Input focus

This page is dedicated to description of input focus management problems and my solutions.

Point of interest:

WM

• actions.c: wSetFocusTo() - set focus to particular window;
• event.c: handleMapRequest(), handleMapNotify(), handleUnmapNotify(), handleDestroyNotify()
• application.c

GNUstep GUI backend (gnustep-back):

• Sources/x11/XGServerEvent.m:

WApplication (application.h)

Every running application has WApplication instance. Normal X11 application exists only if at least one window was mapped.

WApplication instance for registered application should contain defined:

• app_icon - appplication icon
• windows - list of windows (at least one) which belongs to application
• menu_win for GNUstep application

GNUstep application minimal appearance is appicon and menu. For focus handling/switching tasks menu_win must be set to make correct focus switching.

Description of some field inside struct WApplication {}:

main_window - this is the invisible window that identifies application as a group of windows. Also it's called as "group leader". Every WWindow and WAppIcon contains field Window main_window. That's how application icon, menu and windows/panels can be identified as single application.

main_window_desc - generated WWindow structure for main_window. So main_window can be used as managed WWindow.

last_focused - should be set to last window of application that has focus before FocusOut, hide, workspace switch events. Set in wSetFocusTo().

last_workspace - contains workspace number of last_focused window workspace. If, for exmaple, application has 2 windows on different workspaces, double-click on appicon should: switch to workspace where last_focused window resides, set focus to that window (activate application). Set in wSetFocusTo().

New GNUstep application handling by WM

On application start wApplicationCreate() is called:

• creates wapp->windows array
• adds wwin to this array
• saved wwin to wapp->menu_win if it's main menu (normally it is)

When new window opens (MapRequest/MapNotify, event.c) wApplicationAdd() is called:

• adds wwin into wapp->windows array
• wapp->refcount++

When window is closed (UnmapNotify, event.c) and window is not main menu wApplicationRemoveWindow() is called:

• removes wwin from wapp->windows array
• wapp->refcount--

When application quits (DestroyNotify, event.c):

• several calls to wApplicationRemoveWindow() is performed
• wApplicationDestroy() is called:
  • wUnmanageWindow() for wapp->menu_win is called
  • wapp->windows array destroyed
  • wapp->refcount--
  • wapp is freed