example: add font_sdf.zig

examples/text/resources/shaders/glsl100/alpha_discard.fs

@@ -0,0 +1,20 @@
+#version 100
+
+precision mediump float;
+
+// Input vertex attributes (from vertex shader)
+varying vec2 fragTexCoord;
+varying vec4 fragColor;
+
+// Input uniform values
+uniform sampler2D texture0;
+uniform vec4 colDiffuse;
+
+void main()
+{
+    vec4 texelColor = texture2D(texture0, fragTexCoord);
+
+    if (texelColor.a == 0.0) discard;
+
+    gl_FragColor = texelColor*fragColor*colDiffuse;
+}

examples/text/resources/shaders/glsl100/sdf.fs

@@ -0,0 +1,25 @@
+#version 100
+
+precision mediump float;
+
+// Input vertex attributes (from vertex shader)
+varying vec2 fragTexCoord;
+varying vec4 fragColor;
+
+// Input uniform values
+uniform sampler2D texture0;
+uniform vec4 colDiffuse;
+
+// NOTE: Add your custom variables here
+const float smoothing = 1.0/16.0;
+
+void main()
+{
+    // Texel color fetching from texture sampler
+    // NOTE: Calculate alpha using signed distance field (SDF)
+    float distance = texture2D(texture0, fragTexCoord).a;
+    float alpha = smoothstep(0.5 - smoothing, 0.5 + smoothing, distance);
+
+    // Calculate final fragment color
+    gl_FragColor = vec4(fragColor.rgb, fragColor.a*alpha);
+}