From 1e140f92296a04366fc7705d2af33b89c3c5877c Mon Sep 17 00:00:00 2001
From: Josh Holtrop <jholtrop@gmail.com>
Date: Tue, 5 Jul 2016 19:06:06 -0400
Subject: [PATCH] add "text" shader

---
 runtime/shaders/text.f.glsl | 15 +++++++++++++++
 runtime/shaders/text.v.glsl | 27 +++++++++++++++++++++++++++
 2 files changed, 42 insertions(+)
 create mode 100644 runtime/shaders/text.f.glsl
 create mode 100644 runtime/shaders/text.v.glsl

diff --git a/runtime/shaders/text.f.glsl b/runtime/shaders/text.f.glsl
new file mode 100644
index 0000000..c62195a
--- /dev/null
+++ b/runtime/shaders/text.f.glsl
@@ -0,0 +1,15 @@
+#version 410
+
+/* Texture coordinate: s, t */
+in vec2 texture_coord_v;
+
+/* Texture unit */
+uniform sampler2D texture;
+uniform vec4 color;
+
+out vec4 frag_color;
+
+void main(void)
+{
+    frag_color = vec4(1, 1, 1, texture2D(texture, texture_coord_v).a) * color;
+}
diff --git a/runtime/shaders/text.v.glsl b/runtime/shaders/text.v.glsl
new file mode 100644
index 0000000..1901809
--- /dev/null
+++ b/runtime/shaders/text.v.glsl
@@ -0,0 +1,27 @@
+#version 410
+
+/* Viewport width and height */
+uniform ivec2 viewport_size;
+/* Position of lower left corner of glyph */
+uniform ivec2 position;
+
+/* Vertex coordinates: x, y, s, t */
+layout(location = 0) in vec4 coords;
+
+/* Output texture coordinate: s, t */
+out vec2 texture_coord_v;
+
+/**
+ * Map coordinates such that:
+ * (0 .. viewport_size.[xy]) => (-1.0 .. 1.0)
+ */
+vec2 map_to_screen(vec2 position)
+{
+    return 2.0 * position / viewport_size - 1.0;
+}
+
+void main(void)
+{
+    gl_Position = vec4(map_to_screen(vec2(position) + coords.xy), 0, 1);
+    texture_coord_v = coords.zw;
+}