Understanding LibreOffice Source Code

Menu Dropdown

Menu Dropdown

I put a breakpoint at libo/vcl/source/window/winproc.cxx:2405, at the case SAL_EVENTMOUSEDOWN, to see
what happens when I click a mouse. 

I clicked on File Menu, it hit the breakpoint. Then off it goes to calls ImplHandleSalMouseButtonDown () 
with the following details stored in pEvent and pWindow.

pEvent
    mnTime = 78764380 //Time
    mnX = 18 //x co-ordinate
    mnY = 9  //y co-ordinate
    mnButton = 1  //left button, 4 for right click, 2 for clicking with the scroller
    mnCode = 0  //to find whether click is part of some select etc.

pWindow - the window object.
    
The ImplHandleSalMouseButtonDown () function is in ./libo/vcl/source/window/winproc.cxx:2068, it checks
whether shift, ctrl or alt keys were pressed in 2076, and then calls ImplGetMouseButtonMode () with pEvent
(function is at ./libo/vcl/source/window/winproc.cxx:2030) to get further details of whether it is a simple
click event or whether it is part of select, multi (ctrl+click?) or range select, using pEvent's mnCode 
variable. 

The ImplGetMouseButtonMode () function returns nMode as 3. The first two if statements were true, ie.
MOUSE_SIMPLECLICK and MOUSE_SELECT. Once, this returns, ImplHandleSalMouseButtonDown () calls the function
ImplHandleMouseEvent (), with 

    - the window object - pWindow
    - nSVEvent = 1 (EVENT_MOUSEBUTTONDOWN)
    - bMouseLeave = False
    - x,y co-ordinates
    - time of the event nMsgTime
    - nCode = 1, to indicate status of shift,ctrl keys
    - and mode of click , nMode = 3

The function then does the following,
    - gets the details of the frame 
    - checks the previous location of the mouse. 
    - updates the frame data with the latest details 
    - checks whether the mouse has left or entered (?). 
    - finds the window
    - after finding the window 
        - it checks whether the window was disabled
    - it comes to line 666 (after several if conditions turned out to be false), for the mouse click event
        - here it checks for double click.
        - it then updates the details in the child window object
    - It creates the MouseEvent object at line 709
    - It notifies the child window of the event. Off to the next function.
    - In the next call, first the constructor of ImplDelData is called (maybe due to some 
        inheritance) ImplDelData::ImplDelData () at /home/jesso/Downloads/libreoffice/libo/vcl/inc/
        svdata.hxx:424, this is there to protect against the window from getting destroyed.
    - The NotifyEvent object is created.
    - It then checks whether it should bring the window into focus, if it previously didn't have focus,
        close context menus etc.
    - ImplCallPreNotify function
        - calls long Application::CallEventHooks () at ./libo/vcl/source/app/svapp.cxx:1657
        - that function returns 0
        - so it gets the PreNotify () method on the window object in the event object.
    - Finally it calls the MouseButtonDown() method on the pChild pointer, which happens to be 
          MenuBarWindow::MouseButtonDown () at ./libo/vcl/source/window/menu.cxx:5366

The MenuBarWindow::MouseButtonDown () then does the following,
    - It first finds the entry on which the action happened.
    - It then calls ChangeHighlightItem (which needs to be refactored, btw)
    - This decides whether to update the focus etc
    - It then finally creates the pop up in line 5477
    -