722315 - Increase Firefox startup speed by ~5% (-76ms) on Windows by lazy loading CLSID_DragDropHelper

Status: RESOLVED FIXED

(Core :: Widget: Win32, defect)

Description

[Brian R. Bondy [:bbondy]]

Attachment: Patch v1.

When profiling nsWindow.cpp in Windows I found that enabling drag and drop uses ~70ms on app startup.

> NAME: nsWindow::EnableDragDrop 
> Count: 3 
> Total: 0.076:01
> Min: 0.000:00
> Max: 0.076:01
> Average: 0.025:33
> App start time until first paint: 0.890:00


Upon further inspection this all comes from nsNativeDragTarget and in particular: 

> CoCreateInstance(CLSID_DragDropHelper, NULL, CLSCTX_INPROC_SERVER,
                    
>                  IID_IDropTargetHelper, (LPVOID*)&mDropTargetHelper);


mDropTargetHelper isn't needed though until a drag actually happens.
For that reason we can lazy load it instead and save the complete 76ms from startup.

Comment 1

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

Nice.

Comment 2

[Brian R. Bondy [:bbondy]]

http://hg.mozilla.org/integration/mozilla-inbound/rev/740c10e98e7c

Comment 3

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/740c10e98e7c