rework text shader, add basic and rect shaders

runtime/shaders/basic.f.glsl

@@ -0,0 +1,6 @@
+uniform vec4 color;
+
+void main(void)
+{
+    gl_FragColor = color;
+}

runtime/shaders/basic.v.glsl

@@ -0,0 +1,21 @@
+/* Viewport width and height */
+uniform ivec2 viewport_size;
+/* Position of lower left corner of glyph */
+uniform ivec2 position;
+
+/* Vertex coordinates: x, y */
+attribute vec2 coords;
+
+/**
+ * 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), 0, 1);
+}

runtime/shaders/rect.v.glsl

@@ -0,0 +1,23 @@
+/* Viewport width and height */
+uniform ivec2 viewport_size;
+/* Position of lower left corner of rectangle */
+uniform ivec2 position;
+/* Size of the rectangle */
+uniform ivec2 size;
+
+/* Vertex coordinates: x, y (0 or 1) */
+attribute ivec2 coords;
+
+/**
+ * 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 * size)), 0, 1);
+}

runtime/shaders/text.f.glsl

@@ -1,5 +1,7 @@
+/* Texture coordinate: s, t */
 varying vec2 texture_coord_v;
 
+/* Texture unit */
 uniform sampler2D texture;
 uniform vec4 color;
 

runtime/shaders/text.v.glsl

@@ -1,16 +1,25 @@
-uniform vec2 screen_size;
-uniform vec2 position;
+/* Viewport width and height */
+uniform ivec2 viewport_size;
+/* Position of lower left corner of glyph */
+uniform ivec2 position;
 
+/* Vertex coordinates: x, y, s, t */
 attribute vec4 coords;
 
+/* Output texture coordinate: s, t */
 varying 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)
 {
-    // Map coordinates such that:
-    // (0 .. screen_size.x) => (-1.0 .. 1.0)
-    gl_Position = vec4(2.0 * (position.x + coords.x) / screen_size.x - 1.0,
-                       2.0 * (position.y + coords.y) / screen_size.y - 1.0,
-                       0, 1);
+    gl_Position = vec4(map_to_screen((vec2)position + coords.xy), 0, 1);
     texture_coord_v = coords.zw;
 }