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164 lines
5.3 KiB
Plaintext
164 lines
5.3 KiB
Plaintext
This file summarizes primary aspects of the NS port architecture. If
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possible, it should be updated for changes.
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Currently it summarizes the state as of:
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summer 2008 shortly after merging to trunk
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Startup
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-------
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Init sequence:
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emacs.c: ns_alloc_autorelease_pool() nsterm.m
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emacs.c: ns_init_paths() nsterm.m
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- override EMACSLOADPATH, etc. so resources can be found in-bundle
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emacs.c: init_display() dispnew.c
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- sets Vwindow_system (window-system) to 'ns
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emacs.c: loadup.el -> startup.el -> ns-initialize-window-system
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-> x-open-connection (nsfns.m)
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- ns-list-services
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-> nsterm.m: ns_term_init()
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- EmacsApp sharedApplication
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- read NS defaults (org.gnu.Emacs.plist)
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- init X-style color list
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- ns_create_terminal()
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- NSApp run (goes to applicationDidFinishLaunching which terminates
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event loop -- see below)
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Event Loop
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----------
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In an NS application, the event loop is normally managed by system and all
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user code is event-driven. [NSApp run] is called by user and never returns.
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In Emacs, the event loop is managed by emacs itself.
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The NS port mediates between these two styles by intercepting the NS event
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dispatch at [NSApp sendEvent]. If a special event is detected, the event loop
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is broken, and control returned to Emacs. This special event is sent by
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ns_send_appdefined, which is called under these circumstances:
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- if a user input event is received
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- when a timeout fires
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NS event processing is instigated from Emacs through ns_select() and
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ns_read_socket() in nsterm.m. Parts of the codepaths leading to these
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functions are:
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keyboard.c:read_avail_input()
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-> ns_read_socket (ns_send_appdefined) -> [NSApp run]
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process.c:wait_reading_process_output()
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-> ns_select -> gobble_input (global inNsSelect=1)
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-> ns_read_socket (ns_send_appdefined if !expected) -> [NSApp run]
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sysdep.c:sys_select() -> read_input_waiting()
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-> ns_read_socket (send_appdefined) -> [NSApp run]
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[this codepath may not be used]
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Currently ctrl-g is not detected in as many circumstances as other emacsen.
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It is not certain whether this is due to the means of event loop integration,
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or errors of omission in the NS code. One area for exploration is the
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NO_SOCK_SIGIO define. When it is defined, ctrl-g seems to be picked up more
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often, but there are some annoying side effects. Currently it is left off by
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default, unless the --enable-cocoa-experimental-ctrl-g option is passed to
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configure. (Has no effect under GNUstep.) This is an area for improvement.
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Also, see the article here and its containing thread:
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http://article.gmane.org/gmane.emacs.devel/92021/match=handling%5fsignal
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Text Rendering and Font Handling
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--------------------------------
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nsfont.m implements the font driver, responsible for managing fonts and
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rendering text. Fonts are obtained through NSFontManager. Rendering must be
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done at a low level due to emacs' fine control over this process, therefore
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there are different approachs under Cocoa and GNUstep. Under GNUstep, the
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original NeXT Display PostScript (DPS) APIs are available and used. Under
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Cocoa, these were removed and Quartz drawing functions replaced them.
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In both cases, font glyphs are accessed through UTF8 character
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representations. It would be preferable to use unicode indices, but prior
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attempts at this have failed.
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Multi-script fontsets are auto-created in nsfont_make_fontset_for_font() using
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the facilities of NSTextStorage and NSLayoutManager.
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Object Architecture
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-------------------
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Unlike the other GUIs, the NS interface is based on a high-level and
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object-oriented API. This creates some tension in the code because emacs
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itself has been architected around the low-level Xlib and Xt APIs. The NS
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port tries to strike a balance between simplifying code on its side using OO
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features, and keeping code as similar as possible to other ports to ease
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maintenance. The following are the main classes (see nsterm.h):
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EmacsApp : NSApplication
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- event loop integration, interapp comms point for Finder (NSWorkspace) msgs,
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Services
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- one global instance (NSApp)
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- nsterm.m
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EmacsView : NSView <TextInput>
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- handles rendering of text and fringe, interapp comms for drag/drop
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- instance for each frame
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- child of window's content view
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- nsterm.m
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EmacsWindow : NSWindow
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- utility override for resize handling
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EmacsScroller : NSScroller
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- instance for each emacs window, renders scrollbar
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- child of window's content view
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- nsterm.m
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EmacsImage : NSImage
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- image rendering, toolbar icons, stippling, fringe bitmaps
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- instance for each image
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- nsimage.m
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EmacsMenu : NSMenu
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- menu management
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- one tree of instances for menubar, one instance for each popup menu
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- nsmenu.m
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EmacsToolbar : NSToolbar
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- toolbar management, one instance for each frame
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- nsmenu.m
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EmacsDialogPanel : NSPanel
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- popup dialogs, one instance for each
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- nsmenu.m
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EmacsTooltip : NSObject
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- tooltip popups, one instance for each
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- nsmenu.m
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EmacsGlyphStorage : NSObject <NSGlyphStorage>
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- utility for text rendering
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- nsfont.m
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EmacsPrefsController : NSObject
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- utility for preferences panel management, one global instance
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- nsterm.m
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- nextstep/Cocoa/Emacs.base/Contents/Resources/preferences.nib
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- nextstep/GNUstep/Emacs.base/Resources/preferences.gorm
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EmacsSavePanel : NSSavePanel
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EmacsOpenPanel : NSOpenPanel
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- utility override for panel notifications
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