Experiments in early binding com object with D.

[Vinod K Chandran]

On Tuesday, 4 November 2025 at 10:27:13 UTC, Dennis wrote:
> On Monday, 3 November 2025 at 16:51:25 UTC, Vinod K Chandran 
> wrote:
>> I was worrying that there is no com support except the basic 
>> building blocks like IUnknown and siblings. I know there is a 
>> com library in Adam's arsd. But I couldn't successfully use 
>> that. When I first tried Adam's library, I dreamed to write a 
>> com client in D one day. When time permitted, I slowly 
>> collected information about com and gradually made a 
>> confidence to start with early binding. I want to make my 
>> library high performance, so I choose early binding path.
>
> I have succesfully made a D program connect to Excel using 
> arsd.com last year. My strategy was to ask ChatGPT to give 
> examples using Python win32com and then translate those calls 
> to D by sometimes adding extra parenthesis (because of 
> limitations of @property / opDispatch). The resulting code 
> looks something like this:
>
> ```D
> const choice = cell.Value().getD!string.ifThrown!Exception("");
>
> // ...
>
> auto c1 = sheet.Cells()(varsRow + i, varsValueColumn);
> c1.Formula() = "=" ~ cs;
> c1.Interior().Color() = color;
> ```
>
> It's using the dynamic IDispatch interface instead of static 
> bindings, which might be slower, but most calls take 
> milliseconds to complete anyways and I highly doubt that all 
> that time is spent on dynamic dispatch. The COM bridge and MS 
> Office applications seem to be the limiting factor.
>
> I recommend to start with dynamic calls and maybe create 
> bindings from idl files later. If you explain what went wrong 
> using arsd.com maybe I or someone else can help.

Performance is my aim. In tight loops, late binding causes a 
significant delay. So I decided to use early binding, at least 
for MS Word. But yes, I can use a hybrid plan for other COM 
objects. I actually cannot remember the exact problem I faced 
with arsd.com. I was trying to use the COM object provided by 
QTTabBar (my file manager plugin), but ARSD couldn't connect to 
it. At that time, Adam suggested some tweaks, but they didn't 
work well. I think I can reproduce the issue, and I will let you 
know for sure. Thanks for your reply.