From d8ebeb118bb9137fcd7a28119836a317efd5e039 Mon Sep 17 00:00:00 2001 From: Michele Calgaro Date: Sun, 27 Apr 2025 13:40:36 +0900 Subject: kdesktop: add documentation about POSIX signals usage Signed-off-by: Michele Calgaro --- kdesktop/DESIGN | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/kdesktop/DESIGN b/kdesktop/DESIGN index f69ee2198..7e195378f 100644 --- a/kdesktop/DESIGN +++ b/kdesktop/DESIGN @@ -7,6 +7,7 @@ Author : Last modified: 24 Oct 1999 + Overall design of KDesktop : ============================= @@ -14,6 +15,7 @@ KDesktop is the program that handles the desktop icons, the popup menus for the desktop, the mac menubar, and the screensaver system. + Files : ======= @@ -34,6 +36,7 @@ KDesktopIface* : DCOP interface for kdesktop, used by kfmclient lock* : screen saver/locker + Libs used by KDesktop ====================== @@ -41,6 +44,7 @@ tdecore, tdeui, tdefile - usual stuff :) libtdeio - I/O stuff, mimetypes, services, registry libkonq - properties dialog, templates ("new") menu, dir lister, settings + Screensaver =========== @@ -69,6 +73,7 @@ The new background code is in bgrender.cpp and bgmanager.cpp. Some features: * Support for xearth like programs. * Can export a pixmap of the desktop background for pseudo transparency. + Multiple monitors ================= Two monitors showing different things (not a mirror-setup) can be configured @@ -92,3 +97,30 @@ In case of 2 screen (multihead) | | | | desktopGeometry = 3200 x 1200 +----+ +-----+ screenGeometry = 1600 x 1200 (for each monitor) + +Interaction between kdesktop and kdesktop_lock +============================================== +kdesktop and kdesktop_lock interact using POSIX signals to coordinate their activities. +Each time the screensaver or lock is activated and then stopped/unlocked, the current +kdesktop_lock process is terminated and respawned, while kdesktop waits for the new process +to be ready. + +kdesktop to kdesktop_lock communication: + kdesktop uses four signals to request different types of locks. These signals do not activate + the lock/screensaver. Some of the signals can be combined together, for example to request a + lock with blank screen. + + - USR1 : request lock of the screen + - USR2 : request screensaver only, no lock + - WINCH: request lock of the screen using SAK (Secure Attention Key) + - TTIN : request blank screen for saver or lock + + The lock/screensaver is started using a fifth signal. + - TTOU : activate the scrensaver or lock + +kdesktop_lock to kdesktop communication: + kdesktop_lock uses three signals to inform kdesktop of status changes. + + - TTIN: the lock process is ready. This is sent after the process has been created/respawned + - USR2: the lock/screensaver has been activated + - USR1: the lock/screensaver has been unlocked/stopped -- cgit v1.2.3