Bidirectional live programming systems (BLP) enable developers to modify the program by directly manipulating the program output, so that the modified program can produce the manipulated output. One state-of-the-art approach to the construction of BLP systems is operation-based, which captures the developer’s intention of program modification by taking how the developer manipulates the output into account. However, in order to reflect operations on the output to the source program, it needs the trace information between the source code and the manipulated output, and thus requires that direct manipulation users be aware of the source code, which makes “direct” manipulation (on output) be “indirect”.

In this paper, we resolve this problem by presenting a novel operation-based framework for bidirectional live programming, which can automatically fuse direct manipulations into the source code, thus supporting code-insensitive direct manipulations. Firstly, we design a simple but expressive delta language DM capable of expressing common direct manipulations for output values. Secondly, we present a fusion algorithm that propagates direct manipulations into the source functional programs and applies them to the constants whenever possible; otherwise, the algorithm embeds manipulations into the “proper positions” of programs. We prove the correctness of the fusion algorithm that the modified program executes to get the manipulated output. To demonstrate the expressiveness of DM and the effectiveness of our fusion algorithm, we have implemented FuseDM, a prototype SVG editor that supports GUI-based operations for direct manipulation, and successfully designed 14 benchmark examples starting from blank code using FuseDM.