Support combined shaders+allow loading shaders from string

ui/imgui/imgui.go

@@ -149,11 +149,47 @@ func (i *ImguiInfo) AddFontTTF(fontPath string, fontSize float32, fontConfig *im
 	return f
 }
 
+const imguiShdrSrc = `
+//shader:vertex
+#version 410
+
+uniform mat4 ProjMtx;
+
+in vec2 Position;
+in vec2 UV;
+in vec4 Color;
+
+out vec2 Frag_UV;
+out vec4 Frag_Color;
+
+void main()
+{
+    Frag_UV = UV;
+    Frag_Color = Color;
+    gl_Position = ProjMtx * vec4(Position.xy, 0, 1);
+}
+
+//shader:fragment
+#version 410
+
+uniform sampler2D Texture;
+
+in vec2 Frag_UV;
+in vec4 Frag_Color;
+
+out vec4 Out_Color;
+
+void main()
+{
+    Out_Color = vec4(Frag_Color.rgb, Frag_Color.a * texture(Texture, Frag_UV.st).r);
+}
+`
+
 func NewImGUI() ImguiInfo {
 
 	imguiInfo := ImguiInfo{
 		ImCtx: imgui.CreateContext(nil),
-		Mat:   materials.NewMaterial("ImGUI Mat", "./res/shaders/imgui"),
+		Mat:   materials.NewMaterialSrc("ImGUI Mat", []byte(imguiShdrSrc)),
 	}
 
 	imIO := imgui.CurrentIO()