emWin - SEGGER Microcontroller

320 CHAPTER Execution Model: Single Task / Multitask
Example
#define GUI_X_SIGNAL_EVENT GUI_X_SignalEvent
GUI_X_WAIT_EVENT
Description
Defines a function which waits for an event.
Type
Function replacement
Additional information
Per default the GUI needs to periodically check for events unless a function is defined
which waits and one that triggers an event. This macro defines the function which
waits for an event. Makes only sense in combination with GUI_X_SIGNAL_EVENT. The
advantage of using the macros GUI_X_SIGNAL_EVENT and GUI_X_WAIT_EVENT instead
of polling is the reduction of CPU load of the waiting task to 0% while it waits for
input. If the macro has been defined as recommended and the system waits for user
input the defined function should wait for an event signaled from the function defined
by the macro GUI_X_SIGNAL_EVENT.
It is recommended to specify the function GUI_X_WaitEvent() for the job.
Example
#define GUI_X_WAIT_EVENT GUI_X_WaitEvent
GUI_X_WAIT_EVENT_TIMED
Description
Defines a function which waits for an event for a dedicated period of time.
Type
Function replacement
Additional information
Per default the GUI needs to periodically check for events unless a function is defined
which waits and one that triggers an event. This macro defines the function which
waits for an event if a timer is active. Makes only sense in combination with
GUI_X_SIGNAL_EVENT. If the macro has been defined as recommended and the system
waits for user input during a timer is active the defined function should wait until
the timer expires or an event signaled from the function defined by the macro
GUI_X_SIGNAL_EVENT.
It is recommended to specify the function GUI_X_WaitEventTimed() for the job.
Example
#define GUI_X_WAIT_EVENT_TIMED GUI_X_WaitEventTimed
14.7 Kernel interface API
An RTOS usually offers a mechanism called a resource semaphore, in which a task
using a particular resource claims that resource before actually using it. The display
is an example of a resource that needs to be protected with a resource semaphore.
emWin uses the macro GUI_USE to call the function GUI_Use() before it accesses the
display or before it uses a critical internal data structure. In a similar way, it calls
GUI_Unuse() after accessing the display or using the data structure. This is done in
the module GUITask.c.
UM03001 User & Reference Guide for emWin V5.18 © 1997 - 2012 SEGGER Microcontroller GmbH & Co. KG