strings (can't wait for C23 #embed...).

The benefits from this are:

- Improved readability and syntax highlighting.
- Line numbers in shader compiler errors are easier to make sense of.
- Consistency with the Vulkan renderer.
- Shaders will become more complicated as we add color management
  features.

render/gles2/shaders/embed.sh

@@ -0,0 +1,11 @@
+#!/bin/sh -eu
+
+var=${1:-data}
+hex="$(od -A n -t x1 -v)"
+
+echo "static const char $var[] = {"
+for byte in $hex; do
+	echo "	0x$byte,"
+done
+echo "	0x00,"
+echo "};"

render/gles2/shaders/meson.build

@@ -0,0 +1,23 @@
+embed = find_program('./embed.sh', native: true)
+
+shaders = [
+	'quad.vert',
+	'quad.frag',
+	'tex.vert',
+	'tex_rgba.frag',
+	'tex_rgbx.frag',
+	'tex_external.frag',
+]
+
+foreach name : shaders
+	output = name.underscorify() + '_src.h'
+	var = name.underscorify() + '_src'
+	wlr_files += custom_target(
+		output,
+		command: [embed, var],
+		input: name,
+		output: output,
+		feed: true,
+		capture: true,
+	)
+endforeach

render/gles2/shaders/quad.frag

@@ -0,0 +1,7 @@
+precision mediump float;
+varying vec4 v_color;
+varying vec2 v_texcoord;
+
+void main() {
+	gl_FragColor = v_color;
+}

render/gles2/shaders/quad.vert

@@ -0,0 +1,12 @@
+uniform mat3 proj;
+uniform vec4 color;
+attribute vec2 pos;
+attribute vec2 texcoord;
+varying vec4 v_color;
+varying vec2 v_texcoord;
+
+void main() {
+	gl_Position = vec4(proj * vec3(pos, 1.0), 1.0);
+	v_color = color;
+	v_texcoord = texcoord;
+}

render/gles2/shaders/tex.vert

@@ -0,0 +1,9 @@
+uniform mat3 proj;
+attribute vec2 pos;
+attribute vec2 texcoord;
+varying vec2 v_texcoord;
+
+void main() {
+	gl_Position = vec4(proj * vec3(pos, 1.0), 1.0);
+	v_texcoord = texcoord;
+}

render/gles2/shaders/tex_external.frag

@@ -0,0 +1,10 @@
+#extension GL_OES_EGL_image_external : require
+
+precision mediump float;
+varying vec2 v_texcoord;
+uniform samplerExternalOES texture0;
+uniform float alpha;
+
+void main() {
+	gl_FragColor = texture2D(texture0, v_texcoord) * alpha;
+}

render/gles2/shaders/tex_rgba.frag

@@ -0,0 +1,8 @@
+precision mediump float;
+varying vec2 v_texcoord;
+uniform sampler2D tex;
+uniform float alpha;
+
+void main() {
+	gl_FragColor = texture2D(tex, v_texcoord) * alpha;
+}

render/gles2/shaders/tex_rgbx.frag

@@ -0,0 +1,8 @@
+precision mediump float;
+varying vec2 v_texcoord;
+uniform sampler2D tex;
+uniform float alpha;
+
+void main() {
+	gl_FragColor = vec4(texture2D(tex, v_texcoord).rgb, 1.0) * alpha;
+}