Initial font work

shaders/text-overlay/shader.slang

@@ -0,0 +1,28 @@
+float alphaOver(float baseAlpha, float overAlpha)
+{
+	return overAlpha + baseAlpha * (1.0 - overAlpha);
+}
+
+float4 compositeOver(float4 baseColor, float4 overColor)
+{
+	float outAlpha = alphaOver(baseColor.a, overColor.a);
+	float3 outRgb = overColor.rgb + baseColor.rgb * (1.0 - overColor.a);
+	return float4(outRgb, outAlpha);
+}
+
+float4 shadeVideo(ShaderContext context)
+{
+	float2 resolution = max(context.outputResolution, float2(1.0, 1.0));
+	float aspect = resolution.x / resolution.y;
+	float2 textSize = float2(0.72 * scale, 0.09 * scale * aspect);
+	float2 textUv = (context.uv - position) / max(textSize, float2(0.0001, 0.0001));
+
+	float mask = sampleTitleText(textUv);
+	float fill = smoothstep(0.48, 0.54, mask);
+	float outline = smoothstep(0.48 - outlineWidth, 0.54 - outlineWidth, mask);
+
+	float4 base = context.sourceColor;
+	float4 outlineLayer = float4(outlineColor.rgb * outlineColor.a, outline * outlineColor.a);
+	float4 fillLayer = float4(fillColor.rgb * fillColor.a, fill * fillColor.a);
+	return saturate(compositeOver(compositeOver(base, outlineLayer), fillLayer));
+}